1-Anilino-8-naphthalenesulfonate: A fluorescent probe of membrane surface structure, composition and mobility

Abstract

Summary. The binding of the hydrophobic fluorescent probe 1-anilino-8-naphthalenesulfonate (ANS-) on phospholipid vesicle membranes was studied to gain information about the structure and mobility in the polar head group region, and to determine the degree of mixing of lipids on the microscopic scale. The maximal degree of binding of ANS-on dimyristoyl and dipalmitoyl-•-lecithin membranes is one ANS-per four lecithin molecules, indicating a binding site composed of four polar head groups. ANSbound in this site has a long fluorescent lifetime (5 to 9 nsec) and high quantum yield (0.2 to 0.3), indicating that it is relatively inaccessible to the solvent water. The lack of paramagnetic quenching by added Mn 2+ indicates that ANS-bound to those fourmembered sites is also well shielded from added cations. Similarities in the temperature dependence of the binding constant and the reciprocal fluorescent lifetime indicate that the latter is determined by the propensity for polar head group motion and for water and ANS-reorientation during the excited state of the molecule.Membranes composed of lipids which lack a semi-polar head group (phosphatidic acid) or which have unfavorable polar head group conformations or strong interactions between the polar head groups (dimyristoyl ethanolamine) do not support the binding of ANS-with a high quantum yield and long fluorescent lifetime. Incorporation of these lipids in a lecithin membrane decreases the maximal binding of ANS-to a greater extent than can be explained on the basis of dilution of the lecithin with these lipids. A statistical model is presented, in which incorporation of one or more molecules of the second type into a four-membered lecithin binding site destroys the ability of this site to bind ANS-with a long fluorescence lifetime. Agreement between this model and the results obtained with lipid mixtures indicate that egg phosphatidic acid and dimyristoyl ethanolamine mix well with dimyristoyl lecithin on the microscopic scale. The above criterion was also used to show that cholesterol mixes randomly with lecithin. In contrast to the behavior of the phospholipid mixtures, there was evidence for shortlived ANS-species for cholesterol/lecithin mixtures with mole ratios between 0.6 and 1.0. This species is associated with binding sites in which the lecithin polar head groups

Uptake of N-(9-Anthroyloxy) Fatty Acid Fluorescent Probes Into Lipid Bilayers

“…The uptake of small molecules (ligands) into biomembranes is frequently analysed according to classical binding theory, the concentration of unbound ligand in the aqueous phase being taken as the total concentration of free ligand (Haynes and Staerk 1974;Ting and Solomon 1975). This treatment is valid when the membrane possesses specific binding sites for the ligand exposed to the aqueous phase at the membrane-water interface and there is no distribution of ligand between the phases due to a partition process.…”

1-Anilino-8-naphthalenesulphonate Binding Parameters in Red Cell Membranes. Does Diabetes Mellitus Affect Cell Membrane Dynamics?

“…Accumulated evidence confirms the dominance of fluorescence from l -anilino-8-naphthalenesulphonate bound to lecithin-sphingomyelin pockets in natural membranes (19,20,21).…”

“…In membranes com- posed of a mixture of different lipids, most 1-anilino-8-naphthalenesulphonate molecules are bound in lecithin-sphingomyelin pockets, or to a much lesser extent in the shallow binding sites associated with the presence of chplesterol, although cholesterol alone does not bind l^anilino-8-napbthaleriesulphonate at all. Since lecithin and sphingomyelin heads bind l-anilino-8-naphthalenesulphonate most avidly, the first mentioned type of binding will essentially pre--dorpinate (4,19). An increased cholesterol: lecithin molar ratio leads to the other, quite different type of l -anilino-8-naphthalenesulphonate binding, where l-amlino-8-naphthaleüesulphonate molecules are located in cholesterol-legithin pockets, which are much morfc expösed to extrinsic water.…”

A spectrofluorimetric study of the interaction of glycerol mono‐oleate with human erythrocyte ghosts

“…Changes in the packing of ANS between the polar headgroups and changes in the polar headgroup mobility express themselves through changes in the accessibility of water to the ANS and the reduction of the quantum yield [17] . An interpretation of the influence of the fusogen is that the decrease in quantum yield and the red shift are not simply a polarity effect but may be a result of the increased ability of the solvent molecules to rearrange during the lifetime of the excited state, that is, a decrease in the constraint around the probe molecules [ 111 producing a less ordered structure in the headgroup region.…”