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Raman spectroscopy and DSC assay of the phase coexistence in binary DMPC/cholesterol multilamellar vesicles.

Authors
  • Okotrub, K A1
  • Zaytseva, I V2
  • Adichtchev, S V2
  • Surovtsev, N V2
  • 1 Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia. Electronic address: [email protected]
  • 2 Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia.
Type
Published Article
Journal
Biochimica et biophysica acta. Biomembranes
Publication Date
Feb 01, 2021
Volume
1863
Issue
2
Pages
183514–183514
Identifiers
DOI: 10.1016/j.bbamem.2020.183514
PMID: 33232709
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

The phospholipid/cholesterol binary model systems are an example of simple models whose structure has caused controversy and genuine interest over many decades. The cornerstone underlying the description of such models is the answer to the question of whether these membranes are separated into coexisting phases or domains. Here, we apply label-free Raman spectroscopy and differential scanning calorimetry (DSC) to verify the phase coexistence in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/cholesterol binary model. Raman spectra demonstrate the peculiarity at 30% molar fraction of cholesterol. Above this concentration, Raman data demonstrate similar characteristics at T = 291, 298, 303 K. At lower molar fractions, at 303 K, we found the agreement of Raman spectra with the predictions of the lever rule of cholesterol. Taken together, low cooperativity of the transition at 30 mol% and the fulfillment of the lever rule suggest the existence of nanoclusters composed of approximately 4 DMPC and 2 cholesterol molecules. At 298 K, the compliance of the lever rule was found in the range from 0 to 20 mol% of cholesterol. At 291 K, the addition of 5% cholesterol leads to the abrupt change of Raman spectra parameters and their continuous evolution with the further increase of cholesterol molar fraction. It seems that cholesterol plays a twofold role in binary mixtures; it reduces the intermolecular cooperativity and forms clusters whose size and DMPC-to-cholesterol ratio depend on cholesterol concentration and temperature. Copyright © 2020 Elsevier B.V. All rights reserved.

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