Theoretical Investigation of the Structural Properties of Two Crotamines Isolated from the Venom of Crotalus durissus

Abstract

Crotamines 1 and 2 differ only at residue 19 (which is Leu in 1, and Ile in 2), but 1 presents a greater myone- crotic activity. PM3 geometry optimizations of fragments of 1 (I17-C18-L19-P20-P21) and 2 (I17-C18-I19-P20-P21) yielded the minimum energy conformations I-a and II-a, respectively. The HF and DFT calculation of chemical proper- ties (atomic charge, orbital population, and MO energy) of I-a and II-a did not reveal significant differences that would explain the differences in biological activities of the corresponding crotamines. PM3 optimized geometries of full peptides 1 and 2 presented different globular spatial arrangements when disulfide bonds between cysteine residues were consid- ered. This fact may be related to the difference in biological activities observed for the two crotamines.