TY - JOUR

T1 - Normal vibrations of ternary DOPC/DPPC/cholesterol lipid bilayers by low-frequency Raman spectroscopy

AU - Leonov, Dmitry V.

AU - Dzuba, Sergei A.

AU - Surovtsev, Nikolay V.

N1 - This journal is © The Royal Society of Chemistry.

PY - 2019/10/27

Y1 - 2019/10/27

N2 - A lipid bilayer containing a ternary mixture of low- A nd high-melting lipids and cholesterol (Chol) can give rise to domain formation, referred to as lipid rafts. Low-frequency Raman spectroscopy at reduced temperatures allows detection of normal membrane mechanical vibrations. In this work, Raman spectra were obtained in the spectral range between 5 and 90 cm-1 for bilayers prepared from dioleoyl-glycero-phosphocholine (DOPC), dipalmitoyl-glycero-phosphocholine (DPPC) and Chol. A narrow peak detected between 13 and 16 cm-1 was attributed to the vibrational eigenmode of a lipid monolayer (a leaflet). For the equimolar DOPC/DPPC ratio, the Chol concentration dependence for the peak position, width and amplitude may be divided into three distinct ranges: Below 9 mol%, the intermediate range between 9 mol% and 38 mol%, and above 38 mol%. In the intermediate range the peak position attains its minimum, and the peak width drops approximately by a factor of two as compared with the Chol-free bilayers. Meanwhile, this range is known for raft formation in a fluid state. The obtained results may be interpreted as evidence that bilayer structures in the raft-containing fluid state may be frozen at low temperatures. The drop of peak width indicates that at the spatial scale of the experiment (∼2.5 nm) the intermolecular bilayer structure with raft formation becomes more homogeneous and more cohesive.

AB - A lipid bilayer containing a ternary mixture of low- A nd high-melting lipids and cholesterol (Chol) can give rise to domain formation, referred to as lipid rafts. Low-frequency Raman spectroscopy at reduced temperatures allows detection of normal membrane mechanical vibrations. In this work, Raman spectra were obtained in the spectral range between 5 and 90 cm-1 for bilayers prepared from dioleoyl-glycero-phosphocholine (DOPC), dipalmitoyl-glycero-phosphocholine (DPPC) and Chol. A narrow peak detected between 13 and 16 cm-1 was attributed to the vibrational eigenmode of a lipid monolayer (a leaflet). For the equimolar DOPC/DPPC ratio, the Chol concentration dependence for the peak position, width and amplitude may be divided into three distinct ranges: Below 9 mol%, the intermediate range between 9 mol% and 38 mol%, and above 38 mol%. In the intermediate range the peak position attains its minimum, and the peak width drops approximately by a factor of two as compared with the Chol-free bilayers. Meanwhile, this range is known for raft formation in a fluid state. The obtained results may be interpreted as evidence that bilayer structures in the raft-containing fluid state may be frozen at low temperatures. The drop of peak width indicates that at the spatial scale of the experiment (∼2.5 nm) the intermolecular bilayer structure with raft formation becomes more homogeneous and more cohesive.

KW - MODEL MEMBRANES

KW - PHASE-DIAGRAM

KW - DYNAMICS

KW - RAFTS

KW - PHOSPHATIDYLCHOLINE

KW - FLUCTUATIONS

UR - http://www.scopus.com/inward/record.url?scp=85074542997&partnerID=8YFLogxK

U2 - 10.1039/c9ra06114b

DO - 10.1039/c9ra06114b

M3 - Article

C2 - 35530012

AN - SCOPUS:85074542997

VL - 9

SP - 34451

EP - 34456

JO - RSC Advances

JF - RSC Advances

SN - 2046-2069

IS - 59

ER -