FTIR STUDY OF METHYL- METHANETIOSULFONATE INTERACTION WITH LIPID MEMBRANES

M. E. DEFONSI LESTARD; S. B. DÍAZ; M. E. TUTTOLOMONDO; A. BEN ALTABEF

Palermo, Italia

Congreso; 13th European Congress on the Spectroscopy of Biological Molecules; 2009

Biological systems are compartmentalized by membranes whose main structure, the lipid bilayer, becomes stable by phospholipid hydration. The interfacial properties of biological membranes particularly affect its stabilization and the insertion and regulation mechanism of water carrier peptides. For example, water state in the interface of a membrane can affect both processes. Results by Fourier transform infrared spectroscopy have indicated that the main hydration sites are the carbonyl and phosphate groups [1-5]. In 1993 Nakamura [6] et al. isolated S-methyl methanethiosulfonate (MMTS) from cauliflower, Brassica oleracea L. var. Botrytis, and found that it inhibits the UV-induced mutation in Escherichia coli. In 1997 Sugie et al. [7] examined the modifying effect of MMTS on large bowel carcinogenesis and discovered that this organosulfur compound has a strong protective effect. Furthermore, the antioxidant activity against lipid peroxidation of MMTS was confirmed in tests with rabbit erythrocyte membrane ghosts or rat hepatocytes [6].The results of recent research suggest that MMTS is a promising chemopreventive agent for human liver neoplasms [7]. The molecular structure of MMTS, was determined in the gas phase from GED and theoretical calculations. Experimental and theoretical data confirm that both anti and gauche conformers exist [8]. The study of the topological properties of several bond and no-bonding critical point was useful to analyze the Molecular Electronic Potential [9]. The present study is the first step towards the investigation of MMTS interaction with membrane model systems like liposomes. The methyl-methanetiosulfonate (MMTS) interactions with a lipid membrane of dipalmitoilphosphatidilcholine (DPPC) were studied by means of the Fourier Transform infrared spectroscopy.  We studied the changes in the transition temperatures of DPPC-MMTS at different concentrations of MMTS. We observed an increase of the transition temperature that is proportional to the MMTS concentration until reaching a limit value. We obtained the FTIR spectra of the DPPC-MMTS systems in D2O and H2O that helped in assigning the C=O and PO4-2 groups respectively. We observed the diminution in the frequencies of the C=O and PO4-2 groups stretching modes of DPPC and different frequencies for the CH3 stretchings of MMTS. These results are indicative of the hydrogen bonds between these groups and the weakening of the vibrational force constants.