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). Proton-Coupled Electron Transfer in Biology: Results from Synergistic Studies in Natural and Model Systems. Annual Review of Biochemistry, 78(1), 673-699. doi:10.1146/annurev.biochem.78.080207.092132Richert, S., Rosspeintner, A., Landgraf, S., Grampp, G., Vauthey, E., & Kattnig, D. R. (2013). Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes. Journal of the American Chemical Society, 135(40), 15144-15152. doi:10.1021/ja407052tAich, S., & Basu, S. (1998). Magnetic Field Effect: A Tool for Identification of Spin State in a Photoinduced Electron-Transfer Reaction. The Journal of Physical Chemistry A, 102(4), 722-729. doi:10.1021/jp972264mVayá, I., Pérez-Ruiz, R., Lhiaubet-Vallet, V., Jiménez, M. C., & Miranda, M. A. (2010). Drug–protein interactions assessed by fluorescence measurements in the real complexes and in model dyads. Chemical Physics Letters, 486(4-6), 147-153. doi:10.1016/j.cplett.2009.12.091Werner, U., & Staerk, H. (1995). Magnetic Field Effect in the Recombination Reaction of Radical Ion Pairs: Dependence on Solvent Dielectric Constant. The Journal of Physical Chemistry, 99(1), 248-254. doi:10.1021/j100001a038Kattnig, D. R., Rosspeintner, A., & Grampp, G. (2008). Fully Reversible Interconversion between Locally Excited Fluorophore, Exciplex, and Radical Ion Pair Demonstrated by a New Magnetic Field Effect. Angewandte Chemie International Edition, 47(5), 960-962. doi:10.1002/anie.200703488Kattnig, D. R., Rosspeintner, A., & Grampp, G. (2011). Magnetic field effects on exciplex-forming systems: the effect on the locally excited fluorophore and its dependence on free energy. Phys. Chem. Chem. Phys., 13(8), 3446-3460. doi:10.1039/c0cp01517bVayá, I., Lhiaubet-Vallet, V., Jiménez, M. C., & Miranda, M. A. (2014). Photoactive assemblies of organic compounds and biomolecules: drug–protein supramolecular systems. Chem. Soc. Rev., 43(12), 4102-4122. doi:10.1039/c3cs60413fPolyakov, N. E., Taraban, M. B., & Leshina, T. V. (2004). Photo-CIDNP Study of the Interaction of Tyrosine with Nifedipine. An Attempt to Model the Binding Between Calcium Receptor and Calcium Antagonist Nifedipine¶. Photochemistry and Photobiology, 80(3), 565. doi:10.1562/0031-8655(2004)0802.0.co;2Cao, H., Fujiwara, Y., Haino, T., Fukazawa, Y., Tung, C.-H., & Tanimoto, Y. (1996). Magnetic Field Effects on Intramolecular Exciplex Fluorescence of Chain-Linked Phenanthrene andN,N-Dimethylaniline: Influence of Chain Length, Solvent, and Temperature. Bulletin of the Chemical Society of Japan, 69(10), 2801-2813. doi:10.1246/bcsj.69.2801Magin, I. M., Polyakov, N. E., Khramtsova, E. A., Kruppa, A. I., Tsentalovich, Y. P., Leshina, T. V., … Marin, M. L. (2011). Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad. Chemical Physics Letters, 516(1-3), 51-55. doi:10.1016/j.cplett.2011.09.057Khramtsova, E. A., Plyusnin, V. F., Magin, I. M., Kruppa, A. I., Polyakov, N. E., Leshina, T. V., … Miranda, M. A. (2013). Time-Resolved Fluorescence Study of Exciplex Formation in Diastereomeric Naproxen–Pyrrolidine Dyads. The Journal of Physical Chemistry B, 117(50), 16206-16211. doi:10.1021/jp4083147Magin, I. M., Purtov, P. A., Kruppa, A. I., & Leshina, T. V. (2005). Peculiarities of Magnetic and Spin Effects in a Biradical/Stable Radical Complex (Three-Spin System). Theory and Comparison with Experiment. The Journal of Physical Chemistry A, 109(33), 7396-7401. doi:10.1021/jp051115ySubramanian, V., Bellubbi, B. S., & Sobhanadri, J. (1993). Dielectric studies of some binary liquid mixtures using microwave cavity techniques. Pramana, 41(1), 9-20. doi:10.1007/bf02847313Acemioğlu, B., Arık, M., Efeoğlu, H., & Onganer, Y. (2001). Solvent effect on the ground and excited state dipole moments of fluorescein. Journal of Molecular Structure: THEOCHEM, 548(1-3), 165-171. doi:10.1016/s0166-1280(01)00513-9Grosse, S., Gubaydullin, F., Scheelken, H., Vieth, H.-M., & Yurkovskaya, A. V. (1999). Field cycling by fast NMR probe transfer: Design and application in field-dependent CIDNP experiments. Applied Magnetic Resonance, 17(2-3), 211-225. doi:10.1007/bf03162162Magin, I. M., Polyakov, N. E., Khramtsova, E. A., Kruppa, A. I., Stepanov, A. A., Purtov, P. A., … Marin, M. L. (2011). Spin Chemistry Investigation of Peculiarities of Photoinduced Electron Transfer in Donor–Acceptor Linked System. Applied Magnetic Resonance, 41(2-4), 205-220. doi:10.1007/s00723-011-0288-3C. K. Mann and K. K.Barnes, Electrochemical Reactions in Nonaqueous Systems, M. Dekker, New York, 1970N. S. Landolt-Bornstein , Numerical Data and Functional Relationship in Science and Technology: Magnetic Properties of Free Radicals, Springer-Verlag, Berlin, 1988Grigoryants, V. M., Anisimov, O. A., & Molin, Y. N. (1982). Study of the radical-cations of triethylamine and benzene derivatives by the optical detection of the EPR spectra of radical-ion Pairs. Journal of Structural Chemistry, 23(3), 327-333. doi:10.1007/bf00753466Bargon, J. (1977). CIDNP from geminate recombination of radical-ion pairs in polar solvents. Journal of the American Chemical Society, 99(25), 8350-8351. doi:10.1021/ja00467a054Purtov, P. A., & Doktorov, A. B. (1993). The Green function method in the theory of nuclear and electron spin polarization. I. General theory, zero approximation and applications. Chemical Physics, 178(1-3), 47-65. doi:10.1016/0301-0104(93)85050-iPurtov, P. A., Doktorov, A. B., & Popov, A. V. (1994). The green function method in the theory of nuclear and electron spin polarization. II. The first approximation and its application in the CIDEP theory. Chemical Physics, 182(2-3), 149-166. doi:10.1016/0301-0104(93)e0449-6K. M. Salikhov , Yu. N.Molin, R. Z.Sagdeev and A. L.Buchachenko, in Spin Polarization and Magnetic Field Effects in Radical, ed. Yu. N. Molin, Akademiai Kiado, Budapest, 1984Polyakov, N. E., Purtov, P. A., Leshina, T. V., Taraban, M. B., Sagdeev, R. Z., & Salikhov, K. M. (1986). Application of the semiclassical description of hyperfine interaction to studies of the dependence of the CIDNP effect on an external magnetic field. Chemical Physics Letters, 129(4), 357-361. doi:10.1016/0009-2614(86)80358-xShiotani, M., Sjoeqvist, L., Lund, A., Lunell, S., Eriksson, L., & Huang, M. B. (1990). An ESR and theoretical ab initio study of the structure and dynamics of the pyrrolidine radical cation and the neutral 1-pyrrolidinyl radical. The Journal of Physical Chemistry, 94(21), 8081-8090. doi:10.1021/j100384a020De Kanter, F. J. J., den Hollander, J. A., Huizer, A. H., & Kaptein, R. (1977). Biradical CIDNP and the dynamics of polymethylene chains. Molecular Physics, 34(3), 857-874. doi:10.1080/00268977700102161De Kanter, F. J. J., Kaptein, R., & Van Santen, R. A. (1977). Magnetic field dependent biradical CIDNP as a tool for the study of conformations of polymethylene chains. Chemical Physics Letters, 45(3), 575-579. doi:10.1016/0009-2614(77)80093-6Tsentalovich, Y. P., Yurkovskaya, A. V., Sagdeev, R. Z., Obynochny, A. A., Purtov, P. A., & Shargorodsky, A. A. (1989). Kinetics of nuclear polarization in the geminate recombination of biradicals. Chemical Physics, 139(2-3), 307-315. doi:10.1016/0301-0104(89)80143-0Popov, A. V., Purtov, P. A., & Yurkovskaya, A. V. (2000). Calculation of CIDNP field dependences in biradicals in the photolysis of large-ring cycloalkanones. Chemical Physics, 252(1-2), 83-95. doi:10.1016/s0301-0104(99)00293-1Magin, I. M., Shevel’kov, V. S., Obynochny, A. A., Kruppa, A. I., & Leshina, T. V. (2002). CIDNP study of the third spin effect on the singlet–triplet evolution in radical pairs. Chemical Physics Letters, 357(5-6), 351-357. doi:10.1016/s0009-2614(02)00544-4Schulten, K., & Wolynes, P. G. (1978). Semiclassical description of electron spin motion in radicals including the effect of electron hopping. The Journal of Chemical Physics, 68(7), 3292-3297. doi:10.1063/1.436135Kalneus, E. V., Stass, D. V., & Molin, Y. N. (2005). Typical applications of MARY spectroscopy: Radical ions of substituted benzenes. Applied Magnetic Resonance, 28(3-4), 213-229. doi:10.1007/bf03166757Kruppa, A. I., Leshina, T. V., Sagdeev, R. Z., Korolenko, E. C., & Shokhirev, N. V. (1987). Low-field CIDNP study of photoinduced electron transfer reactions. Chemical Physics, 114(1), 95-101. doi:10.1016/0301-0104(87)80022-

Genome Sequence of the Pea Aphid Acyrthosiphon pisum

Aphids are important agricultural pests and also biological models for studies of insect-plant interactions, symbiosis, virus vectoring, and the developmental causes of extreme phenotypic plasticity. Here we present the 464 Mb draft genome assembly of the pea aphid Acyrthosiphon pisum. This first published whole genome sequence of a basal hemimetabolous insect provides an outgroup to the multiple published genomes of holometabolous insects. Pea aphids are host-plant specialists, they can reproduce both sexually and asexually, and they have coevolved with an obligate bacterial symbiont. Here we highlight findings from whole genome analysis that may be related to these unusual biological features. These findings include discovery of extensive gene duplication in more than 2000 gene families as well as loss of evolutionarily conserved genes. Gene family expansions relative to other published genomes include genes involved in chromatin modification, miRNA synthesis, and sugar transport. Gene losses include genes central to the IMD immune pathway, selenoprotein utilization, purine salvage, and the entire urea cycle. The pea aphid genome reveals that only a limited number of genes have been acquired from bacteria; thus the reduced gene count of Buchnera does not reflect gene transfer to the host genome. The inventory of metabolic genes in the pea aphid genome suggests that there is extensive metabolite exchange between the aphid and Buchnera, including sharing of amino acid biosynthesis between the aphid and Buchnera. The pea aphid genome provides a foundation for post-genomic studies of fundamental biological questions and applied agricultural problems

Surprising absence of strong homonuclear coupling at low magnetic field explored by two-field nuclear magnetic resonance spectroscopy

Strong coupling of nuclear spins, which is achieved when their scalar coupling 2πJ is greater than or comparable to the difference Δω in their Larmor precession frequencies in an external magnetic field, gives rise to efficient coherent longitudinal polarization transfer. The strong coupling regime can be achieved when the external magnetic field is sufficiently low, as Δω is reduced proportional to the field strength. In the present work, however, we demonstrate that in heteronuclear spin systems these simple arguments may not hold, since heteronuclear spin–spin interactions alter the Δω value. The experimental method that we use is two-field nuclear magnetic resonance (NMR), exploiting sample shuttling between the high field, at which NMR spectra are acquired, and the low field, where strong couplings are expected and at which NMR pulses can be applied to affect the spin dynamics. By using this technique, we generate zero-quantum spin coherences by means of a nonadiabatic passage through a level anticrossing and study their evolution at the low field. Such zero-quantum coherences mediate the polarization transfer under strong coupling conditions. Experiments performed with a 13C-labeled amino acid clearly show that the coherent polarization transfer at the low field is pronounced in the 13C spin subsystem under proton decoupling. However, in the absence of proton decoupling, polarization transfer by coherent processes is dramatically reduced, demonstrating that heteronuclear spin–spin interactions suppress the strong coupling regime, even when the external field is low. A theoretical model is presented, which can model the reported experimental results.</p

Parahydrogen-Induced Hyperpolarization of Unsaturated Phosphoric Acid Derivatives

Parahydrogen-induced nuclear polarization offers a significant increase in the sensitivity of NMR spectroscopy to create new probes for medical diagnostics by magnetic resonance imaging. As precursors of the biocompatible hyperpolarized probes, unsaturated derivatives of phosphoric acid, propargyl and allyl phosphates, are proposed. The polarization transfer to 1H and 31P nuclei of the products of their hydrogenation by parahydrogen under the ALTADENA and PASADENA conditions, and by the PH-ECHO-INEPT+ pulse sequence of NMR spectroscopy, resulted in a very high signal amplification, which is among the largest for parahydrogen-induced nuclear polarization transfer to the 31P nucleus

Exchange interaction in short-lived flavine adenine dinucleotide biradical in aqueous solution revisited by CIDNP (chemically induced dynamic nuclear polarization) and nuclear magnetic relaxation dispersion

Flavin adenine dinucleotide (FAD) is an important cofactor in many light-sensitive enzymes. The role of the adenine moiety of FAD in light-induced electron transfer was obscured, because it involves an adenine radical, which is short-lived with a weak chromophore. However, an intramolecular electron transfer from adenine to flavin was revealed several years ago by Robert Kaptein by using chemically induced dynamic nuclear polarization (CIDNP). The question of whether one or two types of biradicals of FAD in aqueous solution are formed stays unresolved so far. In the present work, we revisited the CIDNP study of FAD using a robust mechanical sample shuttling setup covering a wide magnetic field range with sample illumination by a light-emitting diode. Also, a cost efficient fast field cycling apparatus with high spectral resolution detection up to 16.4 T for nuclear magnetic relaxation dispersion studies was built based on a 700 MHz NMR spectrometer. Site-specific proton relaxation dispersion data for FAD show a strong restriction of the relative motion of its isoalloxazine and adenine rings with coincident correlation times for adenine, flavin, and their ribityl phosphate linker. This finding is consistent with the assumption that the molecular structure of FAD is rigid and compact. The structure with close proximity of the isoalloxazine and purine moieties is favorable for reversible light-induced intramolecular electron transfer from adenine to triplet excited flavin with formation of a transient spin-correlated triplet biradical F⚫−-A⚫+. Spin-selective recombination of the biradical leads to the formation of CIDNP with a common emissive maximum at 4.0 mT detected for adenine and flavin protons. Careful correction of the CIDNP data for relaxation losses during sample shuttling shows that only a single maximum of CIDNP is formed in the magnetic field range from 0.1 mT to 9 T; thus, only one type of FAD biradical is detectable. Modeling of the CIDNP field dependence provides good agreement with the experimental data for a normal distance distribution between the two radical centers around 0.89 nm and an effective electron exchange interaction of −2.0 mT.</p

Low field photo-CIDNP in the intramolecular electron transfer of 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/C5CP04233J901907182Reece, S. Y., & Nocera, D. G. (2009). Proton-Coupled Electron Transfer in Biology: Results from Synergistic Studies in Natural and Model Systems. Annual Review of Biochemistry, 78(1), 673-699. doi:10.1146/annurev.biochem.78.080207.092132Richert, S., Rosspeintner, A., Landgraf, S., Grampp, G., Vauthey, E., & Kattnig, D. R. (2013). Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes. Journal of the American Chemical Society, 135(40), 15144-15152. doi:10.1021/ja407052tAich, S., & Basu, S. (1998). Magnetic Field Effect: A Tool for Identification of Spin State in a Photoinduced Electron-Transfer Reaction. The Journal of Physical Chemistry A, 102(4), 722-729. doi:10.1021/jp972264mVayá, I., Pérez-Ruiz, R., Lhiaubet-Vallet, V., Jiménez, M. C., & Miranda, M. A. (2010). Drug–protein interactions assessed by fluorescence measurements in the real complexes and in model dyads. Chemical Physics Letters, 486(4-6), 147-153. doi:10.1016/j.cplett.2009.12.091Werner, U., & Staerk, H. (1995). Magnetic Field Effect in the Recombination Reaction of Radical Ion Pairs: Dependence on Solvent Dielectric Constant. The Journal of Physical Chemistry, 99(1), 248-254. doi:10.1021/j100001a038Kattnig, D. R., Rosspeintner, A., & Grampp, G. (2008). Fully Reversible Interconversion between Locally Excited Fluorophore, Exciplex, and Radical Ion Pair Demonstrated by a New Magnetic Field Effect. Angewandte Chemie International Edition, 47(5), 960-962. doi:10.1002/anie.200703488Kattnig, D. R., Rosspeintner, A., & Grampp, G. (2011). Magnetic field effects on exciplex-forming systems: the effect on the locally excited fluorophore and its dependence on free energy. Phys. Chem. Chem. Phys., 13(8), 3446-3460. doi:10.1039/c0cp01517bVayá, I., Lhiaubet-Vallet, V., Jiménez, M. C., & Miranda, M. A. (2014). Photoactive assemblies of organic compounds and biomolecules: drug–protein supramolecular systems. Chem. Soc. Rev., 43(12), 4102-4122. doi:10.1039/c3cs60413fPolyakov, N. E., Taraban, M. B., & Leshina, T. V. (2004). Photo-CIDNP Study of the Interaction of Tyrosine with Nifedipine. An Attempt to Model the Binding Between Calcium Receptor and Calcium Antagonist Nifedipine¶. Photochemistry and Photobiology, 80(3), 565. doi:10.1562/0031-8655(2004)0802.0.co;2Cao, H., Fujiwara, Y., Haino, T., Fukazawa, Y., Tung, C.-H., & Tanimoto, Y. (1996). Magnetic Field Effects on Intramolecular Exciplex Fluorescence of Chain-Linked Phenanthrene andN,N-Dimethylaniline: Influence of Chain Length, Solvent, and Temperature. Bulletin of the Chemical Society of Japan, 69(10), 2801-2813. doi:10.1246/bcsj.69.2801Magin, I. M., Polyakov, N. E., Khramtsova, E. A., Kruppa, A. I., Tsentalovich, Y. P., Leshina, T. V., … Marin, M. L. (2011). Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad. Chemical Physics Letters, 516(1-3), 51-55. doi:10.1016/j.cplett.2011.09.057Khramtsova, E. A., Plyusnin, V. F., Magin, I. M., Kruppa, A. I., Polyakov, N. E., Leshina, T. V., … Miranda, M. A. (2013). Time-Resolved Fluorescence Study of Exciplex Formation in Diastereomeric Naproxen–Pyrrolidine Dyads. The Journal of Physical Chemistry B, 117(50), 16206-16211. doi:10.1021/jp4083147Magin, I. M., Purtov, P. A., Kruppa, A. I., & Leshina, T. V. (2005). Peculiarities of Magnetic and Spin Effects in a Biradical/Stable Radical Complex (Three-Spin System). Theory and Comparison with Experiment. The Journal of Physical Chemistry A, 109(33), 7396-7401. doi:10.1021/jp051115ySubramanian, V., Bellubbi, B. S., & Sobhanadri, J. (1993). Dielectric studies of some binary liquid mixtures using microwave cavity techniques. Pramana, 41(1), 9-20. doi:10.1007/bf02847313Acemioğlu, B., Arık, M., Efeoğlu, H., & Onganer, Y. (2001). Solvent effect on the ground and excited state dipole moments of fluorescein. Journal of Molecular Structure: THEOCHEM, 548(1-3), 165-171. doi:10.1016/s0166-1280(01)00513-9Grosse, S., Gubaydullin, F., Scheelken, H., Vieth, H.-M., & Yurkovskaya, A. V. (1999). Field cycling by fast NMR probe transfer: Design and application in field-dependent CIDNP experiments. Applied Magnetic Resonance, 17(2-3), 211-225. doi:10.1007/bf03162162Magin, I. M., Polyakov, N. E., Khramtsova, E. A., Kruppa, A. I., Stepanov, A. A., Purtov, P. A., … Marin, M. L. (2011). Spin Chemistry Investigation of Peculiarities of Photoinduced Electron Transfer in Donor–Acceptor Linked System. Applied Magnetic Resonance, 41(2-4), 205-220. doi:10.1007/s00723-011-0288-3C. K. Mann and K. K.Barnes, Electrochemical Reactions in Nonaqueous Systems, M. Dekker, New York, 1970N. S. Landolt-Bornstein , Numerical Data and Functional Relationship in Science and Technology: Magnetic Properties of Free Radicals, Springer-Verlag, Berlin, 1988Grigoryants, V. M., Anisimov, O. A., & Molin, Y. N. (1982). Study of the radical-cations of triethylamine and benzene derivatives by the optical detection of the EPR spectra of radical-ion Pairs. Journal of Structural Chemistry, 23(3), 327-333. doi:10.1007/bf00753466Bargon, J. (1977). CIDNP from geminate recombination of radical-ion pairs in polar solvents. Journal of the American Chemical Society, 99(25), 8350-8351. doi:10.1021/ja00467a054Purtov, P. A., & Doktorov, A. B. (1993). The Green function method in the theory of nuclear and electron spin polarization. I. General theory, zero approximation and applications. Chemical Physics, 178(1-3), 47-65. doi:10.1016/0301-0104(93)85050-iPurtov, P. A., Doktorov, A. B., & Popov, A. V. (1994). The green function method in the theory of nuclear and electron spin polarization. II. The first approximation and its application in the CIDEP theory. Chemical Physics, 182(2-3), 149-166. doi:10.1016/0301-0104(93)e0449-6K. M. Salikhov , Yu. N.Molin, R. Z.Sagdeev and A. L.Buchachenko, in Spin Polarization and Magnetic Field Effects in Radical, ed. Yu. N. Molin, Akademiai Kiado, Budapest, 1984Polyakov, N. E., Purtov, P. A., Leshina, T. V., Taraban, M. B., Sagdeev, R. Z., & Salikhov, K. M. (1986). Application of the semiclassical description of hyperfine interaction to studies of the dependence of the CIDNP effect on an external magnetic field. Chemical Physics Letters, 129(4), 357-361. doi:10.1016/0009-2614(86)80358-xShiotani, M., Sjoeqvist, L., Lund, A., Lunell, S., Eriksson, L., & Huang, M. B. (1990). An ESR and theoretical ab initio study of the structure and dynamics of the pyrrolidine radical cation and the neutral 1-pyrrolidinyl radical. The Journal of Physical Chemistry, 94(21), 8081-8090. doi:10.1021/j100384a020De Kanter, F. J. J., den Hollander, J. A., Huizer, A. H., & Kaptein, R. (1977). Biradical CIDNP and the dynamics of polymethylene chains. Molecular Physics, 34(3), 857-874. doi:10.1080/00268977700102161De Kanter, F. J. J., Kaptein, R., & Van Santen, R. A. (1977). Magnetic field dependent biradical CIDNP as a tool for the study of conformations of polymethylene chains. Chemical Physics Letters, 45(3), 575-579. doi:10.1016/0009-2614(77)80093-6Tsentalovich, Y. P., Yurkovskaya, A. V., Sagdeev, R. Z., Obynochny, A. A., Purtov, P. A., & Shargorodsky, A. A. (1989). Kinetics of nuclear polarization in the geminate recombination of biradicals. Chemical Physics, 139(2-3), 307-315. doi:10.1016/0301-0104(89)80143-0Popov, A. V., Purtov, P. A., & Yurkovskaya, A. V. (2000). Calculation of CIDNP field dependences in biradicals in the photolysis of large-ring cycloalkanones. Chemical Physics, 252(1-2), 83-95. doi:10.1016/s0301-0104(99)00293-1Magin, I. M., Shevel’kov, V. S., Obynochny, A. A., Kruppa, A. I., & Leshina, T. V. (2002). CIDNP study of the third spin effect on the singlet–triplet evolution in radical pairs. Chemical Physics Letters, 357(5-6), 351-357. doi:10.1016/s0009-2614(02)00544-4Schulten, K., & Wolynes, P. G. (1978). Semiclassical description of electron spin motion in radicals including the effect of electron hopping. The Journal of Chemical Physics, 68(7), 3292-3297. doi:10.1063/1.436135Kalneus, E. V., Stass, D. V., & Molin, Y. N. (2005). Typical applications of MARY spectroscopy: Radical ions of substituted benzenes. Applied Magnetic Resonance, 28(3-4), 213-229. doi:10.1007/bf03166757Kruppa, A. I., Leshina, T. V., Sagdeev, R. Z., Korolenko, E. C., & Shokhirev, N. V. (1987). Low-field CIDNP study of photoinduced electron transfer reactions. Chemical Physics, 114(1), 95-101. doi:10.1016/0301-0104(87)80022-