Selective fluorescence resonance energy transfer from serum albumins to a bio-active 3-pyrazolyl-2-pyrazoline derivative: A spectroscopic analysis

► FRET from BSA/HSA to PYZ was monitored using steady state and time resolved fluorescence methods. ► Efficient FRET process resulted in BSA-PYZ system in contrast with the HSA-PYZ system. ► Surface bound Trp-134 in BSA facilitates the FRET process with PYZ than the buried Trp-214 in HSA. ► Rigid and complex structure of PYZ also accounts for the FRET selectivity of PYZ with BSA/HSA.