Abstract
The use of dimethylsulfoxide (DMSO) as a cryoprotectant to reduce cellular injury during freezing is well known, however the intermolecular interactions between this amphiphilic molecule and biological membranes that form the basis of this protection are unknown. DMSO–dipalmitoylphosphatidylcholine (DPPC) vesicle interactions were investigated in pulsed‐field gradient NMR (PFGNMR) experiments and spectra analysis allowed for the determination of self‐diffusion coefficients for each species present. The mole fraction of DMSO associated with the DPPC vesicles was then calculated from the diffusion coefficients: the mole fraction increased from 14% to 42% as the membrane was heated from below to above the main phase transition temperature.
Highlights
The study of the interactions of cryoprotectants with cell membranes has become increasingly important because of the expanding need for long-term cryopreservation of cells.An important cryoprotectant widely used in cell cryopreservation is the amphiphilic molecule dimethylsulfoxide (DMSO)
The present study demonstrates the usefulness of pulsedfield gradient NMR (PFGNMR) techniques in the study of the association of DMSO for DPPC large unilamellar vesicles (LUVs)
The self-diffusion coefficient in the absence of vesicles is referred to as that of the ‘free’ species (Dfree) of DMSO, whereas that obtained in the presence of vesicles must take into account the fraction of DMSO bound to the vesicle (Dbound) as well as the effect of obstruction caused by the presence of the vesicles
Summary
The study of the interactions of cryoprotectants with cell membranes has become increasingly important because of the expanding need for long-term cryopreservation of cells. Colligative effects cannot explain this change in membrane transition temperature and it is suspected that DMSO must interact with the membrane in a non-colligative manner [8]. Despite this basic knowledge the precise nature of how DMSO interacts with cell membranes remains poorly understood. To simplify analysis, it is common in the study of membranes to use model systems, as these systems have well defined transition temperatures and their size can be controlled.
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