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Experimental study on aggregation of model dipeptide molecules. V. Stereoselective association of leucine dipeptides
Author(s) -
Cung Manh Thong,
Marraud Michel,
Neel Jean,
Aubry André
Publication year - 1978
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.1978.360170505
Subject(s) - chemistry , dipeptide , stereoselectivity , dimer , molecule , monomer , nuclear magnetic resonance spectroscopy , stereochemistry , leucine , computational chemistry , crystallography , organic chemistry , polymer , amino acid , biochemistry , catalysis
Infrared spectroscopy and 1 H nmr have been used to elucidate the association modes of leucine dipeptides in carbon tetrachloride solution. Two stereoselective types of aggregates have been evidenced. Homochiral molecules are associated in oligomeric aggregates and accommodate a β‐parallel‐like structure which was characterized by x‐ray diffraction. Heterochiral molecules are paired in centrosymmetrical dimers; the latter aggregation mode restricted to the dimer stage predominates in racemic solutions. A theoretical model proposed to account for this aggregation process is consistent with the experimental nmr data. Both homo‐ and heterochiral association constants are estimated from vapor pressure and nmr experiments.