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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Interaction of the meso-tetrakis (4-N-methylpyridyl) porphyrin with gel and liquid state phospholipid vesicles

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Author(s):
Neto, Diogenes de Sousa [1, 2] ; Tabak, Marcel [1]
Total Authors: 2
Affiliation:
[1] Univ Sao Paulo, Lab Biofis Mol, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil
[2] Univ Fed Minas Gerais, Inst Ciencias Agr, BR-14801001 Montes Claros, MG - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Journal of Colloid and Interface Science; v. 381, p. 73-82, SEP 1 2012.
Web of Science Citations: 6
Abstract

The interaction of the cationic meso-tetrakis 4-N-methylpyridyl porphyrin (TMPyP) with large unilamellar vesicles (LUVs) was investigated in the present study. LUVs were formed by mixtures of the zwitterionic 1,2-dipalmitoyl-sn-glycero-phosphatidylcholine (DPPC) and anionic 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) phospholipids, at different DPPG molar percentages. All investigations were carried out above (50 degrees C) and below (25 degrees C) the main phase transition temperature of the LUVs (similar to 41 degrees C). The binding constant values, K-b, estimated from the time-resolved fluorescence study, showed a significant increase of the porphyrin affinity at higher mol% DPPG. This affinity is markedly increased when the LUVs are in the liquid crystalline state. For both situations, the increase of the K-b value was also followed by a higher porphyrin fraction bound to the LUVs. The displacement of the vesicle-bound porphyrins toward the aqueous medium, upon titration with the salt potassium chloride (KCl), was also studied. Altogether, our steady-state and frequency-domain fluorescence quenching data results indicate that the TMPyP is preferentially located at the LUVs Stern layer. This is supported by the zeta potential studies, where a partial neutralization of the LUVs surface charge, upon porphyrin titration, was observed. Dynamic light scattering (DLS) results showed that, for some phospholipid systems, this partial neutralization leads to the LUVs flocculation. (C) 2012 Elsevier Inc. All rights reserved. (AU)