GLOBAL ANALYSIS OF WAVELENGTH-RESOLVED FLUORESCENCE DECAY IN SARCOPLASMIC-RETICULUM CALCIUM-ATPASE

The intrinsic fluorescence decay of sarcoplasmic reticulum Ca2+-ATPase was measured in the frequency-domain at 10 nm intervals across the emission spectrum. Data were globally analysed in terms of a unique set of lifetime values, allowing for changes in fractional intensities of each lifetime across the emission. The wavelength-resolved decay was optimally described by a Lorentzian distribution of lifetimes plus two exponential terms. Analysis of chi-2 surfaces associated with uncertainties in fitting parameters revealed that the recovered parameters were well-defined despite the complexity of the decay. Thus, global analysis enables resolution of ATPase fluorescence into decay-associated spectral components, which should permit investigation of ligand-induced changes in each individual component.