Spin-Lattice Relaxation Rates of Lipid Spin Labels As a Measure of Their Rotational Diffusion Rates in Lipid Bilayer Membranes

Overview

Journal Membranes (Basel)

Date 2022 Oct 27

PMID 36295720

Authors

Witold K Subczynski

Justyna Widomska

Affiliations

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Abstract

The spin-lattice relaxation rate () of lipid spin labels obtained from saturation recovery EPR measurements in deoxygenated membranes depends primarily on the rate of the rotational diffusion of the nitroxide moiety within the lipid bilayer. It has been shown that also can be used as a qualitative convenient measure of membrane fluidity that reflects local membrane dynamics; however, the relation between and rotational diffusion coefficients was not provided. In this study, using data previously presented for continuous wave and saturation recovery EPR measurements of phospholipid analog spin labels, one-palmitoyl-2-(n-doxylstearoyl)phosphatidylcholine in 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine/cholesterol membranes, we show that measured values are linear functions of rotational diffusion of spin labels. Thus, these linear relationships can be used to transfer values into spin label rotational rates as a precise description of membrane fluidity. This linearity is independent through the wide range of conditions including lipid environment, depth in membrane, local hydrophobicity, and the anisotropy of rotational motion. Transferring the spin-lattice relaxation rates into the rotational diffusion coefficients makes the results obtained from saturation recovery EPR spin labeling easy to understand and readily comparable with other membrane fluidity data.

Citing Articles

5-PC as a Lipid Probe Molecule and as a Second Phospholipid in Binary Phospholipid Mixtures: Saturation Recovery EPR Studies.

Subczynski W, Widomska J Int J Mol Sci. 2024; 25(23).

PMID: 39684621 PMC: 11641204. DOI: 10.3390/ijms252312913.

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