Fluorescence quenching of pyrene derivatives by iodide compounds in erythrocyte membranes: an approach of the probe location

Abstract

Probe location in biological membranes is important and predominant positions of five pyrene derivatives in erythrocyte membranes are inferred from their fluorescence properties. The distribution of the probes along the normal to the bilayer surface was studied by fluorescence quenching; the quenching efficiency was correlated with the nature and the rate of access of the quencher to the solubilisation site of the probe. Probes and iodide quenchers with known specificity for certain membrane areas were used to survey membrane dynamics. These probes included pyrene butyric acid (PBA) which partly partitions in water, pyrene carboxy aldehyde (PCA) which binds primary on the membrane surface and pyrene (PY), benzo(a)pyrene (BaP) and pyrene decanoic acid (PDA), which insert at different depths in the hydrocarbon core of membranes. The set of quenchers includes hydrophilic iodobenzene, amphiphilic iodobenzoic and 1-iodo propanoic acids and the long-chain alkyl iododecanoic acid. Comparison of steady state and time-resolved quenching experiments indicates that dynamic quenching is predominant since it contributes by more than 75% to the total quenching. These data suggest that PY, PDA and BaP intercalate in different zones in the bilayer. PY is probably diffusing in a relatively large of the lipid matrix between the centers of the lipid layers, PDA and BaP residing preferentially in a restricted central region of the erythrocyte membrane.