Electronic CD study of a helical peptide incorporating Z-dehydrophenylalanine residues: conformation dependence of the simulated CD spectra.
Electronic circular dichroism (CD) spectra as well as transitions from ground to excited states were predicted for a helical nonapeptide based on alternative sequence--[Z-alpha,beta-dehydrophenylalanine (Delta(Z)Phe)-X]--through semiempirical molecular orbital computation combined with time-dependent (TD) method. The simulation was performed for its various conformers that differ in helix type, helix sense, and Delta(Z)Phe side-chain orientation. These conformational variations have been shown to depend largely on its CD spectra. Comparison between simulated and observed CD profiles reveals that peptide 1 in solution favors a right-handed 3(10)-helix that adopts phenyl (Delta(Z)Phe) planes basically in a vertical orientation with respect to the helix axis. These predictions were essentially supported from CD simulation of a shorter helical analogue at ab inito or density functional TD levels. The theoretical CD-conformation relationship should provide us useful guideline for determination of helix sense in the dehydropeptide, and for estimation of its conformations statistically averaged in solution.
Komori
Hisatoshi
H
Department of Environmental Technology and Urban Planning, Shikumi College, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan.
Inai
Yoshihito
Y
D002942:Circular Dichroism; D003198:Computer Simulation; D004581:Electronics; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D017433:Protein Structure, Secondary; D013997:Time Factors
D010455:Peptides; D010649:Phenylalanine; C018632:phenyldehydroalanine