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Role of Chiral Configuration in the Photoinduced Interaction of D- and L-Tryptophan with Optical Isomers of Ketoprofen in Linked Systems
Authors:Aleksandra A. Ageeva  Ilya M. Magin  Alexander B. Doktorov  Victor F. Plyusnin  Polina S. Kuznetsova  Alexander A. Stepanov  Alexander A. Alekseev  Nikolay E. Polyakov  Tatyana V. Leshina
Affiliation:1.Voevodsky Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk, Russia; (A.A.A.); (I.M.M.); (V.F.P.); (P.S.K.); (A.A.S.); (A.A.A.); (N.E.P.); (T.V.L.);2.Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia
Abstract:
The study of the L- and D-amino acid properties in proteins and peptides has attracted considerable attention in recent years, as the replacement of even one L-amino acid by its D-analogue due to aging of the body is resulted in a number of pathological conditions, including Alzheimer’s and Parkinson’s diseases. A recent trend is using short model systems to study the peculiarities of proteins with D-amino acids. In this report, the comparison of the excited states quenching of L- and D-tryptophan (Trp) in a model donor–acceptor dyad with (R)- and (S)-ketoprofen (KP-Trp) was carried out by photochemically induced dynamic nuclear polarization (CIDNP) and fluorescence spectroscopy. Quenching of the Trp excited states, which occurs via two mechanisms: prevailing resonance energy transfer (RET) and electron transfer (ET), indeed demonstrates some peculiarities for all three studied configurations of the dyad: (R,S)-, (S,R)-, and (S,S)-. Thus, the ET efficiency is identical for (S,R)- and (R,S)-enantiomers, while RET differs by 1.6 times. For (S,S)-, the CIDNP coefficient is almost an order of magnitude greater than for (R,S)- and (S,R)-. To understand the source of this difference, hyperpolarization of (S,S)-and (R,S)- has been calculated using theory involving the electron dipole–dipole interaction in the secular equation.
Keywords:chiral linked systems, diastereomers, enantiomers, electron transfer, resonance energy transfer, magnetic dipole–  dipole interaction of electrons
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