Ion effects on the conformation and dynamics of repetitive domains of a spider silk protein: implications for solubility and β-sheet formation

Chaotropic ions prevent molecular interactions of a spider silk protein, which are required to maintain the solubility, while kosmotropic ions promote hydrogen bond interactions, which are a prerequisite for β-sheet formation.

Séparation des virotoxines du champignon Amanita virosa et étude comparative de leur interaction sur l'actine in vitro

Cyclic peptides have been extracted with methanol from Amanita virosa and separated by preparative HPLC. Six peptides were obtained: phalloidin and five new peptides recently identified by Faulstich as virotoxins. We have compared the interaction of these six peptides with actin in vitro. They increased the rate of polymerization of actin and protected F-actin against several denaturating agents: proteases, heat, chaotropic ions, cytochalasin B, and DNAse I. The five virotoxins have therefore the same biological properties as phalloidin. However, the differential spectra of interaction between actin and the five virotoxins are different than the differential spectra between actin and phalloidin, thus it appears that the molecular interaction of actin with virotoxins is different than with phalloidin. The five virotoxins have the same activity. Although these virotoxins have different functional groups on amino acids 1 and 7, it is concluded that these two amino acids are of minor importance in the interaction of these peptides with actin.