EPR study of the effects of trehalose and sucrose on DMPC bilayers. A. Nicastro, N.M.C. Casado

A. NICASTRO; N.M.C. CASADO; E.A. DISALVO; A.M. GENNARO

Montevideo, Uruguay

Congreso; XXXVI Reunión Anual de la Sociedad Argentina de Biofísica, 6th International Conference on Biological Physics y 5th Southern Cone Biophysics Congress; 2007

SAB- IUPAB- IUPAP

Trehalose and sucrose are sugars found at high concentrations in certain plants capable of surviving extreme dehydration conditions. Previous infrared and calorimetric studies in model systems have shown that both sugars affect the transition phase temperature. In this work, we studied the thermotropic behavior of fully hydrated DMPC bilayers in presence of trehalose and sucrose using EPR spectroscopy. As a probe, we have used the spin label 5-PCSL (1-palmitoyl-2-stearoyl(5-doxyl)-sn-glycero-3-phosphocholine). We evaluate the degree of lipid chain rigidity, related to the phase state of the bilayers, through the hyperfine parameter 2Amax. We performed studies in unilamellar (LUV) systems. The sugars were diluted in the suspension buffer in order to obtain two different sugar/lipid molar ratio: 15:1 and 3:1. The samples were dehydrated and rehydrated to evaluate the effects under this stress condition. Hydration was performed with two different volumes of water in order to modify the sugar/water concentration. Our results show that: i) when hydration is performed in “high volume” of water, the sugars show no effect on the transition phase temperature, ii) when hydration is performed in “low volume” of water, the sugars show differential effects: at the lowest sugar/lipid ratio, trehalose increases the phase transition temperature, but sucrose causes no effect; iii) on the other hand, in low water and at the highest sugar/lipid ratio, both sugars increase the phase transition temperature, causing also a decrease in lipid mobility in the liquid crystalline phase. This last effect could be due to the high viscosity of the suspension media, which could inhibit the lipid rotation through friction with the lipid headgroups.