Clustering of spin-labeled cholesterol analog diluted in bilayers of saturated and unsaturated phospholipids

Sergei A. Dzuba, Maria E. Kardash

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Clustering of spin-labeled cholesterol analog, 3β-doxyl-5α-cholestane (DChl), diluted in bilayers comprised of either saturated dipalmitoyl-glycero-phosphocholine (DPPC) or unsaturated dioleoyl-glycero-phosphocholine (DOPC) phospholipids was studied. DChl molar fraction X varied between 0.005 and 0.04. EPR spectroscopy applied at low temperatures (200 K) enabled exploring magnetic dipole-dipole (d-d) interaction between spin labels. For DOPC bilayers, EPR spectra were found to broaden remarkably with X increase. The broadening was simulated for the models of 2-dimentional (2-D) clusters with enhanced local concentration, Xloc, which was several times larger than X, and for 1-dimensional (1-D) DChl clusters. The distance of closest approach in these simulations attained the intermolecular lateral distance in the membrane (~0.7 nm). For DPPC bilayers, EPR spectra showed only small broadening, which in these simulations could not be reproduced even if Xloc was taken as small as X. However strong concentration dependence was found for electron spin echo (ESE) decays. Both the EPR and ESE data for DPPC bilayers were explained within the model assuming encapsulation of DChl molecules in lipid shells so preventing them to approach each other closer than a certain distance, Rmin. The Rmin value was found to vary between ~2.5 nm and 5 nm, for X varying between 0.04 and 0.005; Xloc in these simulations was several times larger than X. So the DChl clustering in DOPC bilayers is driven by attractive lipid-mediated forces, while in DPPC bilayers long-range nanoscale lipid-mediated repulsive/attractive forces take place for distances smaller and larger Rmin, correspondingly.

Original languageEnglish
Pages (from-to)2527-2531
Number of pages5
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1860
Issue number12
DOIs
Publication statusPublished - 1 Dec 2018

Keywords

  • Biological membrane
  • Electron spin echo
  • Lipid rafts
  • Lipid-mediated interactions
  • Long-range interactions
  • PR
  • EPR
  • PLASMA-MEMBRANE
  • BIOLOGICAL-MEMBRANES
  • ORGANIZATION
  • MIXTURES
  • MODEL MEMBRANES
  • PHASE
  • ELECTRON-PARAMAGNETIC-RESONANCE
  • LIPID RAFTS
  • MOLECULAR-DYNAMICS SIMULATIONS
  • Electron Spin Resonance Spectroscopy
  • Cholesterol/chemistry
  • Phospholipids/chemistry
  • Spin Labels
  • Magnetics
  • Lipid Bilayers/chemistry

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