Circular dichroism studies on conformational transitions of phytohemagglutinins effected by some alcohols

The effects of methanol, ethanol, 1-propanol and 2,2,2,-trifluoroethanol (TFE) on conformation of 10 phytohemagglutinins (lectins) were examined by applying the circular dichroism (CD) method. Concanavalin A and the lectins isolated from pea (Pisum sativum), lentil (Lens culinaris), soybean (Glycine max), peanut (Arachis hypogaea), Dolichos biflorus, Sophora japonica, Lotus tetragonolobus, Ulex europaeus I, and Phaseolus vulgaris (leucoagglutinin) were used. Slight changes in the structure of these proteins were observed at relatively low concentrations (5-20 vol. %, pH 7.2-8.2, at 22-25 degrees) of the perturbants, and the effectiveness of the alcohols increased with their concentration and molecular weight. The circular dichroism bands related to the aromatic side chain chromophores decreased in the presence of the alcohols. The secondary structure was reorganized by high concentrations (30-80 vol. %) of the alcohols, as indicated by CD at 187-250 nm. Curves typical for proteins of relatively high alpha-helix content (strong positive CD bands at 191 nm and negative bands at 206-208 and 222 nm) were recorded in the presence of high concentrations of trifluoroethanol.