Emission-wavelength-dependent decay of the fluorescent probe |
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Authors: | ED Matayoshi AM Kleinfeld |
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Institution: | Biophysical Laboratory, Harvard Medical School, Boston, MA 02115 U.S.A. |
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Abstract: | We have measured the fluorescence decay of using the phase-modulation method, in several solvent systems and egg phosphatidylcholine vesicles. The decay is monoexponential in pure solvents (both polar and non-polar) of low viscosity. In polar viscous solvents or in non-polar solvents containing an added polar solute, the decay is heterogeneous and emission wavelength dependent. In such cases, dielectric relaxation and/or excited-state complexing give rise to a shift of the emission spectrum on the nanosecond time scale. Emission-wavelength-dependent decay was also observed when was bound to egg phosphatidylcholine vesicles. From these results as well as the position of the emission spectral maximum, we conclude that probes the ester-carbonyl region of the phospholipid acyl chains, where it undergoes an excited-state reaction. This result contradicts the often made assumption that probes the deeper hydrocarbon region of the bilayer. |
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Keywords: | Fluorescence decay N-Phenyl-1-naphthylamine Phosphatidylcholine vesicle |
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