Nile Red and DCM Fluorescence Anisotropy Studies in C12E7/DPPC Mixed Systems

The lipid/surfactant mixed interactions between the lipid dipalmitoylphosphatydilcholine (DPPC) and the nonionic surfactant C12E7 (C12H25(OCH2CH2)7OH) were studied by the use of fluorescence anisotropy of nile red and DCM laser dye. Three different regions consisting of mixed micelles, mixed vesicle...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2002-12, Vol.106 (49), p.12841-12846
Main Authors: Coutinho, Paulo J. G, Castanheira, Elisabete M. S, Céu Rei, M, Real Oliveira, M. Elisabete C. D
Format: Article
Language:English
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Summary:The lipid/surfactant mixed interactions between the lipid dipalmitoylphosphatydilcholine (DPPC) and the nonionic surfactant C12E7 (C12H25(OCH2CH2)7OH) were studied by the use of fluorescence anisotropy of nile red and DCM laser dye. Three different regions consisting of mixed micelles, mixed vesicles, and both aggregates were identified. Nile red fluorescence anisotropy is wavelength-dependent, the spectra being decomposed into two log-normal functions. These results are consistent with a solvent relaxation process, with distinct anisotropies for the relaxed and unrelaxed states. The spectral properties (anisotropy and maximum emission wavelength) of the relaxed state show higher sensitivity to the environment than those of the unrelaxed state. DCM fluorescence anisotropy shows similar trends. This was interpreted as a result of a trans−cis photoisomerization process. The observed anisotropy spectrum was decomposed in two Gaussian functions reflecting a distinct anisotropy for each isomer.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp026479u