Interaction Between Three Sulfur-Containing Amino Acids in Garlic and Bovine Serum Albumin Determined by Fluorescence Spectrometry

Sulfur-containing amino acids (SAA) such as S-allyl cysteine (SAC), S-allyl cysteine sulfoxide (SACS), and S-allyl mercapto cysteine (SAMC) from garlic (Allium sativum L. ) have many bioactivities like anti-tumor, antioxidant and so on. These bioactivities should be directly related to the interaction between the above-mentioned SAA and biomacromolecules such as proteins in organisms. In order to elucidate the relationship, the modle system was made of by bovine serum albumin (BSA) and SAA. The interaction between SAC, SACS or SAMC arid BSA was investigated in Tris-HCl buffer solution at pH 7. 40 by fluorescence spectroscopy (FS) and ultraviolet absorption spectroscopy (UVS). FS was determined by scanning from 300 to 400 nm at 280 nm excitation wavelength. And UVS was determined by scanning the SAMC solution from 300 to 400 nm. FS and UVS results show that the quenching type of BSA with SAC or SACS is dynamic quenching, and the one of BSA and SAMC is static quenching. The binding constants of BSA and SAMC solution at 298 K and 310 K are 6. 18 X 10(3) and 5. 54 x 10(3) L . mol(-1), respectively, with strong binding effect. The number of the binding site of BSA and SAMC at above temperature is approximating to 1, i. e. forming a 1 , 1 complex, which can be deduced that SAMC is well stored and transported in organisms. The binding distance between BSA and SAMC is 1. 61 nm. The binding Delta G of BSA and SAMC is - 21. 63 and -22. 21 kJ . mol(-1) at 298 and 310 K, respectively, indicating that the reaction is a spontaneous process. The binding PH is about 7. 06 kJ . mol(-1) at the checking temperature; the binding Delta G of BSA and SAMC is 48. 89, 46. 99 J . mol(-1) at 298 K and 310 K, respectively. The electrostatic attraction is dominated between BSA and SAMC, based on their Delta H and Delta S. It could be concluded that SAMC has a strong binding with BSA, which provides a theoretical basis for SAMC as a drug molecule. At the same time, these results also provide a theoretical basis for further study of the interaction, development and utilization SAA and other macromolecules.