Probing the binding interaction of a phenazinium dye with serum transport proteins: a combined fluorometric and circular dichroism study.

In the present investigation, an attempt has been made to study the interaction of phenosafranin (PSF), a cationic phenazinium dye with the transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA), employing steady-state and time-resolved fluorometric and circular dichroism (CD) techniques. The photophysical properties of the dye are altered on binding with the serum proteins. An explicit study with respect to the modification of the fluorescence and fluorescence anisotropy upon binding, effect of denaturant, fluorescence lifetime and CD measurements reveal that the dye binds to both BSA and HSA with almost the same affinity. Far-UV CD spectra indicate a decrease in the percentage of alpha-helicity only for BSA upon binding with the probe. Near-UV CD responses indicate an alteration in the tertiary structure of both the transport proteins because of binding.