Temperature Dependence of the Structure and Dynamics of a Dye-Labeled Lipid in a Planar Phospholipid Bilayer: A Computational Study
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Fluorescent probes are widely employed to label lipids for the investigation of structural and dynamic properties of model and cell membranes through optical microscopy techniques. Although the effect of tagging a lipid with an organic dye is generally assumed to be negligible, optically modified lipids can nonetheless affect the local lipid structure and, in turn, the lipid lateral mobility. To better assess this potential issue, all-atom (MD) molecular dynamics simulations have been performed to study structural and dynamic effects in a model DOPC membrane in the presence of a standard Rhodamine B-labeled DOPE lipid (RHB) as a function of temperature, i.e., 293 K, 303 K, and 320 K. As the temperature is increased, we observe similar changes in the structural properties of both pure DOPC and RHB-DOPC lipid bilayers: an increase of the area per lipid, a reduction of the membrane thickness and a decrease of lipid order parameters. The partial density profile of the RHB headgroups and their orientation within the lipid bilayer confirm the amphiphilic nature of the RHB fluorescent moiety, which mainly partitions in the DOPC glycerol backbone region at each temperature. Moreover, at all temperatures, our results on lipid lateral diffusion support a non-neutral role of the dye with respect to the unlabeled lipid mobility, thus suggesting important implications for optical microscopy studies of lipid membranes.
KeywordsLipid lateral diffusion DOPC Rhodamine B-labeled lipids Temperature dependence Molecular dynamics simulations
G.B. acknowledges the financial support of the INFN, the Scuola Normale Superiore research program, and the FAS Salute Regione Toscana Project “DIAMANTE.” The CINECA and Avogadro computing centers are also thanked.
MJA and LS contributed equally to this work. MJA, LS, and AC performed all the simulations and the analysis of this work. NB and TDA helped with the analysis of the results. AC and GB conceived the idea, designed and supervised the research work, and wrote the manuscript supported by all other authors.
Compliance with Ethical Standards
Conflict of interest
The authors declare no kind of competing interests.
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