The fluorescence and circular dichroism of proteins in reverse micelles: application to the photophysics of human serum albumin and N-acetyl-L-tryptophanamide.

Evidence is presented that a compartmentalised protein exists in its native state only within a particular size of aqueous cavity. This behaviour is shown to exist in AOT reverse micelles using fluorescence quenching and circular dichroism (CD) studies of human serum albumin (HSA). In particular, far ultraviolet CD measurements show that a reduction in quencher accessibility to the fluorophore is consistent with the protein being nearest to its native conformation at a waterpool size of around 80 A diameter. We also show that the biexponential fluorescence decay of N-acetyl-L-tryptophanamide (NATA) in AOT reverse micelles arises from the probe being located in two distinct sites within the interfacial region. The more viscous of these two sites is located on the waterpool side of the interface and the other is located on the oil side of the interface.

Multiplexed time-correlated single-photon counting.

We review the technique of multiplexed time-correlated single-photon counting whereby multiple fluorescence decay curves are recorded in parallel by statistically time-sharing a single time-to-amplitude converter. Application of the multiplexing technique to measuring the fluorescence lifetime topography of a self-absorbing sample is demonstrated. Further possibilities are discussed for multiplexed optical fiber sensor networks with built-in intelligence for detecting and discriminating between different metal ions in solution.