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Nanoscale probing of cholesterol-rich domains in single bilayer dimyristoyl-phosphocholine membranes using near-field spectroscopic imaging

journal contribution
posted on 15.02.2021, 22:29 by Arif SiddiqueeArif Siddiquee, Aamd Houri, Kibret A Messalea, Jiao Lin, Torben Daeneke, Brian AbbeyBrian Abbey, Adam MechlerAdam Mechler, Shanshan KouShanshan Kou
Cholesterol is believed to induce the formation of membrane domains, "rafts", which are implicated in a range of natural and pathologic membrane processes. Therefore, it is important to understand the role that cholesterol plays in the formation of these structures. Here, we use label-free spectroscopic imaging to investigate cholesterol fractioning in supported bilayer membranes at nanoscale. Scattering-Type scanning near-field optical microscopy (s-SNOM) was used to visualize the formation of cholesterol-induced domains in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes. Our results revealed the coexistence of phase separated domains in DMPC lipids with 10 mol % cholesterol content, whereas a mostly homogeneous bilayer was found at low (5 mol %) and high (15 mol %) cholesterol content. Near-field nano-FTIR spectroscopy was used to identify the cholesterol-rich domains based on their qualitative chemical compositions. It was determined that cholesterol binds to phosphodiester and alkyl glycerol ester moieties, likely via hydrogen bonding of the alcohol to either of the ester oxygens. The results also confirm the existence of an ideal cholesterol-lipid mixture ratio (â 15:85) with a geometrically defined packing. At lower cholesterol content there is phase separation between liquid ordered and almost neat DMPC domains. Thus, the liquid ordered phase exists at an energy minimum at a given lipid-cholesterol ratio.

History

Publication Date

27/10/2020

Journal

Journal of Physical Chemistry Letters

Volume

11

Issue

21

Pagination

9p. (p. 9476-9484)

Publisher

American Chemical Society

ISSN

1948-7185

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