TY - JOUR

T1 - Clustering of spin-labeled cholesterol analog diluted in bilayers of saturated and unsaturated phospholipids

AU - Dzuba, Sergei A.

AU - Kardash, Maria E.

N1 - Copyright © 2018 Elsevier B.V. All rights reserved.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - 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.

AB - 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.

KW - Biological membrane

KW - Electron spin echo

KW - Lipid rafts

KW - Lipid-mediated interactions

KW - Long-range interactions

KW - PR

KW - EPR

KW - PLASMA-MEMBRANE

KW - BIOLOGICAL-MEMBRANES

KW - ORGANIZATION

KW - MIXTURES

KW - MODEL MEMBRANES

KW - PHASE

KW - ELECTRON-PARAMAGNETIC-RESONANCE

KW - LIPID RAFTS

KW - MOLECULAR-DYNAMICS SIMULATIONS

KW - Electron Spin Resonance Spectroscopy

KW - Cholesterol/chemistry

KW - Phospholipids/chemistry

KW - Spin Labels

KW - Magnetics

KW - Lipid Bilayers/chemistry

UR - http://www.scopus.com/inward/record.url?scp=85054180519&partnerID=8YFLogxK

U2 - 10.1016/j.bbamem.2018.09.017

DO - 10.1016/j.bbamem.2018.09.017

M3 - Article

C2 - 30273579

AN - SCOPUS:85054180519

VL - 1860

SP - 2527

EP - 2531

JO - Biochimica et Biophysica Acta - Biomembranes

JF - Biochimica et Biophysica Acta - Biomembranes

SN - 0005-2736

IS - 12

ER -