QUANTUM-THEORY OF THE STRUCTURE AND BONDING IN PROTEINS .2. SIMPLE DIPEPTIDE

The conformational energy map for the simplest possible dipeptide is obtained from the ab initio Gaussian-70 package using the STO-3G basis set. This map may be interpreted using standard chemical ideas to give clear evidence for the existence of a C7 hydrogen bond and non-bonded repulsions, together with additional but less clear-cut evidence for torsional barriers and a possible induction effect. Quantitative estimates of these effects are reported. The present evidence casts doubt on the nature of the alleged C5 hydrogen bond which stabilises the extended form of the protein. © 1979.