- 15N Chemical Shift Tensors of Uracil Determined from 15N Powder Pattern and 15N-13C Dipolar NMR Spectroscopy
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The 15N chemical shift tensors of uracil are reported using 15N powder pattern techniques.The principal values of the 15N uracil tensors are obtained from the spectra of uracil and uracil, and the tensor orientations are determined from the spectrum of 2,2-13C>uracil by including the effects of the direct dipolar interaction in the spectral fitting routine.Ambiguities in the orientational assignments, which arise from the axial symmetry of the direct dipolar tensor, are resolved using molecular symmetry considerations and results of ab initio calculations of 15N chemical shielding tensors.The N1 nitrogen has principal values of 196, 114, and 30 ppm and the N3 nitrogen 200, 131, and 79 ppm with respect to 15NH4NO3.Assuming that the smallest (most shielded) chemical shift tensor components are oriented perpendicular to the molecular plane, the largest components are found to lie 18 deg and 9 deg off the N1-H and N3-H bonds, respectively, rotated toward C2 and C4.These orientations are in good agreement with those calculated theoretically.In addition, inclusion of intermolecular hydrogen bond effects in the theoretical calculations significantly improves the correlation between the calculated and experimental principal values.
- Anderson-Altmann, Karen L.,Phung, Cu G.,Mavromoustakos, Stylianos,Zheng, Zhiwen,Facelli, Julio C.,et al.
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- Synthetic method of double-labeled uridine-(C,N2)
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The invention relates to a synthetic method of double-labeled uridine-(C,N2). The method comprises the following steps: carrying out a cyclization reaction on double-labeled urea-(C,N2) and propiolic acid in a solvent anhydrous benzene to obtain double-labeled uracil-(C,N2); and mixing the double-labeled uracil-(C,N2) with 1-acetoxy-2,3,5-tribenzoyloxy-beta-D-ribofuranose in a solvent acetonitrile in Ar2 atmosphere, adding hexamethyldisilazane and trimethylsilyl trifluoromethanesulfonate, post-processing above materials to obtain an intermediate, and hydrolyzing the intermediate with ammonia water to obtain the double-labeled uridine-(C,N2). Compared with the prior art, the method disclosed in the invention has the advantages of simple process, high yield, no decrease of the isotope abundance, and suitableness for laboratory production of the double-labeled uridine-(C,N2).
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Paragraph 0012; 0023-0024; 0028-0029; 0033-0034; 0038-0039
(2017/08/27)
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- Synthesis of isotopically labelled DNA degradation products for use in mass spectrometric studies of cellular DNA damage
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Thirteen substituted purines and pyrimidines bearing from three to five carbon, nitrogen and/or deuterium isotopic labels have been synthesized in yields ranging from 1 to 70%. Most of the products originate from the same small number of commercially available labelled starting materials, and in several cases one intermediate leads to two products, thus minimizing the expense and time required. The parent compounds are found in tissue as the result of DNA damage often linked with carcinogenesis and mutagenesis. The synthesized compounds serve as internal standards for the study of DNA damage using mass spectrometry.
- Nelson, Victor C.
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p. 713 - 723
(2007/10/03)
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