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 n ative state only within a particular size of aqueous cavity, This beha viour is shown to exist in AOT reverse micelles using fluorescence que nching and circular dichroism (CD) studies of human serum albumin (HSA ). In particular, far ultraviolet CD measurements show that a reductio n in quencher accessibility to the fluorophore is consistent with the protein being nearest to its native conformation at a waterpool size o f around 80 Angstrom diameter. We also show that the biexponential flu orescence decay of N-acetyl-L-tryptophanamide (NATA) in AOT reverse mi celles arises from the probe being located in two distinct sites withi n the interfacial region, The more viscous of these two sites is locat ed on the waterpool side of the interface and the other is located on the oil side of the interface.