An exploratory ab initio study of the full conformational space of N-acetyl-L-cysteine-N-methylamide

The full conformational space of N-acetyl-L-cysteine-N-methylamide was expl ored by ab initio MO computations. On the Ramachandran hypersurface of four independent variables E= E(phi, psi, chi (1), chi (2)), 47 conformers were located instead of the expected 3(4) = 81 stable structures. The relative stabilities of the various conformers were analyzed in terms of side-chain- backbone interactions covering both hydrogen bonding and charge-transfer ty pes. The stabilization energies exerted by the side-chain of cysteine on th e backbone were compared to those of other amino acids. (C) 2001 Elsevier S cience B.V. All rights reserved.