LAURDAN since Weber: The Quest for Visualizing Membrane Heterogeneity

Abstract

Any chemist studying the interaction of molecules with lipid assemblies will eventually be confronted by the topic of membrane bilayer heterogeneity and may ultimately encounter the heterogeneity of natural membranes. In artificial bilayers, heterogeneity is defined by phase segregation that can be in the nano-and micrometer range. In biological bilayers, heterogeneity is considered in the context of small (10-200 nm) sterol and sphingolipid-enriched heterogeneous and highly dynamic domains. Several techniques can be used to assess membrane heterogeneity in living systems. Our approach is to use a fluorescent reporter molecule immersed in the bilayer, which, by changes in its spectroscopic properties, senses physical-chemistry aspects of the membrane. This dye in combination with microscopy and fluctuation techniques can give information about membrane heterogeneity at different temporal and spatial levels: going from average fluidity to number and diffusion coefficient of nanodomains. LAURDAN (6 dodecanoyl-2-(dimethylamino) naphthalene), is a fluorescent probe designed and synthesized in 1979 by Gregorio Weber with the purpose to study the phenomenon of dipolar relaxation. The spectral displacement observed when LAURDAN is either in fluid or gel phase permitted the use of the technique in the field of membrane dynamics. The quantitation of the spectral Corresponding AuthorSusana A. Sánchez -

Enantioselective Total Synthesis of the Archaeal Lipid Parallel GDGT‐0 (Isocaldarchaeol)**

“…Differential scanning calorimetry (DSC) studies of 13 and 16 were unable to identify any endothermic transitions between −40 °C and 90 °C, indicating that no significant phase transitions were observed within this temperature range. In order to further study the packing characteristics of these lipids, we measured the fluorescence spectra across various temperatures of the solvatochromic dye Laurdan incorporated into membranes of 13 and 16 [32] . A gradual decrease in generalized polarization occurred in both lipid samples as the temperature was increased, suggesting the membranes were becoming increasingly fluid.…”

Phasor-Based Multi-Harmonic Unmixing for In-Vivo Hyperspectral Imaging

“…We wanted to use a solvatochromic probe to evaluate the membrane’s physical order or dynamics in combination with dyes for specific organelles. LAURDAN is perhaps the probe more studied on in vitro and in vivo systems [11,30]. Its unique photophysics and lack of affinity for subcellular membranes enable LAURDAN to study the membrane order in any subcellular organelle in a fair comparison.…”

“…LAURDAN is a membrane probe sensitive to its dipolar environment and can relax dipole active molecules around it [11]. In membranes, LAURDAN is used to measure supramolecular membrane organization, often known as fluidity or lipid order [25].…”

Enantioselective Total Synthesis of the Archaeal Lipid Parallel GDGT-0

“…In order to further study the packing characteristics of these lipids, we measured the fluorescence spectra across various temperatures of the solvatochromic dye Laurdan incorporated into membranes of 13 and 16. 32 A gradual decrease in generalized polarization occurred in both lipid samples as the temperature was increased, suggesting the membranes were becoming increasingly fluid. However, consistent with the DSC experiments, no discrete phase transitions were observed from the spectra.…”