Photo-CIDNP study of adenosine 5'-monophosphate. Pair-substitution effects due to cation radical deprotonation

Scheek, Ruud M.; Stob, S; Schleich, Thomas; Alma, N. C. M.; Hilbers, C. W.; Kaptein, Robert

doi:10.1021/ja00409a062

Cited by 27 publications

(33 citation statements)

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“…In particular, Close suggested that the low p K a value predicted by Sevilla and co‐workers was due to an inappropriate calculation method and that the p K a of A .+ is not actually ≤1 but 3.9, which is close to the experimental value determined by Kobayashi . We note that the pH value of approximately 4.6, at which the spectral change is observed, is close to the p K a of A .+ reported by Kobayashi, Close, and Scheek et al . Thus, we suggest that the p K a of N6‐H of A .+ is about 4.6.…”

Section: Resultssupporting

confidence: 87%

“…These spectral changes indicate that the origin of the absorption band at around 600 nm changes at pH≈4.6. Kobayashi and Scheek et al . reported p K a values of 4.2 and 4 for A .+ , respectively, whereas Steenken reported a much lower value (≤1), which was supported by Sevilla and co‐workers through their EPR study and theoretical calculations.…”

Section: Resultsmentioning

confidence: 71%

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Proton Transfer Accompanied by the Oxidation of Adenosine

Choi

Tojo

Ahn

et al. 2019

Chemistry A European J

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Despite numerous experimental and theoretical studies, the proton transfer accompanying the oxidation of 2'-deoxyadenosine 5'-monophosphate 2'-deoxyadenosine 5'monophosphate (5'-dAMP, A)i ss till under debate. To address this issue, we have investigated the oxidation of A in acidic and neutral solutions by using transient absorption (TA) and time-resolved resonance Raman( TR 3 )s pectroscopic methods in combination with pulse radiolysis. The steadystate Raman signal of A was significantly affected by the solution pH, but not by the concentration of adenosine (2-50 mm). More specifically,t he A in acidic and neutral solutions exists in its protonated (AH + (N1 + H + )) and neutral( A) forms, respectively.O nthe one hand, the TA spectral changes observed at neutral pH revealed that the radical cation (AC + )g enerated by pulse radiolysis is rapidly converted into AC(N6ÀH) through the loss of an imino protonf rom N6. In contrast, at acidic pH (< 4), AHC 2 + (N1 + H + )g enerated by pulse radiolysis of AH + (N1 + H + )d oes not undergo the deprotonationp rocess owing to the pK a value of AHC 2 + (N1 + H + ), whichi sh igher than the solutionp H. Furthermore, the resultsp resented in this study have demonstrated that A, AH + (N1 + H + ), and their radical species exist as monomers in the concentrationr ange of 2-50 mm.C ompared with the Ramanb ands of AH + (N1 + H + ), the TR 3 bandso fAHC 2 + (N1 + H + )a re significantly down-shifted, indicatingadecrease in the bond order of the pyrimidine and imidazole rings due to the resonance structure of AHC 2 + (N1 + H + ). Meanwhile, AC(N6ÀH) does not show aR aman band corresponding to the pyrimidine + NH 2 scissoring vibration due to diprotonation at the N6 position. These resultss upport the final products generated by the oxidation of adenosine in acidic and neutrals olutions being AHC 2 + (N1 + H + )a nd AC(N6ÀH), respectively.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 71%

Proton Transfer Accompanied by the Oxidation of Adenosine

Choi

Tojo

Ahn

et al. 2019

Chemistry A European J

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“…As photosensitizers, which are used to initiate a photo‐reaction giving rise to CIDNP, various dyes are used, which are listed in Scheme . These dyes are 2,2‐dipyridyl (DP),– 4‐carboxy‐benzophenone (4‐CBP),,, 3,3′,4,4′‐tetracarboxybenzophenone (TCBP),, and flavins with different substituents (flavin mononucleotide, FMN, is shown in Scheme ) ,,,. For running experiments under special conditions, i. e., at very low concentrations, one can also use other dyes, such as fluorescein .…”

Section: Cidnp Of Amino Acids and Nucleotidessupporting

confidence: 84%

Time‐Resolved Chemically Induced Dynamic Nuclear Polarization of Biologically Important Molecules

Morozova

Ivanov

2018

ChemPhysChem

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In this work, we review the hyperpolarization technique named chemically induced dynamic nuclear polarization (CIDNP), focusing on the time‐resolved variant of this method and its biological applications. We introduce the main principles of polarization formation in liquids at high magnetic fields, provided by the so‐called spin sorting mechanism. Applications of CIDNP to studying fast reactions of short‐lived free radicals of biologically important molecules are discussed, as well as the potential of the method to probe the structure and magnetic parameters of such radicals. We also explain the principles of protein CIDNP and discuss applications of time‐resolved CIDNP to studies of protein structure and dynamics.

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“…In a much earlier NMR spectral study (360 MHz) of one-electron-oxidized adenine produced via laser CIDNP in 5′-AMP at various pH’s, the p K a of A• + in aqueous (D 2 O) solution is reported as 4 ± 0.2. 23 Theoretical calculations predict the p K a of A• + as ca. 2 20a and 3.2.…”

Section: Introductionmentioning

confidence: 99%

Effect of Base Stacking on the Acid−Base Properties of the Adenine Cation Radical [A•⁺] in Solution: ESR and DFT Studies

et al. 2008

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In this study, the acid–base properties of the adenine cation radical are investigated by means of experiment and theory. Adenine cation radical (A•+) is produced by one-electron oxidation of dAdo and of the stacked DNA-oligomer (dA)6 by Cl2•− in aqueous glass (7.5 M LiCl in H2O and in D2O) and investigated by ESR spectroscopy. Theoretical calculations and deuterium substitution at C8–H and N6–H in dAdo aid in our assignments of structure. We find the pKa value of A•+ in this system to be ca. 8 at 150 K in seeming contradiction to the accepted value of ≤ 1 at ambient temperature. However, upon thermal annealing to ≥160 K, complete deprotonation of A•+ occurs in dAdo in these glassy systems even at pH ca. 3. A•+ found in (dA)6 at 150 K also deprotonates on thermal annealing. The stability of A•+ at 150 K in these systems is attributed to charge delocalization between stacked bases. Theoretical calculations at various levels (DFT B3LYP/6-31G*, MPWB95, and HF-MP2) predict binding energies for the adenine stacked dimer cation radical of 12 to 16 kcal/mol. Further DFT B3LYP/6-31G* calculations predict that, in aqueous solution, monomeric A•+ should deprotonate spontaneously (a predicted pKa of ca. −0.3 for A•+). However, the charge resonance stabilized dimer AA•+ is predicted to result in a significant barrier to deprotonation and a calculated pKa of ca. 7 for the AA•+ dimer which is 7 pH units higher than the monomer. These theoretical and experimental results suggest that A•+ isolated in solution and A•+ in adenine stacks have highly differing acid–base properties resulting from the stabilization induced by hole delocalization within adenine stacks.

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Photo-CIDNP study of adenosine 5'-monophosphate. Pair-substitution effects due to cation radical deprotonation

Cited by 27 publications

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Proton Transfer Accompanied by the Oxidation of Adenosine

Proton Transfer Accompanied by the Oxidation of Adenosine

Time‐Resolved Chemically Induced Dynamic Nuclear Polarization of Biologically Important Molecules

Effect of Base Stacking on the Acid−Base Properties of the Adenine Cation Radical [A•⁺] in Solution: ESR and DFT Studies

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Photo-CIDNP study of adenosine 5'-monophosphate. Pair-substitution effects due to cation radical deprotonation

Cited by 27 publications

References 0 publications

Proton Transfer Accompanied by the Oxidation of Adenosine

Proton Transfer Accompanied by the Oxidation of Adenosine

Time‐Resolved Chemically Induced Dynamic Nuclear Polarization of Biologically Important Molecules

Effect of Base Stacking on the Acid−Base Properties of the Adenine Cation Radical [A•+] in Solution: ESR and DFT Studies

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Effect of Base Stacking on the Acid−Base Properties of the Adenine Cation Radical [A•⁺] in Solution: ESR and DFT Studies