Translator Disclaimer
1 March 2004 pH-Dependent Modification of Lipophilicity of Porphyrin-type Photosensitizers
Author Affiliations +
Abstract

Structural modifications of photosensitizers (changes in protonation, ionic state and aggregation state) under different environmental conditions should be precisely determined to understand the interaction of the photosensitizers with biological systems. In the present study partition coefficients of hematoporphyrin IX (HpIX), disulfonated meso-tetra-phenylporphine, meso-tetra(3-hydroxyphenyl)porphine (mTHPP) and meso-tetra(3-hydroxyphenyl)chlorin in the 1-octanol–phosphate buffer system were determined in the pH region 4.0–8.0. Only the partition coefficients of HpIX and mTHPP were found to be pH dependent. Computer processing of fluorimetric titration data was applied to estimate pKa values of the imino nitrogens of mTHPP. Monoprotonated species of mTHPP seem to be unstable or nonexistent. The possibility that both imino nitrogens of this dye are protonated according to a common pKa is proposed. The pKa value of the imino nitrogens of mTHPP was found to be 2.99 ± 0.04 after the application of a model taking aggregation of the drug into account. The contributions of various aqueous ionic species of mTHPP as functions of pH were calculated and compared with partition coefficients.

Beata Čunderlíková, Olav Kaalhus, Róbert Čunderlík, Anton Mateášik, Johan Moan, and Magne Kongshaug "pH-Dependent Modification of Lipophilicity of Porphyrin-type Photosensitizers," Photochemistry and Photobiology 79(3), 242-247, (1 March 2004). https://doi.org/10.1562/0031-8655(2004)79<242:PMOLOP>2.0.CO;2
Received: 20 August 2003; Accepted: 1 December 2003; Published: 1 March 2004
JOURNAL ARTICLE
6 PAGES

This article is only available to subscribers.
It is not available for individual sale.
+ SAVE TO MY LIBRARY

SHARE
ARTICLE IMPACT
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top