UA cloudflare authentication

Browsing by Author "Bowman, Michael"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Exploring the interactions of short RNAs with the human 40S ribosomal subunit near the mRNA entry site by EPR spectroscopy
    (Oxford University Press, 2019) Malygin, Alexey A.; Krumkacheva, Olesya A.; Graifer, Dmitry M.; Timofeev, Ivan O.; Ochkasova, Anastasia S.; Meschaninova, Mariya, I; Venyaminova, Alya G.; Fedin, Matvey, V; Bowman, Michael; Karpova, Galina G.; Bagryanskaya, Elena G.; Institute of Chemical Biology & Fundamental Medicine, Siberian Branch of the RAS; Russian Academy of Sciences; Vorozhtsov Novosibirsk Institute of Organic Chemistry; Novosibirsk State University; International Tomography Center, Siberian Branch of Russian Academy of Sciences; University of Alabama Tuscaloosa
    The features of previously unexplored labile complexes of human 40S ribosomal subunits with RNAs, whose formation is manifested in the cross-linking of aldehyde derivatives of RNAs to the ribosomal protein uS3 through its peptide 55-64 located outside the mRNA channel, were studied by EPR spectroscopy methods. Analysis of subatomic 40S subunit models showed that a likely site for labile RNA binding is a cluster of positively charged amino acid residues between the mRNA entry site and uS3 peptide 55-64. This is consistent with our finding that the 3'-terminal mRNA fragment hanging outside the 40S subunit prevents the cross-linking of an RNA derivative to this peptide. To detect labile complexes of 40S subunits with RNA by DEER/PELDOR spectroscopy, an undecaribonucleotide derivative with nitroxide spin labels at terminal nucleotides was utilized. We demonstrated that the 40S subunit channel occupancy with mRNA does not affect the RNA derivative binding and that uS3 peptide 55-64 is not involved in binding interactions. Replacing the RNA derivative with a DNA one revealed the importance of ribose 2'-OH groups for the complex formation. Using the single-label RNA derivatives, the distance between the mRNA entry site and the loosely bound RNA site on the 40S subunit was estimated.
  • Thumbnail Image
    Item
    Gareth R. Eaton: On the Occasion of His 80th Birthday
    (Springer, 2021) Bowman, Michael; Fielding, Alistair; Tseytlin, Mark; University of Alabama Tuscaloosa; Liverpool John Moores University; West Virginia University