The parity-violating energy difference between enantiomeric molecules

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The parity-violating weak neutral current perturbation of the groundstate electronic energy has been calculated, by ab initio methods, for the (S)-isomer of hydrogen peroxide, over a range of standard Gaussian basis sets. The STO-N-31G, but not the STO-NG, sets give energy shifts Epv which converge with increasing N towards the corresponding Epv value given by an extended basis. Calculations for ±-amino acids, peptides, model helical systems, with the STO-6-31G basis, or with an analogous set for corre-sponding sulphur analogues, show that the Epv shift is sensitive in sign and magnitude to the molecular conformation generally. It is found that L-alanine and the L-peptides in the ±-helix and the -sheet conformation have a lower ground state energy than the corresponding D-enantiomers due to the WNC interaction. The energy shift Epv only approximates to an expected Z5 proportionality, and it does not correlate consistently in sign with the handedness of a helical system.

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Bibliography, Theoretical or Mathematical/ ab initio calculations GO calculations hydrogen compounds STO calculations weak interactions (molecular physics)/ alpha-helix conformation H 2O 2 parity-violating energy difference enantiomeric molecules parity-violating weak neutral current perturbation ground-state electronic energy ab initio methods ( S)-isomer standard Gaussian basis sets STO-N-31G energy shifts alpha-amino acids peptides model helical systems L-alanine L-peptides beta-sheet conformation/ A3120 Specific calculations and results for atoms and molecules A3520W Molecular weak interactions