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Chain conformation in polyretropeptides: Quantum mechanical and empirical force field calculations on 2,6,8‐trioxo‐3,5,9‐triazadecane, a model compound for poly(retro‐glycine)
Author(s) -
Alemán Carlos,
Bella Jordi
Publication year - 1995
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.360350302
Subject(s) - chemistry , force field (fiction) , molecule , maxima and minima , polymer , crystallography , chain (unit) , crystal structure , copolymer , torsion (gastropod) , stereochemistry , computational chemistry , quantum mechanics , organic chemistry , mathematics , surgery , medicine , mathematical analysis , physics
We report here our results on semiempirical AM1 calculations for the conformational preferences of 2,6,8‐trioxo‐3,5,9‐triazadecane, a model compound for polymers made of retropeptide units. We have evaluated the effect of applying symmetry constraints between chemically equivalent torsion angles. These results suggest that preferred conformations around the NHCH 2 NH group are quite independent from those on the COCH 2 CO unit, so all possible combinations generate the complete set of energy minima for the model compound. We have analyzed the implications of the different minimum energy conformation in an infinite chain model and we have explored the conformational space of regular polyretropeptides. This shows a close relation to that of regular polypeptides but with significant differences arising from the change of orientation of the peptide units along the polymer molecule. The energy calculations also support previously proposed models for the crystal structure of the simplest polyretropeptide, poly( retro ‐glycine). Finally, we discuss the consequences of retropeptide‐peptide copolymerization as well as the expected conformations for regular alternate terpolymers. © 1995 John Wiley & Sons, Inc.