Kinetics of the redistribution of porphyrins between the proteins of blood and membranes

A comparative investigation of the kinetics of the redistribution of porphyrins between the lipoproteins of plasma and biological membranes is made. Isolated proteins were colored by the derivatives of chlorin e₆ and Zn-phthalocyanine, and the dynamics of the redistribution of pigments from the protein-carrier onto biological membranes (unilamellar lipid vesicles) were recorded by fluorescent methods. It is found that the rate of redistribution depends on the polarity of the molecule of the pigment. The time needed to attain equilibrium distribution of porphyrin increases on decrease in the degree of polarity from several seconds for chlorin e₆ to tens of minutes for nonpolar pigments. Very slow redistribution (several hours) was observed on displacement of the trimethyl ester of chlorin e₆ and Zn-phthalocyanine from low-density lipoproteins. It is shown that this effect can be attributed to the specific features of the localization of the centers of binding extremely nonpolar porphyrins in the composition of low-density lipoproteins. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 541–545, July–August, 1999.