Photoelectron spectra and bonding in phosphorus compounds
Abstract
A theoretical study of the electronic structure of phosphine oxide and trimethylphosphine oxide and the donor–acceptor properties of phosphine and trimethylphosphine
The results of ab initio SCF MO calculations on phosphine oxide and trimethylphosphine oxide are described and used to discuss the donor–acceptor properties of the phosphines. In both molecules the P–O bond has significant σ- and π-contributions, the latter involving to a large extent the phosphorus 3d-orbitals.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.