Fluorescence probe partitioning between Lo/Ld phases in lipid membranes

Abstract

Fluorescence microscopy imaging is an important technique for studying lipid membranes and is increasingly being used for examining lipid bilayer membranes, especially those showing macroscopic coexisting domains. Lipid phase coexistence is a phenomenon of potential biological significance. The identification of lipid membrane heterogeneity by fluorescence microscopy relies on membrane markers with well-defined partitioning behavior. While the partitioning of fluorophores between gel and liquid-disordered phases has been extensively characterized, the same is not true for coexisting liquid phases. We have used fluorescence microscopy imaging to examine a large variety of lipid membrane markers for their liquid phase partitioning in membranes with various lipid compositions. Most fluorescent lipid analogs are found to partition strongly into the liquid-disordered (L(d)) phase. In contrast, some fluorescent polycyclic aromatic hydrocarbons with a flat ring system were found to partition equally, but others partition preferentially into liquid-ordered (L(o)) phases. We have found these fluorescent markers effective for identification of coexisting macroscopic membrane phases in ternary lipid systems composed of phospholipids and cholesterol.

Spatiotemporal analysis of endocytosis and membrane distribution of fluorescent sterols in living cells

“…Up to this concentration, DHE mimics cholesterol fairly well in its ability to order phospholipid acyl chains in model membranes (Scheidt et al 2003) as well as is potential to stiffen lipid bilayers (Garvik et al 2008). Probe partitioning measurements using fluorescence microscopy showed recently that CTL partitions preferentially into the liquid ordered phase of a ternary model system and we confirm this in an independent study for DHE (Baumgart et al 2007;Garvik et al 2008). Thus, the fluorescent sterols DHE and CTL are suitable as a cholesterol marker to monitor distribution of cholesterol in cellular membranes.…”

Partitioning of Membrane-Anchored DNA between Coexisting Lipid Phases

“…77,78 Indeed, we are aware of four different fluorescently labeled cholesterol molecules whose partitioning between coexisting liquid phases has been investigated: three of these modified cholesterols preferentially segregated into L R domains, while the fourth enriched in the L o phase. 79,80 Therefore, the chol-DNAs cannot be assumed to partition in the same proportions as chol between these coexisting phases, since the perturbations in structure of chol-DNA from that of pure chol will have some significance in the molecular insertion into each phase.…”

Application of nucleic acid–lipid conjugates for the programmable organisation of liposomal modules

“…When impurities (e.g. fluorescent lipids) are incorporated into phase separated membranes in trace compositions, they thermodynamically partition into domains according to the relative free energy cost of insertion into each phase [97]. Therefore it is most common for impurities to partition into the most disordered phase available so that they do not incur a free energy penalty by disrupting the packing structure within the more ordered domains.…”