A fluorescence study of A23187 interaction with phospholipid vesicles
The fluorescence of the ionophore A23187 has been monitored in suspensions of egg yolk phosphatidylcholine (EYPC) and dipalmitoyl phosphatidylcholine (DPPC) vesicles. Both the protonated form of A23187 and the Ca/sup 2 +/ complex exhibit fluorescence enhancement when extracted into a hydrophobic environment. Measurements of fluorescence intensity versus lipid concentration were thus used to establish lower limits to the lipid/water partition coefficients. Values obtained in this way were greater than or equal to50 ml water/mg phosphatidylcholine. Quenching of A23187 fluorescence by the spin labels 5NMS (methyl ester of 5-nitroxyl stearate), 12NMS, 16NMS, and TEMPO stearamide in EYPC and DPPC vesicles was also investigated. In EYPC all the labels yielded fairly linear Stern-Volmer plots, with TEMPO stearamide quenching about half as strong as the other probes. Quenching in DPPC was generally much stronger than in EYPC, but 12 NMS and 16NMS gave hyperbolic Stern-Volmer plots, apparently due to clustering of the labels. In all the cases the protonated form of A23187 was quenched approximately twice as efficiently as the Ca/sup 2 +/ complex, possibly due to a longer fluorescence lifetime for the former. Calculations based on measured spectral properties were performed which indicate that the Forster transfer mechanism extends the nitroxides' quenching range to approximately 10 angstrom.
- Research Organization:
- Univ. of Rochester, NY
- DOE Contract Number:
- AC02-76EV03490
- OSTI ID:
- 5177844
- Journal Information:
- Arch. Biochem. Biophys.; (United States), Vol. 206:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBOXYLIC ACIDS
FLUORESCENCE
CALCIUM COMPLEXES
CATIONS
ENERGY TRANSFER
PARTITION
PHOSPHOLIPIDS
PROTONS
QUENCHING
SOLUBILITY
SPECTRAL RESPONSE
SPIN
ALKALINE EARTH METAL COMPLEXES
ANGULAR MOMENTUM
BARYONS
CHARGED PARTICLES
COMPLEXES
ELEMENTARY PARTICLES
ESTERS
FERMIONS
HADRONS
IONS
LIPIDS
LUMINESCENCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PARTICLE PROPERTIES
550200* - Biochemistry