Direct observation of «cholesterol - model of biological membrane» complex by NMR spectroscopy

Abstract

Interaction and aggregation of cholesterol and sodiumdodecyl sulfate molecules were studied in this paper.Sodium dodecyl sulfate was taken as a model for biologicalmembranes. Cholesterol-sodium dodecyl sulfate complex wasdescribed by modern methods of nuclear magnetic resonancespectroscopy.Nuclear magnetic resonance spectra were recorded on«Avance-500» spectrometer (Bruker).To assign 1Н signals of cholesterol, sodium dodecylsulfate and cholesterol+sodium dodecyl sulfate mixturein nuclear magnetic resonance spectra literature datawas used, and 2D homo- end hetero-correlation nuclearmagnetic resonance spectra were recorded. To study theformation of sodium dodecyl sulfate micelles and complexof cholesterol-sodium dodecyl sulfate micelles selectivenuclear Overhauser effect spectroscopy experiments werecarried out.The formation of sodium dodecyl sulfate micelles in dimethylsulfoxide solution was confirmed by nuclear Overhauser effectspectroscopy data. The presence of a complex between sodiumdodecyl sulfate micelles and cholesterol molecules has beenproven by selective nuclear Overhauser effect spectroscopyexperiments. Nuclear Overhauser effect between OHgroupof cholesterol and «tail» groups of sodium dodecylsulfate hydrophobic part was observed in the experiment.This observation corresponds to close spatial arrangementof these parts of different molecules and the presence ofa complex between cholesterol and sodium dodecyl sulfatemicelles.On the basis of the nuclear magnetic resonanceexperiments was established that molecules of sodiumdodecyl sulfate form micelles in dimethyl sulfoxide solutionat concentrations above the critical micelle concentration.Cholesterol molecules form an intermolecular complex withsodium dodecyl sulfate micelles by interaction of the OH groupof cholesterol and СН3-1 and СН2-2 «tail» aliphatic groupsof sodium dodecyl sulfate. This interaction is similar to thebehavior of cholesterol in phospholipid bilayer membranes inwhich cholesterol enters its cyclic part in the hydrophobictails of phospholipid molecules oriented primarily across thebilayers.

Keywords

Nuclear magnetic resonance spectroscopy / cholesterol / sodium dodecyl sulfate / micelles / nuclear Overhauser effect

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