title: Oxidation of purine nucleotides by Triplet 3,3',4,4'-benzophenone tetracarboxylic acid in aqueous solution: pH-dependence.
abstract: The photo-oxidation of purine nucleotides adenosine-5'-monophosphate (AMP) and guanosine-5'-monophosphate (GMP) by 3,3',4,4'-benzophenone tetracarboxylic acid (TCBP) has been investigated in aqueous solutions using nanosecond laser flash photolysis (LFP) and time-resolved chemically induced dynamic nuclear polarization (CIDNP). The pH dependences of quenching rate constants and of geminate polarization are measured within a wide range of pH values. As a result, the chemical reactivity of reacting species in different protonation states is determined. In acidic solution (pH < 4.9), the quenching rate constant is close to the diffusion-controlled limit: kq = 1.3 × 10(9) M(-1) s(-1) (GMP), and kq = 1.2 × 10(9) M(-1) s(-1) (AMP), whereas in neutral and basic solutions it is significantly lower: kq = 2.6 × 10(8) M(-1) s(-1) (GMP, 4.9 < pH < 9.4), kq = 3.5 × 10(7) M(-1) s(-1) (GMP, pH > 9.4), kq = 1.0 × 10(8) M(-1) s(-1) (AMP, pH > 6.5). Surprisingly, the strong influence of the protonation state of the phosphoric group on the oxidation of adenosine-5'-monophosphate is revealed: the deprotonation of the AMP phosphoric group (6.5) decreases the quenching rate constant from 5.0 × 10(8) M(-1) s(-1) (4.9 < pH < 6.5) to 1.0 × 10(8) M(-1) s(-1) (pH > 6.5).
authors.affiliation: International Tomography Center, Institutskaya 3a, 630090 Novosibirsk, Russia.
authors.forename: Natalya N
authors.initials: NN
authors.lastname: Saprygina
authors.forename: Olga B
authors.initials: OB
authors.lastname: Morozova
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Abramova
authors.forename: Günter
authors.initials: G
authors.lastname: Grampp
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Yurkovskaya
mesh_terms: D001577:Benzophenones / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D011685:Purine Nucleotides / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry
chemical_list: C580652:3,3',4,4'-benzophenone tetracarboxylic acid; D001577:Benzophenones; D002264:Carboxylic Acids; D011685:Purine Nucleotides; D012996:Solutions; D014867:Water