BROMOTHYMOL BLUE AS A PROBE FOR STRUCTURAL-CHANGES OF MODEL MEMBRANESINDUCED BY HEMOGLOBIN

The effect of methemoglobin on the structure of model membranes compos ed of phosphatidylcholine and diphosphatidylglycerol (18: 1, mol:mol) was studied with the help of pH-indicator dye bromothymol blue. The pa rtition coefficients characterizing the dye binding to methemoglobin o r model membranes were derived from the pK(alpha)(a) dependences on th e protein or phospholipid concentration. The observed character of the dye partitioning in the lipid or lipid-protein systems is interpreted in terms of the traditional electrostatic approach and some modern th eories of membrane electrostatics. It is assumed that methemoglobin af fects the structural and physicochemical parameters of lipid-water int erface. (C) 1998 Elsevier Science B.V.