Bubble dynamics inside a liquid medium and its interactionswithhydrophobic and hydrophilic surfaces are crucial for many industrialprocesses. Electrospinning of polymers has emerged as a promisingfabrication technique capable of producing a wide variety of hydrophobicand hydrophilic polymer nanofibers and membranes at a low cost. Thus,knowledge about the bubble interactions on electrospun hydrophobicand hydrophilic nanofibers can be utilized for capturing; separating;and transporting macro-, micro-, and nanobubbles. In this study, poly(methylmethacrylate) (PMMA) and PMMA–poly(ethylene glycol) (PEG) electrospunnanofibers were fabricated to investigate gas bubble interactionswith submerged nanofiber mats. To improve their durability, the nanofiberswere reinforced with a plastic mesh. The ultimate tensile strengthsof PMMA and PMMA-30%PEG nanofibers were measured as 0.35 and 0.30MPa, respectively. With the use of reinforcement mesh, the mechanicalproperties of final membranes could be improved by a factor of 70.The gas permeability of the electrospun and reinforced nanofiberswas also studied using the high-speed visualization technique anda homemade setup to investigate the effect of electrospun nanofiberson the bubble coalescence and size in addition to the frequency ofreleased bubbles from the nanofiber mat. The diffusion rate of airbubbles in hydrophobic PMMA electrospun nanofibers was measured as10 L/s for each square meter of the nanofiber. However, the PMMA-30%PEGmat was able to restrict the diffusion of gas bubbles through itspores owing to the van der Waals force between the water moleculesand nanofiber surface as well as the high stability of the thin waterlayer. It has been shown that the hydrophobic electrospun nanofiberscan capture and coalesce the rising gas bubbles and release them withpredictable size and frequency. Consequently, the diameter of bubblesintroduced to the hydrophobic PMMA membrane ranged between 2 and 25mm, whereas the diameter of bubbles released from the hydrophobicelectrospun nanofibers was measured as 8 ± 1 mm. The proposedmechanism and fabricated electrospun nanofibers can enhance the efficiencyof various systems such as heat exchangers, liquid–gas separationfilters, and direct air capture (DAC) systems. The gas–liquid separatorsare one of the critical components of air-conditioning systems10 and compression systems.11 Improving the separator efficacy and decreasing the liquidresidence time inside them can significantly affect the time and costof the separation process.12Recent developments in surface engineeringand synthesis of hydrophobicand hydrophilic surfaces have enabled their applications in a varietyof fields, including biotechnology,13 Thus, developinga novel methodology to scavenge the floating micro- and nanobubbleswithin the medium and to merge them into larger bubbles can help inimproving the efficiency of gas–liquid separators. The sameapproach can also be applied to other applications such as capturingmethane gas bubbles from bodies of water. Methane gas bubble emissionsfrom man-made and natural water bodies are among the sources of greenhousegas emissions.14 Capturing the releasedmethane gas bubbles before they enter the atmosphere could reducetheir negative impact on the environment and global warming. Additionally,storing the harvested methane bubbles can be considered a potentialenergy source for power plants.Furthermore,nanofibers and nanoporous materials can be utilizedto resolve the problem of long-term floating micro- and nanobubbleswithin the liquid medium. The micro- and nanobubbles have a lowerrising velocity in the liquid medium than macrobubbles, and sincethey have a lower buoyancy force, they can remain buoyant in the mediumfor an extended time period.15 Surfaces with a lower contactangle than 90° are considered hydrophilic. Hydrophobic and superhydrophobicmaterials repel the liquid phase to maintain contact between the solidsurface and gaseous phase and to avoid formation of a new solid–liquidinterface. Surface wettability can be altered by manipulating thechemical properties and surface energy16 and with the surface roughness and microstructures.17 Functionalizing the surface using nonpolar hydrophobic materialscan improve the hydrophobicity by repelling the polar water molecules.18 The surface roughness elements, which can becreated as precisely engineered surface porosities, are able to trapgas pockets and prevent liquid molecules from penetrating into theporosities.19 Using both of these approaches,it is possible to enhance the hydrophobicity of a surface. The higherprojected surface area in the functionalized porous materials increasesthe surface density of the hydrophobic functional groups and booststheir effectiveness in repelling the liquid molecules. On superhydrophobicsurfaces, the surface porosities can retain miniature gas bubblesand minimize the droplet’s contact with the surface in theCassie–Baxter state. Under this condition, the surface tensionof the penetrating liquid and the pressure of the gas bubble in theporosity play essential roles in preventing the liquid from leakinginto the porosities.20 In the case of hydrophobicsurfaces, the droplet can penetrate into the porosities in the Wenzelstate.21Water repellent surfaces canbe classified as hydrophobic (watercontact angle (WCA) > 90) and superhydrophobic (WCA > 150),dependingon their WCA.22 The chemical properties of nanofibers can betuned by selecting the appropriate polymers and their mixing ratio.It was reported in the literature that electrospun poly(methyl methacrylate)(PMMA) nanofibers have a high WCA and low water uptake.23 Our recent study confirmed that the WCA of electrospunPMMA nanofibers is about 124°, and the water droplets on thesurface of the nanofiber are stable and do not penetrate into itsstructure.24 However, PMMA thin films andnonfibrous structures have been recognized as hydrophilic polymerswith the WCA of 60–70°.25 Thedifference between the WCA of nanofiber and the thin film of PMMAcan be attributed to the surface roughness and porosity. The air andwater permeability of the membrane is greatly affected by the membrane’shydrophobicity and hydrophilicity. Blending hydrophilic polymers suchas poly(ethylene glycol) (PEG) with PMMA has been shown to significantlyaffect the hydrophobicity and swelling of electrospun nanofibers.24 Also, their physical properties, permeability, and surface roughnesscan be tailored to achieve the desired properties such as nanofiberdiameter by optimizing the electrospinning parameters such as theaccelerating voltage, spinneret to target distance, and humidity.Increasing the surface roughness on functionalized hydrophobic surfacesincreases the projected surface area for mounting hydrophobic functionalgroups, which increases the stability of air packets within the porosities.26 Employing a dual strategy by engineering thechemical properties of the surface and its morphology leads to a higherWCA and more stable hydrophobicity.Electrospinning is an emergingfabrication technique for producingscalable, cost-effective, and easily controllable polymer nanofibersand membranes with hydrophobic and hydrophilic properties.27 nevertheless, it was reported that this relationshipcould be violated on the surfaces with higher surface roughness andhigher water contact angle hysteresis (CAH).29 The recent attempts to understand the interactions of hydrophobicand hydrophilic porous materials with liquid and gas bubbles revealedtheir potential in separating the gas phase from the two-phase media.30 Chen et al. fabricated a superhydrophobic material by modifyinga sponge surface to study the methane bubble separation from water.31 They demonstrated that superantiwetting spongescan selectively absorb, store, and continuously transport marine methanebubbles. Ma et al. fabricated superhydrophobic three-dimensional (3D)gradient porous interconnected network surfaces to study the possibilityof macro- and microgas bubble transportation in a liquid medium.32 The prepared and treated copper wires in thatstudy could maintain a constant gas film underwater for an extendedperiod of time and transported the gas film using the Laplace pressuredifference. Chen et al. investigated the air bubble interactions withJanus wettability membranes, which had an asymmetric surface wettability.They showed that while the air bubbles on the hydrophilic side ofthe membrane tended to penetrate upward into the mesh, the air bubbleson the superhydrophobic side favored horizontal spreading on the surfaceof the fabricated air “diode”.33 Although there are some studies on the interactions of hydrophobicand hydrophilic surfaces with air bubbles, the mechanism of air bubblecapture, its penetration behavior, and transportation through electrospunnanofibers are yet to be explored. Therefore, revealing the mechanismof the trapped bubbles on nanofibers and understanding their interactionsare of utmost importance, particularly for the researchers and engineersworking on bubble dynamics, capture, separation, and transportation.There has been extensiveresearch on the hydrophobicity and hydrophilicityof electrospun nanofibers in an air medium. However, their interactionwith gas bubbles under submerged conditions has not been sufficientlyexplored. The interactions of the submerged hydrophobic and hydrophilicsurfaces with gas bubbles can be estimated by studying the behaviorof water droplets on their surface in the air medium. In additionto WCA, bubble contact angle (BCA) can also be useful for discerningthe hydrophobic properties of submerged materials. The relationshipbetween the BCA on a submerged surface and the WCA of the materialin the air has been reported to be complementary on smooth surfaces;In this study, hydrophobic and hydrophilic electrospun nanofibersof PMMA and PMMA–PEG were fabricated to investigate the gasbubble interactions on submerged nanofiber mats. PMMA nanofibers wereselected as hydrophobic polymers, and the PEG polymer was added tothe PMMA polymer for tuning the hydrophobicity of PMMA–PEGnanofibers. The WCA and underwater BCA of the electrospun nanofiberswere measured. The behavior of gas bubbles, including bouncing andattachment and penetration in the vicinity of the nanofibers, wasextensively examined using a high-speed camera, and the gas-phasediffusion mechanism was explored in detail. The prepared nanofiberswere reinforced by a plastic mesh to improve their durability. Themechanical properties of the electrospun nanofibers and reinforcednanofibers were studied via a tensile test stand. The gas permeabilityof the electrospun and reinforced nanofibers was also visualized usinga homemade setup to investigate the effect of electrospun nanofiberson the bubble coalescence and size in addition to the frequency ofreleased bubbles from the nanofiber mat. The reported results showedthat the presented novel approach could be used to separate the gasphase from the liquid by sorting and reducing the size distributionof gas bubbles.N,N-Dimethylformamide(≥99%), PMMA (Mw = 3 50 000g/mol), and PEG (average Mn ∼ 400)were purchased from Sigma-Aldrich  and were usedwithout any purification. A Milli-Q device was used to obtain deionizedwater (resistance 18.2 MΩ cm).24 Based on the reported properties, the PMMA and PMMA-30%PEG nanofiberswere electrospun using a 12 kV electric field, spinneret and collectordistance of 20 cm, and flowrate of 0.6 mL h–1.The electrospinning of nanofibers was carried out based on ourresearch group’s recent study, where optimization of the electrospinningparameters and characterization of the physical and chemical propertiesof electrospun nanofibers were reported.A plastic mesh with 2 mm × 2 mm apertures was used as a supportto improve the mechanical properties of the membrane. The mechanicalproperties of electrospun nanofibers and reinforced mat with the plasticmesh were characterized using a Mark-10 ESM 303 motorized tensiletest stand and M7–020 digital force gauge based on the ASTMD882-10 standard test method for tensile properties of thin plasticsheeting. The surface of electrospun nanofibers was studied usingthe field emission scanning electron microscopy technique .WCA measurements were conducted using the AttensionTheta Lite tensiometer. After accumulating a 5 μL droplet ofdistilled water (18.2 MΩ mm at 25 °C) on the tip of theneedle, the droplet was released by moving the syringe downward andcontacting the sample surface. The BCA on submerged electrospun nanofibersand the diffusion mechanism of air bubbles through electrospun nanofiberswere investigated by assembling the reinforced nanofibers on a glassfunnel, as shown in 24 20,30, and 40% PMMA–PEG solutions were prepared, and the propertiesand uniformity of the electrospun nanofibers were investigated. Althoughthe addition of different amounts of PEG to the PMMA polymer couldhave a significant impact on its wettability properties, its impacton the electrospinning conditions and quality of the prepared nanofibersshould not be underestimated. This study showed that a lower amountof the PEG polymer could not have any noticeable effect on the wettabilityproperties of nanofibers. A higher amount of PEG decreases the uniformityof the electrospun nanofibers and causes the generation of beads onthe surface of the mat. These beads not only reduce the topographicaluniformity of the surface but also have a negative impact on the uniformityof the nanofiber chemical composition. Taking all of the abovementionedeffects into consideration, the PMMA-30%PEG was selected in this studyas an optimum mixing ratio to exploit the best properties from theprepared electrospun nanofibers.In a recent study of the authors,34 The oxygen atoms on ether groupsin the backbone of PEG absorb hydrogen atoms, resulting in a highsolubility of PEG in water.35 The WCA ofthe thin film of PMMA was reported as 65° in the literature;25 however, this value can reach higher valuessuch as 160° in fibrous mats.23 Thisbehavior can be attributed to the effect of surface roughness on hydrophobicity.Blending these two polymers leads to hydrophobic and hydrophilic regionson the surface of electrospun nanofibers and reduces the WCA of PMMA-30%PEGin comparison with PMMA. Meanwhile, PMMA reduces water molecules’accessibility to PEG and prevents their dissolution. Therefore, despitethe high water solubility of PEG, PMMA-30%PEG is stable in water.232) of freshelectrospun nanofibers were placed in a ventilated oven at 40 °Cfor 4 h and then weighed using a four-digit analytical balance. Thedried nanofiber was submerged in water for 1, 2, 5, 10, 24, and 72h and then dried again in the oven for 4 h to get rid of the infusedwater into the structure of the electrospun nanofibers. The weightchanges of the nanofibers were measured with a precision of 0.1 mg,and almost no weight difference was measured during the experiments.Therefore, it can be concluded that PMMA-30%PEG is completely stablein an aqueous environment.The water stability of the electrospun nanofiberswas characterizedby measuring the weight changes of the submerged electrospun nanofibersin different time intervals. Samples  close to zero as shownin the absorption stage and sliding stage in 35 Meanwhile, the attraction forces between the electrospunnanofiber and the approaching gas bubble are insufficient to overcomethe van der Waals forces between the water layer and nanofibers. Therefore,the air bubble cannot penetrate into the porosities of the hydrophilicnanofiber net. Furthermore, sliding off the air bubble on the surfaceof the electrospun nanofiber with a BCAH of close to zero confirmsthe presence of the thin water layer.36 The hydrophobic properties of PMMA cause theapproaching gas bubble to dissipate more energy and bounce less thanthe gas bubble on hydrophilic PMMA-30%PEG.Interestingly, the bouncing bubble on the surfaceof PMMA-30%PEGreaches the terminal velocity for a complete detachment from the surfaceof the membrane 6a–d; howAfter stabilization of the gas bubble on the membranes’surface, the bubble on hydrophilic nanofibers does not diffuse intoits porosities. However, the hydrophobic nanofiber absorbs the bubblewithin about 400 ms. The air and water diffusion mechanisms in PMMAand PMMA-30%PEG electrospun nanofibers are illustrated in The stress–strain curve of PMMA and PMMA-30%PEGelectrospunnanofibers and supporting plastic mesh is displayed in Furthermore, the consumed materials required forelectrospinningthe nanofiber mat and their costs can also increase. In this regard,a cheap and mechanically durable plastic mesh was used to improvethe mechanical properties of the membrane without having a negativeimpact on its performance. Supporting the electrospun nanofibers usingthe plastic mesh increases the mechanical properties of the finalmembrane by a factor of 70 8. The pl37 The addition of the PEG polymer to the solutionincreases the conductivity of the polymer blend, thereby leading toan amplification in the effect of the electrical field on the electrospinningjet. The electrospun nanofibers are subjected to a higher force andstretch during the electrospinning process. Therefore, the diameterof the nanofibers decreases upon addition of the PEG polymer.38SEM images of electrospun PMMA and PMMA-30%PEGnanofibers are shownin 39 These properties can be adjusted by engineeringthe chemical composition of the nanofibers and their electrospinningparameters.40 This study proves that itis possible to capture a wide size distribution of air bubbles usingelectrospun nanofibers and to release them with a constant diameter.These observations are consistent with the mechanism displayed in In this study, the interaction of gas bubbleson submerged nanofibermats made of hydrophobic and hydrophilic electrospun nanofibers, whichwere fabricated from PMMA and PMMA–PEG polymers, was investigated.The WCA measurements showed that PMMA and PMMA-30%PEG nanofibers haveWCAs of 125 and 45°, respectively. The oxygen atoms on ethergroups in the backbone of PEG absorb hydrogen atoms in water, resultingin a high solubility of PEG; however, mixing it with PMMA reducesthe water molecules’ accessibility to PEG and prevents theirdissolution. Therefore, PMMA-30%PEG becomes a hydrophilic and undissolvablepolymer in water. High-speed visualization of the rising gas bubblesrevealed that they have no tendency to spread on the surface of thePMMA mat; they bounce off a few times to dissipate their kinetic energyand rupture the thin layer of water on the surface. The bouncing stagetakes 47 and 106 ms long for hydrophobic PMMA and hydrophilic PMMA-30%PEGnanofibers, respectively. The time difference in stabilizing the airbubble on the surface suggests the difference in the van der Waalsinteractions of the water molecules and the surface of each nanofiber.The hydrophobic properties of the surface reduce the effect of thevan der Waals forces and facilitate the bubble absorption on the surface.Considering the air bubble volume and its occupied area on the nanofiber,the diffusion rate of air bubbles in PMMA electrospun nanofibers is10 L/s for each square meter of the nanofiber.Furthermore,sliding off the air bubble on the surface of the hydrophilicelectrospun nanofiber with a BCAH of close to zero confirms the presenceof the thin water layer on the surface. The bouncing bubble on thehydrophobic nanofiber cannot be detached from the surface of the membraneafter the first impact; however, it can be detached from the hydrophilicmembrane. Therefore, the terminal velocity for detachment of the gasbubble from the membrane is greater than 0.33 m/s and less than 0.64m/s. The ultimate tensile strengths of the PMMA and PMMA-30%PEG nanofiberswere measured as 0.35 and 0.30 MPa, respectively, and the reinforcednanofibers have 70 times more strength. The conductivity of the solutionin PMMA–PEG blend was higher than the PMMA electrospinningsolution. Therefore, the PMMA–PEG electrospinning jet was stretchedmore under the same electric field, and the diameter of the electrospunnanofibers decreased in comparison with PMMA nanofibers. Finally,the diameter of the bubbles introduced into the membrane ranges from2 to 25 mm, while the diameter of the bubbles released from the hydrophobicelectrospun nanofibers is 8 ± 1 mm. These results show that thereinforced hydrophobic electrospun PMMA–PEG nanofibers havea high potential in capturing, sorting, and releasing the gas bubbleswith a predictable frequency and size distribution.


Among the various methods for drug design, the approach using molecular descriptors for quantitative structure–activity relationships (QSAR) bears promise for the prediction of innovative molecular structures with bespoke pharmacological activity. Despite the growing number of successful potential applications, the QSAR models often remain hard to interpret. The difficulty arises from the use of advanced chemometric or machine learning methods on the one hand, and the complexity of molecular descriptors on the other hand. Thus, there is a need to interpret molecular descriptors for identifying the features of molecules crucial for desirable activity. For example, the development of structure–activity modeling of different molecule endpoints confirmed the usefulness of H-GETAWAY  descriptors in molecular sciences. However, compared with other 3D molecular descriptors, H-GETAWAY interpretation is much more complicated. The present study provides insights into the interpretation of the HATS5m descriptor (H-GETAWAY) concerning the molecular structures of the 4-thiazolidinone derivatives with antitrypanosomal activity. According to the published study, an increase in antitrypanosomal activity is associated with both a decrease and an increase in HATS5m  values. The substructure-based method explored how the changes in molecular features affect the HATS5m value. Based on this approach, we proposed substituents that translate into low and high HATS5m. The detailed interpretation of H-GETAWAY descriptors requires the consideration of three elements: weighting scheme, leverages, and the Dirac delta function. Particular attention should be paid to the impact of chemical compounds’ size and shape and the leverage values of individual atoms. QSAR models combine different computational and multivariate statistical or machine learning techniques to establish the relationship between structure and biological activity, physicochemical properties, or toxicity of compounds. The main task of QSAR analysis, namely predicting the activity or properties of new compounds, is accomplished in many applications thanks to dynamically developing computational methods. Recently, comprehensive reviews about the development of QSAR modeling and its role in different fields have been published ,2,3. DurThe first reports dedicated entirely to the theory of the GEometry, Topology, and Atom-Weights AssemblY (GETAWAY) descriptors were published in 2002 ,7. The pThe ability to create a direct link between moieties, molecular descriptors, and biological activity should be an integral part of the research ,20. UnfoThis paper presents a comprehensive analysis of the similarity/diversity of the structural features of 4-thiazolidinone derivatives using HATS5m  molecular descriptor (belonging to the H-GETAWAY type). The first section briefly summarized the definitions, formulas, and mathematical properties of HATS descriptors. The second part illustrates the interpretation of HATS5m for Random Forest and Gaussian processes regression models of 4-thiazolidinones antitrypanosomal activity presented in . This stlag) is relevant to the biological activity under study. The Dirac-delta function selects only those atomic pairs within a distance indicated by the QSAR model. The Dirac-delta function is defined byijd is the topological distance between the ith and jth atoms and k = 1, 2, …, d. The calculation algorithm for HATS indices utilizes information about molecular structure in two different ways: topological and geometrical. To fully understand both ways of encoding chemical information through HATS indices, explaining the ideas of the molecular graph, Dirac-delta function, Molecular Influence Matrix, and leverages is necessary. Topological reasoning involves visualizing the molecular structure as a graph, where the vertices correspond to atoms while the edges represent bonds. The molecular graph representation is 2D data with no spatial relationships between atoms. The number of bonds (edges) between atoms (vertices) on the shortest possible path  is determined topological distance matrix. The QSAR equation supplies information on what topological distance .Molecular Influence Matrix (MIM), denoted by H, is defined in terms of the molecular matrix M asT refers to the transposed matrix. The M matrix is formed from A rows corresponding to the atoms in a molecule and three columns corresponding to the centered Cartesian atomic coordinates x, y, z. The molecules should have explicit hydrogen atoms. GETAWAY descriptors are invariant to translation and rotation due to the calculation of atomic coordinates concerning the geometrical center of the molecule. In the context of molecular structure, the H matrix evaluates the impact of atoms on each other. The diagonal elements of the symmetric H matrix, iih, are called leverages and satisfy:h denotes elements of the molecular influence matrix, A is the number of atoms, D is the rank of the molecular matrix, and The ith atom impacts the molecular shape of the whole molecule. The non-diagonal elements have a value in the  range. A large value of iih (high leverage) indicates that the ith atom is distant from the center of the Cartesian coordinates of the molecule. Molecular Influence Matrix (MIM) is a convenient tool for considering information about the size and shape, especially concerning symmetry and molecular branches. In a series of molecules with similar sizes, lower leverages can be found for atoms in molecules of spherical shape than in more linear ones. It can be explained by a significantly smaller total distance of atoms from their geometrical center. In a set of compounds with similar shapes, an increase in the number of atoms cause a decrease in leverages [The 3D-molecular geometry is the mutual distribution of atoms in the space around the molecular center. Leverage expresses how much the everages ,28. The topological and geometrical approaches mentioned above describe only the molecular structure without considering the physicochemical properties of the atoms. This limitation may be removed by using atom weights. For example, the weighting schemes encode atomic mass (m), atomic polarizability (p), atomic electronegativity (e), or van der Waals atomic volume (v). All of them are scaled up by relating the carbon atom, which weight equals one. A is the number of atoms, iw and jw are the weights of the ith and jth atoms, h denotes elements of the molecular influence matrix (leverages), ijd is the topological distance between the ith and jth atoms for respective lag (k). Usually, k is from 1 to 8. The HATS indices are defined as autocorrelation descriptors and calculated according to the following equations :(6)HATS0lag 5) and weighted by atomic masses (m). A graphic illustration of the HATS  descriptor value calculation for an exemplary molecule (chlorobenzene) is shown in Evaluating QSAR model quality is ubiquitous and essential in many disciplines, such as risk assessment, toxicity prediction, drug discovery, and drug optimization ,30. Howelag 5) and weighted by atomic mass, i.e., HATS5m. To illustrate the impact of the Dirac-delta function on the HATS5m value, we considered the exemplary molecules with similar sizes (approximately 60 atoms) and various shapes: n-icosane C20H42, fullerene C60, and graphene-like structure C42H18  than in linear n-icosane. Hence, it could be expected that fullerene may have the lowest HAT5m value among these compounds, but contrary to this, significantly different values are obtained. In fact, fullerene’s descriptor value is greater (0.75) than n-icosane (0.01). HATS5m was calculated only for atoms spaced at five bonds (as an arbitrary choice) for these compounds. Based on the Dirac-delta function, these compounds are differentiated by the number of atomic pairs distinct at five bonds (lag 5): 300, 231, and 153 for fullerene, graphene-like structure, and n-icosane, respectively. Many atoms in a specified distance with relatively low leverages in fullerene translate to a much higher descriptor value than n-icosane and a graphene-like sheet containing a small number of atoms with high leverages at the periphery structure. In addition, the weights of atoms also have a significant impact on the descriptor value of these compounds. The low HATS5m value of graphene-like structure compared to fullerene C60 results from high leverage and low weight values of hydrogen atoms. Therefore, the sum of the low weights and high leverages products translates to a low descriptor value (see Equation (7)). The interpretation of the HATS indices and the correlation with shape should combine all elements: weighting scheme, leverages, number, and distribution of atomic pairs separated by a given topological distance (obtained from Dirac delta).The n-icosane is acyclic, an unbranched hydrocarbon with elongated conformation, while the fullerene Clag 5, weighted by atomic masses), we took the molecular structures and their biological activity from the study of Kryshchyshyn and co-workers [Despite the GETAWAY descriptor’s proven usefulness, a more detailed analysis seems needed, particularly regarding the scope, interpretation, and practical application. To better understand and interpret the HATS5m  can help capture and understand the molecular features of compounds encoded in the model constructed in [The molecular structures of the 4-thiazolidinone derivatives reported in  differ sucted in .substructure-based method as a straightforward way to explore how the changes in molecular features of compounds affect the HATS5m value  4-thiazolidinone and substituents R1, R2, R3, and R4. The set of compounds was split into five subsets with different common cores (Φs) . To bettThe substructure-based approach emphasizes that the common cores of 4-thiazolidinone derivatives (n = 132) have an unequal impact on the descriptor value. The minimum and maximum HATS5m values are 0.0329 and 0.9343, respectively, while the median value is 0.1063. In a subsequent part of the article, we focused on assessing the impact of the weights of atoms , size S, and shaUnweighted descriptors treat each atom equally, while weighting is intended to distinguish between the atoms. For calculating the molecular descriptor, atomic weighting schemes involving specific atomic properties are used. The atomic properties often used as atomic weights are: atomic mass (m), van der Waals volume (v), the electronegativity of the atom (e), atomic polarizability (p), and ionization potential (i).The effect of atomic mass on the HATS5m value is investigated using the compound Les1 , the different number of atomic pairs covers 80% of the descriptor value. In addition, the descriptor values from HATS1m to HATS8m also differ. The interpretation of the HATS descriptor is based on identifying the atomic pairs with the largest contribution to the descriptor’s value. All substructures consist of two fragments: common core (red) and benzylidene substituents (blue). The differences in the HATS5m value of substructures 1-4 are mainly related to the blue fragment (R4). Therefore, we want to check whether introducing a halogen atom in the meta ring position changes the leverage value and the HAST5m descriptor. Geometry optimization is not performed to maintain reproducible conditions. lag, the HATS descriptor value also depends on the type of atomic weightings. To show the weighting scheme impact, we calculated the contributions of atomic pairs (five bonds distant) to HATS5(w) descriptor values, by using the atomic mass, electronegativity, ionization potential, and van der Waals volume. For comparison, the atomic pair contributions to the unweighted HATS5 descriptor value  were computed. Results are presented in Apart from changing the In turn, The substructure-based analysis of the Les3 examines the effects of molecular size on the HATS5m value. The Les3 is decomposed into moieties treated as new independent structures numbered 5, 6, 7, and 8 . The sizA comparison of the inter-fragment effects of substructures 5, 6, and 7 reveals the impact of molecular size on leverages. Molecular similarity is a crucial topic in protein–ligand and protein–protein interaction recognition. Many molecular similarity evaluation approaches use molecular fingerprints, molecular alignment, pharmacophore, and 3D molecular descriptors. Combining HATS5m with a substructure-based approach and hierarchical cluster analysis leads to a view of the descriptor as a tool for differentiating the molecular structures according to their shape. A series of Les5 (Les-3834) conformers examine the similarity comparison. The numbering of atoms and the division Les5 into fragments are presented in Twenty structures are generated using the Conformer Plugin of Chemaxon’s Marvin software. The method of Molecular mechanics (MM) is the same as in the publication  to maintFurthermore, to investigate the conformers’ shape variability, cluster analysis was performed using the unweighted pair group method with arithmetic mean (UPGMA) and the Euclidean distance as a measure of similarity . The CopThe comparative analysis of contributions of atomic pairs enhances the interpretation of conformers. For further study, three compounds were selected: the original compound Les5, two conformers: 10 as nonlinear, and linear 14. The highest descriptor value had nonlinear conformer 10, intermediate Les5, while the lowest value had linear conformer 14. The Dirac-delta function indicated 117 atomic pairs distant at a topological distance of 5. However, each molecule had a different number of atomic pairs, which account for 80% of the HATS5m descriptor value, and their quantity is 21, 13, and 29 atomic pairs for Les5 and conformer 10 and 14, respectively.6H5. The atomic pairs of the green substituent are essential to exploring the 3D geometry of the conformer 10, unlike the compound Les5. In conformer 14, the most critical atomic pairs describe the R4 substituent (blue) linear arrangement concerning the common core (red). The blue fragment is essential to characterize the linear shape of conformer 14, in contrast to Les5 and Les5_10.As shown above, the HATS5m descriptor is affected by many factors, including weighting scheme, molecular size, and shape. Therefore, to properly assess the intra- and inter-fragment contributions of individual substituents, the source compounds (Les) were modified  to contain only the common core and the chosen substituent. The significance of substituents R1 (orange), R2 (green), and R4 (blue) was investigated with 46, 30, and 54 substructures, respectively. Finally, we prepared the group of 130 various substructures of 4-thiazolidinones derivatives. Molecular geometry re-optimization was not applied to keep the initial spatial arrangement of atomic pairs. All substructures are given in the Based on the video files , it is pThe set of 132 4-thiazolidinone derivatives, with biological activities taken from the literature, was used to develop an interpretation procedure of H-GETAWAY class of molecular descriptors on the example of HATS5m. In cooperation with the New Technologies Department of Softmaks.pl, the InterDescPy software tool was developed to explore the magnitudes of intra- and inter-fragment effects related to HATS5m. The InterDescPy was implemented in the Python programming language. In addition, the program provides the values of the atomic leverages and the contributions of the atomic pairs that compose the value of the HATS5m descriptor. Open-source PyMOL software was used to visualize the molecular structures leverage values of individual atoms. The geometry optimization of conformational sampling of Les5 (Les-3834) was performed by resorting to MarvinView 18.21.0 (2018), available from ChemAxon, by performing Molecular Mechanics calculations through the MMFF94 force field. The cluster analysis was carried out using a freeware statistical software PAST 4.03This paper has attempted to highlight the need for interpretations of H-GETAWAY descriptors (focusing on the HATS5m) and has presented various factors that may affect the conclusions drawn. However, interpretation of the H-GETAWAY descriptors is complex and requires the simultaneous consideration of three components: weighting scheme, leverages, and the Dirac delta function. Each of these three components describes the molecular structure differently. The weighting scheme encodes the physicochemical property of atoms. Leverages encode the arrangement of atoms in three-dimensional space around the geometric center of the molecule. In turn, The Dirac-delta function topologically treats the 3D structure as a two-dimensional object. The HATS descriptor value is the sum of the contributions (expressed as a sum of the products of weights and leverages) of the atomic pairs indicated by the Dirac-delta function. The difficulty in interpreting is that the leverages are calculated for the whole molecule, not just for the atoms selected by the Dirac-delta function. Thus, the leverages of selected atomic pairs also depend on the arrangement of the other atoms in the molecule. The interpretation of H-GETAWAY requires adopting a substructure-based approach augmented with the cutting of molecules.


Background: β-blockers are widely used for lowering heart rate (HR) during coronary computed tomography angiography (CCTA); however, they should be used with caution for patients with heart failure as they may have a negative inotropic effect.Objective: To clarify the effects of β-blockers  on cardiac function using CCTA.Methods: A total of 244 patients  suspected of having ischemic cardiac disease and had undergone echocardiography within 3 months before and after CCTA were included in the study. Systematic errors in ejection fraction (EF) were corrected by calculating ΔEF from the EF difference between echocardiography and CCTA in patients not using β-blockers. Univariate and multivariate analyses were performed for factors affecting ∆EF. In addition, HR between, before, and during CCTA were compared by Wilcoxon’s test.Results: Temporary oral or intravenous administration of β-blockers at the CCTA had no significant effects on EF (p = 0.70), whereas HR was significantly decreased (p < 0.001). However, regular administration of β-blockers increases the EF on CCTA.Conclusion: The administration of β-blockers immediately before CCTA affects HR but not EF. Premedication with β-blockers can be safely used for patients who undergo CCTA, and CCTA is useful for EF evaluation, independent of the use of β-blockers. The recent rapid development of diagnostic imaging techniques has enabled minimally invasive visualization of coronary arteries , 2. The Imaging of the heart is affected by motion artifacts caused by the heartbeat and vertical movement of the diaphragm during respiration. CCTA is therefore performed under respiratory arrest and in synchronization with the heartbeat to reduce these artifacts. However, there is a limitation of the gantry speed during CT, which determines the temporal resolution of CT. The main method used to overcome this problem is heart rate (HR) suppression with β-blockers, where usability has been well established in the literature , 6. Thisβ-blockers used to induce bradycardia during CCTA imaging are widely administered to treat hypertension and ischemic heart disease. Together with angiotensin-converting enzyme inhibitor (ACE-I) / angiotensin II receptor blocker (ARB) and diuretics, β-blockers play a central role in treating heart failure . On the 22.1This retrospective single-center study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the institutional ethics board of Tokyo Medical University (NO.: T2018-0061), and individual consent for this retrospective analysis was waived.2.2Using the radiological reporting system, we selected consecutive subjects suspected of having ischemic cardiac disease between April 2015 and March 2018 and who had undergone echocardiography within 3 months before and after CCTA. Patients were excluded from the study if they had an implanted cardiac pacemaker or defibrillator; lacked any part of patient characteristics; or had atrioventricular block; atrial fibrillation or extrasystoles at the time of CCTA or echocardiography. In addition, patients who were pregnant, lactating, possibly pregnant, or desiring to become pregnant during the study period were excluded.2.31).Three ultrasound (US) machines were used  to measure standard references for the analysis of ejection fraction (EF). The mean duration between echocardiography and CCTA was 21.7 days (median: 13 days). All patients were placed in the left lateral decubitus position for the imaging. Images were obtained in standard apical 4-chamber views and 2-chamber views by seven medical technologists who specialized in echocardiography and were blinded to the CCTA data. Left ventricular end-diastolic dimension (DD) and end-systolic dimension (DS) were also measured using M-mode echocardiography. DS, DD, and corrected EF were analyzed ) for the chest as the investigated anatomical region. Other imaging conditions were as follows: tube voltage, 120 kV; tube current, 500–750 kV; collimation: 64 rows × 0.625 mm; X-ray tube rotation speed: 0.35 second/rotation; helical pitch ≤ 0.24; field of view, 200 mm.The CT equipment used was a single-source 64-MDCT . The rotation speed of the X-ray tube was set to the maximum. Nonionic contrast medium, iopamidol (370 mg/mL), was rapidly injected intravenously at 3 to 4.5 mL/s using a 2-channel injector, followed by 20 to 30 mL saline. The effective doses for the nonenhanced scans and CCTA were estimated from the dose-length product and a conversion coefficient (2.5Image reconstruction was performed by the retrospective electrocardiogram (ECG)-gated reconstruction method, with a slice thickness for reconstruction of 0.625 mm.2).The patient characteristics of sex, age, height, body weight, body mass index, systolic blood pressure, diastolic blood pressure, HR on monitoring, HR on CT, and clinical diagnosis were analyzed. The medication history and use of beta-blockers at the time of CCTA were also analyzed. End-diastolic volume (EDV), end-systolic volume (ESV), EF, myocardial weight, and HR at the time of CCTA were measured by cardiac function analysis using Volume Analyzer SYNAPSE VINCENT  as the image processor. Image analyses were performed by a cardiologist with 30 years of experience and a radiologist with 5 years of experience, with a consensus reading .To compare the data from echocardiography and CCTA, data correction was performed based on the same EFs in both modalities by analyzing systemic error using the Bland-Altman plot . The exip-value of less than 0.1 by univariate analysis. Factors with a variance inflation factor (VIF) of greater than 10 were highly multicollinear and were excluded from the multivariate analyses. Patients were divided into two groups, those regularly taking β-blockers and those who were not, and the data were analyzed by the Mann–Whitney U test. We also analyzed the data according to the presence of beta-blocker side effects at the time of examination.Univariate analyses were performed for the patient characteristics, clinical diagnoses, regular drugs, and pre-study β-blockers affecting ΔEF. In addition, multivariate linear regression analyses with ordinary least squares regression were carried out to analyze the effects of possible confounding factors associated with the EF. Multivariate analyses were performed on factors with a The EF and HR during CCTA in patients who were given oral or intravenous β-blockers were compared with the EF on echocardiogram plus ΔEF and HR on echocardiogram by Wilcoxon’s test, respectively.http://www.r-project.org/). A p-value of less than 0.05 was considered statistically significant.All statistical analyses were performed using R software v. 3.5.3 , 48 with ischemic heart disease (19.7%), and 10 with cardiomyopathy (4.10%). There were 124 patients classed as “other” (50.8%).The study sample consisted of 244 patients, as shown in Table 2). Pre-study β-blockers were used in 236 (96.7%) cases, of which bisoprolol fumarate was used in 96 (40.7%), metoprolol in 203 (86.0%), and landiolol in 142 (60.2%).There were 148 patients (60.7%) who were taking medications. Of the patients taking regular medications, 94 took β-blockers (38.5%). A total of 72 patients (48.6%) regularly took more than 2 drugs. Eight patients were not given temporary β‒blockers  at the time of CCTA as the HR at CCTA was less than the cut-off line (Table 3).US measurements were DS 31.2 ± 5.38 mm and DD 47.6 ± 4.90 mm. The corrected EF on US was 49.7 ± 8.36%. On CCTA, ESV was 65.8 ± 28.5(mL), EDV was 133 ± 36.3 mL, SV was 66.5 ± 16.1 mL, and CO was 3.52 ± 0.814 L/min). The EF on CT was 51.7 ± 9.61%, and myocardial weight was 107 ± 36.7 g (Table 3.2p < 0.05) (Table 4). HR on CT was excluded from the factors as it was closely correlated with landiolol administration (VIF = 24.0) by multivariate analysis. Multivariate analyses also showed that the regular use of β-blockers and ECG abnormalities were factors affecting EF (Table 5). Oral and intravenous administration of β-blockers  used temporarily at CCTA had no significant effects on ΔEF.Univariate analysis identified age, landiolol administration, HR on CT, regular use of β-blockers, and ECG abnormalities, as significant factors affecting ∆EF (3.33). The mean value was −13.7 (95% C.I: −8.4–18.9).The correlation between ΔEF, as EF on CCTA-EF on US (%), and average EF on CCTA and US is shown in Fig. (3.4p < 0.001).EF on CCTA in patients with temporary oral or intravenous administration of β-blockers showed no significant difference compared with EF on echocardiogram; however, HR showed a significant difference  . On the other hand, the coefficient of ΔEF in the group of patients with abnormal ECGs was 3.1% lower than that of the group of patients without ECG abnormalities (Table 5). No side effects were noted after the imaging analyses, regardless of the administration of β-blockers or the dose administered.The effects of the regular administration of β-blockers on cardiac function are shown in Table 4In this study, the oral and intravenous administration of β-blockers  at the time of CCTA had no significant effects on ΔEF. No side effects were noted after CCTA, regardless of the administration of β-blockers or the dose. Therefore, our results suggest it is safe to administer β-blockers as a pretreatment for CCTA. In addition, there have been concerns about a possible excessive decrease in EF in patients routinely taking β-blockers, however, such a decrease was not observed, indicating that β-blockers can be used relatively safely, except for patients who are contraindicated for β-blockers , 6.Left ventricular EF is one of the most important prognostic factors in patients with chronic heart failure -14. TherIn this study, ∆EF was significantly affected by the regular administration of β-blockers and the presence of ECG abnormalities. The rate of change was −3.1%, even in patients with ECG abnormalities, which was the factor that reduced EF most. Therefore we believe that β-blockers can be administered relatively safely. Risks at the time of CCTA can be determined by checking whether the patient takes β-blockers regularly and whether there are any ECG abnormalities. Therefore, by taking the patient’s medical history, performing a medical examination, and performing an ECG and echocardiography, it is possible to carry out CCTA more safely even when using β-blockers. In our study, patients regularly taking β-blockers showed increased EFs on CCTA. This is probably because a large amount of the contrast agent flows into the myocardium, which is expanded by the β-blocker, resulting in an increase in the preload and a temporary increase in EF compared with US evaluation.et al. reported that the correlation coefficients of cardiac function measurements by referencing MRI with CCTA and echocardiography showed a high correlation of 0.98 and 0.87, respectively [There are some limitations to this study. First, it was retrospective. Prospective or interventional studies will be needed in the future. Secondly, we used different modalities, cardiac ultrasonography and CCTA, to measure cardiac function. It is difficult to measure cardiac function using echocardiography before and after CCTA as the effects of landiolol disappear in up to 30 minutes. In addition, CCTA imaging both with and without the administration of β-blockers in one patient at the same time, is of little clinical significance and is not acceptable from the viewpoint of radiation exposure. Several studies have reported that the analysis of cardiac function by CCTA is comparable to that by cardiac ultrasonography . Wu et aectively . Althougβ-blockers can be safely administered as a premedication for CCTA, and the additional injection of β-blockers just before CCTA does not affect the analysis of cardiac function. However, regular administration of β-blockers may increase the EF on CCTA.


This method provides new opportunities for the design and manufacture of various tissue scaffolds, photonic and electronic sensors.During electrospinning, the fibers deposited on the collector are usually randomly oriented in a disordered form. Researchers hope to generate periodic structures to expand the application of electrospinning, including improving the sensing properties of electronic and photonic devices, improving the mechanical properties of solid polymer composites and directional growth of human tissues. Here, we propose a technique to control the preparation of aligned foodborne nanofibers by placing dielectric polymers on microfluidic devices, which does not require the use of metal collectors. This study was conducted by introduced PEDOT:PSS polymer as a ground collector to prepare aligned foodborne nanofibers directly on the microfluidic platform. The fluidity of the electrolytic polymer collector makes it possible to shape the grounding collector according to the shape of the microcavity, thus forming a space adjustable nanofiber membrane with a controllable body. The simplicity of dismantling the collector also enables it extremely simple to obtain a complete electrospun fiber membrane without any additional steps. In addition, nanofibers can be easily stacked into a multi-layer structure with controllable hierarchical structures. The Caco-2 cells that grow on the device formed a compact intestinal epithelial layer that continuously expresses the tightly bound protein ZO-1. This intestinal barrier, which selectively filters small molecules, has a higher level of TEER, reproducing intestinal filtration functions similar to those of  Nanofibers can mimic the structure of the extracellular matrix structure due to their high specific surface area, which is a research focus in the field of biomedicine and biomaterials. Organized various types of nanofiber structures controllable and orderly is one of the crucial challenges in this field. Electrospinning is a simple method that can control the layout of nanofibers. This technology makes it possible to prepare nanofibers with diameters from 10 nanometers to several microns simply and multifunction by selecting a variety of materials, including metals, ceramics, synthetic and natural polymers . For exaMicrofluidic devices, also known as lab-on-chips, are characterized by the flexible combination and scale integration of various cell technologies on the micro controllable platform . The plaIn this article, we propose a novel method for the preparation of edible aligned fibers based on microfluidic devices simply, which needn’t to use metal collectors and toxic chemicals. This study introduced patterned PEDOT:PSS polymer as a ground collector to prepare ordered nanofibers directly on the microfluidic platform. The fluidity of the electrolytic polymer collector makes it possible to shape the grounding collector according to the shape of the microcavity, thus forming a space controllable nanofiber membrane with a complex structure. The simplicity of dismantling the collector also enables it extremely simple to obtain a complete electrospun fiber membrane independently without any additional steps. In addition, nanofibers can be easily stacked into a multilayer structure with controllable hierarchical structure for modeling intestine barriers This method provides further opportunities for the design and manufacture of new health food customization, tissue scaffolds, photon and electronic sensors.Poly-poly(styrenesulfonate) (PEDOT:PSS) was provided by aladdin as a surfactant-free aqueous dispersion with 1.5 wt% in deionized water. Polyvinylpyrrolidone (PVP) , Zein , β-Cyclodextrin , Photoresist , SYLGARD™ 184 silicone elastomer kit .Microfluidic device was fabricated by the standard soft lithography method we previously reported . In shorIn this study, the electrospinning equipment used which included high pressure supply units, pinning nozzle, syringe pump and collection unit . The polA microfluidic device with microchannel and microcavity was fabricated by using the soft lithography technology. The surface of microchannel was modified by plasma treatment  to obtain hydrophilic surface. A conductive solution is added at inlet of the microchannel (PEDOT:PSS), and the electrolyte solution was evenly distributed on the hydrophilic pattern on count of the wetting characteristics of the microchannel. Then drying for 24 h, which enable to establish the position-selective patterning of the electrolyte solution in microfluidic device. Next, high voltage is applied between the metal needle and the patterned electrode on the microfluidic device for electrospinning, and the aligned nanofiber mats are generated on the surface of the dielectric patterned electrode. As the control experiment, copper strips was used to collect the nanofibers.2. After the preparation of the chip, ultraviolet disinfection was carried out for 2 h before the start of the experiment. The hose was connected to the chip and the DMEM medium was perfused overnight. Finally, the Caco-2 cells were digested with trypsin and made into a mixed suspension, and the cell suspension with a density of 1 × 106 cell/mL was inoculated into the channel. After the cells were settled for 2 h, the microchip was placed in a cell incubator for 24 h until the cells grew to form an intact intestinal barrier. The cell viability was detected by CCK-8 method, that is, 10 μL CCK-8 reagent and 90 μL cell culture medium were added into the chip channel, and the absorbance at 450 nm was measured by microplate reader after 2 h of incubation  were cultured in high glucose DMEM medium containing 10% fetal bovine serum and 1% penicillin-streptomycin solution at 37 °C and 5% COcubation .The resulting intestinal barrier was subsequently morphologically characterized by immunohistochemistry. To assess tight junctions between cells at the top of the intestinal barrier, confocal immunofluorescence microscopy was used to stain the tight junction protein ZO-1, After rapid cell rinsing using 1 × PBS, Caco-2 cells were fixed with 4% paraformaldehyde for 15 min and permeabilized with 0.2% Triton-X 100 for 2 min before incubation with fluorescently labeled ZO-1 antibody at 4 °C for 12 h. Samples were further incubated with antibody for 1 h and counterstained with 4′, 6-diamidino-2-phenylindole (DAPI) for 15 min. After three final washes with PBS, microscopy was performed using a Leica laser confocal microscope.e.g., 4-nitroaniline) was quantified at 405 nm in a microplate reader. Then, the TEER value was obtained by multiplying the specific resistance which subtracted baseline resistance value (without cells) by the total cell culture surface area on the membrane. DMEM medium served as blank control group.On the basis of establishing the morphological integrity of the intestinal microarray barrier, the functional integrity of the human intestinal barrier was assessed by quantifying the specific activity of apical brush border alkaline phosphatase (ALP) and transepithelial electrical resistance (TEER). The specific activity of ALP was determined by obtaining the culture medium from the upper and lower chambers after 5 days of cell culture, transferring the solution to a 96-well plate, and cleaving the product (2), dQ/dt is the steady state flux (g/s) and C0 is the initial concentration (mg/mL) of the FD20 solution applied on the apical cell surface.After establishing tight junction integrity, the apparent permeability coefficient  of intestinal cell monolayers was determined. Papp measurement was achieved primarily by measuring the transit of isosulphate luciferin (FITC)-labeled glucose  over time on the intestinal barrier chip. FD20 solution (1 mg/mL) was added to the intestinal barrier on-chip chamber and samples collected hourly from the lower chamber outlet were analyzed to quantify the amount of FD20 that crossed the intestinal barrier. The fluorescence intensity (490 nm excitation/520 nm emission) of the sample collected from the lower chamber was immediately measured to quantify the amount of FD20 transported from the cell apex to the basolateral surface. Papp was calculated according to Papp (cm/s) = (dQ/dt)(1/AC0) where A is the culture surface area (cmhttp://rsb.info.nih.gov/ij/).The morphology of the nanofibers was studied by inverted microscope  and field emission scanning electron microscope . The fibers used in SEM were collected on the conductive adhesive, dried in air, and plated with gold by sputtering gold plating machine  for 60 s (to obtain a gold plating layer of about 10 nm), so as to improve its conductivity. The scanning electron microscope was operated under 15 kV accelerating voltage. Image J software was used to measure the size, orientation angle and distribution of nanofibers , the Coulomb force is not enough to overcome the surface tension, resulting in the formation of spinning branches. When the applied voltage exceeds a limit voltage , the thickness of the fiber increases and the irregular structure is formed. The reason is that the Coulomb force is much greater than the viscoelastic force and the jet velocity is much faster. Therefore, there is not enough time for solvent evaporation to form coarse and irregular fibers, which is consistent with the previous results  with ~500 nm and ~200 nm average fiber diameter, respectively. Edible nanofibers have good biocompatibility and exhibit good proliferative capacity of human hepatocytes and mouse fibroblasts, but are limited to very poor mechanical properties (e.g. proteins or enzymes), nanoparticles , inorganic nanowires, etc  and placing three layers of uniaxially aligned nanofibers with their long axis rotated by 60 degrees. The chemical properties, surface morphology and structure of biomaterials can affect the function of cells . To furtin vitro intestinal barrier. As shown in in vivo.In addition to cytomorphic characterization, we further characterize the intestinal barrier function of the intestinal chip. Alkaline phosphatase (ALP) is commonly used marker for intestinal epithelial cell differentiation as a brush border enzyme. The results showed that cell cultured in the microfluidic device with oriented nanofibers got 2.6-fold higher ALP activity when compared to the cells cultured in control , 7B. Thein situ spinning within the microfluidic devices. The electrospun fibers are arranged in parallel along the direction of the microfluidic patterned electrode. This method also allows the construction of multidimensional structures based on other complex shapes of parallel arrays (such as meshes). The simplicity of dismantling the collector also enables the electrospun nanofiber membrane to exist independently without any additional steps. The ability of microfluidic devices to produce periodically ordered structures can broaden the application of nanofibers, such as in food manufacturing, nanoelectronic devices, polymer composites and tissue engineering.In conclusion, we show a simple and effective method to prepare edible micro nanofibers with a large area and suitable arrangement. This method does not require the use of metal collectors and toxic chemicals. Only a small amount of PEDOT:PSS aqueous solution is involved to perform 10.7717/peerj.13513/supp-1Supplemental Information 1Click here for additional data file.


In this study, we determined the enthalpies of vaporisation for a suitable set of molecular and ionic liquids using modern techniques for vapour pressure measurements, such as the quartz crystal microbalance, thermogravimetric analysis (TGA), and gas chromatographic methods. This enabled us to measure reasonable vapour pressures, avoiding the problem of the decomposition of the ionic liquids at high temperatures. The enthalpies of vaporisation could be further analysed by applying the well-known “group contribution” methods for molecular liquids and the “centerpiece” method for ionic liquids. This combined approach allowed for the dissection of the enthalpies of vaporisation into different types of molecular interaction, including hydrogen bonding and the dispersion interaction in the liquid phase, without knowing the existing species in both the liquid and gas phases. Nevertheless, the vaporisation enthalpies, At room temperature, methane, ethane, propane, and butane are gases, but pentane and hexane are already very volatile liquids. Admittedly, the weak van der Waals attractions are the obvious reason these non-polar molecules are held together in the liquid phase. At room temperature, the first representative of the homologous series of alkanols, methanol, is already a volatile liquid. The inter-molecular hydrogen bonding is the obvious reason for such behaviour of these polar molecules. The energetics of inter-molecular interactions of molecules in the liquid phase (and thus their volatility) can be quantitatively determined using vaporisation thermodynamics. According to the textbook, a vaporisation enthalpy is the amount of energy required to disrupt the network of inter-molecular interactions in the liquid and to transfer one mole of molecules in the ideal gas, where interactions between molecules are assumed to be absent. Admittedly, the enthalpy of vaporisation is the “bulk” thermodynamic quantity that fails to distinguish between the energetics of van der Waals forces and the energetics of hydrogen bonding coexisting in typical chniques , challenchniques ,3,4 and chniques ,13,14,15The association of the hydroxyl-containing molecules  in the liquid phase via the OH···O and OH···N hydrogen bond types see  is a welThe formation of both the inter- and intra-types of association is theoretically feasible, but in practice, most molecules  in the liquid are connected via the OH···O and OH···N inter-molecular hydrogen bonds, which are more thermodynamically favourable ,3,4. In Furthermore, in the gas phase, the interpretation of the intra-HB by the free-flying IL molecule is thwarted with complications. Although we have only recently shown that the OH group in the hydroxyl-containing ILs is definitely linked to the anion, the coexistence of numerous intra-molecular H-bonded conformers with comparatively low energy makes it difficult to properly quantify the HB strength.HBinter) and intra-molecular (HBintra) hydrogen bonding in both MLs and the corresponding ILs.We hope that the apparent structural similarity of molecules chosen for this work see  could enHBinter hydrogen bond in alkanols is to use the method of homomorphs [NTf2] series  for the [N-CnOH-Py][NTf2] ionic liquids are listed in The summary of results relevant for the discussion in the frame of this work is given in −1  is determined by comparing the H-bonded and non-H-bonded frequencies, shifts, conformers, etc. In terms of vaporisation thermodynamics, the main challenge is to find a suitable reference system that mimics the desired molecule without the intra-HB. In our earlier work, we proposed the reference system based on conventional group additivity  ionic liquids was not the aim of this work, as we could measure them for both series  and two additional groups does not contain intra-molecular hydrogen bonding a priori, as it is composed of groups in which intra-molecular hydrogen bonding is originally absent. Therefore, the difference between the experimental vaporisation enthalpy of 1-piperidine-propanol and that of its framework, HBGA, in this molecule:Although we developed the “centerpiece” approach, it is worth noting that predicting the enthalpies of vaporisation of hydroxy-alkyl-piperidines and hydroxy-alkyl-pyridinium  follows the same pattern as is shown in The development of the “non-hydrogen-bonded” framework for calculating the intra-molecular hydrogen-bonding strength, HBGA values calculated for 1-piperidine-propanol and for 1-(2-hydroxyethyl)pyridinium [NTf2] according to Equation (2), as well as for other MLs and ILs of interest for this work, are given in FW are also given in these tables. The application of the GA method is straightforward and easy and allows for the estimation of intra-molecular hydrogen bond strengths, particularly conveniently in homologous series. However, this method required some preliminary work to develop the system of groups and the selection of the appropriate “centerpiece”.The 2].Another alternative way to create the “non-hydrogen-bonded” reference system is shown in 2] as examples. The task-specific interaction in piperidine ethanol is the intra-molecular hydrogen bond. To extract this interaction, we balanced this molecule with n-butane, n-propyl-piperidine, and propanol so that the stoichiometry is retained but the intra-HB is missing from the left part of the equation. Therefore, the difference in enthalpy between the right and left sides can be considered as a measure of the intra-molecular hydrogen bonding strength, HBWBE, in this molecule:The idea comes from the quantum chemical calculations, where the enthalpies of formations are derived using isodesmic, homodesmic, well-balanced reactions, etc. . The maiHBWBE values calculations for 1-(2-hydroxyethyl)pyridinium [NTf2] shown in HBWBE values are given in The same logistic was applied for −1) and for phenyl-ethanol (≈5 kJ·mol−1) from the GA and WBE methods. It is interesting to note that a very subtle interplay of intra- and inter-HB can be revealed for phenyl-methanol and phenyl-ethanol as calculated by both methods. Taking into account the average inter-HB strength of −25 kJ·mol−1 in aliphatic alcohols  correctly worked, we applied this equation to the aliphatic alcohol series with the completely negative result see , along whols see , it can −1 pyridinium [BF4] and 1-(3-hydroxypropyl)pyridinium [DCA], the intra-HB strength increased to ≈−24 kJ·mol−1 , and gas chromatographic methods. Applying the well-known “group contribution” methods for molecular liquids and the “centerpiece” method for ionic liquids, we were able to dissect the enthalpies of vaporisation into different types of molecular and ionic interaction, such as hydrogen bonding and dispersion interactions. Considering molecular mimics of the IL cations and thus combining both approaches even allowed for the distinguishing between inter- and intra-molecular hydrogen bonding, which is shown here for the first time.


Diversity in the healthcare workforce enhances access to care, reduces health disparities, and improves quality of care for underserved populations. Yet there is a paucity of women and underrepresented minority physicians in cardiology training programs, and progress toward achieving a diverse cardiology workforce has been slow. Here we review the merits of diversity in health care, the current landscape of the cardiology workforce, barriers to increasing the proportion of women and underrepresented minority cardiologists, and specific strategies that have been proposed to sustain and enhance diversity in cardiology training programs. Physician gender has been shown to impact quality of care,45 and patient-physician gender concordance has been associated with improved control of cardiovascular disease (CVD) risk factors.6 A randomized controlled trial studying the effect of physician-patient racial concordance on preventive services utilization found that Black men sought more cardiovascular preventive services—particularly invasive services—after meeting with Black physicians compared with non-Black physicians and estimated that this intervention could decrease the Black-White male gap in cardiovascular mortality by 19%.7In 2004, the Institute of Medicine issued a landmark report unequivocally stating that diversity in the healthcare workforce is critical to improving the United States (US) healthcare system.8 Given the jarring disparities in CVD treatment and outcomes in racial/ethnic minority populations and women,91011 the need to rapidly diversify the cardiovascular clinical workforce could not be more pressing. In this review, we discuss the current climate of diversity in CVD fellowship training, outline the barriers to improving diversity, equity, inclusion, and belonging (DEIB), and summarize strategies to enhance DEIB in training programs. For the purposes of this review, we focus on women and underrepresented minorities as traditionally defined in graduate medical education.In 2019, the Accreditation Council for Graduate Medical Education (ACGME) updated its Common Program Requirements to reflect an expectation that all training programs promote recruitment and retention of a diverse workforce.12 recently explained the evidence base supporting the merits of a diverse cardiovascular workforce. These benefits included (1) improved clinical care, as minoritized individuals are more likely to receive standard of care and follow medical advice when treated by a racially/ethnically concordant physician due to better communication, trust, and reduced implicit bias; (2) greater access to care in underserved communities, as underrepresented minority (URM)13 physicians more often choose to care for historically excluded populations; (3) enhanced cultural competence, as non-URM physicians working in diverse settings become better equipped to care for diverse populations; and (4) improved research quality, as diverse research teams broaden the scope of research questions, priorities, and participant enrollment.Capers et al.141516 The percentage of women matriculating in medical school and internal medicine residency has steadily increased over the past decades, and in 2019, women comprised over 50% of US medical students for the first time.17 Despite this, cardiology continues to suffer from the “residency-to-fellowship cliff” as the specialty has seen the slowest rate of increase in women trainees over time and continues to be the least diverse internal medicine specialty.1618 Only 24% of US cardiovascular disease fellows are women, with even lower proportions in procedural cardiology subspecialties—14.5% in interventional cardiology and 11% in clinical cardiac electrophysiology.19 Over the past 5 years, the percentage of women applying to cardiology fellowships has stalled at around 25%,18 and between 2006 and 2018, the proportion of female adult cardiovascular disease fellows only increased from 16% to 21%.1420 In other procedural specialties such as pulmonary and critical care medicine, gastroenterology, and general surgery, women comprise 35%, 38%, and 45% of trainees, respectively.19Despite extensively documented benefits of a diverse healthcare workforce, women and URM physicians remain underrepresented in cardiology.1421 URM trainees represent 9.9%, 8.9%, 7.4%, and 10.2% of cardiovascular disease, interventional cardiology, clinical cardiac electrophysiology, and advanced heart failure and transplant cardiology fellows, respectively.22 In the 5 years prior to 2022, URM trainees have only comprised 9% to 11% of the cardiovascular disease fellowship applicant pool,19 and between 2006 and 2016, the percentage of URM cardiovascular disease fellows increased marginally from 11% to 12%.14 Comparatively, URM comprise 9%, 10.4%, and 15.4% of pulmonary and critical care medicine, gastroenterology, and general surgery trainees.22Unlike the relatively high numbers of women in medical school and internal medicine residencies, URM physicians continue to be underrepresented at every stage of medical training.15Recent research has aimed to uncover drivers of increased diversity in training programs. A 2018 survey of 130 cardiology fellowship program directors found a correlation between program size and trainee diversity, with smaller programs being less likely to have female and URM fellows. All medium and large programs had at least one female fellow; however, 16% of small programs had none. There were no URM fellows in 40% of small programs compared to 30% of medium and 19% of large programs.14 making the field of cardiovascular medicine poorly representative of the patients whom it serves.Ultimately, these longstanding disparities reverberate across the workforce, with women and URM representing only 13% and 7.5%, respectively, of practicing adult cardiologists,Figure 1). A survey of internal medicine residents’ professional development priorities and preferences found that work-life integration, female friendliness, and positive role models ranked highest in professional development needs. Among residents, the strongest perception of the field of cardiology was of a negative culture due to adverse job conditions, interference with family life, and lack of diversity. These factors influenced career choice decisions: women and residents who did not choose careers in cardiology placed more value on work-life balance and had more negative perceptions of cardiology than those who pursued cardiology.23Several factors pose a threat to a sustainably diverse and inclusive cardiovascular workforce, including negative perceptions of culture, lack of role models and structured mentorship, biased recruitment practices, and slow adoption of evidence-based merits of diversity at the leadership level, among others  Women in Cardiology Section highlighted several of these barriers through a survey of female cardiologists, which demonstrated that over half of respondents felt pressure to take shorter maternity leave than was available—60% among fellow respondents—and only 46% reported breastfeeding beyond 6 months. Highly cited barriers to breastfeeding included inadequate breaks during clinical practice and lack of appropriate pumping space.26 For women interested in pursuing procedural cardiology subspecialties, factors such as lack of female role models, radiation exposure during childbearing years, sexual discrimination and harassment concerns, and the “old boys’ club” culture are additional deterrents.2829Women who choose to pursue cardiology contend with inequities in compensation3031 In a survey regarding barriers to increasing diversity in cardiology training programs, program directors identified the lack of “qualified candidates” and the overall culture of cardiology as the most significant barriers, followed by the lack of diversity in faculty and the program’s surrounding community.32 Although much is made of the URM pipeline problem, this does not fully explain the underrepresentation of URM physicians in cardiovascular medicine and medicine in general.The dearth of URMs entering the physician pipeline continues to be one of the most important barriers to diversifying cardiovascular medicine, owing to a combination of structural racism; lack of adequate educational resources, role models, and mentorship; and bias and discrimination at all stages of education.3334 Resource limitation is also a reported obstacle to implementing and sustaining DEIB, especially in smaller, non–university-based programs. Compared to larger and university-based programs, smaller cardiovascular training programs are less diverse and have fewer institutional support mechanisms for URM and female fellows, peer support groups, and formal mentorship/sponsorship programs.32The hostile training and workplace environments that URM physicians experience is another significant barrier to recruitment, retention, and advancement. Studies investigating training experiences of URM residents found that many experience harsher consequences for mistakes, daily microaggressions, bias, and discrimination. Additionally, they are burdened with leading and promoting institutional diversity, feel pressured to conceal parts of their racial/ethnic identity, and experience social isolation.35Finally, the lack of prioritizing diversity, inclusion, and equity by the workforce’s gatekeepers is a formidable barrier. Surprisingly, 31% of surveyed cardiology fellowship program directors were uncertain or did not believe that diversity improves quality of care. Only 6% considered diversity among the top three priorities when ranking fellowship applicants, and the majority of those who believed in the merits of diversity could not provide evidence supporting the benefits of a diverse and inclusive workforce.Figure 2).A multipronged approach is critical to enhance and sustain DEIB in cardiovascular medicine, summarized here in six major strategies: (1) prioritization of DEIB by leadership; (2) holistic applicant review; (3) implicit bias training of gatekeepers; (4) investment in pipeline and pathway programs; (5) cultural transformation and creation of support systems for women and URMs to enhance retention and advancement; and (6) leveraging resources from other key stakeholders . After learning bias mitigation techniques during the subsequent interview cycle, 48% of committee members were conscious of their bias when interviewing and 21% reported that knowledge of their IAT results impacted their admissions decisions. Since the institution of annual implicit bias reduction workshops for the selection committee, the school has consistently matriculated one of the most broadly diverse student populations in the country.3142Healthcare professionals are not immune from harboring negative implicit biases against people of color and women,3138Other bias mitigation strategies include diversification of selection committee members, intentional reflection on individual implicit biases and their impacts, provision of bias mitigation strategies on interview days, structured interviews, and blinded application reviews in which candidates’ photos and academic metrics that are subject to racial bias are concealed from committee members.4. Investment in Pipeline and Pathway Programs31 building pipeline programs complete with mentorship and networking opportunities is paramount for efforts to enhance DEIB in cardiovascular medicine. Duvernoy et al. suggested investing in outreach programs spanning the entire educational curriculum, from grade school to internal medicine residency, to ensure early exposure to careers in cardiovascular medicine and dedicated mentorship for women and URM medical students and residents.30Due to the paucity of URMs at every stage of the medical education pipeline,43 the Internal Medicine Cardiology Programs for women, Black, and Hispanic/Latinx trainees;44 and the annual Clinical Trials Research boot camp programs.45 Similarly, as another example, the American Heart Association (AHA) provides scholarships to a number of students from Historically Black Universities and Colleges to pursue advanced training in biomedical sciences, and its Supporting Undergraduate Research Experiences (SURE) program funds mentored research in cardiovascular medicine for URM students across several academic institutions.46 The Association of Black Cardiologists (ABC) has a long track record of early and longitudinal mentorship and sponsorship for its early career members. Other professional societies also are accelerating their structured efforts in this arena.Cardiology professional societies have also accelerated efforts to build pathway programs to bolster early interest in medicine and cardiology. As one example, the ACC provides complimentary society membership to medical students and residents and has created several leadership development programs for women and URMs to connect them with career opportunities, mentors, peer networks, and educational resources, including the Young Scholars Program for high school and college students;5. Cultural Transformation and Creation of Support Systems for Women and URMs47 Provision of transparent and flexible leave policies to accommodate unforeseen pregnancy complications, radiation safety training, adequate breaks, and private spaces to facilitate lactation will contribute to a culture of inclusion and support for cardiologists with parenting responsibilities.26Efforts to enhance DEIB in cardiovascular medicine will not succeed without a concurrent cultural transformation to meet the unique challenges faced by women and URM physicians. To enhance retention and career advancement of women cardiologists, Sharma et al. advocate for structured mentorship and sponsorship programs to ensure equitable access to research grants, promotion, leadership roles, and pay parity; creative promotion pathways that do not penalize women for childbearing responsibilities; flexible training pathways that optimize work-life integration; adoption of zero tolerance policies for workplace harassment and discrimination; and transparent compensation policies.48 To this end, cardiovascular education leaders have suggested building an antiracist culture in cardiovascular fellowship training by formalizing education on systemic racism, health disparities, and social determinants of health; establishing implicit bias training and standardized mechanisms for addressing and reporting discrimination and microaggressions; actively mentoring and extending scholarly opportunities to URM physicians; ensuring shared responsibility for diversity and inclusion efforts across the program and rewarding these efforts through promotion and advancement; and seeking to understand URM personal experiences with racism and microaggressions through deliberate conversations.48Efforts to enhance retention of URM physicians will need to tackle implicit and explicit discrimination, professional isolation, lack of mentorship and sponsorship, and the “minority tax” that URM physicians face.49Eberly et al. proposed integrating antiracism practice into the clinical and research training components of the cardiovascular fellowship program through community engagement, funded opportunities for equity-focused quality improvement initiatives, and application of critical race theory to research methodology.50Cardiology fellows are also uniquely positioned to promote a culture of DEIB in their own programs. When leading diverse teams, Njoroge et al. suggest strategies such as setting rotation expectations, facilitating goal-setting, and avoiding competition among trainees; swiftly addressing bias and microaggressions against team members; actively sponsoring trainees by involving them in research projects, connecting them to mentors, providing positive feedback to their training programs; and advocating for a more inclusive culture to program leadership.6. Leverage Resources from Other Key Stakeholders32 Training programs should leverage external resources from the various professional societies that have committed resources to increasing DEIB in cardiology. For instance, since its inception in 1974, the ABC has provided scholarship and mentorship opportunities to people of color at every stage of the physician pipeline, created fellowship programs in interventional cardiology and clinical cardiac electrophysiology, formed strategic partnerships to enhance investigator diversity in clinical trials, and championed several other diversity and inclusion initiatives across the nation.5152 As another example, gender-specific mentoring in interventional cardiology is available through the Society for Cardiovascular Angiography and Interventions Women in Innovations committee’s mentoring program, aimed at connecting trainees to potential mentors across the country.53 The ACC has created resources to guide programs in recruiting a diverse workforce, held workshops to share diversity and inclusion best practices, and provided hands-on training in implicit bias mitigation to program directors.45 These resources require widespread dissemination through both formal and informal channels to reach the broader fellowship training community.Many CVD fellowship program directors lack a strategic plan to increase diversity in their programs. Nearly half reported that having access to best practice tools for candidate selection, implicit bias training, parental leave and harassment policies, and guidance with mentoring programs initiation would assist their efforts.Despite widespread recognition of the unique barriers to recruitment and retention of women and URM physicians in cardiovascular medicine, a few fellowship programs have shared successful initiatives aimed at addressing these barriers within their programs. Here, we highlight such initiatives.40In 2005, the Ohio State University Medical Center cardiovascular disease fellowship program overhauled its recruitment process to increase its fellowship diversity by (1) setting diversity as a program priority; (2) actively reaching out to external URM residents interested in cardiology; (3) emphasizing mentorship opportunities on interview day; (4) dedicating time for URM applicants to interact with URM fellows and faculty members; and (5) engaging in personalized post-interview communications with competitive applicants to reinforce the program’s interest and commitment to mentorship. Since implementing these interventions, the program has matched URM fellows for 5 consecutive years.54In 2017, the University of Pennsylvania’s female fellows-in-training (FIT) and faculty established the Penn Women in Cardiology (PWIC) program to promote the recruitment, retention, and advancement of women cardiologists. Since its inception, the PWIC has facilitated (1) skill development through targeted workshops; (2) leadership and sponsorship of FITs and early career cardiologists through attendance of national leadership conference and nominations for leadership roles in professional societies; (3) networking through institutional mentoring sessions and meetings with visiting female grand rounds speakers; (4) mentorship pairing of medical students and residents considering careers in cardiology with PWIC members who connect them with clinical and research opportunities and provide guidance through the fellowship application process; and (5) advocacy to enhance recruitment and create supportive workplace environments.54 and has developed practice guidelines to enable lactating FITs to meet their breastfeeding goals.55 These guidelines stipulate that lactating women should have access to well-equipped and appropriately designated clean and private pumping spaces and should be allowed to step away from clinical duties and mandatory engagements at needed intervals for expressing milk. Dissemination of these guidelines across the institution has allowed FITs to better integrate work and parenting responsibilities and created a more supportive environment for fellows growing their families.55As a result of the PWIC initiatives, several women have served in leadership roles in multiple professional organizations, and an increasing number of women internal medicine residents at the institution have matriculated into cardiology. PWIC also has advocated successfully for increasing dual-physician-trainee parental leave duration from 6 to 12 weeks56In 2017, the Duke Cardiovascular Disease fellowship program created multilayered interventions to increase diversity among its fellows, including (1) securing departmental commitment to diversity; (2) formation of a diversity and inclusion task force to devise best practices for recruitment; (3) diversification of program leadership and recruitment committee; (4) restructuring of the application screening process by removing US Medical Licensing Examination score criteria, blinding application reviewers to applicant photos, ensuring women and URM applicants represent at least 25% of those interviewed, and ensuring that all URM applicants are independently reviewed by the URM members of the recruitment committee; (5) restructuring the interview day to maximize interaction between women/URM applicants and potential mentors and colleagues and highlight institutional commitment to diversity; (6) soliciting input from recruitment committee, women, and URM faculty and fellows to ensure diversity in highly ranked candidates; and (7) ensuring structured mentorship for matched women and URM fellows. These interventions resulted in a sustained increase of women and URM fellows matching into the program, more than a doubling compared to the preintervention years.There remains an urgent need to diversify the cardiovascular workforce and to simultaneously change workplace culture to promote inclusion, equity, and belonging. These efforts are largely focused at the fellowship level, and adequate education and training at this early stage is necessary to cultivate a representative clinician workforce that is well equipped to care for all patients with cardiovascular disease. Achieving success in these domains will require the intentional reformation of policies, practices, and systems that persistently discriminate against women and URM physicians. Continued benchmarking, systematic assessment of the impact and effectiveness of these strategies, and dissemination of successful strategies will be critical to advance DEIB for the entire cardiovascular training community.Despite evidence that healthcare diversity improves care and reduces health disparities, women and underrepresented minority (URM) physicians remain underrepresented in the cardiology workforce.The lack of a supportive, inclusive, and equitable culture in the cardiovascular training community continues to thwart diversification efforts.Durably enriching the cardiovascular training community will require prioritization of diversity, equity, inclusion, and belonging by academic leaders; investment in pipeline programs providing mentorship and exposing women and URMs to the field of cardiology; holistic recruitment practices; universal implicit bias training with a focus on professional gatekeepers; and eradication of policies, practices, and systems that persistently discriminate against women and URM physicians.Systematic monitoring, evaluation, and dissemination of best practices for diversity, equity, inclusion, and belonging will benefit the entire cardiovascular training community.Houston Methodist is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.1 AMA PRA Category 1 Credit™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.Houston Methodist designates this Journal-based CME activity for a maximum of learn.houstonmethodist.org/MDCVJ-18.3.Click to earn CME credit:


ACSCentral Science, Fiedler and co-workers report a new approachto elucidate the structures of myo-inositol polyphosphates(InsPs) and quantify them as part of complex mixtures, which was previouslypossible only to a very limited extent.1 An NMR-based method was developed to characterize compounds arisingfrom the metabolism of InsPs. With structural information on the metabolitesin hand, the authors then studied the actions of an enzymatic modulator,the phosphatase MINPP1, on different substances in detail.1 Their investigations reveal two distinct metabolicpathways as well as potential mechanisms of regulation and make significantprogress toward a fully assigned network of the different inositolphosphate metabolites.In this issue of myo-inositol and can act as signaling molecules, among other biologicalroles.2 The study of these molecules ischallenging due to the presence of multiple isomers, and many currentmethods rely on radioactive labeling or require separation of thecompounds prior to analysis.3 Frequently,isolation is based on exploiting the highly charged nature of InsPs,which creates a bias against less charged metabolites such as InsP2. Additionally, some InsPs are chiral, and both enantiomersbehave identically in conventional purification methods. To overcomethese limitations, Nguyen Trung et al. combine 13C-labelingof myo-inositol with an NMR method that suppressesany signals from protons bound to 12C, that is unlabeledmaterial.4 This strategy allows for selectivemonitoring of 13C-labeled myo-inositolmetabolites in a complex sample such as cellular extracts and therebycircumvents the need for isolation of the metabolites of interest.In this study, the 2D HMQC signals of 19 different InsPs and inositol pyrophosphates (PP-InsPs) were assigned and collated in order to identify the metabolites bytheir NMR signals. This “map” of NMR signals shows clusteringdependent on the position of the group and its phosphorylation status,and importantly provides a reference for the assignment of observedsignals in samples. As a limitation, unknown products resulting fromother pathways may be observed but cannot be assigned yet withouta reference spectrum, as was the case for the labeled metabolic extractsof Schizosaccharomyces pombe. To resolve the identityof chiral InsPs asymmetrically labeled myo-inositol was added to cells, resulting in NMR signals only fromthe proton attached to the labeled carbon atom(s)  1a. Using13C atom and that there are no other modifications that resultin a highly similar signal. For this to be the case, the metabolicmodification needs to be close to the CH group of interest. Additionally,a reference library of known metabolites is necessary to assign chemicalshifts. If these requirements can be met, this strategy is a highlypromising avenue for fields that are facing similar challenges asthe study of InsPs.Excitingly, this method is theoretically applicable for studyingthe metabolism of other types of compounds. A prerequisite for successfulassignment is that metabolism of the labeled molecule results in anobservable change in chemical shift of a proton attached to a 13C-labeledmetabolites was then applied in this study for the detailed characterizationof the only human enzyme known to dephosphorylate InsP6, MINPP1.1 Previously unassigned metaboliteswere identified in MINPP1-deficient cells, and InsPs resulting from MINPP1 acting on two different substrates, InsP5[2OH] and InsP6, were quantified in invitro assays. A potential limitation is the sensitivity ofthe NMR method, which precludes the assignment of less abundant species.Addressing this issue, experiments requiring higher sensitivity such as kinetic analysis or metabolic flux were carried out by combiningthe metabolic labeling with capillary electrophoresis coupled to massspectrometry (CE-MS),5 which also distinguishesdifferently labeled metabolites. By adding differently labeled myo-inositol at different time points, the sequence of (de)phosphorylationevents in cells could be determined.The established NMR analysis methodology of 2 was shown to be dependent on MINPP1 and appearednot to be an intermediate in the biosynthesis of higher InsPs. Theyalso discovered that InsP6 acts as a competitive inhibitor,alluding to a potential regulatory mechanism. Regulation of thesepathways is of particular interest, since, at least in vitro, MINPP1is capable of acting on a minimum of 12 substrates, although not allmetabolites observed in vitro were observed in cellular extracts.In addition, results from this work point toward the existence ofan additional unknown 3-phosphatase that acts on InsP6.It is therefore likely that not all of these reactions are catalyzedby MINPP1 in cells. Nonetheless, the multitude of potential reactionscatalyzed by MINPP1 and their potential signaling roles indicate thatregulation is required. The newly discovered substrate inhibitionby InsP6, possibly in conjunction with spatial separation,may be one mechanism of directing flux toward certain metabolites.Maintaining the delicate balance between different InsPs is importantfor cellular function, as an imbalance of InsPs has been linked tomutations of MINPP1 in a subtype of pontocerebellar hypoplasia, agroup of early onset neurodegenerative disorders.6 Interestingly, the involvement in disease appears to relateto the type of mutations, as different mutations in MINPP1 were suggestedto play a role in a subset of malignant follicular thyroid tumors,7 while the complete absence of MINPP1 in micedid not lead to a disease phenotype.8 Theherein established methodologies in combination with CE-MS open upthe possibility to identify InsP metabolites with high sensitivityin the presence of different mutations in disease settings, whichpromises to advance our understanding of the effects of MINPP1 mutationsin the disease mechanisms.The powerof the newly developed methodology primarily lies in the detailedstructural information it can provide. Importantly, in this work theauthors demonstrate how this information can be harnessed to uncovertwo completely distinct metabolic pathways that both involve MINPP11b. The gOverall, the newly developed methodologyenables mapping out the mammalian InsP metabolitenetwork 1b. A sim