We demonstrated theoretically that the renormalization of the electron energy spectrum near the Dirac point of graphene by a strong high-frequency electromagnetic field (dressing field) drastically depends on polarization of the field. Namely, linear polarization results in an anisotropic gapless energy spectrum, whereas circular polarization leads to an isotropic gapped one. As a consequence, the stationary (dc) electronic transport in graphene strongly depends on parameters of the dressing field: A circularly polarized field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized one results in both giant anisotropy of conductivity (which can reach thousands of percents) and the oscillating behavior of the conductivity as a function of the field intensity. Since the predicted phenomena can be observed in a graphene layer irradiated by a monochromatic electromagnetic wave, the elaborated theory opens a substantially new way to control electronic properties of graphene with light. Since the discovery of graphene24The methodology of quantum optics lies at the basis of various exciting fields of modern physics, including quantum information81016418192021222425262728293031323435363738394044454647z axis [see 23For definiteness, we will restrict our consideration to the case of electron states near the Dirac point of a single graphene sheet subjected to an electromagnetic wave propagating perpendicularly to the graphene plane. Let the graphene sheet lie in the plane axis see . Then elv is the electron velocity in graphene near the Dirac point, e is the electron charge, and ω, lies far from the resonant frequencies of graphene, where we can obtain both the energy spectrum of electrons dressed by the electromagnetic field, For the case of the circularly polarized electromagnetic field with the vector potentialwe arrive at the energy spectrum of the dressed electrons,where signs “+” and “−” correspond to the conduction band and valence band of graphene, respectively,ω is assumed to satisfy the condition of is the field-induced band gap in graphene, π-orbitals of the two crystal sublattices of graphene)S is the graphene area, and θ is the azimuth angle of electron in the space of wave vector, where In the case of linearly polarized electromagnetic field with the vector potentialx axis, the energy spectrum of the dressed electrons reads asdirected along the and the corresponding wave functions of dressed electrons arewhereThe energy spectra of dressed electrons, (2) and 5), are pictured schematically in , are picIn order to calculate transport properties of dressed electrons, we have to solve the scattering problem for nonstationary electron states (4) and (6). Following the scattering theory for dressed conduction electronswhere wherefor the case of circularly polarized dressing field, andfor the case of linearly polarized dressing field.ω, meets the conditionIn what follows, we will assume that the wave frequency, where J, is given by the expressionLet us focus our attention on the dc conductivity of the dressed electrons. Generally, the density of the conduction electrons can be tuned by applying a bias voltage which fixes the Fermi energy, where Substituting the scattering probability of dressed electron (8) into Eq. s-wave approximationTo simplify calculations, let us consider the electron scattering within the x axis, the conductivity is plotted in where ude  see . For theIt is seen in We have shown that the transport properties of electrons in graphene are strongly affected by a dressing field. Namely, a circularly polarized dressing field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized dressing field results in the oscillating behavior of the conductivity and its giant anisotropy. As a result, the dc transport properties of graphene can be effectively controlled by a strong high-frequency electromagnetic field. From the viewpoint of possible applications, the discussed effect can make graphene more tunable. Particularly, the switching times for conductivity of graphene controlled by a high-frequency field are expected to be shorter then for the case of conventional electrostatic control of conductivity by gate electrodes. This can create physical prerequisites for novel graphene-based optoelectronic devices.How to cite this article: Kristinsson, K. et al. Control of electronic transport in graphene by electromagnetic dressing. Sci. Rep. 6, 20082; doi: 10.1038/srep20082 (2016).


C9ORF72 gene is the most common genetic change seen in familial Frontotemporal Lobar Degeneration (FTLD) and familial Motor Neurone Disease (MND). Pathologically, expansion bearers show characteristic p62 positive, TDP-43 negative inclusion bodies within cerebellar and hippocampal neurons which also contain dipeptide repeat proteins (DPR) formed from sense and antisense RAN (repeat associated non ATG-initiated) translation of the expanded repeat region itself. ‘Inappropriate’ formation, and aggregation, of DPR might therefore confer neurotoxicity and influence clinical phenotype. Consequently, we compared the topographic brain distribution of DPR in 8 patients with Frontotemporal dementia (FTD), 6 with FTD + MND and 7 with MND alone  using a polyclonal antibody to poly-GA, and related this to the extent of TDP-43 pathology in key regions of cerebral cortex and hippocampus. There were no significant differences in either the pattern or severity of brain distribution of DPR between FTD, FTD + MND and MND groups, nor was there any relationship between the distribution of DPR and TDP-43 pathologies in expansion bearers. Likewise, there were no significant differences in the extent of TDP-43 pathology between FTLD patients bearing an expansion in C9ORF72 and non-bearers of the expansion. There were no association between the extent of DPR pathology and TMEM106B or APOE genotypes. However, there was a negative correlation between the extent of DPR pathology and age at onset. Present findings therefore suggest that although the presence and topographic distribution of DPR may be of diagnostic relevance in patients bearing expansion in C9ORF72 this has no bearing on the determination of clinical phenotype. Because TDP-43 pathologies are similar in bearers and non-bearers of the expansion, the expansion may act as a major genetic risk factor for FTLD and MND by rendering the brain highly vulnerable to those very same factors which generate FTLD and MND in sporadic disease.A hexanucleotide (GGGGCC) expansion in The online version of this article (doi:10.1186/2051-5960-2-70) contains supplementary material, which is available to authorized users. MAPT) [GRN) [CHMP2B[C9ORF72[C9ORF72 gene, occurring in patients with either FTLD or MND, or a combination of both [Frontotemporal Lobar Degeneration (FTLD) is a clinical, pathological and genetically heterogeneous condition. The major clinical syndromes principally involve personality and behavioural change  or language alterations of a fluent (semantic dementia) or non-fluent (progressive non-fluent aphasia) nature . All thrMAPT) , progranT) [GRN) , 4, CHMP [CHMP2B, and mos[C9ORF72–8. This  of both –8, and cPathologically, most FTLD cases with the expansion , 10–13, TMEM106B genotype has been claimed to be a genetic modifier of FTLD [C9ORF72 carriers from FTD [APOE) genotype since there have many studies claiming an increased frequency of APOE ϵ4 allele in FTLD   , and 7 with MND  bore expansions in C9ORF72 had a pure/predominant bvFTD phenotype, whereas the other 6 showed a mixed bvFTD and MND phenotype. Five of the FTLD patients without known mutation showed bvFTD phenotype, 3 had a progressive non-fluent aphasia (PNFA) phenotype and 6 showed a mixed bvFTD and MND phenotype. Pathologically, among the C9ORF72 expansion bearers with FTLD, all 8 patients with bvFTD had FTLD-TDP type A histology, whereas all 6 patients with FTD + MND had FTLD-TDP type B histology . These were usually skein-like in appearance, but occasionally more rounded, solid-appearing inclusions were also present.From clinical and neuropsychological assessments, 8 of the 14 FTLD cases with an expansion in al. 2011 ). Of theParaffin sections were cut (at a thickness of 6 μm) from formalin fixed blocks of representative regions of brain to include (where available) frontal cortex (BA8/9), temporal cortex (BA21/22), cingulate gyrus, insular cortex, motor cortex, inferior parietal and occipital (BA17/18) cortex. Blocks were also cut from the amygdala and posterior hippocampus, basal ganglia , substantia nigra (to include oculomotor nucleus), pons , medulla , cerebellum (with dentate nucleus) and cervical and lumbar spinal cord (where available).8 peptide with cysteine at N-terminus, conjugated to m-maleimidobenzoyl-N-hydrosuccinimide ester-activated thyroglobulin. The thyroglobulin-peptide complex (200 μg) emulsified in Freund’s complete adjuvant was injected subcutaneously into a New Zealand White rabbit, followed by 4 weekly injections of peptide complex emulsified in Freund’s incomplete adjuvant, starting after 2 weeks after the first immunization. Immunoreactivity of the antisera was characterized by ELISA as follows. The peptide immunogens were coated onto microtiter plates. The plates were blocked with 10% fetal bovine serum (FBS) in PBS, incubated with the rabbit antisera diluted in 10% FBS/ PBS at room temperature for 1.5 h, followed by incubation with HRP-goat anti-rabbit IgG (Bio-Rad) at 1:3000 dilution, and reacted with the substrate, 0.4 mg/mL o-phenylenediamine, in citrate phosphate buffer . The absorbance at 490 nm was measured using Plate Chameleon (HIDEX). In addition, sections of temporal cortex with hippocampus from 11 (non-expansion bearing) cases with other histological and genetic forms of FTLD, other neurodegenerative disorders and healthy controls (see Table Sections from each brain region were immunostained with a poly-GA antibody (courtesy of M Hasegawa), as described previously . The antFurther sections of frontal cortex and temporal cortex with hippocampus were immunostained for both phosphorylated (at Ser 409/410), and non-phosphorylated, TDP-43 .0 = no DPR immunostained NCI present in any field.0.5 = rare/single DPR immunostained NCI present in entire section.1 = a few DPR immunostained NCI present, in some but not all fields.2 = a moderate number of DPR immunostained NCI present in each field.3 = many DPR immunostained NCI present affecting many cells in each field.4 = very many DPR immunostained NCI present, affecting nearly all cells in every field.The presence of DPR immunostained NCI within nerve cells was assessed at ×20 magnification in those brain regions where all cases could be represented, according to:C9ORF72 expansions. Brain regions were grouped on an anatomical or a ‘functional’ basis. Hence, scores from frontal, temporal, cingulate, insular, parietal and occipital cortical regions were summated to generate a total ‘cortical’ score for each case. Scores from hippocampus and adjacent regions of subiculum, entorhinal cortex and fusiform gyrus were summated to give a total medial temporal lobe score for each case. Scores for caudate nucleus, putamen, globus pallidus, thalamus, substantia nigra, locus caeruleus and dorsal raphe were summated to give a total ‘subcortical’ score. Scores in motor cortex and in X and XII cranial nerve nuclei were summated to give a total ‘motor’ score. Scores in cerebellar granule and Purkinje cells, and in cells of the dentate nucleus, inferior olives and pontine nuclei were summated to give a total ‘cerebellar’ score. Due to the unavailability of tissue in all cases, it was not possible to include scores for amygdala (absent from 5/21 cases) or spinal cord (absent from 10/21 cases) within the medial temporal lobe or motor region analyses, respectively.Scores per assessed area were summated across those regions where these were available for all 21 individuals with 0 = no TDP-43 immunostained NCI and/or neurites.0.5 = rare/single TDP-43 immunostained NCI and/or neurite present in entire section.1 = very few TDP-43 immunostained NCI and/or neurites.2 = a moderate number of TDP-43 immunostained NCI and/or neurites.3 = many TDP-43 immunostained NCI and/or neurites, affecting many cells in every field.4 = very many immunostained NCI and/or neurites present, affecting nearly all cells in every field.The frequency of TDP-43 pathological changes  in each of frontal and temporal cortex  and hippocampus (dentate gyrus granule cells), was scored semi-quantitatively according to:TDP-43 pathology cores per assessed area were summated across those regions where these were available for all individuals. Hence, scores from dentate gyrus of hippocampus, and from frontal and temporal cortex, were summated  to give a total TDP-43 pathology score for each case.TMEM106B assay was genotyped by allelic discrimination using the Applied Biosystems pre-developed assay cat number C_7604953_10. Genotyping was carried out using the Applied Biosystems 7900, and genotypes were assigned automatically using the SDS 2.3 software. APOE was genotyped according to Wenham [DNA was extracted from blood or frozen brain tissue by routine phenol-chloroform extraction. The o Wenham .Rating data was entered into an excel spreadsheet and analyzed using Statistical Package for Social Sciences (SPSS) software (version 17.0). Kruskal-Wallis or Mann–Whitney test was used to compare inclusion scores between several groups or pairs of groups, respectively. All correlations were performed using Spearman rank correlation test. In all instances, a p-value of less than 0.05 was considered statistically significant.C9ORF72 associated FTD, FTD + MND and MND groups, FTD associated with GRN mutation, non-mutational FTD, FTD + MND and MND groups are shown in Table Mean ages at onset, death and duration of illness for 6,51 = 0.27, p = 0.946) or death , though duration of illness differed between the groups . As would be expected, post-hoc analysis showed that duration of illness was significantly less in C9ORF72 cases with MND than C9ORF72 associated FTD (p = 0.014), but not less than C9ORF72 associated FTD + MND (p = 0.281), nor was there any difference in disease duration between C9ORF72 associated FTD and C9ORF72 associated FTD + MND (p = 0.815). Again, as expected, non-mutational MND showed a shorter duration of illness than non-mutational FTD (p = 0.022) and non-mutational FTD + MND (p = 0.013). However, there were no significant differences in duration of illness between C9ORF72 associated FTD, non-mutational FTD or GRN associated FTD , or between C9ORF72 associated FTD + MND and non-mutational FTD + MND (p = 0.900), or between C9ORF72 associated MND and non-mutational MND (p = 0.605).ANOVA comparison of age at onset, death and duration of illness between all 7 diagnostic groups revealed no significant differences in age at onset  or duration of illness , though duration of illness tended to differ between the 3 groups .ANOVA comparison of age at onset, death and duration of illness between All cases had been previously classified on the basis of the type and distribution of TDP-43 immunoreactive changes according to Mackenzie et al. 2011 [C9ORF72, but none were seen in any of the cases bearing GRN mutations, nor in any of the other FTLD cases or MND cases not known to be associated with any FTLD or MND linked mutation.In cases of FTD and FTD + MND, DPR were observed to be most frequent within the cerebral neocortex, hippocampus and cerebellum. They were infrequent or absent in basal ganglia regions, and were rare or usually absent in mid brain, brainstem, medulla and spinal cord regions. DPR were present in neuronal cytoplasmic inclusions (NCI) throughout all cortical layers in all regions of the cerebral cortex examined. In outer cortical layers they were mostly present in small non-pyramidal neurons appearing as dots or clusters of granules , hippocampal , motor , subcortical  or cerebellar  regions, or for total score summated across all 5 subregions  , hippocampal , motor  and for total score summated across all 5 subregions , but not for subcortical  or cerebellar  regions. However, there was no significant correlation between the severity of DPR pathology and duration of disease, except weakly so in cerebellum .When all cases were grouped, there were significant correlations between the severity of DPR pathology and age at onset of disease for cortical . No significant differences in DPR severity scores were found between ϵ4 allele bearers and non-bearers, either overall (p = 0.240) or according to subregion , hippocampal (p = 0.189), motor (p = 0.887), subcortical (p = 0.506) or cerebellar (p = 0.640).Comparisons of DPR severity scores according to possession of at least one copy of TMEM106B genotypes were only available for 7 of the 14 FTLD cases, and 1 of the 7 MND cases, bearing C9ORF72 expansions, 9 of the 12 GRN mutation carriers, and 10 of the 14 FTLD cases and 1 of the 20 MND cases without known mutation. Because TMEM106B SNPs rs1020004, rs1990622 and rs6966915 were in complete linkage disequilibrium, pathological analyses were confined to rs 1990622. Unfortunately, only one of the FTLD, and none of the MND cases, irrespective of type or presence of mutation, was homozygous for the minor allele at any SNP. Of the C9ORF72 expansion bearers, 4 of the FTLD cases were homozygotes for the major allele and 3 were heterozygotes, with the MND case being homozygous for the major allele. Of the GRN mutation bearers, 5 of the FTLD cases were homozygotes for the major allele and 4 were heterozygotes. Of the non-mutational FTLD cases, 6 were homozygotes for the major allele, 2 were heterozygotes and 1 was homozygous for the minor allele.Due to availability of DNA, Nonetheless, comparisons of DPR severity scores were performed between FTLD cases heterozygous (TC) and homozygous (TT) for the major allele. No significant differences in DPR severity scores were found between bearers of TC or TT genotypes, either overall (p = 0.881) or according to subregion , hippocampal (p = 0.549), motor (p = 0.495), subcortical (p = 0.546) or cerebellar (p = 0.878).C9ORF72, FTLD cases without expansions, and FTLD cases with GRN mutation for either frontal cortex , temporal cortex  or dentate gyrus of hippocampus , or as total TDP-43 severity score . Moreover, there were no significant differences in the severity of TDP-43 pathology scores between FTLD cases with type A histology bearing an expansion in C9ORF72, FTLD cases with type A histology but without expansion in C9ORF72 mutation, and FTLD cases with GRN mutation and type A histology for either frontal cortex , temporal cortex  or dentate gyrus of hippocampus , or as total TDP-43 severity score . Similarly, there were no significant differences in the severity of TDP-43 pathology scores between FTLD cases with type B histology bearing an expansion in C9ORF72 and FTLD cases with type B histology but without expansion in C9ORF72 mutation for either frontal cortex (p = 0.570), temporal cortex (p = 0.147) or dentate gyrus of hippocampus (p = 0.344), or as total TDP-43 severity score (p = 0.254).Composite rating scores for TDP-43 pathology are shown for each case in Table C9ORF72 expansion carriers, there were no significant correlations between the severity of TDP-43 pathology and either age at onset of disease, or duration of illness, for either cortical, hippocampal or total scores. Neither was there any correlation between TDP-43 scores and clinical phenotype (ie FTD versus FTD + MND).Within the APOE ϵ4 allele were performed on 36/39 FTLD cases (for whom DNA was available for genotyping), irrespective of the presence or absence of mutation. No significant differences in the severity of TDP-43 pathology scores were seen between FTLD cases with APOE ϵ4 allele and FTLD cases without APOE ϵ4 allele for either frontal cortex (p = 0.187), temporal cortex (p = 0.293) or dentate gyrus of hippocampus (p = 0.171), or as total TDP-43 severity score (p = 0.261). Similarly, comparisons of TDP-43 severity scores according to heterozygosity (TC) or homozygosity (TT) for major allele in TMEM106B were performed on 24/39 FTLD cases (where these data were available), irrespective of the presence or absence of mutation. No significant differences in the severity of TDP-43 pathology scores between FTLD cases with TC and TT genotypes were seen for either frontal cortex (p = 0.301), temporal cortex (p = 0.592) or dentate gyrus of hippocampus (p = 0.768), or as total TDP-43 severity score (p = 0.519).Comparisons of TDP-43 severity scores according to possession of at least one copy of C9ORF72, neither the topographical distribution, nor the relative severity, of DPR differs between cases of FTD alone, FTD + MND or MND alone. Secondly, neither the morphological appearance, nor relative severity, of TDP-43 immunoreactive changes differ in cases of FTLD bearing an expansion in C9ORF72 from that in non-expansion bearing cases of FTLD (ie sporadic forms of FTLD), or from cases of FTLD bearing mutations in GRN. These findings support the observations of Mackenzie and colleagues [per se in causing FTLD or MND.There are two major outcomes from this study. Firstly, that in cases of FTLD or MND bearing expansions in lleagues  who likeC9ORF72 have been postulated to invoke disease by 3, mutually non-exclusive, mechanisms: firstly involving a loss of C9orf72 protein through haploinsufficiency [Expansions in ficiency , secondlficiency , 21, andficiency , 22, 23.Firstly, in both the present, and in other studies , the disSecondly, it is hard to conceive how a seemingly identical topographical pattern of DPR pathology could determine, or even predispose towards, such diverse clinical phenotypes as FTD or MND. To explain such an apparent paradox, Mackenzie et al. 2013  invoked per se. Although, there is no a priori reason to suspect that patients with an expansion in C9ORF72 should ‘naturally’ carry a higher burden of TDP-43 pathology than non-expansion carriers, it is nonetheless important to observe that such differences do indeed not exist. Moreover, if the expansion were directly driving a TDP-43 proteinopathy, it is hard to reconcile this with observations of different TDP-43 histologies. FTLD-TDP Type B  is the most common TDP-43 histological subtype associated with the expansion [The second observation from this study indicates that as far as the TDP-43 proteinopathy is concerned, there are again no distinctions in pathology between expansion bearers and non-bearers of the expansion, either overall or more specifically in respect of FTLD-TDP type A or type B histologies. This also supports observations by Mackenzie et al.  and furtxpansion , 24, thoxpansion , and rarxpansion . How sucC9ORF72 could be that the expansion acts as a risk factor for FTLD and MND, though does not drive the (TDP-43) pathological process directly, acting more as a ‘gatekeeper’ to disease, rendering the brain susceptible to the ‘development’ of all sporadic forms of FTLD-TDP, and sporadic forms of MND associated with TDP-43. Such a scenario could accommodate the present observations of the different histological types of TDP-43 proteinopathy being associated with disease, and the relative proportions with which they occur, and with findings that the extent of TDP-43 pathology is the same in expansion and non-expansion bearers both in terms of either type A or type B histologies.An alternative explanation of the role of C9ORF72. Indeed, there has been one Belgian case with C9ORF72 expansion and clinical FTLD which lacks detectable TDP-43 pathology, but shows FTLD-UPS pathology [GRN with C9ORF72[MAPT with C9ORF72[GRN or MAPT) mutation prevails.There is other evidence in support of this latter line of argument. Firstly, although rare, pathologies other than FTLD or MND, such as corticobasal degeneration , 17, Alz C9ORF72, 55 or M C9ORF72–57  has been claimed to be a genetic modifier of FTLD in both GRN and C9ORF72 mutation carriers [C9ORF72 carriers from FTD [TMEM106B allele with FTLD-TDP type A histology appeared to have a lower TDP-43 burden than homozygous carriers of the major allele. Therefore, we investigated whether variations at this locus might influence both the distribution and severity of both DPR and TDP-43 pathologies in FTLD cases associated with either C9ORF72 expansions or GRN mutations. Unfortunately, no homozygous bearers of TMEM106B minor allele were available in the present study for either mutation, but we did not find any differences in DPR and TDP-43 pathology between heterozygotes and those homozygous for the major allele suggesting that heterozygosity, at least, does not confer a ‘partial’ protection in either C9ORF72 or GRN mutation carriers. Similarly, although possession of at least one copy of APOE ϵ4 allele has been (variably) claimed to increase risk of FTLD [carriers , 28, 29,from FTD , 28, 29. of FTLD –33, we fin vivo, and in vitro, as well as the role RNA foci might play in causing the disease. However, there is evidence of C9orf72 haploinsufficiency in expansion carriers [RAB38 as a risk factor for bvFTD [GRN[TMEM106B[How the expansion might act in a ‘gatekeeper’ role is not clear. Much attention has been levied towards a determination of the nature and effect of DPR carriers , though carriers , 23, 58,carriers . In thisor bvFTD . RAB38 hor bvFTD , 62 and or bvFTD , and impor bvFTD . Indeed,FTD [GRN and TMEMTMEM106B. ConsideC9ORF72 are not without ‘pathological expression’, what DPR might translate into in clinical terms is not clear, and whether these structures confer anything beyond diagnostic utility still remains to be demonstrated.Nonetheless, if such a ‘gatekeeper role’ is true, then the almost complete penetrance of the mutation needs to be explained. In this respect the expansion might be viewed as providing an ‘open door’ to disease, but without actually causing disease directly, and in this regard the DPR pathology may be a ‘red herring’ without pathogenetic consequence. Clearly, until we know more about the normal function of C9orf72 protein, what cells it is present in, and where in the cell it is located, all is mere speculation. The concept of the expansion being a risk factor for disease, rather than a cause, is tempting since it would neatly accommodate the observed diversity of clinical and histological subtypes associated with the expansion. However, were the expansion to act as a risk factor, it appears to act  selectively for FTLD and MND since expansions are only infrequently, and then maybe only coincidentally, seen in more common disorders such as Alzheimer’s and Parkinson’s disease –53. TherSelected clinical, pathological and genetic details for 40 cases of Frontotemporal Lobar degeneration and 27 cases of Motor Neurone disease.(XLSX 18 KB)Additional file 1:


PD-L1-negative tumors assessed by immunohistochemistry often still respond to PD-1 blockade. PD-L1 is inducible by interferon, therefore, absolute negative tumors are the ones unable to up-regulate PD-L1 in response to interferons. Genetic mutations in the interferon receptor signaling pathway leading to loss of PD-L1 up-regulation were hypothesized to exhibit innate resistance to PD-1 blockade.After optimization, 50 primary human melanoma cell lines were exposed to interferons  and PD-L1 expression was measured. Interferon signaling was assessed by single cell phospho-proteomics, pSTAT1 (Y701), pSTAT3, pSTAT5, pSTAT6 expression level by flow cytometry (FACS LSRII). Western blot assessed JAK1/JAK2/IRF1 as well as STAT/pSTAT expression and Whole exome sequencing was performed by next generation sequencing for three selected melanoma cell lines and on biopsies from 25 patients with advanced melanoma treated with anti-PD-1 therapy.Three out of 50 melanoma cell lines were unable to up-regulate PD-L1 in response to interferon gamma; two of them had disruptive mutations in JAK1 or JAK2, and a third one had a defect in expression of IRF1 in response to interferons. Western blot analysis confirmed loss of function for the JAK1/JAK2 mutations and loss of downstream IRF1/STAT1/3/5 phosphorylation events. Whole exome sequencing of biopsies from 15 patients with metastatic melanoma who had objective response to PD-1 blockade (pembrolizumab) showed no homozygous inactivating mutations in interferon signaling pathway genes. Interestingly, one patient with the highest mutational load out of 10 patients without clinical response to PD-1 blockade had an amplified allele of JAK1 with a P429S mutation in the src-homology (SH2) domain. A cell line derived from this patient showed lack of sustained up-regulating of PD-L1 expression in response to interferon gamma by, and Western blot confirmed loss of JAK1 expression. Immunohistochemistry of tumor biopsy for this patient showed few CD8+ T cells.This study has defined genetic mechanisms of innate resistance to PD-1 blockade which lead to inhibition of adaptive PD-L1 expression in patients with advanced melanoma. This work suggests lack of interferon-gamma induced PD-L1 upregulation has the potential to be a negative selective marker for PD-1 blockade therapy.


Graphene can be synthesized from polyacrylonitrile (PAN) polymer through pyrolysis. A metal catalyst such as nickel (Ni) is required for the conversion of the polymer to graphene. The metal catalysts can be placed either atop or underneath the polymer precursor. We observed that spatially non-uniform and disconnected graphene was fabricated when PAN film coated with a Ni layer was pyrolyzed, resulting in flake-like graphene. Formation of the flake-like graphene is attributed to the dewetting of the Ni layer coated on the PAN film. Dewetting phenomenon can be reduced by decreasing the pyrolysis temperature, and hence, more uniform graphene could be prepared. The effects of Ni coating thickness and the pyrolysis temperature on the fabricated graphene have been experimentally analyzed. Ever since the discovery of graphene , researc2 is required for the application to electronic device [The solid-phase method employs transition metals such as Ni and Cu as a catalyst to form graphene from solid-state carbon sources such as polymer, SiC, small molecule, and self-assembled monolayer. Particularly, in the method using polymer as a precursor of graphene, various polymers like polyacrylonitrile (PAN), polystyrene, and polymethylmethacrylate were used, and the polymer placed either atop or underneath metal catalysts were pyrolyzed in a reductive gas to form graphene -23. Whenc device ,24. Thisc device ,23.2/Si substrate from PAN coated with a Ni film through pyrolysis. The Ni coating layer tends to be aggregated to form particulates due to dewetting [Here, we present systematic experimental results to synthesize graphene on a SiOewetting  at a higMw =150,000) (0.5 wt.%) dissolved in N,N-Dimethylformamide  was spin-coated on 1 × 1 cm2 SiO2 (300 nm thickness)/Si wafers. Subsequently, a Ni layer was coated on the spin-coated PAN/SiO2/Si substrates with a magnetron sputtering system. The sputtering rate was approximately 10 nm/min, and the thickness of the Ni layer was changed by the sputtering time. The Ni-coated PAN/SiO2/Si samples were pyrolyzed in a high-vacuum furnace; the vacuum level in the furnace was roughly 10-5 Torr.Polyacrylonitrile  is easily agglomerated in the vacuum atmosphere. So the temperature of 1,050°C was selected as the maximum temperature. In the case of the minimum temperature range, the temperature where graphene is formed and the agglomeration of the nickel layer is suppressed was selected as the minimum temperature. Therefore, the temperature ranged from 1,050°C to 700°C was selected for the pyrolysis).After the pyrolysis, the coated Ni layer was removed with a Ni etchant  at approximately 35°C for 2 to 4 h.The synthesized graphene on the substrate was characterized by Raman spectroscopy  and Raman mapping . The surface morphologies of the products were observed using a field-emission scanning electron microscope   and approximately 1,590 cm-1 (G peak) and no second-order Raman peak at 2,600 to 2,800 cm-1 corresponding to 2D peak of graphene was observed. This indicates that the PAN film was converted to amorphous carbon on the surface of the SiO2/Si substrate [-1 appeared  continuously decreased  of the Raman spectra shown in Figure -1, and the intensity ratio of G to 2D peaks (IG/I2D) was approximately 2  if tThe authors declare that they have no competing interests.HK carried out the experiments, contributed to the interpretation of the data and drafted the manuscript. JMH contribute to measure Raman spectrum. SHY and GA assisted in the experiments. SOC supervised the whole study. All authors read and approved the final manuscript.


In particular, the Dirac peaks shift very rapidly when the pressure decreases from ~2 × 10−3 Torr to ~5 × 10−5 Torr within 5 minutes. These Dirac peak shifts are known as adsorption and desorption of environmental gases, but the shift amounts are considerably different depending on the fabrication process. The high gas sensitivity of the device fabricated by shadow mask is attributed to adsorption on the clean graphene surface.To pattern electrical metal contacts, electron beam lithography or photolithography are commonly utilized, and these processes require polymer resists with solvents. During the patterning process the graphene surface is exposed to chemicals, and the residue on the graphene surface was unable to be completely removed by any method, causing the graphene layer to be contaminated. A lithography free method can overcome these residue problems. In this study, we use a micro-grid as a shadow mask to fabricate a graphene based field-effect-transistor (FET). Electrical measurements of the graphene based FET samples are carried out in air and vacuum. It is found that the Dirac peaks of the graphene devices on SiO Also, an inhomogeneity of electron-rich and hole-rich puddles arises due to the charged impurity and substrate-induced disorder. This inhomogeneity32 surface, and trapped charges19142 and hBN were investigated under various conditions.Graphene123567910111213141516Employing e-beam or photolithography while patterning electrical contacts unnecessarily exposes the graphene surface to chemicals . These chemical residues have been reported to be nearly impossible to completely remove, thereby degrading graphene device quality22232 substrates, where p+ doped Si (ρ ∼ 3 × 10−3 Ωcm) was used as the bottom gate electrode and SiO2  as the gate dielectric. First, the Si/SiO2 substrates were sonicated in acetone, then in isopropanol, and later rinsed by DI water. Highly oriented pyrolytic graphite  and natural Kish graphite were used to produce graphene flakes by mechanical exfoliation via adhesive tape . The graphene based FETs were also fabricated on the hBN substrate. For graphene on hBN fabrication, hBN flakes were first deposited on the Si/SiO2 wafer using the mechanical exfoliation method. Then, a microscope was utilized to select one appropriate hBN flake, which was the substrate for fabricating graphene FET. A graphene layer was transferred to the hBN substrate using the dry transferring method14The graphene channel of FETs was supported on Si/SiOElectron-beam evaporation was used to make electrodes with Ti (1 nm) followed by Au (80 nm) for electrical contacts at both ends of the graphene FET channel (‘source’ and ‘drain’). The electrodes were evaporated onto the graphene through square holes in a commercial grid for transmission electron microscopy (TEM), which was used as a shadow mask. Two kinds of TEM grids  were employed, and the specifications are listed in Table 1 of the 2/Si substrate is shown in 2. To pattern the electrodes, we used a polydimethylsiloxane (PDMS) slab as a supporting layer carrying the TEM grids. The PDMS slab has a dimension of 5 × 5 × 1 mm3 with a punched hole (1–2 mm dia.), where the center of the TEM grid was located. After that, the PDMS slab was affixed to a glass slide. The slide with the PDMS slab was inverted and attached to a micromanipulator. The micro manipulator was then utilized to position the TEM grid covering the chosen part of the graphene flake on the hBN substrate. Using a micromanipulator while monitoring the area through an optical microscope, the TEM grid was carefully positioned on the graphene flake of interest  so that one of the TEM bars covered the graphene, leaving its opposite side ends uncovered between the bar of the mask. After the first evaporation, a square array pattern of the fine TEM grid was created as shown in A schematic drawing of our back-gated graphene FET supported on a SiORtot versus Vg curves were found at a significantly positive Vg  for most of the fabricated samples. This positive Dirac peak shift of the graphene devices on the SiO2 substrate has been observed in other studies128As our device fabrication process involves shadow-masking to make electrical contacts, this method has the crucial advantage of being a resist-free process. After finishing the fabricating process, no other treatments , the doping polarity was completely reversed at a pressure of 1 × 10−5 Torr without heating. The Dirac point was shifted down to Vg < −40 V at high vacuum conditions. This n-doping source in vacuum should be different from p-type dopant at ambient. The p-type dopants acting as electron acceptors are gases (or water vapor) adsorbed on graphene surface and at the interface between the graphene substrate under ambient conditions. The adsorbates were desorbed in a high vacuum without annealing, and the p-doping effect disappeared.The graphene channel (10 μm long and 3 μm wide) supported on the SiO2 surface act as gas adsorption sites to adsorb gas and water molecules2O, O2, and NO2 lead to the p-type doping of graphene, while ammonia leads to the n-type1030−3 Torr in The Dirac peak at a positive gate voltage implies that the major carrier holes dominate the electrical transport at zero gate voltage. It is known that the defects at the SiO2 surface or directly adsorbed on the graphene surface2) and NO2 gases could serve as additional dopants existing in air, as they also adsorb weakly to graphene, acting as an electron acceptor33Usually, under ambient conditions oxygen and water molecules can be adsorbed on the SiO2. The graphene FETs supported on hBN of a few nm thickness were fabricated by the same method with TEM grids as shadow masks. The p-type doping behavior also occurred in the graphene on hBN as shown in Vg > +40 V at room temperature. When the chamber pressure decreased to 1 × 10−3 Torr, the peak shifted to lesser Vg, but the VD was still over +40 V. The results were very similar to those obtained with graphene on SiO2. The sample was then kept at 1 × 10−3 Torr at room temperature for 7 hours and measured again. The Dirac peak was still higher than +40 V, confirming that the desorption process does not depend on the duration time but the pressure mainly. This p-doping effect of the graphene on hBN can be explained by adsorbed gases and water moisture from the surrounding environment, which is similar to the graphene on SiO2. The mobility of this sample was estimated as 1.96 × 103 cm2/V/s from the Drude formula.To study the effect of the underlying substrate on doping graphene, hBN was employed as a substrate along with SiORtot/Vg curves of the sample measured under ambient conditions at 1 × 10−3 and 1 × 10−5 Torr at room temperature are depicted in 2/V/s, which is somewhat lower than that of the device fabricated by the TEM grid. This device also displayed a p- doped state in air, but the p-doping effect was weaker than that of the devices fabricated using the shadow mask. This difference may be due to the residue remaining on the graphene surface  were fabricated depositing the metal contact pads using e-beam lithography. The face See  and the Rtot versus back-gate bias Vg of the graphene on SiO2 device used in The 2 dielectric. This graphene layer was confirmed as a single layer graphene (SLG) by Raman spectroscope, so the thickness should be about 0.3 nm. However, the thickness of the graphene layer was estimated to be ~30 nm  adsorbed gases were removed from graphene. A high vacuum environment, along with heating, has been used to degas water vapor and adsorbed gasses on both the graphene surface and the interface between graphene and substrate33To confirm the degassing of the adsorbed gases and water vapor due to vacuum pumping, AFM scanning of the same sample was performed after it was placed in vacuum at 1 × 10M images . There iM images  was abouM images . This iset al. suggested that the observed n-type behavior is associated with a low work function of SiO2 substrate (W = 3.03 to 3.41 eV)g = 4.23 to 4.48 eV)2 substrate and the graphene layer depends on atomic configurations of SiO22 has an amorphous structure and transfers electrons to graphene. Additionally, the number of electrons transferred from the SiO2 substrate to graphene increases rapidly as the graphene is close to SiO2. In our work, the n-doping effect of graphene at high vacuum occurs with not only graphene on SiO2, but also graphene on hBN substrate. Few-nanometer-thick hBN was not enough to shield the low surface potential of SiO2, resulting in the n-doped graphene, because the Fermi level shift in graphene, due to hBN with several layers, was approximately 0.15 V from density functional theoryet al. reported an identification of a strong contamination source for graphene in vacuum systemsUnexpected n-doping behavior of graphene on hBN was occasionally found even on high quality samples by others, but no clear theoretical explanation has been suggested beyond attributing it to contamination14Rtot and Vg of the graphene on SiO2 measured at room temperature in water is shown in We also conducted a Dirac point measurement of graphene FETs in different liquid environments in order to confirm the effects of the adsorbed water layer. The relationship between resistance 2 with electric contact pads fabricated using e-beam lithography as shown in The same measurement was performed in ethanol as shown in et al. found that the top dielectric can induce significant changes in the back-gate capacitance due to the finite width of graphene deviceset al. confirmed that the back gate capacitance was increased by up to 2 orders of magnitude in water, by measuring the Hall-effect, which was dependent on the dielectric constant of the mediumThese electrical characteristics of the graphene based FETs in liquid dielectric environments can be explained by the change of effective back-gate capacitanceA lithography free method was demonstrated to eliminate polymer and solvent residues remaining on the graphene surface. In this study, we used a shadow mask to fabricate graphene based FET. The commercial TEM grids were utilized as a shadow mask for evaporation to deposit electrical metal contacts. Patterning with a shadow mask eliminates the use of polymers and solvents that are unavoidable in e-beam lithography or photo lithography. Our clean graphene device fabricated by shadow mask patterning indicated high sensitivity in both gas and liquid environments.2 and on hBN were investigated in various levels of vacuum, in ambient conditions, and in liquid. We found that graphene FETs were heavily p-doped as prepared in air, and this p-doping in electrical behavior of graphene was reversed into n-doped during vacuum pumping at room temperature. During the vacuum pumping process, the absorbed gases on the graphene surface under ambient conditions were able to be removed without annealing. From the AFM data showing inflated graphene and slow adsorption and desorption processes, the water is supposed to be a main source of the doping effect. The reversible changes at room temperature in the adsorption and desorption cycling imply the occurrence of physisorption rather than chemisorption. As water possesses a much lower saturation vapor pressure at room temperature, the majority of adsorbates should be water molecules. The n-type doping effect was found at 1 × 10−5 Torr in clean graphene surfaces supported on both SiO2 and hBN at room temperature. This n-doping effect from the substrates was explained by the work function of SiO2 being lower than graphene. The liquid environment measurement showed narrowing of the Dirac peak, which was attributed to the increment of the gate capacitance. Most results measured in our sample were similar to those reported previously by other groups, but our results were more sensitive to the environment as the sample was prepared in dry conditions without using polymer resist. As a result, the dominant doping source for the graphene device was not polymer residue, but water in air. The clean surface of graphene adsorbs surrounding water molecules strongly, while conventionally processed devices should be covered with polymer residue on top of graphene, preventing the adsorptions. Thus, the device fabricated by the resist-free method showed higher sensitivity in environmental gas than the device with polymer resist. By encapsulating the graphene in vacuum after the metal deposition using a shadow mask method, a high quality graphene device can be fabricated.The electrical properties of the graphene based FETs on SiONatural Kish graphite (Grade 300) was mechanically exfoliated on a Si wafer. The TEM grid was attached at the center of a hole punched in a PDMS slab. The TEM grid was carefully positioned using a micro-translator in the xy-plane, to locate the TEM grid into the target position. After alignment, z-directional contact made the PDMS slab stick to the wafer, due to its adhesive property. The adhesion was sustained in a high vacuum evaporation process, where Au contact pads were deposited through square holes of the TEM grid.The transport characteristics of the devices with three terminals were measured in air and vacuum at room temperature. During the vacuum pumping process, the absorbed gases on the graphene surface were able to be removed under ambient conditions in the laboratory. The semiconductor characterization system  was employed for accurate electrical measurements. A bias voltage was applied between the source and drain terminals of the graphene channel. The Si substrate was used as a global back-gate; this bias field controls the carrier concentration and polarity in the graphene layer. The voltage applied to gate terminal was swept continuously during the measurements. The output signal was converted to the resistance of the device and then used to plot the graph. The Dirac point of the device was determined from the graph. AFM measurements were performed using a commercial AFM . Pt/Cr (Multi75E-G) coated cantilevers with stiffness 3 N/m were utilized in noncontact mode for the AFM imaging.How to cite this article: Tien, D. H. et al. Characterization of Graphene-based FET Fabricated using a Shadow Mask. Sci. Rep.6, 25050; doi: 10.1038/srep25050 (2016).


Introns represent almost half of the human genome, yet their vast majority is eliminated from eukaryotic transcripts through RNA splicing. Nevertheless, they feature key elements and functions that deserve further interest. At the level of DNA, introns are genomic segments that can shelter independent transcription units for coding and non-coding RNAs which transcription may interfere with that of the host gene, and regulatory elements that can influence gene expression and splicing itself. From the RNA perspective, some introns can be subjected to alternative splicing. Intron retention appear to provide some plasticity to the nature of the protein produced, its distribution in a given cell type and timing of its translation. Intron retention may also serve as a switch to produce coding or non-coding RNAs from the same transcription unit. Conversely, splicing of introns has been directly implicated in the production of small regulatory RNAs. Hence, splicing of introns also appears to provide plasticity to the type of RNA produced from a genetic locus . We addressed these aspects to add to our understanding of mechanisms that control the fate of introns and could be instrumental in regulating genomic output and hence cell fate. In eukaryotes, the process of making a messenger RNA (mRNA) involves the co-transcriptional excision of introns in the nucleus, whereas joined-exons are exported to the cytoplasm to be translated. As a consequence, introns are inherently non-protein-coding sequences in that they are transcribed but not translated  into protein. Because, and by definition, introns always lie between 2 exons, they were called “Intervening” or INtrons. By opposition, exons are those sequences that are EXpressed and EXported to the cytoplasm.a posteriori, an explanation on how eukaryotes diversify their proteome from just a few genes. We now know that the fate of introns is not simply a matter of being eliminated to allow formation of mRNA coding for proteins.In 1993, the Nobel Prize was awarded to Phillip A. Sharp and Richard J. Roberts for their discovery that genes can be split into segments and, as a consequence, transcripts that originate from them are matured into messenger RNA (mRNA) smaller in size. Hence, introns are segments of a gene between exons, which are transcribed but do not participate in the production of the final protein product as they are removed before translation, allowing joining of exons through a process known as splicing. With the discovery that various combinations of segments may be included in the final RNA molecule, this has changed our view on how genetic information is expressed and provided, Introns are classified in four groups based on splicing mechanisms. 1) Spliceosomal introns are found in coding genes of eukaryotes and utilize spliceosomes (large protein-RNA complexes) for splicing  Spliceos that incSplicing of both Group II and pre-mRNA introns involve the formation of a lariat suggesting that they may be evolutionary related. However, origin and evolution of spliceosomal introns is still a matter of debate, opposing “introns early” to “introns late” theories , the maiBeing eliminated to allow formation of messenger RNA and inherently non-coding, introns have long been kept in the now famous “junk DNA” drawer. However, and maybe against all odds, high sequence conservation among homologous introns of closely related species suggests functional constraints on intronic sequences throughout evolution . Many stWe review here aspects of introns that are perhaps less known but made them see a renewed interest lately.i.e., introns, which cover more than 1.7 billion bases pairs and represent 45% to 55% of the human genome . However, overall, a typical coding gene contains 10.8 exons and 9.8 introns . The absolute record is held by the titin gene, which contains 363 exons . About er genes , but onler genes , were aser genes . The majer genes .BAI3; chr6:69,232,406–69,389,511) gene.Nested genes that produce small regulatory RNAs independently of the transcription of the host gene have also been described ,14. ExamAlthough it has been proposed that a compact genome allows for quicker replication rate in prokaryotes, the functional benefits for mammalian genomes to hold nested genes are still unclear. Still, the presence of nested transcription units in introns raises the questions of their concerted transcription and regulation. It is likely that the host gene and its nested gene transcribed from the opposite strand are inversely regulated and transcribed, owing to promoter competition or steric hindrance of RNA polymerase and transcription factors. In contrast, if the nested and host genes are transcribed from the same strand, it is quite straightforward to predict a concerted model of transcriptional regulation of both genes to allow expression, if not in the same pathways, at least in the same cellular context or in response to the same environmental cues.Through classical mechanisms than we will not detail here, pre-mRNA splicing is precisely controlled in a spatial and temporal manner to generate mature RNAs . If one(1) The recursive splicing consists in the stepwise removal of introns by sequential splicing reactions starting from the most 5' donor site and progressing towards the most 3' acceptor site ,22. To d(2) The intra-splicing or nested splicing first requires internal splicing, using internal canonical donor and acceptor sites, followed by external splicing involving the most outer donor and acceptor sites . This prDMD; chrX:31,137,345–33,357,726) is one of the largest annotated genes, spanning more than 2 Mbp and generating transcripts containing up to 79 coding exons. Strikingly, DMD transcripts are only 14 kb long since more than 99% of the gene sequence is composed of introns, whose lengths vary from 107 nt (intron 14) to 248,401 nt (intron 44) [EPB41) gene in which Exon 1A and exon 2 are joined through two nested splicing events [The human dystrophin gene (tron 44) . Intron g events .In eukaryotes, splicing occurs in the nucleus in a transcription-coupled manner where the spliceosome complex catalyzes intron removal, deposits exon–junction complexes (EJC) to mark sites of intron removal but also participates in nuclear retention of incompletely spliced pre-mRNAs. Quality control of incompletely spliced pre-mRNAs to prevent their translation into aberrant proteins involves at least two mechanisms; the nuclear degradation of pre-mRNAs that failed to be exported to the cytoplasm, and the cytoplasmic degradation through nonsense-mediated decay (NMD) of intron-retaining RNAs with a premature stop codon 5' of an EJC .The major spliceosome comprises 5 small nuclear RNAs (snRNA) and a multitude of associated protein factors to form small nuclear ribonucleoprotein particles (snRNPs), U1, U2, U4, U5, and U6 . SpliceoA minor spliceosome has been reported in plants, insects, and vertebrates, which is specialized in the splicing of a rare class of introns  Transcripts with unspliced minor introns can be found in the cytoplasm, together with components of the minor spliceosome. In addition, the specific inhibition of minor spliceosome components in the cytoplasm, using antisense morpholino conjugated to a nuclear-export sequence, leads to accumulation of unspliced U12-introns in the cytoplasm .(2) The minor spliceosome, unlike its major counterpart, seems to evade mitotic down-regulation, to be able to operate during mitosis and to function independently of transcription ,32,33. I(3) Along the same lines, platelets, which are specialized hemostatic cells that circulate in the blood as anucleate cytoplasts, contain essential spliceosomal proteins and small nuclear ribonucleic acids (snRNAs), as well as a subset of pre-mRNAs that are further spliced into mature message in response to platelet activation . This me(4) Additional support for the functionality of RNA splicing in the cytoplasm was provided in neurons. Neurons have a cell body containing the nucleus and core cytoplasmic components surrounded by highly specialized cytoplasmic extensions called dendrites and axons. Certain not fully spliced intron-retaining mRNAs are directed toward neuronal dendrites where they fully mature ,36. As m(5) Cytoplasmic splicing is one of the major regulatory mechanisms of the unfolded protein response (UPR), although it occurs through unconventional mechanisms . SplicinIn sum, cytoplasmic splicing offers an efficient way to diversify cellular phenotypes without the need for nuclear activation of sets of genes as well as allowing for rapid regulation of local environment and subcellular proteomes and hence, for a quasi instant response to environmental cues.miRNAs play pivotal roles in diverse biological functions, mainly through the repression of target genes. Less than half of intronic miRNAs are transcribed independently of their host gene, as long primary capped and polyadenylated transcripts (pri-miRNAs) by RNA polymerase II (RNA pol II), which undergo a series of maturation steps via the formation of a hairpin-forming precursor (pre-miRNA) until the production of mature miRNAs in the cytoplasm. These intronic miRNAs should be named intragenic or nested miRNAs to distinguish them from independent intergenic miRNAs. In contrast, the other half of so-called intronic miRNAs share promoter and regulatory elements with their host gene ,41,42,43Interestingly, there are cases where small regulatory RNAs are directly produced by way of splicing of the intron from the host transcript and thus, are strictly dependent on both transcription and splicing of the host gene.GRCh38).In the case of snoRNAs, while some have their own promoter and are transcribed by RNA pol II, the majority is produced through splicing of the host intron. Whereas most of the host transcripts are mRNAs, some examples of long non-coding RNA (lncRNA) hosting snoRNAs exist such as the growth arrest-specific transcript 5 (GAS5) that contains 10 different snoRNAs, almost one in each one of its introns  . NoteworAt least two alternative pathways in the biogenesis of miRNAs use splicing to produce pre-miRNA-like transcripts independently of the microprocessor complex: the mirtron and the simtron pathways .i.e., dependency on splicing and debranching machineries, has been experimentally validated for a handful of them [Unlike canonical miRNAs that require the microprocessor complex to produce the hairpin pre-miRNA, the so-called mirtron pathway is thought to require debranching of the lariat-intron produced by splicing, by a debranching enzyme dbr1, as a prerequisite to produce a hairpin pre-miRNA-like structure . Until n of them . More re of them ,52 but nEmbedding of genetic information for small regulatory RNAs within a longer mRNA or ncRNA provides an attractive concerted model for eukaryotic gene regulation, whereby multiple actors in the same pathways or in a given cellular context are produced from interdependent transcripts. The co-linear expression of miRNA and protein-coding genes may also function to ensure negative feedback on the protein-coding gene to prevent its over-expression. Indeed, while some intronic miRNAs are transcribed from their own promoter as independent transcription units, expression of intronic miRNAs has been widely linked to the regulation of expression of their host gene ,53. FurtSplicing of introns may also lead to the production of long non-coding RNAs with a circular structure (ciRNA). In human cells, Zhang and colleagues  have rec. Alternative splicing (AS) is a mechanism that allows the inclusion of non-coding sequences (introns) or excision of coding segments (exons) within mature mRNAs. While AS of introns represents a major event in plants, it accounts for only 2 to 5% of all alternative events in humans ,62. HoweWe already mentioned examples where incompletely spliced intron-retaining transcripts are exported to the cytoplasm where their maturation is completed under certain physiological or cellular contexts. This may seem surprising since, in the majority of cases, intron retention leads to premature stop codons that trigger the cellular surveillance machinery and degradation of such transcripts by the nonsense-mediated decay pathway (NMD) . Why andLY6G5B and LY6G6D genes located in the major histocompatibility complex (MHC) class III region on chromosome 6 can produce leukocyte antigen-6 (Ly6)-producing mRNA as well as intron-retaining non-coding transcripts that seem to be more abundant and stable than the correctly spliced isoform in most cell lines tested, and to escape NMD [Besides the already mentioned example of intron-retention that allows for fine tuning of protein production at the right place and at the right moment in dendritic cells and neurons ,36, intrcape NMD . This meWhen it is tightly coupled to NMD, orchestrated intron retention allows for fine control of expression levels of proteins involved in the immune response . It alsoMore directly, intron-retention participates in the diversification of the proteome, although, as we already mentioned, it is less commonly used in mammals than in plants. et al. [Other examples of intron-retained transcript together with their biological function in mammals can be found in et al. .i.e., RNAs for which both coding capacity and activity as functional RNA have been described [It is now evident that the transcriptional output of mammalian genomes is much more complex than estimates based on the number of protein-coding genes, and that non-coding RNA widely increase the source of regulatory molecules. We recently characterized a new class of ncRNAs, called bifunctional RNAs, escribed ,77,78,79et al. [Historically, the pioneer member of this new class of RNAs is SRA (Steroid Receptor RNA Activator). SRA was first identified as a structural ncRNA molecule in hormone receptor complexes, characterized by discrete stem-loop structures required for its function as a co-activator ,81 as exet al. . A few yet al. ,77,82,83et al. ,77. Wheret al.  which isi.e., in which intron retention disrupts the ORF permitting transcription of a ncRNA [An example of such a genetic locus producing both coding and non-coding RNA, depending primarily on an event of AS of intron , is no l a ncRNA . Specifi a ncRNA . Whereas a ncRNA . More in a ncRNA . Convers a ncRNA ,79. OtheCombined, the recent findings that alternative splicing of introns could produce RNAs with coding capacity or acting as functional ncRNAs and that splicing could directly generate small regulatory RNAs raise the fascinating assumption that a single transcription unit could generate multiple molecules including proteins, long or smaller regulatory ncRNAs such as miRNAs, and bring to light the central role of mammalian introns in the diversification of both proteome and transcriptome depending upon the need of the cell to respond to particular environmental settings.Introns have been regarded for a long time as “junk DNA” and remnants of archaic ancestral genomes. Questions about their origin and function arose immediately after their discovery in 1977, in particular regarding the energy waste that this represents for the cell to transcribe introns if they have to be eliminated from transcripts. Since then, accumulating evidence lent support to their fundamental importance in the regulation of mammalian gene expression programs, from transcriptional initiation, termination and stability, through recruitment of the exon-junction complex to recruitment of chromatin remodelers through the spliceosome.With introns representing more than half of the genome in higher eukaryotes and being absent from prokaryotic genomes, the apparent correlation between the genomic fraction occupied by introns and organism complexity must have some functional significance.In essence, eukaryotic cells use a variety of strategies to control their transcriptional output that employ a large number of regulatory factors that, in turn, must be tightly regulated. We provided examples whereby introns, as genetic entities or RNA segments, facilitate or participate in this amazing regulation feat by sheltering information for small regulatory RNAs allowing for concerted expression of multiple molecules in a given context, influencing where and when a messenger RNA is spliced and translated, preventing or attenuating translation off context or, on the contrary, diversifying the type and function of the molecules produced depending on the internal and external environment.All these intron-linked mechanisms add some levels of sophistication in the way mammalian cells gain their phenotypic variability and opened a whole new field of investigation where introns take central stage and emerge as key elements in shaping cell identity.


Rorippa indica, a wild crucifer, has been previously reported as the first identified plant in the germplasm of Brassicaceae known to be tolerant towards the mustard aphid Lipaphis erysimi Kaltenbach. We herein report the full-length cloning, expression, purification and characterization of a novel R. indica defensin (RiD) and its efficacy against L. erysimi. Structural analysis through homology modeling of RiD showed longer α-helix and 3rd β-sheet as compared to Brassica juncea defensin (BjD). Recombinant RiD and BjD was purified for studying its efficacy against L. erysimi. In the artificial diet based insect bioassay, the LC50 value of RiD against L. erysimi was found to be 9.099 ± 0.621 µg/mL which is far lower than that of BjD (43.51 ± 0.526 µg/mL). This indicates the possibility of RiD having different interacting partner and having better efficacy against L. erysimi over BjD. In the transient localization studies, RiD signal peptide directed the RiD: yellow fluorescent protein (YFP) fusion protein to the apoplastic regions which indicates that it might play a very important role in inhibiting nutrient uptake by aphids which follow mainly extracellular route to pierce through the cells. Hence, the present study has a significant implication for the future pest management program of B. juncea through the development of aphid tolerant transgenic plants.The online version of this article (doi:10.1186/s40064-016-2144-2) contains supplementary material, which is available to authorized users. Brassica juncea (Indian mustard) is one of the most important crops cultivated in India. More than three dozen insect pests are found to be associated with mustard crops in India, of which mustard aphid  is the most dreaded. These pests are able to reduce the yield up to 96 %  Hiern, a wild crucifer and an occasional shade loving weed was noted to be tolerant against mustard aphid. R. indica is found in the Indian subcontinent and Asia  were seen to be differentially regulated  for the present study.Vigna radiata  in transgenic rice  and belong to the γ-thionin family . Homology modelling was done to study the differences between the model structures of RiD and BjD. The RiD and BjD coding sequence were cloned, expressed and purified using prokaryotic expression system. For further characterization, transient localization of RiD was studied and finally the insecticidal potential of expressed RiD as well as that of BjD was checked through artificial diet based insect bioassay against L. erysimi.In the aforementioned background, the present study was conducted to characterize and study the efficacy of RiD against R. indica started to decline sharply with the appearance of the winged  form of the aphids. Among all the sets of infested and non-infested plants as shown in Fig. R. indica was seen to have lower aphid population with increasing days post infestation than B. juncea. The challenged R. indica plants were found to show normal development like the non-infested control plants  Fig. . After 4R. indica as well as in B. juncea was studied using the primers from the EST as previously described  through 9.45 and 9.67-fold at 24 and 48 h respectively  and B. juncea defensin (243 bp). A single intron in the RiD gene and a short region of 393 bp upstream element containing TATA box and other cis-acting elements were also identified , Arabidopsis (GenBank accession—NM106233.3), Sinapis alba (GenBank accession—AY998243) and Brassica rapa (GenBank accession—XM009106448) respectively at nucleotide level . Homology modelling clearly shows that despite having 86 % similarity at the amino acid level, the α-helix and 3rd β-sheet of RiD are little longer as compared with BjD  was used to calculate the electrostatic surface of the proteins. For both RiD and BjD, the outer surfaces of the proteins were seen to have more positive charge Fig. d–g.RiD and BjD were transformed into Rosetta (DE3) pLysS cells individually. The expression constructs produced a 6His-RiD and 6His-BjD fusion protein respectively, which were purified by Ni–NTA column. The maximum expression of RiD and BjD was obtained at 1 mM IPTG at 20° C after 16 h of incubation. As shown in Fig. The recombinant pET28a+ vectors harbouring the coding sequence of R. indica defensin, and other defensin-like proteins. The observed monoisotopic mass of tryptically digested peptides obtained by MALDI-TOF/TOF–MS and their position with respect to matched protein sequence are presented in Table R. indica, gi694199016) with score 47 and 48 % with defensin-like protein 1  with score 50.A MALDI-TOF/TOF–MS analysis was performed to verify the molecular mass of the purified RiD protein. MS analysis yielded a mass of 9067.364 Da for the purified peptide Fig. : Fig. S2R. indica defensin showed that RiD also has a putative N-terminal secretory signal peptide  and thus to the secretory pathway. A SignalP analysis  was calculated from the Abbot’s formula (Abbott P′ = C + P (1 − C), considering a population (P) which would have survived in the absence of the insecticidal agent used in the experiment and where C is natural mortality without the agent. LC50 value of RiD and BjD against L. erysimi were calculated accordingly using the statistical Probit analysis. LC50 value of RiD against L. erysimi was found to be 9.099 ± 0.621 µg/mL, whereas of BjD was found to be 43.51 ± 0.526 µg/mL  genes  has been successfully cloned, expressed, purified and characterized. Analysis of RiD and BjD through homology modelling showed structural difference through the presence of longer α-helix and 3rd β-sheet in the former one, despite having significant similarity in nucleotide level. Plant defensins are reported to have a broad spectrum of biological activities  with LC50 value of 13.47 ± 0.23 µg/mL  with LC50 value 20.7 ± 0.21 µg/mL  with LC50 value of 11.87 ± 0.229 µg/mL , temperature of 25 ± 2 °C and 75 % relative humidity. Mustard aphids (L. erysimi) were collected from the Madhyamgram Experimental Farm, Bose Institute, India. Thirty aphids of third-instar stage were forcedly infested upon each plant (under laboratory conditions previously mentioned), which were used for further experiments. Three plants with 30 aphids each were used as replicates.R. indica and B. juncea at an interval of every 24 h for 7 days, with three plants for each time point. Student’s t test at a significance level of P ≤ 0.05 was carried out to determine the significance of the infestation noted over the time course.The total aphid population was studied in both −∆∆Ct method  of all the infested plants at different time points as well as the non-infested control plants using Trizol reagent . First strand cDNA was synthesized using iScript-cDNA synthesis kit . The obtained cDNA was used for semi-quantitative analysis for the expression of PDF1.2c homolog and real-time PCR analysis using iQ SYBR Green Supermix (Bio-Rad Laboratories) in a iQ5 Multicolor Real-Time PCR Detection System (Bio-Rad Laboratories). Primers were designed on the basis of the previously identified EST (GenBank Accession—JK034054) . Genome walk was carried out according to the protocols of BD genome Walker™ Universal Kit . The primers were designed according to the sequence derived from RACE  to generate 3D coordinates of both RiD and BjD. Both the sequences were searched for a structure using Prime v3.4 module of Schrödinger molecular modelling suite  using RiDexp-F/RiDexp-R (for RiD) and BjDexp-F/BjDexp-R (for BjD) containing the BamHI  and SacI  sites  pLysS cell line . The recombinant cells were induced with 1 mM isopropyl-β-d-thiogalactopyranoside (IPTG) and incubated with constant shaking at 20 °C for 16 h. The recombinant cells were pelleted by centrifugation at 5000g at 4 °C for 30 min, resuspended in lysis buffer  and sonicated 30 times for 30 s each. The cell suspension was centrifuged at 10,000g for 30 min at 4 °C, and the supernatant was incubated for 2 h in 2 mL of nickel–nitrilotriacetic acid (Ni–NTA) column equilibrated with lysis buffer. The column was washed with wash buffer with 20 mM imidazole, pH 7.4 to remove nonspecific proteins, and finally, the target fusion protein was eluted with elution buffer with 250 mM imidazole, pH 7.4. All purification steps were carried out at 4 °C. The expression and purification of the recombinant proteins were analyzed in 12 % SDS-PAGE stained with Coomassie Brilliant Blue. The expressions of the proteins were further confirmed by western blot analysis using anti-His antibody (1: 5000) .The full-length coding sequence of Protein structures may lead to anomalously fast migration in SDS-PAGE  using RiDloc-F and RiDloc-R  was placed on each parafilm and was covered with another parafilm to make a pouch. The entire experiment was done in triplicate. Another experiment was set up with a range of different doses of BjD . Water was used as a no diet control to show that the provided liquid diet (without RiD and BjD) in comparison with water, can support the survival of the aphids. Aphid survivability was then recorded at every 12 h interval. Abbot’s formula was used to calculate the corrected mortality .Second instar nymphs were used for this experiment. Artificial diet was formulated using the original description by Dadd and Mittler . The expy Abbott . Statistthod Chi  was perf


Solvothermal processes are considered efficient approaches for the gram-scale production of graphene. Further modification of graphene by chemical doping is an important approach to tailor its properties. In this work, we successfully synthesized sulfur-doped graphene by using a solvothermal method with dimethyl sulfoxide as a precursor, which is a common laboratory reagent. Nitrogen-doped graphene was produced to demonstrate the generality of this process. These heteroatom-doped graphene materials exhibited high surface areas and high contents of heteroatoms. Furthermore, the lithium-ion storage properties and oxygen reduction reaction catalytic activity of these materials were also investigated. The success of this approach might facilitate the development of other advanced graphene-based materials with relative simplicity, scalability, and cost effectiveness for use in various potential applications. Graphene has attracted great interest in many research areas because of its unique structure and outstanding properties7912132, H2S, CS2, and benzyl disulfide) were studied as sources, and the catalyst activities of S-doped graphene for the oxygen reduction reaction (ORR) were investigated17232415Various elements  were selected in order to introduce into carbon frameworks to produce heteroatom-doped graphene151617181520213CH3SO, DMSO) into S-doped graphene. Furthermore, N-doped graphene was also synthesized using dimethylformamide , which is a N-containing organic molecule. These precursors are commonly used as low-cost solvents. It provides the benefits of a single step reaction with relatively mild synthesis conditions, gram-scale products, and higher contents of the heteroatom. The lithium-ion storage properties and electrocatalytic behaviors of heteroatomic-doped graphene were investigated.In this research, we describe a novel approach to fabricate S-doped graphene via a solvothermal method using S-containing organic molecules as a precursor. This method directly converts dimethyl sulfoxide  and carbon source (CCl4)2 hybridized carbon  mapping was carried out. ectively . The speectively . Graphitectively  correspo2 adsorption and desorption isotherms and pore size distributions of the heteroatom-doped graphene were also analyzed (2 g−1 and 317 m2 g−1 with the pore volumes (PVs) of 0.82 cm3 g−1 and 0.91 cm3 g−1, respectively. After annealing at high temperature (900°C) under an inert atmosphere, the respective BET surface areas of the S-doped graphene and N-doped graphene were increased to 1564 m2 g−1 (PV = 1.53 cm3 g−1) and 2255 m2 g−1 (PV = 1.73 cm3 g−1).The Nanalyzed . The Bru2-hybridization  was observed, and the samples produced a small peak corresponding to C-O bonds, carbonyls (C = O), and carboxylates (O-C = O) 17For elucidating the chemical structure of the S-doped graphene, X-ray photoelectron spectroscopy (XPS) was employed. The XPS spectra of the solvothermal graphene derived from methanol confirmed that carbon and oxygen were the only atoms present. However, sulfur and nitrogen signals could be clearly observed in the XPS spectra of the S-doped graphene and N-doped graphene, respectively . The higO-C = O) 30. The hO-C = O) . Lines a−1 at room temperature (−1). Interestingly, the specific capacities decrease during initial 30 cycles and gradually increase as the number of cycles increases in the S-doped graphene and solvothermal graphene. These activation processes can also be observed in other graphene-based electrodes3111th to 150th cycle was 97.2%, which is a relatively high value, but those of the S-doped and N-doped graphene were much higher . It was demonstrated that half-cell Coulombic efficiency could affect cycle retention in full lithium ion cells3111−1, respectively, at current density of 2500 mA g−1, which correspond to the respective delivered capacities of 44.9%, 40.7%, and 53.1% at a current density of 200 mA g−1. The theoretical capacity of graphene is 744 mAh g−1 through the formation of LiC3 in a condition where all the graphene layers present as monolayers35−1 to more than 1500 mAh g−1  as platinum electrode. The activity of doped carbon for the ORR has been improved by a combination of many factors, which have not yet been clarified4041174344RHE (see RHE) to compare the electron transfer number in 46To investigate the electrocatalytic activity of the S-doped graphene and N-doped graphene for the ORR and to confirm the doping effect, we performed rotating-disk electrode (RDE) voltammetry in 0.1 M KOH electrolyte . The N-doped graphene shows higher ORR activity than pristine solvothermal graphene. Further, N-doped graphene has a similar onset potential -doped graphenes were successfully synthesized by using a simple, single-step solvothermal method with heteroatom-containing organic molecules as precursors. This process provides for a gram-scale production using common laboratory reagents. The solvothermal (S or N)-doped graphenes exhibited high heteroatom content and surface area, and their characterization data indicate that they could be utilized in various energy storage and conversion applications. We believe that heteroatom-doped graphenes can be further extended to applications in sensors, electronics and biological research. We expect that our synthetic approach will be developed to produce doped carbon materials based on other elements  which can then increase the method's potential applications.2 gas flow. The colorless mixture was boiled at around 250°C and was slowly thickened. After boiling for ~24 h, the liquid was converted into a black cake-like substance. Finally, the samples were washed with hydrochloric acid (10 wt%) and deionized water several times, and then dried in an oven at 90°C. The final yield of S-doped graphene is ~35 mg per 1 ml of DMSO  and deionized water several times, and then dried in an oven at 90°C.Solvothermal graphene were prepared according to a literature procedure using methanol as the precursorTEM images and TEM-EDS images were obtained using a JEOL JEM-1010 and JEM-2100F, respectively. AFM images were obtained using a Veeco atomic force microscope. Raman spectroscopy measurements were carried out on a Dongwoo DM500i Raman spectrometer using green (514.5 nm) laser excitation. BET surface area and BJH pore size distributions were measured by using a Micromeritics Tristar 3000. XPS was carried out using a Kratos AXIS-HSi. Elemental analysis was performed using a Thermo Scientific Flash 2000 analyzer at NCIRF .2 for battery applications. For the preparation of working electrodes, a well-mixed slurry of synthesized graphene, Super P and poly (vinylidene fluoride) in N-methyl-2-pyrrolidone (at a weight ratio of 70:10:20) was coated on a copper current collector. After drying, the electrodes were pressed and dried again at 120°C under vacuum. Two electrode 2016-type coin cells were fabricated with prepared working electrodes and lithium foil (as both counter and reference electrodes) in argon filled glove box. 1.0 M LiPF6 dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 in volume ratio) was used as the organic electrolyte. All the voltage ranges for the battery tests in this study were set between 3.0 and 0.01 V (vs. Li+/Li). The specific capacities were calculated only according to the weight of the active material and the weights of additives (binder and conductive agent) were not included.Samples were prepared by heat treatment at 600°C in N2 for electrocatalytic applications. Electrochemical measurements were conducted using an Autolab PGSTAT 101 in a standard three-compartment electrochemical cell. In all experiments, a Ag/AgCl reference electrode was used as the reference electrode, and Pt wire was used as the counter electrode. All potentials referred to in these ORR experiments were converted to the pH-independent reversible hydrogen electrode (RHE) using the hydrogen oxidation reaction. Three kinds of graphene samples (5 mg) and 20 μL of 5 wt% Nafion ionomer were each dispersed 0.4 mL of 2-isopropyl alcohol by sonication for 10 min. For RDE, 7 μL of catalyst ink was loaded onto an RDE with a 0.000196 m2 glassy carbon disk. The electrode rotation speed was 1600 rpm , 0.1 M KOH electrolyte. To calculate the electron transfer number (0.6 VRHE), RDE measurements were conducted using different rotating speeds 400, 900, 1200, and 1600 rpm.Samples were prepared by heat treatment at 600°C in NB.Q. proposed the concept and performed the experiment. S.-H.Y. and A.J. carried out lithium storage properties. D.Y.C. carried out electrocatalytic performances. J.H.P. carried out the AFM data. Y.P., B.Q. and S.-H.Y. co-wrote the manuscript. Y.P. and Y.-E.S. coordinated and supervised the work.Single Source Precursor-based Solvothermal Synthesis of Heteroatom-doped Graphene and Its Energy Storage and Conversion Applications


The superior photoconductive behavior of a simple, cost-effective n-GaN nanorod (NR)-graphene hybrid device structure is demonstrated for the first time. The proposed hybrid structure was synthesized on a Si (111) substrate using the high-quality graphene transfer method and the relatively low-temperature metal-organic chemical vapor deposition (MOCVD) process with a high V/III ratio to protect the graphene layer from thermal damage during the growth of n-GaN nanorods. Defect-free n-GaN NRs were grown on a highly ordered graphene monolayer on Si without forming any metal-catalyst or droplet seeds. The prominent existence of the undamaged monolayer graphene even after the growth of highly dense n-GaN NRs, as determined using Raman spectroscopy and high-resolution transmission electron microscopy (HR-TEM), facilitated the excellent transport of the generated charge carriers through the photoconductive channel. The highly matched n-GaN NR-graphene hybrid structure exhibited enhancement in the photocurrent along with increased sensitivity and photoresponsivity, which were attributed to the extremely low carrier trap density in the photoconductive channel. The vapor-liquid-solid (VLS) technique25In the present study, we sought to form a GaN NR-graphene hybrid structure using the MOCVD technique while maintaining the original properties of the GaN nanorods and graphene. The material and electrical features of this integrated heterostructure were analyzed to assess their potential for developing high-efficiency photoconductive devices. Moreover, the growth of this hybrid structure was achieved on a bare Si substrate without forming silicon dioxide or silicon nitride; furthermore, to avoid contamination, no metal-catalyst was used to grow the GaN NRs. The aim of this study was to demonstrate the highly matched co-existence of well-formed monolayer graphene and GaN NRs in a hybrid structure grown on a Si substrate without using any metal catalyst utilizing the MOCVD process to minimize the production costs. The realization of a high-performance ultraviolet photoconductive device using this hybrid structure was another purpose of this work.−1 and a 2D-band at approximately 2673 cm−1, which are typical peak positions for defect-free graphene282) that predominantly exhibit typical monolayer properties, as identified by the IG/I2D ≤ 0.38 and the FWHM of the 2D band of ≤38 cm−1. Chu et al.2/Si (100) with a G-band/2D-band peak intensity ratio ≤0.4, whereas Kwak et al.G/I2D ≈ 0.38) grown using the CVD process and then transferred to a Si (111) substrate. To our knowledge, this study represents the finest graphene layer transferred directly to a Si substrate reported thus far29S from 4 to 500 μm. A geometry correction was extracted by fitting the measured resistances to the following equation3132The fabrication sequences involved in the process used to synthesize n-GaN NR-graphene hybrid structures are shown in RT is the total resistance between the channel spacing of the contact pads, Rs is the sheet resistance of the graphene films, r1 is the radius of the inner circular contact, S is the channel spacing of the contact pads, and LT is the transfer length. From the linear fit (red line), the estimated sheet resistance and transfer length of the graphene films were Rs ≈ 483 ohm/sq and LT ≈ 13.60 μm, respectively, implying that highly crystalline monolayer graphene films were transferred onto the Si substrate.Here, c-plane. With the integration of a graphene layer, the XRD peaks indicated the existence of GaN NRs grown along the c-plane, i.e., along the (002) and (004) planes (2O3 listed in the Joint Committee on Powder Diffraction Standards (JCPDS) cards No. 50-0792 and 20-0426, respectively.) planes ; the str−1 and 567 cm−1, respectively  images showed that the n-GaN NRs were uniformly grown along the irection . To veriirection ; in addiP is defined as (Imaxdark) at a specific bias voltage22P/Idark) with bias for the bare Si substrate and for n-GaN NRs on the same substrate without and with a graphene layer; the sensitivity was estimated to be approximately 10%, 4%, and 60%, respectively, at a bias voltage of The photocurrent behavior of the bare semi-insulating Si (111) substrate during photoconductivity measurements is shown in  results . The low results , might b results , enhance results  and impr results  of the GP/(Illuminated area × Power density of light)22 and maintained the same dimensions of the illuminated area for all of the channels. At a bias of 2.0 V, the absolute photoresponsivity was calculated to be 20, 21, and 106 mA/W, respectively, for the bare Si substrate, n-GaN NRs grown without graphene and n-GaN NRs with graphene. As et al.214237The same behavior of the photocurrent and sensitivity was repeated when the photoresponsivity of these three channels was compared . The phop ∞ Px235p would increase linearly with increasing optical power when the trap level density is lower. To support this fact, the exponent x should be approximately 1 in the power law. If the photoconductive channel possesses a high density of trap levels, x should be significantly smaller than 1. When the photocurrent values were fitted in 2. The evidence of minimal defects or trap states in the channel reveals why this MOCVD-grown n-GaN NR-graphene hybrid structure on Si is ideal for use in cost-effective, highly efficient photoconductive device applications. The photocurrent values, which are associated with the spectral response, were measured to be almost constant at approximately 36 mA at wavelengths up to an abrupt cut-off wavelength of 380 nm  substrate using a high-quality graphene transfer method and the relatively low-temperature MOCVD process with a high V/III ratio. Raman spectroscopy and HR-TEM images confirmed the presence of monolayer graphene highly matched with n-GaN NRs in the hybrid structure. The excellent electrical conduction properties of the graphene monolayer transferred on Si (111) not only affected the growth of defect-free, highly dense n-GaN NRs but also improved the material quality. As a result, the n-GaN NR-graphene hybrid structure under study represents the superior characteristics of an ultraviolet photoconductive device with extremely low carrier trap density. Moreover, the synthesis of the hybrid structure directly on a Si substrate by the growth of n-GaN NRs without using metal-catalyst or droplet seeds added special significance. To our knowledge, such simple, cost-effective and highly efficient ultraviolet photoconductive devices fabricated using highly matched n-GaN NR-graphene hybrid structures are reported here for the first time.3PO4 (85%) solution to obtain a flat and smooth Cu foil surface with a root-mean-square surface roughness of less than 15 nm (in the scanning area of 100 μm × 100 μm). After the Cu foil was loaded into a low-pressure chemical vapor deposition (LP-CVD) system, it was heated to a process temperature of 1050 °C and maintained for 60 min under 5 sccm of H2 for in situ surface cleaning. A monolayer graphene film was then grown for 15 min under a CH4/H2 mixture  with a reactor pressure of approximately 90 mTorr. After graphene growth, the chamber was rapidly cooled to room temperature with a flow of H2. Following graphene growth, the graphene film was transferred onto a Si substrate for further investigation. In all of our growth experiments, monolayer graphene was observed to grow on both sides of the Cu foil; therefore, the backside of the Cu foil was pre-treated with oxygen plasma to remove the undesired graphene film. To transfer the graphene film to a Si substrate, poly(methyl methacrylate) (PMMA) was spin-coated onto the graphene grown on Cu foil, and the PMMA/graphene/Cu foil was then cured on a hot plate at 180 °C for 1 min. The Cu foil was then etched from the PMMA/graphene/Cu foil assembly using an aqueous solution of (NH4)2S2O8. The PMMA/graphene assembly was subsequently washed with deionized water, transferred onto a semi-insulating Si (111) substrate and dried. The PMMA was then removed using acetone.First, a Cu foil  was electrochemically polished in H3), respectively; silane (SiH4) gas was used for n-type doping, and hydrogen was used as the carrier gas. To grow n-GaN nanorods, TMGa, NH3 and SiH4 were introduced into the reactor chamber for 45 min at flow rates of 0.2 sccm, 3.0 SLM and 10 sccm, respectively . To protect the graphene layer from thermal damage during the growth of the n-GaN nanorods, the growth temperature was fixed at 870 °C, which is relatively low compared to the usual temperatures of greater than 1000 °Cn-GaN nanorods were grown on the graphene-transferred Si (111) substrate using a relatively low-temperature MOCVD process and a high V/III ratio without the formation of any metal-catalyst or droplet seeds. The precursors for gallium and nitrogen were trimethylgallium (TMGa) and ammonia  within the range of 300–550 nm. A monochromator (Oriel Cornerstone 130) was used to provide the monochromatic light incident on the channel.Raman spectroscopy was performed using a WiTec Alpha 300R M-Raman system; the excitation wavelength was 532 nm. The results of the Raman study were used to confirm the existence of highly ordered graphene films. The surface morphology of the n-GaN NRs was analyzed using FE-SEM. A Hitachi S-7400 system was used for the FE-SEM study; it was operated at 15 kV and at a 13° tilt-view. Single-crystal XRD measurements were performed using a Rigaku diffractometer equipped with a Cu-Kα radiation source. The morphology of the n-GaN NR-graphene heterostructures was further revealed by cross-sectional HR-TEM. A JEOL JEM 2010 system operated at 200 kV was used for the HR-TEM study. Samples of the hybrid structure were prepared by being coated with platinum using a dual-beam focused ion beam  technique with a beam current of 65 nA and a resolution of 7 nm at 30 kV. The optical properties of the n-GaN NRs were investigated by photoluminescence (PL) spectroscopy at room temperature using the 325 nm line of a He-Cd laser as an excitation source. For photoconductivity measurements of the fabricated ultraviolet photoconductive device, we utilized a solar simulator (McScience Lab 100) as a light source. This light source generated white light with a maximum power density of 100 mW/cmHow to cite this article: Kang, S. et al. Ultraviolet photoconductive devices with an n-GaN nanorod-graphene hybrid structure synthesized by metal-organic chemical vapor deposition. Sci. Rep.5, 10808; doi: 10.1038/srep10808 (2015).