Investigation of Interaction of Dimethylsulfoxide with Lipid Membranes via Small-Angle Neutron Scattering

The influence of dimethyl sulfoxide (CH3)(2)SO (DMSO) on the structure of membranes of 1,2-dimiristoyl-sn-glycero-3-phosphatidylcholine (DMPC) in an excess of a water-DMSO solvent is investigated over a wide range of DMSO molar concentrations 0.0 <= X-DMSO <= 1.0 at temperatures T = 12.5 and 55 degrees C. The dependences of the repeat distance d of multilamellar membranes and the thickness d(b) of single vesicles on the molar concentration X-DMSO in the L-beta. gel and L-alpha liquid-crystalline phases are determined by small-angle neutron scattering. The intermembrane distance, is determined from the repeat distance d and the membrane thickness d(b). It is shown that an increase in the molar concentration X-DMSO leads to a considerable decrease in the intermembrane distance and that, at X-DMSO = 0.4, the neighboring membranes are virtually in steric contact with each other. The use of the deuterated phospholipid (DMSO-D6) and the contrast variation method makes it possible, for the first time, to determine the number of DMSO molecules strongly bound to the membrane