Browsing by Author "Fedin, Matvey"

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    Electron Spin Relaxation of Photoexcited Porphyrin in Water-Glycerol Glass
    (MDPI, 2020) Sannikova, Natalya; Timofeev, Ivan; Bagryanskaya, Elena; Bowman, Michael; Fedin, Matvey; Krumkacheva, Olesya; International Tomography Center, Siberian Branch of Russian Academy of Sciences; Russian Academy of Sciences; University of Alabama Tuscaloosa
    Recently, the photoexcited triplet state of porphyrin was proposed as a promising spin-label for pulsed dipolar electron paramagnetic resonance (EPR). Herein, we report the factors that determine the electron spin echo dephasing of the photoexcited porphyrin in a water-glycerol matrix. The electron spin relaxation of a water-soluble porphyrin was measured by Q-band EPR, and the temperature dependence and the effect of solvent deuteration on the relaxation times were studied. The phase memory relaxation rate (1/T-m) is noticeably affected by solvent nuclei and is substantially faster in protonated solvents than in deuterated solvents. The T-m is as large as 13-17 mu s in deuterated solvent, potentially expanding the range of distances available for measurement by dipole spectroscopy with photoexcited porphyrin. The 1/T-m depends linearly on the degree of solvent deuteration and can be used to probe the environment of a porphyrin in or near a biopolymer, including the solvent accessibility of porphyrins used in photodynamic therapy. We characterized the noncovalent binding of porphyrin to human serum albumin (HSA) from 1/T-m and electron spin echo envelope modulation (ESEEM) and found that porphyrin is quite exposed to solvent on the surface of HSA. The 1/T-m and ESEEM are equally effective and provide complementary methods to determine the solvent accessibility of a porphyrin bound to protein or to determine the location of the porphyrin.
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    Reversible Dimerization of Human Serum Albumin
    (MDPI, 2020) Chubarov, Alexey; Spitsyna, Anna; Krumkacheva, Olesya; Mitin, Dmitry; Suvorov, Daniil; Tormyshev, Victor; Fedin, Matvey; Bowman, Michael K.; Bagryanskaya, Elena; Institute of Chemical Biology & Fundamental Medicine, Siberian Branch of the RAS; Russian Academy of Sciences; Novosibirsk State University; Vorozhtsov Novosibirsk Institute of Organic Chemistry; International Tomography Center, Siberian Branch of Russian Academy of Sciences; University of Alabama Tuscaloosa
    Pulsed Dipolar Spectroscopy (PDS) methods of Electron Paramagnetic Resonance (EPR) were used to detect and characterize reversible non-covalent dimers of Human Serum Albumin (HSA), the most abundant protein in human plasma. The spin labels, MTSL and OX063, were attached to Cys-34 and these chemical modifications of Cys-34 did affect the dimerization of HSA, indicating that other post-translational modifications can modulate dimer formation. At physiologically relevant concentrations, HSA does form weak, non-covalent dimers with a well-defined structure. Dimer formation is readily reversible into monomers. Dimerization is very relevant to the role of HSA in the transport, binding, and other physiological processes.