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Browsing by Author "Tormyshev, Victor M."

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    Electron spin dynamics and spin-lattice relaxation of trityl radicals in frozen solutions
    (Royal Society of Chemistry, 2016) Chen, Hanjiao; Maryasov, Alexander G.; Rogozhnikova, Olga Yu.; Trukhin, Dmitry V.; Tormyshev, Victor M.; Bowman, Michael K.; University of Alabama Tuscaloosa; Voevodsky Institute of Chemical Kinetics & Combustion SB RAS; Russian Academy of Sciences; Vorozhtsov Novosibirsk Institute of Organic Chemistry; Novosibirsk State University
    Electron spin-lattice relaxation of two trityl radicals, d(24)-OX063 and Finland trityl, were studied under conditions relevant to their use in dissolution dynamic nuclear polarization (DNP). The dependence of relaxation kinetics on temperature up to 100 K and on concentration up to 60 mM was obtained at X-and W-bands (0.35 and 3.5 Tesla, respectively). The relaxation is quite similar at both bands and for both trityl radicals. At concentrations typical for DNP, relaxation is mediated by excitation transfer and spin-diffusion to fast-relaxing centers identified as triads of trityl radicals that spontaneously form in the frozen samples. These centers relax by an Orbach-Aminov mechanism and determine the relaxation, saturation and electron spin dynamics during DNP.
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    Facile and High-Yielding Synthesis of TAM Biradicals and Monofunctional TAM Radicals
    (Georg Thieme Verlag, 2016) Trukhin, Dmitry V.; Rogozhnikova, Olga Yu.; Troitskaya, Tatiana I.; Vasiliev, Vladimir G.; Bowman, Michael K.; Tormyshev, Victor M.; Russian Academy of Sciences; Vorozhtsov Novosibirsk Institute of Organic Chemistry; Novosibirsk State University; University of Alabama Tuscaloosa
    Facile and high-yielding procedures for the synthesis of monocarboxylic acid derivatives of triarylmethyl radicals (TAM) were developed. Reaction of methyl thioglycolate with tris(2,3,5,6-tetrathiaaryl)methyl cation smoothly afforded the monosubstituted TAM derivative, which was hydrolyzed to a monocarboxylic acid, with the TAM moiety attached to thioglycolic acid via the sulfur atom. Alternatively, the diamagnetic tricarboxylic acid precursor of Finland trityl was transformed to a trimethyl ester and partially hydrolyzed under controlled conditions. The diester product was isolated, and the remaining fractions were converted back into the trimethyl ester for production of more diester. The first representatives of TAM biradicals with different TAM cores and interspin distances were obtained by reaction of these new TAM monocaboxylic acids with N,N-dimethylethylenediamine.
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    Preparation of Diversely Substituted Triarylmethyl Radicals by the Quenching of Tris(2,3,5,6-tetrathiaaryl)methyl Cations with C-, N-, P-, and S-Nucleophiles
    (Wiley-VCH, 2014) Tormyshev, Victor M.; Rogozhnikova, Olga Yu.; Bowman, Michael K.; Trukhin, Dmitry V.; Troitskaya, Tatiana I.; Vasiliev, Vladimir G.; Shundrin, Leonid A.; Halpern, Howard J.; Russian Academy of Sciences; Vorozhtsov Novosibirsk Institute of Organic Chemistry; Novosibirsk State University; University of Alabama Tuscaloosa; University of Chicago
    C-, N-, P-, and S-nucleophiles reacted with symmetrical tris(2,3,5,6-tetrathiaaryl)methyl cations, generated from the corresponding triarylmethanols by strong acids, to give a variety of asymmetrical monosubstituted persistent triarylmethyl (TAM) radicals as the major products. The only by-products were symmetrical TAMs.
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    A radical containing injectable in-situ-oleogel and emulgel for prolonged invivo oxygen measurements with CW EPR
    (Elsevier, 2019) Lampp, Lisa; Rogozhnikova, Olga Yu.; Trukhin, Dmitry V.; Tormyshev, Victor M.; Bowman, Michael K.; Devasahayam, Nllathamby; Krishna, Murali C.; Maeder, Karsten; Imming, Peter; Martin Luther University Halle Wittenberg; Russian Academy of Sciences; Vorozhtsov Novosibirsk Institute of Organic Chemistry; Novosibirsk State University; University of Alabama Tuscaloosa; National Institutes of Health (NIH) - USA; NIH National Cancer Institute (NCI)
    Molecular oxygen, reactive oxygen species and free radicals derived from oxygen play important roles in a broad spectrum of physiological and pathological processes. The quantitative measurement of molecular oxygen in tissues by electron paramagnetic resonance (EPR) has great potential for understanding and diagnosing a number of diseases, and for developing and guiding therapies. This requires improvements in the free radical probe systems that sense and report molecular oxygen levels in vivo. We report on the encapsulation of existing free radical probes in lipophilic gel implants: an in-situ-oleogel and an emulgel, based only on well-known, safe excipients for the incorporation of lipophilic and hydrophilic radicals, respectively. The EPR signals of encapsulated radicals were not altered compared to dissolved radicals. The high solubility of oxygen in lipophilic solvents enhanced oxygen sensitivity. The gels extended the lifetime of the radicals in tissues from tens of minutes to many days, simplifying studies with extended series of measurements. The encapsulated radicals showed a good in vivo response to changes in oxygen supply and seem to circumvent concerns from toxicity of the radical probes. These gels simplify the development of new oxygen-sensitive free radical probes for EPR oximetry by making their in vivo stability, persistence and toxicity a function of the encapsulating gel and not a set of additional requirements for the free radical probe.