Km. Hirshfield et al., A NANOSECOND FLUORESCENCE STUDY OF THE SIMULTANEOUS INFLUX OF CA2+ AND CD2+ INTO LIPOSOMES, Biophysical chemistry, 71(1), 1998, pp. 63-72
Nanosecond fluorescence decay characteristics of the calcium-binding p
robe Quin2 and two of its cation complexes were examined by time-resol
ved fluorescence spectroscopy. Binding of Ca2+ and Cd2+ resulted in, f
luorescence lifetime enhancements as compared to that of free Quin2 ([
tau] = 0.9 ns). The Quin2-Ca2+ complex displays a monoexponential deca
y of tau = 7.4 ns, while the cadmium complex gives an average decay ti
me of ca. 4 ns. Lifetime measurements made on heterogeneous cationic s
olutions demonstrate that decay times for individual complexes can be
retrieved. Time-resolved measurements were used to monitor the kinetic
s of ionomycin-mediated calcium and cadmium transport across artificia
l membranes. Fluorescence decays, collected on the time-scale of secon
ds, were sufficient to measure individual ion fluxes or those of mixtu
res into liposomes. The combination of steady-state and time-resolved
fluorescence techniques offers the unique advantage of simultaneously
detecting other cations in the presence of calcium. (C) 1998 Elsevier
Science B.V.