Photooxidation of Histidine by 3,3′,4,4′-Benzophenone Tetracarboxylic Acid in Aqueous Solution: Time-Resolved and Field-Dependent CIDNP Study

• DOI: 10.1007/s00723-014-0577-8
• Publication Date: 2014-09-08T11:02:13Z
• Authors: Mikhail S. Panov; Natalya N. Saprygina; Olga B. Morozova; Alexey S. Kiryutin; Yuri A. Grishin; Alexandra V. Yurk...
• Keywords: CIDNP; Ketyl

The photooxidation reaction between 3,3′,4,4′-benzophenone tetracarboxylic acid (TCBP) and l-histidine (His) has been investigated in neutral aqueous solution using the technique of chemically induced dynamic nuclear polarization (CIDNP). Relative values of 13C isotropic hyperfine couplings in the TCBP and His radicals were obtained from the 13C-time-resolved CIDNP spectrum, recorded during the photoreaction of TCBP with His at natural abundance of the magnetic isotope 13C. Good agreement was found for the hyperfine coupling constants of the TCBP ketyl radical calculated using methods of density functional theory, and those obtained from the 13C-time-resolved CIDNP spectrum. The mechanism of the quenching reaction of triplet-excited TCBP by His in neutral aqueous solution was established. 1H CIDNP field dependencies for the photoreaction of TCBP with His were obtained and the g-factor of the histidyl radical was found.