FLUORESCENCE QUENCHING OF PYRENE DERIVATIVES BY IODIDE COMPOUNDS IN ERYTHROCYTE-MEMBRANES - AN APPROACH OF THE PROBE LOCATION

Probe location in biological membranes is important and predominant po sitions of five pyrene derivatives in erythrocyte membranes are inferr ed from their fluorescence properties. The distribution of the probes along the normal to the bilayer surface was studied by fluorescence qu enching; the quenching efficiency was correlated with the nature and t he rate of access of the quencher to the solubilisation site of the pr obe. Probes and iodide quenchers with known specificity for certain me mbrane areas were used to survey membrane dynamics. These probes inclu ded pyrene butyric acid (PEA) which partly partitions in water, pyrene carboxy aldehyde (PCA) which binds primary on the membrane surface an d pyrene (PY), benzo(a)pyrene (BaP) and pyrene decanoic acid (PDA), wh ich insert at different depths in the hydrocarbon core of membranes. T he set of quenchers includes hydrophilic iodobenzene, amphiphilic iodo benzoic and 1-iodo propanoic acids and the long-chain alkyl iododecano ic acid. Comparison of steady state and time-resolved quenching experi ments indicates that dynamic quenching is predominant since it contrib utes 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 p robably diffusing in a relatively large area of the lipid matrix betwe en the centers of the lipid layers, PDA and BaP residing preferentiall y in a restricted central region of the erythrocyte membrane.