Ab initio study of thiol aqueous phase ionization energies. Methyl mercaptan and cysteamine
- Oakland Univ., Rochester, MI (United States)
The ionization energies of two thiol model compounds (methyl mercaptan and cysteamine) are calculated at the ROHF/6-31G* level to aid our understanding of the mechanisms involved in DNA radioprotection. Methyl mercaptan, the thiolate anion, and its trihydrated form are fully geometry optimized. The resulting gas-phase Koopmans ionization energies are 9.68, 1.67, and 3.63 eV, respectively. The ionization energy for the solvated methylthiolate anion, CH[sub 3]S[sup [minus]](aq), calculated through the use of the SCRF model ([epsilon] = 78), the Born charge term, and a discrete hydration shell, leads to a Koopmans value of 5.6 eV. This result is in good agreement with the corrected vertical solution-phase ionization energy calculated by using the same model (5.4 eV) and with experiment (5.7 [+-] 0.2 eV). The gas-phase ionization energy of cysteamine, its cation, zwitterion, and the pentahydrated form of the latter are reported. We find the Koopmans ionization energy of the anti-configuration of the zwitterion to be ca. 6.0 eV. 53 refs., 6 figs., 2 tabs.
- DOE Contract Number:
- FG02-86ER60455
- OSTI ID:
- 7070030
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:41; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400600* -- Radiation Chemistry
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
AMINES
AQUEOUS SOLUTIONS
CALCULATION METHODS
CHEMICAL BONDS
COMPILED DATA
DATA
DISPERSIONS
DNA
ELECTRON TRANSFER
HYDRATION
INFORMATION
IONIZATION
MIXTURES
NUCLEIC ACIDS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
RADIATION PROTECTION
RADICALS
SOLUTIONS
SOLVATION
THIOLS