Raman spectroscopic detection and examination of the interaction of amino acids, polypeptides and proteins with the phosphatidylcholine lamellar structure

Abstract

Raman spectral peaks in the vicinity of 1100 and 2900 cm −1 for phosphatidylcholine were found to be 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 I 1064/ I 1089 indicating an increase in the gauche hydrocarbon chain character of the lipid. The increase in the lipid approx. 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 · HCl and l-lysine · 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 produced a decrease in the lipid Raman intensity ratio I 1064/ I 1089 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 were found to increase the I 2890/ I 2850 dimyristoyl phosphatidylcholine Raman intensity ratio while decreasing the I 2850/ I 2930 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.