Two β-forms and the α-helix of N-octanoyl-L-glutamic acid oligomers

Abstract

N-Octanoyl-L-glutamic acid oligomers (residue number, N = 3-6, 8, 10, 12, 14, 16, 18, 20 and 22) have been synthesized in order to study their molecular conformations in the solid state. The X-ray diffraction powder patterns and the vibrational spectra of these oligomers have been investigated and compared with those of two /?-forms (fil and /?*) and the a-helix of poly(L-glutamic acid). The results are summarized as follows. These oligomers take up a plor /?,-like structure, similar to that of the two /?-forms of poly(L-glutamic acid). The methods used to precipitate the samples are related to the conformational preferences in the solid state. P1 t) p2 interconversion is possible by reprecipitation of the sample. Preferential stabilization of the P1or /?,-forms is strongly dependent on the residue number. Films of the oligorners, made by casting them from a dimethylformamide solution onto NaCl or KBr plates, take up an a-helical structure, and the a -+ P1 or a -+ p2 transition depends on the residue number of the cast film.

Fourier transform IR study of aggregational behavior of N‐acetyl‐L‐ and N‐butyloxycarbonyl‐L‐glutamic acid oligomeric benzyl esters in dioxane and benzene: β‐Turn → antiparallel β‐sheet transition

“…The A N p Z and BOC N p Z with exact residue numbers were prepared from N ‐ tert ‐butyloxycarbonyl‐ L ‐glutamic acid γ‐dibenzyl ester and L ‐glutamic acid α,γ‐dibenzyl ester toluene p ‐sulfonate (The Peptide Institute, Inc., Osaka, Japan) by the stepwise procedure described previously 33…”