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Quantum topology phase diagrams for the cis ‐ and trans ‐isomers of the cyclic contryphan‐Sm peptide
Author(s) -
Figueredo Fernando A.,
Maza Julio R.,
Kirk Steven R.,
Jenkins Samantha
Publication year - 2014
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24784
Subject(s) - topology (electrical circuits) , chemistry , peptide , atoms in molecules , molecule , cyclic peptide , quantum , folding (dsp implementation) , cis–trans isomerism , amino acid , crystallography , stereochemistry , computational chemistry , quantum mechanics , physics , mathematics , combinatorics , organic chemistry , biochemistry , electrical engineering , engineering
Within the quantum theory of atoms in molecules (QTAIM) framework we present a quantum topology phase diagram (QTPD) using the Poincaré–Hopf relation of a total of 17 all new QTAIM topologies of the cis ‐ and trans ‐isomers of the cyclic contryphan‐Sm peptide. The resultant QTPD consists of separate regions for the cis ‐ and trans ‐isomers that only overlap for topologies associated with the lowest energy minima of the cis ‐ and trans ‐isomers. We determine the QTAIM topologies of 29 “missing” isomers. A new, contracted formulation of the QTPD is presented, this contracted formulation includes the interamino acid bond critical points (BCPs) that link together the amino acid units, the disulphide bridge “pivot” BCP and side chain bonding interactions. The seven interamino acid BCPs linking the amino acid units coincide with the so‐called peptide backbone, the conventional qualitative approach to reduce the complexity of the peptide. We expand the interpretation of ellipticity to include the associated eigenvectors and find that higher values of the ellipticity ɛ are associated with a greater preference to conserve folding states. We quantify previous qualitative findings that suggested the disulfide bond is central to the folding behavior of the cyclic contryphan‐Sm peptide and why the cis ‐isomer is the major form of the cyclic contryphan‐Sm peptide. © 2014 Wiley Periodicals, Inc.