Low field photo-CIDNP in the intramolecular electron transfer in naproxen-pyrrolidine dyads

[EN] Photoinduced processes with partial (exciplex) and full charge transfer in donor-acceptor systems are of interest because they are frequently used for modeling drug-protein binding. Low field photo-CIDNP (chemically induced dynamic nuclear polarization) for these processes in dyads, including the drug, (S)-and (R)-naproxen and (S)-N-methyl pyrrolidine in solutions with strong and weak permittivity have been measured. The dramatic influence of solvent permittivity on the field dependence of the N-methyl pyrrolidine H-1 CIDNP effects has been found. The field dependences of both (R, S)-and (S, S)-dyads in a polar medium are the curves with a single extremum in the area of the S-T+ terms intersection. Moreover, the CIDNP field dependences of the same protons measured in a low polar medium present curves with several extrema. The shapes of the experimental CIDNP field dependence with two extrema have been described using the Green function approach for the calculation of the CIDNP effects in the system without electron exchange interactions. The article discusses the possible causes of the differences between the CIDNP field dependence detected in a low-permittivity solvent with the strong Coulomb interactions and in a polar solvent.This study was supported by the grant 14-03-00-192 of the Russian Foundation of Basic Research. The authors are also deeply grateful to Professor Hans-Martin Vieth for the given opportunity to conduct experiments on his unique equipment.Magin, I.; Polyakov, N.; Kruppa, AI.; Purtov, P.; Leshina, TV.; Kiryutin, AS.; Miranda Alonso, MÁ.... (2016). Low field photo-CIDNP in the intramolecular electron transfer in naproxen-pyrrolidine dyads. Physical Chemistry Chemical Physics. 18(2):901-907. https://doi.org/10.1039/C5CP04233JS901907182Reece, S. Y., & Nocera, D. G. (2009). 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Impact of chirality on the photoinduced charge transfer in linked systems containing naproxen enantiomers

[EN] The model reaction of photoinduced donor-acceptor interaction in linked systems (dyads) has been used to study the comparative reactivity of a well-known anti-inflammatory drug, (S)-naproxen (NPX) and its (R)-isomer. (R)- or (S)-NPX in these dyads is linked to (S)-N-methylpyrrolidine (Pyr) using a linear or cyclic amino acid bridge (AA or CyAA), to give (R)-/(S)-NPX-AA-(S)-Pyr flexible and (R)-/(S)-NPX-CyAA-(S)-Pyr rigid dyads. The donor-acceptor interaction is reminiscent of the binding (partial charge transfer, CT) and electron transfer (ET) processes involved in the extensively studied inhibition of the cyclooxygenase enzymes (COXs) by the NPX enantiomers. Besides that, both optical isomers undergo oxidative metabolism by enzymes from the P450 family, which also includes ET. The scheme proposed for the excitation quenching of the (R)- and (S)-NPX excited state in these dyads is based on the joint analysis of the chemically induced dynamic nuclear polarization (CIDNP) and fluorescence data. The H-1 CIDNP effects in this system appear in the back electron transfer in the biradical-zwitterion (BZ), which is formed via dyad photoirradiation. The rate constants of individual steps in the proposed scheme and the fluorescence quantum yields of the local excited (LE) states and exciplexes show stereoselectivity. It depends on the bridge's length, structure and solvent polarity. The CIDNP effects (experimental and calculated) also demonstrate stereodifferentiation. The exciplex quantum yields and the rates of formation are larger for the dyads containing (R)-NPX, which let us suggest a higher contribution from the CT processes with the (R)-optical isomer.The work was supported by the Russian Foundation for Fundamental Research (14-03-00192, 14-03-00692). All QS calculations were carried out on a cluster computer in the regional center for shared computer equipment at the Ufa Institute of Chemistry of RAS.Khramtsova, E.; Sosnovsky, D.; Ageeva, A.; Nuin Plá, NE.; Marín García, ML.; Purtov, P.; Borisevich, S.... (2016). Impact of chirality on the photoinduced charge transfer in linked systems containing naproxen enantiomers. Physical Chemistry Chemical Physics. 18(18):12733-12741. https://doi.org/10.1039/C5CP07305GS1273312741181

A program for representing and simulating population genetic phenomena

The paper describes a computer program for representing and simulating population genetic phenomena, such as the distribution of gene and genotype frequencies under different mating systems (panmixia, inbreeding and assortative mating systems) and under influence of evolution factors (mutation, selection, gene flow and genetic drift). The program was written in Visual Basic (Microsoft, Inc.) and is able to run in any IBM-PC compatible computer running Windows 3.1 or later versions