Ultrafast resonance energy transfer in bio-molecular systems

In this article, we present our consistent efforts to explore the dynamical pathways of the migration of electronic radiation by using ultrafast (picosecond/femtosecond time scales) Forster resonance energy transfer (FRET) technique. The ultrafast non-radiative energy migration from an intrinsic donor fluorophore (Tryptophan, Trp214) present in domain IIA of a transporter protein human serum albumin (HSA) to various non-covalently/covalently attached organic/inorganic chromophores including photoporphyrin IX (PPIX), polyoxovanadate [V15As6O42(H2O)](-6) clusters (denoted as V-15) and CdS quantum dots (QDs) has been explored. We have also used other covalently/non-covalently attached extrinsic fluorogenic donors (NPA, ANS) in order to exploit the dynamics of resonance energy migration of an enzyme alpha-chymotrypsin (CHT). The use of extrinsic donor instead of intrinsic Trp in CHT avoids ambiguity in the location of the donor molecule as seven tryptophans are present in the enzyme CHT. We have labeled CHT with ANS (1-anilinonaphthalene-8-sulfonate) and NPA (4-nitrophenyl anthranilate) and studied FRET. Labeling of DNA has also been done in the context that the DNA bases have very low quantum yield for fluorescence. We have also validated FRET model over nano-surface energy transfer technique (NSET) in the case of quantum clusters and applied the findings to other QDs. The use of QDs over organic fluorophore was justified by least photo-bleaching of QDs compared to organic fluorophore. Our studies may find relevance in the exploration of alternate pathway for ultrafast migration of electronic radiation through FRET to minimize the detrimental effect of UV radiation in living organism.