CONFORMATIONAL BEHAVIOR AND FLEXIBILITY OF MET-ENKEPHALIN

The conformation potential energy hypersurface of met-enkephalin has been analyzed by a molecular mechanics method in combination with the programs ROSE, DAISY, CICADA and PANIC. LOW energy conformations and conformational transitions (conformational channels) have been located. Global and fragmental relative f and absolute phi flexibility, and conformational softness f(0) have been calculated for each conformer as well as the entire molecule. The calculations have been performed for dielectric constant 78.5. It is concluded that met-enkephalin in a polar solvent is a fairly flexible molecule. The number of low energy conformers found is significantly higher than is found by other methods (31 and 590 within 1 kcal mol(-1) and 4 kcal mol(-1) energy window, respectively). It is also revealed that the backbone flexibility is, in the majority of low energy areas of the conformational space, higher than that of the side chain.