Journal
JOURNAL OF PHYSICAL CHEMISTRY B
Volume 122, Issue 1, Pages 40-53Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcb.7b09515
Keywords
-
Categories
Funding
- CUNY Doctoral Student Research Grant
- PSC-CUNY Research Award
- Queens College Research Enhancement Award
- National Science Foundation [CHE 1464171]
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1464171] Funding Source: National Science Foundation
Ask authors/readers for more resources
We report a kinetic and mechanistic study on the title reactions, in which O-1(2) was generated by the reaction of H2O2 with Cl-2 and bubbled into an aqueous solution of guanine and 9-methylguanine (9MG) at different pH values. Oxidation kinetics and product branching ratios were measured using online electrospray ionization mass spectrometry coupled with absorption and emission spectrophotometry, and product structures were determined by collision-induced dissociation (CID) tandem mass spectrometry. Experiments revealed strong pH dependence of the reactions. The oxidation of guanine is noticeable only in basic solution, while the oxidation of 9MG is weak in acidic solution, increases in neutral solution, and becomes intensive in basic solution. 5-Guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) were detected as the major oxidation products of guanine and 9MG, and Sp became dominant in basic solution. A reaction intermediate was captured in mass spectra, and assigned to gemdiol on the basis of CID measurements. This intermediate served as the precursor for the formation of Gh. After taking into account solution compositions at each pH, first-order oxidation rate constants were extracted for individual species: that is, 3.2-3.6 X 10(7)M(-1)s(-1)for deprotonated guanine, and 1.2 X 10(6)and 4.6-4.9 X 10(7)M-(1)-(1)for neutral and deprotonated 9MG, respectively. Guided by approximately spin-projected density-functional-theory-calculated reaction potential energy surfaces, the kinetics for the initial O-1(2) addition to guanine and 9MG was evaluated using transition state theory (TST). The comparison between TST modeling and experiment confirms that O-1(2) addition is rate-limiting for oxidation, which forms endoperoxide and peroxide intermediates as determined in previous measurements of the same systems in the gas phase.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available