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Investigates the gramicidin A folding process and determines the intermediates involved during the incorporation of gramicidin A into the channel state in a model membrane environment. Gramicidin A's adoption of various conformations depending on its environment; Conformational transitions to form ion channels in sodium dodecyl sulfate (SDS) micelles.

The 31P shielding tensor for PH3 has been calculated without electron correlation (self-consistent field) and with electron correlation (second-order Mo\llet–Plesset) using the gauge including atomic orbital method. The best results obtained for the absolute isotropic chemical shielding constant (608.09 ppm) and chemical shielding anisotropy (64.54 ppm) compare quite favorably with the experimental values of 600 and 64.5 ppm. The contribution of electron correlation to the absolute shielding value has been found to be significant. The convergence of the calculated shielding tensor with respect to the quality of the basis set employed and the importance of d and f polarization orbitals are discussed. [ABSTRACT FROM AUTHOR]

Investigates Gramicidin-lipid interactions using diacylphosphatidylcholines (PC) containing two identical acyl chains of varying length. Conformation of Gramicidin A (gA); Micellar organization of PC; Fractionation of gA proportional to acyl chain length; Factors affecting channel structure; Reciprocal gramicidin-lipid interactions.

Following on from our previous work on Sc, Fe, Cr, and Al (Part I; see J. Phys. Chem. A, 105 (2001) 238), the geometries and infrared spectra of the trivalent metal tris-acetylacetonate complexes (M[O2C5H7]3; M=Ti, V, Mn, Co) have been studied both experimentally and theoretically using nonlocal hybrid density functional theory with a split-valence plus polarization basis for the ligand and valence triple-ξ for the metal. Unlike the D3 complexes studied in Part I, those of Ti, V and Mn are candidates for Jahn-Teller distortion due to fractional d-shell occupancy. Using scale factors transferred from Part I, our calculated frequencies are in very good agreement with experimentally observed fundamentals. Our investigation shows that the V and Mn complexes distort to C2 ground states, but D3 Ti tris-acetylacetonate is stable. Further investigation of the weak band observed around 800 cm−1 in the Fe complex (and present in almost all studied first-row transition metal tris-acetylacetonates), which we were unable to assign theoretically in Part I, supports the argument that this band is not a fundamental but is due to Fermi resonance. [Copyright &y& Elsevier]

Investigates the structures of gramicidins A, B, and C incorporated into sodium dodecyl sulfate micelles. Channel-forming antibiotic; Gramicidin family of linear polypeptides; Correlation of amino acid composition; Mixture of nine pantadecapeptides; Monovalent cation transport; Incorporation of the structures into deuterated sodium dodecyl sulfate micelles.