THE GAS-PHASE CONFORMATIONS OF VALINE - AN AB-INITIO STUDY

A survey of 108 possible gas-phase conformations of valine led to 26 u nique conformers at the HF/6-31G level. Relative energies are reporte d at the MP2/6-31+G//HF/6-31G* level with corrections for zero-point vibrational energies. The results indicate that the preferred orientat ion of the isopropyl group depends on the interaction between the carb oxyl and the amino group. In comparison to alanine, it does not appear that the larger size of the side chain significantly biases the confo rmational preferences. (C) 1997 Elsevier Science B.V.