Fourier transform IR study of aggregational behavior of N-acetyl-L- and N-butyloxycarbonyl-L-glutamic acid oligomeric benzyl esters in dioxane and benzene: beta-turn --> antiparallel beta-sheet transition.
Oligomeric N-acetyl-L-glutamic acid benzyl esters (AN(p)Z) with exact residue numbers (N(p) = 2, 3, 4, and 5) and N-butyloxycarbonyl-L-glutamic acid benzyl esters (BOCN(p)Z) with exact residue numbers (N(p) = 4, 5, 6, and 8) are synthesized by a stepwise procedure in a liquid phase. The aggregational behavior of these oligomeric molecules in dioxane and benzene is examined by Fourier transform IR spectra. In particular, the concentration dependence of the IR spectra for the AN(p)Z solutions with N(p) values of 4 (A4Z) and 5 (A5Z) shows that the predominant antiparallel beta-sheet structure is stabilized above the critical aggregation concentration (cac), while other conformations including beta-turns may coexist below the cac. This fact provides evidence that aggregation induces the conformational transition from other conformers (probably beta-turns) to an antiparallel beta-sheet form. The IR results for the A3Z and A2Z solutions indicate that specific conformers (beta-turns), which are different from the beta-sheet structure, may be preferentially stabilized upon aggregation. Thus, the critical residue number of the AN(p)Z oligopeptides, which is essential for formation of a rodlike aggregate in dioxane and benzene, is 4 or 5.
Okabayashi
Hirofumi
H
Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso-Cho, Showa-Ku, Nagoya 466-8555, Japan. fwiw4348@mb.infoweb.ne.jp
Ishida
Makoto
M
Tamaoki
Harushiko
H
Masuda
Hideki
H
O'Connor
Charmian J
CJ
D000595:Amino Acid Sequence; D001554:Benzene / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry*; D004951:Esterification; D004952:Esters / Q000737:chemistry*; D005971:Glutamates / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry; D011091:Polyesters / Q000138:chemical synthesis*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
D004146:Dioxanes; D004952:Esters; D005971:Glutamates; C467666:N-acetyl-L-glutamic acid benzyl ester; D009842:Oligopeptides; D011091:Polyesters; D018698:Glutamic Acid; D001554:Benzene; C025223:1,4-dioxane