{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,17]],"date-time":"2026-01-17T05:02:52Z","timestamp":1768626172891,"version":"3.49.0"},"reference-count":132,"publisher":"AIP Publishing","issue":"8","funder":[{"DOI":"10.13039\/100000165","name":"Division of Chemistry","doi-asserted-by":"publisher","award":["1856362"],"award-info":[{"award-number":["1856362"]}],"id":[{"id":"10.13039\/100000165","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2023,8,28]]},"abstract":"<jats:p>Nitric oxide (\u25cfNO) participates in many biological activities, including enhancing DNA radiosensitivity in ionizing radiation-based radiotherapy. To help understand the radiosensitization of \u25cfNO, we report reaction dynamics between \u25cfNO and the radical cations of guanine (a 9HG\u25cf+ conformer) and 9-methylguanine (9MG\u25cf+). On the basis of the formation of 9HG\u25cf+ and 9MG\u25cf+ in the gas phase and the collisions of the radical cations with \u25cfNO in a guided-ion beam mass spectrometer, the charge transfer reactions of 9HG\u25cf+ and 9MG\u25cf+ with \u25cfNO were examined. For both reactions, the kinetic energy-dependent product ion cross sections revealed a threshold energy that is 0.24 (or 0.37) eV above the 0\u00a0K product 9HG (or 9MG) + NO+ asymptote. To interrogate this abnormal threshold behavior, the reaction potential energy surface for [9MG + NO]+ was mapped out at closed-shell singlet, open-shell singlet, and triplet states using density functional and coupled cluster theories. The results showed that the charge transfer reaction requires the interaction of a triplet-state surface originating from a reactant-like precursor complex 3[9MG\u25cf+(\u2191)\u22c5(\u2191)\u25cfNO] with a closed-shell singlet-state surface evolving from a charge-transferred complex 1[9MG\u22c5NO+]. During the reaction, an electron is transferred from \u03c0\u2217(NO) to perpendicular \u03c0\u2217(9MG), which introduces a change in orbital angular momentum. The latter offsets the change in electron spin angular momentum and facilitates intersystem crossing. The reaction threshold in excess of the 0\u00a0K thermochemistry and the low charge-transfer efficiency are rationalized by the vibrational excitation in the product ion NO+ and the kinetic shift arising from a long-lived triplet intermediate.<\/jats:p>","DOI":"10.1063\/5.0160921","type":"journal-article","created":{"date-parts":[[2023,8,28]],"date-time":"2023-08-28T10:25:19Z","timestamp":1693218319000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":4,"title":["Spin-orbit charge transfer from guanine and 9-methylguanine radical cations to nitric oxide radicals and the induced triplet-to-singlet intersystem crossing"],"prefix":"10.1063","volume":"159","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7790-6420","authenticated-orcid":false,"given":"Jonathan","family":"Benny","sequence":"first","affiliation":[{"name":"Department of Chemistry and Biochemistry, Queens College of the City University of New York 1 , 65-30 Kissena Blvd., Queens, New York 11367, USA"},{"name":"The Ph.D. Program in Chemistry, The Graduate Center of the City University of New York 2 , 365 5th Ave., New York, New York 10016, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9577-3740","authenticated-orcid":false,"given":"Jianbo","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry, Queens College of the City University of New York 1 , 65-30 Kissena Blvd., Queens, New York 11367, USA"},{"name":"The Ph.D. Program in Chemistry, The Graduate Center of the City University of New York 2 , 365 5th Ave., New York, New York 10016, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"317","published-online":{"date-parts":[[2023,8,28]]},"reference":[{"key":"2024082800011812900_c1","doi-asserted-by":"publisher","first-page":"617","DOI":"10.1021\/ja962255b","article-title":"How easily oxidizable is DNA? 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