Spectroscopic studies of intermolecular chiral recognition processes.

摘要

The time-resolved circularly polarized luminescence technique is used to measure chiral recognition in two types of systems of biological importance. The technique experimentally determines the kinetics of enantioselective excited-state quenching occurring via electronic energy transfer between chiral lanthanide (donor) and transition metal (acceptor) complexes in solution. One set of experiments utilizes diastereomerically pure transition metal ATP isomers as quenchers of a racemic lanthanide tris (pyridine-2,6-dicarboxylate) species in solution. The transition metal ATP quenchers contain either Cr3+ or Rh3+, and the lanthanide is either Tb3+ or Eu3+. Twenty-one luminophore-quencher combinations are studied, and molecular modeling is performed on the various luminophore/quencher systems. The other set of experiments uses the tris (pyridine-2,6-dicarboxylate)terbium luminophore as an indirect probe of small molecule/DNA binding interactions. Five different quencher complexes are studied. All quenchers have the structural form [Ru(phen)2(5-X-phen)]2+ Where X = Cl, Br, CH 3, C6H5, or H. For these experiments, the solution contains racemic luminophore, racemic quencher, and calf thymus DNA. The DNA acts as a chiral resolving agent by enantiopreferentially binding one quencher enantiomer and removing it from the free quencher population of the solution. The resulting unbound enantiomeric excess of the opposite quencher enantiomer is then available to enantiopreferentially quench the racemic luminophore population. Data are also collected for solutions containing racemic luminophores and enantiomerically enriched quenchers both in the presence and absence of DNA. The theory quantifying chiral quenching interactions for this type of system is developed.