Protein-Mediated Efficient
Synergistic “Antenna
Effect” in a Ternary System in D<sub>2</sub>O Medium
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Abstract
A ternary system consisting of a protein, catechin (either
+ or
– epimer), and Tb(III) in suitable aqueous buffer medium at
physiological pH (= 6.8) has been shown to exhibit highly efficient
“antenna effect”. Steady state and time-resolved emission
studies of each component in the binary complexes (protein with Tb(III)
and (+)- or (−)-catechin with Tb(III)) and the ternary systems
along with the molecular docking studies reveal that the efficient
sensitization could be ascribed to the effective shielding of microenvironment
of Tb(III) from O–H oscillator and increased Tb–C (+/−)
interaction in the ternary systems in aqueous medium. The ternary
system exhibits protein-mediated efficient antenna effect in D<sub>2</sub>O medium due to synergistic ET from both the lowest ππ*
triplet state of Trp residue in protein and that of catechin apart
from protection of the Tb(III) environment from matrix vibration.
The simple system consisting of (+)- or (−)-catechin and Tb(III)
in D<sub>2</sub>O buffer at pH 6.8 has been prescribed to be a useful
biosensor