Ab initio molecular orbital calculations on DNA radical ions. 3. Ionization potentials and ionization sites in components of the DNA sugar phosphate backbone

Journal Article · Thu Jul 29 04:00:00 EDT 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100132a045· OSTI ID:6140607

Colson, A O; Sevilla, M D ^[1]; Besler, B ^[2]

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1. Oakland Univ., Rochester, MI (United States)
2. Wayne State Univ., Detroit, MI (United States)

Ab initio molecular orbital calculations of various fragments of the DNA backbone have been performed to aid our understanding of charge localization and transfer following DNA irradiation. Koopmans ionization potentials of H[sub 3]PO[sub 4], H[sub 2]PO[sub 4][sup [minus]] and several hydrated forms of the H[sub 2]PO[sub 4][sup [minus]]-Na[sup +] complex were determined at the ROHF/3-21G level. Counterion interaction and progressive hydration result in a substantial increase in the phosphate ionization potential, hence gradually disfavoring the phosphate group as a potential localization site for the hole. The binding energy of the waters of hydration progressively decreases as saturation is approached. In the triply hydrated system, the average water-sodium binding energy is 31.2 kcal/mol H[sub 2]O while the average water-phosphate oxygen hydrogen bond energy is 9.4 kcal/mol H[sub 2]O. The Koopmans ionization potential of 2[prime]-deoxyribose was determined, leading to the following trend in IP: base < deoxyribose (D) < phosphate (P). Calculations performed on DP, DPD, and PDP reveal that the joining of D to DP results in a decrease in IP of D-P while joining of P to D-P raises its IP. Subsequent hydration of DP and DPD via a sodium counterion results in a slight decrease in Koopmans IP. 62 refs., 5 figs., 4 tabs.

• OSTI ID: 6140607
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:30; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

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