DMSO-induced dehydration of DPPC membranes studied by X-ray diffraction, small-angle neutron scattering, and calorimetry

Abstract

The influence of dimethyl sulfoxide (DMSO) on membrane thickness, multilamellar repeat distance, and phase transitions of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) was investigated by X-ray diffraction and small-angle neutron scattering (SANS). The differential scanning calorimetry (DSC) study of water freezing and ice melting was performed in the ternary DPPC /DMSO /water and binary DMSO /water systems. The methods applied demonstrated the differences in membrane structure in three sub-regions of the DMSO mole fraction (X DMSO ): from 0.0 to 0.3 for the first, from 0.3 to 0.8 for the second, and from 0.9 to 1.0 for the third sub-region. The thickness of the intermembrane solvent at T =20 o C decreases from 14.4 ± 1.8 Å at X DMSO =0.0 to 7.8 ± 1.8 Å at X DMSO =0.1. The data were used to determine the number of free water molecules in the intermembrane space in the presence of DMSO. The results for 0.0 ≤ X DMSO ≤ 0.3 were explained in the framework of DMSO-induced dehydration of the intermembrane space.Keywords: dimethyl sulfoxide, cryoprotection, phospholipid, dehydration, scattering. Journal of Alloys and Compounds 286 (1999) 195-202 INTRODUCTIONDimethyl sulfoxide has two very important biological properties: a) ability to protect a variety of cells from the damaging effects of freezing and storage at a very low temperature, b) the modification of X-ray induced damage in cells and whole animals when DMSO is present before and during exposure to radiation [1].The main purpose of cryobiology is to find an "optimal" way of cooling biological systems to low temperatures (about the temperature of liquid nitrogen) and, at the same time, prevent the formation of ice inside the biological tissue. The mechanism of DMSO cryoprotection is still debated and, on the molecular level, it is not clear [2].DMSO makes hydrogen bonds with water molecules. The structure of the binary DMSO /water system has been studied by means of the spin-lattice relaxation and the chemical shift behavior of water and DMSO protons [3]. It was found that DMSO and water molecules tend to form hydrogen bonds in the relation 1/2 (mole DMSO fraction X DMSO = 0.33) or 1/3 (X DMSO = 0.25). The DMSO /water phase diagram is well known [4] and the phase behavior of the binary DPPC /water system has been investigated by calorimetry [5]. The influence of DMSO fraction on the pre-transition existence and on the repeat distance of the DPPC multilamellar structure has been studied for the region of a small DMSO mole fraction, X DMSO ≤ 0.13. From the calculation of the electron density profile, it was established that the intermembrane solvent space decreases with the increasing DMSO concentration [6].In the present paper, the influence of DMSO on 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) membranes was studied by X-ray diffraction, small-angle neutron scattering (SANS), and differential scanning calorimetry (DSC). Our purpose was to obtain information on changes in the structure of DPPC in the presence of DMSO at T=20 o C ...

A sucrose solutions application to the study of model biological membranes

“…The small-angle neutron scattering experiments (SANS) with unilamellar vesicles were carried out at YuMO spectrometer in Dubna, Russia [1,2,16]. The model of infinitely thin sphere was applied for the interpretation of the SAXS curves in the region of scattering vector q from 0.005Å -1 to 0.04Å -1 [3].…”

“…The structure and properties of phospholipids membranes, as they serve as a simple and appropriate model for biological membranes, are investigated intensively by X-ray and neutron scattering techniques [1][2][3][4]8,9,16,19]. The structural investigation of drug delivery systems based on the lipid vesicles (liposomes) is a perspective direction for SR application [5].…”

Sucrose solutions as prospective medium to study the vesicle structure: SAXS and SANS study

“…The Guinier approximation of SANS spectra was used for the calculation of membrane thickness of egg yolk phosphatidylcholine vesicles (d l =41.7Å at 20 o C), dipalmitoylphosphatidylcholine (DPPC) vesicles (d l =49.6Å at 20 o C), and mixed lipid/surfactant vesicles [6][7][8]. A strip-function model of evaluating SANS curves was developed recently which allows to determine important membrane parameters describing the geometry and hydration of large oligolamellar vesicles [9].…”

Correlating steric hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid–DMSO–H 2 O system

“…Concentrations of DMSO above 10 mol% (1 DMSO molecule per 9 water molecules) at 25°C induce a subgel phase (14), which is characterized by different head group ordering. Small-angle X-ray and neutron scattering studies (15)(16)(17) have shown that DMSO substantially decreases the solvent gap thickness (equilibrium separation) between lamellae of both gelphase and fluid PC multilamellar vesicles. Explanations for the phase behavior and equilibrium separation phenomena often implicate some mechanism of head group dehydration/ desolvation brought about by DMSO (14,16,18).…”