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Vibrational and electronic optical activity of the chiral disulphide group: Implications for disulphide bridge conformation
Author(s) -
Bednárová Lucie,
Bouř Petr,
Maloň Petr
Publication year - 2009
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20772
Subject(s) - chemistry , raman optical activity , degenerate energy levels , chirality (physics) , sign (mathematics) , group (periodic table) , molecule , symmetry (geometry) , computational chemistry , crystallography , stereochemistry , symmetry breaking , quantum mechanics , organic chemistry , geometry , physics , mathematical analysis , chiral symmetry breaking , mathematics , nambu–jona lasinio model
Using dihydrogendisulphide (H 2 S 2 ), dimethyl‐ ((CH 3 ) 2 S 2 ), and diethyldisulphide ((CH 3 CH 2 ) 2 S 2 )as model molecules, theoretical ECD, VCD, and ROA spectra of nonplanar disulphides were calculated by DFT methods. Most of the calculated electronic and vibrational chiroptical features suffer an equivocal relation between calculatedsigns of ECD, VCD, or ROA and the sense of disulphide nonplanarity as noted earlier for low‐lying ECD bands. This is a consequence of local C 2 symmetry of a disulphide group causing most electronic and vibrational transitions to occur as pairs falling to alternative A, B symmetry species, which become degenerate and switch their succession (and consequently the observed chiroptical sign pattern) at the energetically most favorable perpendicular conformation. According to present calculations, the key to resolving this ambiguity may involve the SS stretching vibrational mode at ∼500 cm −1 . The relation of signs of the relevant VCD and ROA features to sense of disulphide chirality seems simpler and less ambiguous. The right‐handed arrangement of the SS group (0 < χ SS < 180°) results in mostly negative VCD signals. Although relation to ROA still suffers some ambiguity, it gets clearer along the series H 2 S 2 –(CH 3 ) 2 S 2 –(CH 3 CH 2 ) 2 S 2 . ROA is also attractive for the analysis of disulphide‐containing peptides and proteins, because applying it to aqueous solutions is not problematic. Chirality, 2010. © 2009 Wiley‐Liss, Inc.