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Interaction of Dicarboxylic Metalloporphyrins with Liposomes. The Effect of pH on Membrane Binding Revisited ¶
Author(s) -
Kępczyński Mariusz,
Ehrenberg Benjamin
Publication year - 2002
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2002)0760486iodmwl2.0.co2
Subject(s) - liposome , chemistry , biophysics , membrane , biochemistry , biology
The acid–base properties of Zn‐hematoporphyrin IX (ZnHP) and Zn‐mesoporphyrin IX (ZnMP) and the effect of pH on their binding to liposomes have been studied. The ionization constants for the two carboxylate groups of ZnHP were calculated by principal component analysis and are 5.7 ± 0.1 and 6.9 ± 0.05. The neutral species and the mono‐ and dianionic forms all bind to liposomes, but a strong pH effect on the binding constant was observed for both the investigated compounds. We also observed a decrease in the binding of the two anionic species when the membranes carried a negative charge. These results indicate that the porphyrins partition into the membrane with their carboxylic moieties near the lipid–water interface so that their deprotonation, leading to a charged molecule, does not prevent the insertion of the tetrapyrrole ring into the lipid environment of neutral liposomes.