Conformational potential energy surfaces of a Lycopene model

Ab initio conformational analysis has been carried out at the RHF/3-21G lev el of theory. Computations were performed on a tail-end lycopene (Model B). Both the all-trans and the 5-cis-isomers were studied. The fully planar st ructure turned out to be a second-order saddle point, which indicated that lycopene itself is not planar. Most of the conformers of the 5-cis-isomer a re more stable than the corresponding conformers of the all-trans-isomer. T his stability is in agreement with the observation that even though lycopen e is biosynthesized in plants as the all-trans form, in the human body over 65% exists in one of the cis-forms and less than 35% remains in its all-tr ans form. (C) 2001 Elsevier Science B.V. All rights reserved.