Dataset Information

MS-CASPT2 Studies on the Photophysics of Selenium-Substituted Guanine Nucleobase.

ABSTRACT: The MS-CASPT2 method has been employed to optimize minimum-energy structures of 6-selenoguanine (6SeGua) and related two- and three-state intersection structures in and between the lowest five electronic states, i.e., S2(1??*), S1(1 n?*), T2(3 n?*), T1(3??*), and S0. In combination with MS-CASPT2 calculated linearly interpolated internal coordinate paths, the photophysical mechanism of 6SeGua has been proposed. The initially populated S2(1??*) state decays to either S1(1 n?*) or T2(3 n?*) states through a three-state S2/S1/T2 intersection point. The large S2/T2 spin-orbit coupling of 435 cm-1, according to the classical El-Sayed rule, benefits the S2 ? T2 intersystem crossing process. The S1(1 n?*) state that stems from the S2 ? S1 internal conversion process at the S2/S1/T2 intersection point can further jump to the T2(3 n?*) state through the S1 ? T2 intersystem crossing process. This process does not comply with the El-Sayed rule, but it is still related to a comparatively large spin-orbit coupling of 39 cm-1 and is expected to occur relatively fast. Finally, the T2(3 n?*) state, which is populated from the above S2 ? T2 and S1 ? T2 intersystem crossing processes, decays to the T1(3??*) state via an internal conversion process. Because there is merely a small energy barrier of 0.11 eV separating the T1(3??*) minimum and an energetically allowed two-state T1/S0 intersection point, the T1(3??*) state still can decay to the S0 state quickly, which is also enhanced by a large T1/S0 spin-orbit coupling of 252 cm-1. Our proposed mechanism explains experimentally observed ultrafast intersystem crossing processes in 6SeGua and its 835-fold acceleration of the T1 state decay to the S0 state compared with 6tGua. Finally, we have found that the ground-state electronic structure of 6SeGua has more apparent multireference character.

SUBMITTER: Fang YG

PROVIDER: S-EPMC6649137 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

MS-CASPT2 Studies on the Photophysics of Selenium-Substituted Guanine Nucleobase.

Fang Ye-Guang YG Peng Qin Q Fang Qiu Q Fang Weihai W Cui Ganglong G

ACS omega 20190604 6

The MS-CASPT2 method has been employed to optimize minimum-energy structures of 6-selenoguanine (6SeGua) and related two- and three-state intersection structures in and between the lowest five electronic states, i.e., S2(1ππ*), S1(1 nπ*), T2(3 nπ*), T1(3ππ*), and S0. In combination with MS-CASPT2 calculated linearly interpolated internal coordinate paths, the photophysical mechanism o ...[more]

PMID: 31460068

Similar Datasets

Project description:A reliable and fast liquid chromatography-tandem mass spectrometry method has been developed for the simultaneous determination of three oxidized nucleic acid damage products in urine, 8-oxoguanine (8-oxoGua), 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo). We applied this method to assess the effect of various urine workup procedures on the urinary concentrations of the oxidized nucleic acid products. Our results showed that frozen urine samples must be warmed (i.e., to 37 °C) to re-dissolve any precipitates prior to analysis. We showed that common workup procedures, such as thawing at room temperature or dilution with deionized water, are not capable of releasing fully the oxidized nucleic acid products from the precipitates, and result in significant underestimation (up to ~ 100% for 8-oxoGua, ~ 86% for both 8-oxodGuo and 8-oxoGuo). With this method, we further assessed and compared the ability of the three oxidized nucleic acid products, as well as malondialdehyde (MDA, a product of lipid peroxidation), to biomonitor oxidative stress in vivo. We measured a total of 315 urine samples from subjects with burdens of oxidative stress from low to high, including healthy subjects, patients with chronic obstructive pulmonary disease (COPD), and patients on mechanical ventilation (MV). The results showed that both the MV and COPD patients had significantly higher urinary levels of 8-oxoGua, 8-oxodGuo, and 8-oxoGuo (P < 0.001), but lower MDA levels, compared to healthy controls. Receiver operating characteristic curve analysis revealed that urinary 8-oxoGuo is the most sensitive biomarker for oxidative stress with area under the curve (AUC) of 0.91, followed by 8-oxodGuo (AUC: 0.80) and 8-oxoGua (AUC: 0.76). Interestingly, MDA with AUC of 0.34 failed to discriminate the patients from healthy controls. Emerging evidence suggests a potential clinical utility for the measurement of urinary 8-oxoGuo, and to a lesser extent 8-oxodGuo, which is strongly supported by our findings.

Dataset Information

MS-CASPT2 Studies on the Photophysics of Selenium-Substituted Guanine Nucleobase.

Publications

MS-CASPT2 Studies on the Photophysics of Selenium-Substituted Guanine Nucleobase.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets