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Conformational properties of the sequential polyproline analogs poly(Pro‐Aze‐Pro) and poly(Aze‐Pro‐Aze)
Author(s) -
Boni R.,
Di Blasi R.,
Farina A.,
Verdini A. S.
Publication year - 1976
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.1976.360150702
Subject(s) - polyproline helix , chemistry , pyrrolidine , peptide , proline , stereochemistry , solvent , azetidine , residue (chemistry) , amino acid , organic chemistry , biochemistry
The lack of the positive band at around 226 nm in the CD spectra of poly(prolyl‐azetidine‐2‐carbonyl‐proline) in trifluoroethanol and of poly(azetidine‐2‐carbonyl‐prolyl‐azetidine‐2‐carboxylic) acid in F 3 EtOH and water, the hyperchromism of the absorption maximum at about 202 nm, and the extremely small intensity of the C β ‐Pro, C γ ‐Pro, and C β ‐Aze signals for the cis peptide bonds in the 13 C nmr spectrum of poly(Pro‐Aze‐Pro) in F 3 EtOH indicate that both polyproline analogs exist as disordered chains in this solvent, the trans peptide group being maintained. The disordering of the chains is attributed to an increase in the accessible range of ψ due to the reduced dimensions of the square ring of L ‐azetidine‐2‐carboxylic acid residue relative to the pyrrolidine ring of proline and to strong interactions of the haloalcohol with the peptide groups of the chains.