COMPARATIVE-STUDY ON THE CONFORMATION OF PHALLOIDIN, VIROISIN, AND RELATED DERIVATIVES IN AQUEOUS-SOLUTION

We investigated the conformations of toxic phalloidin and viroisin in aqueous solution using 500-MHz H-1-NMR spectroscopy in conjunction wit h molecular modeling. The conformations of two nontoxic phalloidin der ivatives, secophalloidin and dethiophalloidin, were also corresponding ly studied for comparison purposes. Results indicate that the non-toxi c peptides have a multiple conformation, whereas the toxic peptides ar e comprised of a rigid molecule. It was found that the conformation of phalloidin partially resembles that of viroisin in the region of Cys3 -Pro4-Ala5-Trp6, bring different from that of the non-toxic peptides; thereby suggesting this region plays an important role leading to thei r toxicity.