Atomistic picture of fluorescent probes with hydrocarbon tails in lipid bilayer membranes: an investigation of selective affinities and fluorescent anisotropies in different environmental phases

TL;DR

This study uses fluorescence spectroscopy to analyze how fluorescent probes with hydrocarbon tails behave in different lipid bilayer membrane phases, revealing differences in orientation, location, and efficiency related to membrane composition.

Contribution

It provides new insights into the orientation and location of specific fluorescent probes in lipid membranes, highlighting differences based on membrane composition and phase.

Findings

DiI-C18(5) is located in the headgroup region near water molecules.

DiI-C18(5) exhibits distinctive anisotropy behavior in SM:Chol membranes.

The BODIPY probe is located deeper in the membrane and shows different behavior.

Abstract

By reverting to spectroscopy, changes in the biological environment of a fluorescent probe can be monitored and the presence of various phases of the surrounding lipid bilayer membranes can be detected. This study highlights the important differences in orientation and location and therefore in efficiency between the probes when they are used in fluorescence microscopy to screen various lipid bilayer membrane phases. Dependent on the lipid composition, the angle between the transition state dipole moments of both probes and the normal to the membrane are found to deviate clearly from 90{\deg}. It is seen that the DiI-C18(5) probe is located in the headgroup region of the SM:Chol mixture, in close contact with water molecules. A fluorescence anisotropy study indicates also that DiI-C18(5) gives rise to a distinctive behavior in the SM:Chol membrane compared to the other considered membranes. The latter behavior has not been seen for the studied BODIPY probe, which is located deeper in the membrane.