Influence of total Saponins of Panax notoginseng on the conformation of BSA

The interaction between total saponins of Panax notoginseng (TSPN) and bovine albumin serum (BSA) was investigated by FT-ATR-IR combined with fluorescence and ultraviolet spectroscopy. The difference IR spectra before and after the interaction between drug and protein and fluorescence quenching of BSA provided the evidences of conformation changes of BSA. The binding constants of two saponins with BSA were determined by ultraviolet spectra. The varieties of BSA secondary structure after binding with TSPN were analyzed quantitatively by curve-fitting of amide I and amide III bands. The results showed that the alpha-helix structure of BSA was decreased about 3% and the beta-sheet was increased about 5% with the increasing of TSPN concentration, but the other structures were almost unchanged. The reduction of the alpha-helix in favor of the beta-sheet structure is indicative of a partial unfolding of protein in the presence of TSPN at a high drug concentration.