RAMAN SPECTROSCOPIC DETECTION AND EXAMINATION OF INTERACTION OF AMINO-ACIDS, POLYPEPTIDES AND PROTEINS WITH PHOSPHATIDYLCHOLINE LAMELLAR STRUCTURE

Raman spectral peaks in the vicinity of 1100 and 2900 cm-1 for phosphatidylcholine were sensitive to interactions with amino acids, polypeptides and plasma proteins. The amino acids L-leucine, L-isoleucine, L-tryptophan, L-arginine HCl, L-histidine HCl, L-threonine and L-aspartic acid decreased the dipalmitoyl phosphatidylcholine Raman intensity ratio I1064/I1089 indicating an increase in the gauche hydrocarbon chain character of the lipid. The increase in the lipid of approx. [approximately] 2930 cm-1 peak intensity in relation to the approx. 2850 and approx. 2890 cm-1 peaks upon the addition of the amino acids L-arginine HCl, L-histidine.cntdot. HCl and L-lysine .cntdot. HCl to the lipid dispersion indicates that the lipid hydrocarbon chain environment becomes more polar in their presence. The lipid-alamethecin and lipid-valinomycin interactions decreased the lipid Raman intensity ratio I1064/I1089 again, indicating an increase in the gauche hydrocarbon chain character of dicyristoyl phosphatidylcholine while producing no change in this ratio for dipalmitoyl phosphatidylcholine. Human fibrinogen and bovine serum albumin increased the I2890/I2850 dimyristoyl phosphatidylcholine Raman intensity ratio while decreasing the I2850/I2930 dimyristoyl phosphatidylcholine Raman intensity ratio, indicating that the lipid underwent a conformational change and that the hydrocarbon chain environment was more polar in the presence of albumin or fibrinogen.