Premium
Structural versatility of peptides from C α,α ‐dialkylated glycines. I. A conformational energy computation and x‐ray diffraction study of homo‐peptides from C α,α ‐diethylglycine
Author(s) -
Benedetti E.,
Barone V.,
Bavoso A.,
Di Blasio B.,
Lelj F.,
Pavone V.,
Pedone C.,
Bonora G. M.,
Toniolo C.,
Leplawy M. T.,
Kaczmarek K.,
Redlinski A.
Publication year - 1988
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.360270302
Subject(s) - chemistry , pentamer , tripeptide , dipeptide , crystallography , peptide , monomer , stereochemistry , residue (chemistry) , side chain , crystal structure , polymer , organic chemistry , biochemistry
Conformational energy computations on a derivative and a homo‐dipeptide of C α,α ‐diethylglycine were performed. In both cases the N‐ and C‐terminal groups are blocked as acetamido and methylamido moieties, respectively. It was found that the C α,α ‐diethylglycine residues are conformationally restricted and that the minimum energy conformation corresponds to the fully extended C 5 structure when the NC α C′ bond angle is smaller than 108° (as experimentally observed). The results of the theoretical analysis are in agreement with the crystal‐state structural propensity of the complete series of N ‐trifluoroacetylated homo‐peptides of this C α,α ‐dialkylated residue from monomer to pentamer, determined by x‐ray diffraction and also described in this work. Interestingly, for the first time, a crystallographically planar peptide backbone was observed (in the protected tripeptide). A comparison with peptides of C α,α ‐dimethylglycine, C α ‐methyl, C α ‐ethylglycine, and C α,α ‐di‐ n ‐propylglycine indicates that the fully extended conformation becomes more stable than the helical structures when both amino acid side‐chain C β atoms are substituted.