Investigation of the interaction of dimethyl sulfoxide with lipid membranes by small-angle neutron scattering

The influence of dimethyl sulfoxide (CH3)2SO (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°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 β’ gel and L α liquid-crystalline phases are determined by small-angle neutron scattering. The intermembrane distance d s 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.