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FIZIKA A 16 (2007) 3 , 117-128
 
EPR SPECTROSCOPY OF 5-YL RADICALS IN GAMMA-IRRADIATED SINGLE CRYSTALS OF 2-THIOTHYMINE
E. BEŠIĆ and J. N. HERAK
Department of Biophysics, Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10002 Zagreb, Croatia
E-mail address: [email protected]
Received 7 July 2006 Revised manuscript received 24 September 2007
Accepted 17 October 2007 Online 8 February 2008
Single crystals of 2-thiothymine (5-methyl-2-thiouracil) have been
g-irradiated at 300 K and studied using EPR spectroscopy. The 5-thymil (5-yl)
radical, formed by a net hydrogen-atom addition to the C(6) of 2-thiothymine
base, has been studied in detail. The hyperfine tensors of methyl and methylene
proton couplings are given together with the g-tensor. It has been shown that
the calculated hyperfine proton couplings and relative orientation of the
coupling tensors along the pyrimidine ring are similar to those observed earlier
in 5-yl radicals in the single crystals of thymine and its derivatives. Although
no large differences in the hyperfine couplings were found, calculated values of
the g-tensor are appreciably larger in comparison to the other thymine-like
systems, what is expected due to the presence of sulfur at C(2) in
2-thiothymine.
PACS numbers: 71.20.Rv, 76.30.-v
UDC 539.194
Keywords: 5-yl radicals, EPR spectroscopy, 2-thiothymine
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