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Evidence for stereospecific collision complexes of cyclo(tri‐ L ‐prolyl) with benzene
Author(s) -
Torchia D. A.,
Deber C. M.
Publication year - 1972
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.1972.360110310
Subject(s) - chemistry , stereospecificity , toluene , benzene , nitrobenzene , ring (chemistry) , peptide , chemical shift , stereochemistry , resonance (particle physics) , solvent , crystallography , organic chemistry , catalysis , biochemistry , physics , particle physics
NMR spectra of cyclo(tri‐ L ‐prolyl), c‐(P) 3 , show large shifts of the H α resonance on adding C 6 D 6 to a solution of c‐(P) 3 in CD 2 Cl 2 . CPK models and observed coupling constants indicate a rigid c‐(P) 3 conformation, independent of solvent composition, suggesting that these shifts result from formation of stereospecific C 6 D 6 –c‐(P) 3 collision complexes in which the c‐(P) 3 H α lie near the face of the aromatic ring. The temperature dependence of the H α shifts and the solvent dependent shifts observed on adding toluene‐ d 8 or nitrobenzene‐ d 5 to the c‐(P) 3 solution suggest that preferred C 6 D 6 –c‐(P) 3 orientations result from attractive interactions between the electron‐rich aromatic ring and the electropositive H α 's and/or δ + nitrogen atoms in the peptide backbone. Reports of such interactions in increasingly diverse peptide model systems suggest that they may play a role in stabilizing protein structures.