Ultrafast resonance energy transfer in bio-molecular systems

In this article, we present our consistent efforts to explore thedynamical pathways of the migration of electronic radiation by usingultrafast (picosecond/femtosecond time scales) Förster resonance energytransfer (FRET) technique. The ultrafast non-radiative energy migration froman intrinsic donor fluorophore (Tryptophan, Trp214) present in domain IIA ofa transporter protein human serum albumin (HSA) to variousnon-covalently/covalently attached organic/inorganic chromophores includingphotoporphyrin IX (PPIX), polyoxovanadateV₁₅As₆O₄₂(H₂O)]^-6clusters (denoted as V₁₅) and CdS quantum dots (QDs) has beenexplored. We have also used other covalently/non-covalently attachedextrinsic fluorogenic donors (NPA, ANS) in order to exploit the dynamics ofresonance energy migration of an enzyme α-chymotrypsin (CHT). Theuse of extrinsic donor instead of intrinsic Trp in CHT avoids ambiguity inthe location of the donor molecule as seven tryptophans are present in theenzyme CHT. We have labeled CHT with ANS (1-anilinonaphthalene-8-sulfonate)and NPA (4-nitrophenyl anthranilate) and studied FRET. Labeling of DNA hasalso been done in the context that the DNA bases have very low quantum yieldfor fluorescence. We have also validated FRET model over nano-surface energytransfer technique (NSET) in the case of quantum clusters and applied thefindings to other QDs. The use of QDs over organic fluorophore was justifiedby least photo-bleaching of QDs compared to organic fluorophore. Our studiesmay find relevance in the exploration of alternate pathway for ultrafastmigration of electronic radiation through FRET to minimize the detrimentaleffect of UV radiation in living organism.