Electron transfer in dinucleoside phosphate anions

Abstract

The electron transfer reaction within various dinucleoside phosphate radical anions has been investigated by ESR spectroscopy and pulse radiolysis. In the ESR work electrons are produced by photolysis of KiFeCCNje in a 12 M LiCl glass at 77 K. Upon photobleaching the electrons react with the dinucleoside phosphate to form the anion radical. The anions of the four DNA nucleosides were also produced and their ESR spectra were appropriately weighted and summed by computer to simulate the spectra found for the dinucleoside phosphate anions. From the analysis the relative amounts of each of the nucleoside anions in the dinucleoside phosphate anion were determined. For example in thymidylyl-(3'-5')-2/-deoxyadenosine (TdA), where the bases are likely stacked so as to allow electron transfer to the base with the greatest electron affinity, the electron is found to localize on thymine. Whereas in equal mixtures of T and dA in which the molecules are isolated in the aqueous medium anions of both nucleosides are found in approximately equal amounts. These results and those found for the other dinucleosides studied (TdC, TdG, dAdC, TT) suggest the electron affinity of the pyrimidine bases are greater than the purine bases; however, the results are not sufficient to distinguish between the individual purine or pyrimidine. When dinucleoside phosphate anions containing thymidine are warmed protonation occurs only on thymine to produce the well known "thymyl" spectrum. Pulse radiolysis experiments on individual nucleotides (TMP, dAMP), mixtures of these nucleotides and the dinucleoside phosphate, TdA, in aqueous solution at room temperature show that in the TdA anion electron transfer occurs from adenine to thymine, whereas no electron transfer is found for mixtures of individual nucleotides. Protonation is found to occur only on thymine in the TdA anion in agreement with the ESR results.

CHARACTERIZATION OF THE TRANSIENT SPECIES IN THE 266‐nm LASER PHOTOLYSIS OF ADENINE AND ITS DERIVATIVES

“…The pulse radiolysis of neutral aqueous solutions of dAMP at 25°C (Sevilla et al, 1976) produces a transient absorption spectra with a strong absorption at 320 nm and a much weaker absorption at 540 nm. These absorptions decay with a half-life of 16 ps, while a new absorption grows with onset at 490 nm and maximum at 350 nm and a shoulder at 440 nm.…”

Abiogenic Photophosphorylation of ADP to ATP Sensitized by Flavoproteinoid Microspheres

“…There is much evidence for the formation of the ADP radical molecule (Moorthy et al 1975;Sevilla et al 1976;Scheek et al 1981;Losinova et al 1986;Mailer 1990). The participation of this radical in a riboflavin-sensitized phosphorylation of ADP by orthophosphate in aqueous solution was considered and experimentally substantiated (Losinova et al 1983(Losinova et al , 1986Nedelina 1997).…”

Radicals Produced by γ-Irradiation of Hyperquenched Glassy Water Containing 2′-Deoxyguanosine-5′-monophosphate

“…In irradiated glassy systems containing DNA constituents, the radical anions of nucleobases are formed at 77 K and below due to scavenging of electrons ejected from water molecules. 2,13,[21][22][23] The guanine radical anion, G -· , has been identified in ESR spectra as a singlet with the peak-topeak width of ∼8-9 G. 21,24,25 A signal attributable to G -· was extracted by the procedure illustrated in Figure 5. First, we have removed from the initial spectrum (top spectrum in Figure 2) the normalized benchmark signal of OH · radicals (cf., Figure 1).…”

“…Bottom spectrum, simulated signal of G -· anionradical; simulation parameters: A H(C8) [5.5; 3.0; 0.5] G, g [2.0028; 2.0037; 2.0026], line width 6 G 25,26. …”