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Structural versatility of peptides from C α, α ‐disubstituted glycines: Crystal‐state conformational analysis of homopeptides from C α ‐methyl, C α ‐benzylglycine [(αMe)Phe] n
Author(s) -
Valle Giovanni,
Pantano Monica,
Formaggio Fernando,
Crisma Marco,
Toniolo Claudio,
Précigoux Gilles,
Sulzenbacher Gerlind,
Boesten Wilhelmus H. J.,
Broxterman Quirinus B.,
Schoemaker Hans E.,
Kamphuis Johan
Publication year - 1993
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360331011
Subject(s) - tripeptide , dipeptide , chemistry , tetrapeptide , intramolecular force , stereochemistry , crystal structure , chirality (physics) , amino acid , helix (gastropod) , peptide , crystallography , chiral symmetry , ecology , biochemistry , nambu–jona lasinio model , physics , quantum mechanics , snail , biology , quark
The molecular and crystal structures of one derivative and three homopeptides (from the di‐to the tetrapeptide level) of the chiral, C α, α ‐disubstituted glycine C α ‐methyl, C α ‐benzylglycine [(αMe)Phe], have been determined by x‐ray diffraction. The derivative is mClAc‐ D ‐(αMe)Phe‐OH, and the peptides are p BrBz‐[ D ‐(αMe)Phe] 2 ‐NHMe, p BrBz‐[ D ‐(αMe)Phe] 3 ‐OH hemihydrate, and p BrBz‐[ D ‐(αMe)Phe] 4 ‐O t Bu sesquihydrate. All (αMe)Phe residues prefer ϕ,ψ torsion angles in the helical region of the conformational map. The dipeptide methylamide and the tripeptide carboxylic acid adopt a β‐turn conformation with a 1 ← 4 CO…HN intramolecular H bond. The structure of the tripeptide carboxylic acid is further stabilized by a 1 ← 4 CO…HO intramolecular H bond, forming an “oxy‐analogue” of a β‐turn. The tetrapeptide ester is folded in a regular (incipient) 3 10 ‐helix. In general, the relationship between (αMe)Phe chirality and helix screw sense is opposite to that exhibited by protein amino acids. A comparison is made with the conclusions extracted from published work on homopeptides from other C α ‐methylated α‐amino acids. © 1993 John Wiley & Sons, Inc.