16 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Cytosine"  
Results: 1 - 16
open access

Mechanisms for radiation damage in DNA. Progress report, January 1, 1982-December 31, 1982

Description: In this project several mechanisms are proposed for radiation damage to DNA constituents and DNA, and a series of experiments utilizing electron spin resonance spectrometry to test the proposed mechanisms have been detailed. In the past studies have concentrated chiefly on the direct effect of radiation on DNA. We are currently investigating irradiated systems of DNA constituents which may shed light on indirect effects. In addition, studies of radiation effects on lipids have been undertaken w… more
Date: May 1, 1982
Creator: Sevilla, M. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

[Ionizing radiation-induced DNA damage and its repair in human cells]. Progress report, [April 1, 1993--February 28, 1994]

Description: The excision of radiation-induced lesions in DNA by a DNA repair enzyme complex, namely the UvrABC nuclease complex, has been investigated. Irradiated DNA was treated with the enzyme complex. DNA fractions were analyzed by gas chromatography/isotope-dilution mass spectrometry. The results showed that a number pyrimidine- and purine-derived lesions in DNA were excised by the UvrABC nuclease complex and that the enzyme complex does not act on radiation-induced DNA lesions as a glycosylase. This m… more
Date: July 1, 1994
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Radiation physics, biophysics, and radiation biology. Progress report, December 1, 1993--November 30, 1994

Description: Research at the Center for Radiological Research is a blend of physics, chemistry and biology and epitomizes the multidisciplinary approach towards understanding the mechanisms involved in the health problems resulting from human exposure to ionizing radiations. To an increasing extent, the focus of attention is on biochemistry and the application of the techniques of molecular biology to the problems of radiation biology. Research highlights from the past year are briefly described.
Date: May 1, 1994
Creator: Hall, E. J. & Zaider, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Electronic structure and spectroscopy of nucleic acid bases: Ionization energies, ionization-induced structural changes, and photoelectron spectra

Description: We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C) and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using equation-of-motion coupled-cluster method for ionization potentials with single and do… more
Date: August 2, 2010
Creator: Bravaya, Ksenia B.; Kostko, Oleg; Dolgikh, Stanislav; Landau, Arie; Ahmed, Musahid & Krylov, Anna I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Molecular-scale studies of single-channel membrane pores : final report.

Description: We present our research results on membrane pores. The study was divided into two primary sections. The first involved the formation of protein pores in free-standing lipid bilayer membranes. The second involved the fabrication via surface micromachining techniques and subsequent testing of solid-state nanopores using the same characterization apparatus and procedures as that used for the protein pores. We were successful in our ability to form leak-free lipid bilayers, to detect the formation … more
Date: October 1, 2003
Creator: Fleming, James Grant; Evans, Kervin O.; Burns, Alan Richard & Swartzentruber, Brian Shoemaker
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Ionization of cytosine monomer and dimer studied by VUV photoionization and electronic structure calculations

Description: We report a combined theoretical and experimental study of ionization of cytosine monomers and dimers. Gas-phase molecules are generated by thermal vaporization of cytosine followed by expansion of the vapor in a continuous supersonic jet seeded in Ar. The resulting species are investigated by single photon ionization with tunable vacuum-ultraviolet (VUV) synchrotron radiation and mass analyzed using reflectron mass spectrometry. Energy onsets for the measured photoionization efficiency (PIE) s… more
Date: December 14, 2009
Creator: Kostko, Oleg; Bravaya, Ksenia; Krylov, Anna & Ahmed, Musahid
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Lethal and mutagenic effects in microorganisms grown in $sup 3$H$sub 2$O. Final report

Description: Results are summarized from studies of lethal and mutagenic effects in microorganisms grown in tritiated water. It was concluded that the effects of radiation alone are sufficient to explain the biological effects observed. Studies on the effect of tritium decays accumulated during growth of organisms in the presence of tritiated nucleic acid precursors showed that the mutation rates per decay for continuous growth and for storage conditions were identical and that tritium-labeled adenine and c… more
Date: January 1, 1974
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Chloroethyinitrosourea-derived ethano cytosine and adenine adducts are substrates for escherichia coli glycosylases excising analogous etheno adducts

Description: Exocyclic ethano DNA adducts are saturated etheno ring derivatives formed mainly by therapeutic chloroethylnitrosoureas (CNUs), which are also mutagenic and carcinogenic. In this work, we report that two of the ethano adducts, 3,N{sup 4}-ethanocytosine (EC) and 1,N{sup 6}-ethanoadenine (EA), are novel substrates for the Escherichia coli mismatch-specific uracil-DNA glycosylase (Mug) and 3-methyladenine DNA glycosylase II (AlkA), respectively. It has been shown previously that Mug excises 3,N{su… more
Date: May 5, 2004
Creator: Guliaev, Anton B.; Singer, B. & Hang, Bo
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Mechanisms for radiation damage in DNA. Progress report, June 1, 1973-- May 31, 1974

Description: A mechnnism has been proposed for radiation damage to DNA and a series of experiments detailed utilizing electron spin resonance spectrometry to test the proposed mechanism. Thus far we have produced and investigated the positive and negative ions of a number of purine and pyrimidine DNA bases in aqueous glasses. The g values and hyperfine couplings, both anisotropic and isotropic, have been determined when possible. The 5-methyl substituted pyrimidine cations (thymine, thymidine, 5-methylcytos… more
Date: January 1, 1974
Creator: Sevilla, M. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Photochemistry and photobiology of DNA containing 5-iodouracil and 5-iodocytosine. [Escherichia coli, Bacillus subtilis]

Description: The quantum yields for the photolysis of iodinated derivatives of cytosine (leading to the loss of iodine) has been measured for 313 nm radiation and found to decrease from 0.024 for IodCMP down to 0.007 for both Poly(C) and DNA containing 5-IodCyt. In DNA, approximately 1 clean chain break and 1 alkali-labile bond were formed for every 10 iodines lost. Incorporation of iodinated cytosine or uracil into the DNA of Escherichia coli or Bacillus subtilis was shown to have a large effect on the bio… more
Date: January 1, 1978
Creator: Rahn, R.O.; Stafford, R.S. & Hadden, C.T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Electron damage and defects in organic crystals

Description: The nature of the defects discernable from and the radiation damage that is induced by high resolution electron microscopy is reported. The structural aspects of the radiation damage process can be correlated to the expected radiochemical decomposition of these materials and these effects identified. The types of local defect formed by radiation damage are often clearly distinguishable, in high resolution images, from those inherent in the microstructure. Techniques used in this type of electro… more
Date: June 1, 1976
Creator: Howitt, D. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Nanodosimetry and nanodosimetric-based models of radiation action for radon alpha particles. Final performance technical report

Description: The goal of this project was to develop theoretical/computational tools for evaluating the risks incurred by populations exposed to radon alpha particles. Topics of concern include the following: compound dual radiation action (general aspects); a mathematical formalism describing the yield of radiation induced single-and double-strand DNA breaks, and its dependence on radiation quality; a study of the excited states in cytosine and guanine stacks in the Hartree-Fock and exciton approximations;… more
Date: December 31, 1997
Creator: Zaider, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Final Report: Theoretical Studies on Radiation-Induced Transformations in Nucleic Acid Bases, May 1, 1993 - April 30, 1996

Description: In the proposal we identified several elemental molecular properties related to the effects observed in genetic material exposed to ionizing irradiation, and we studied them by means of the ab-initio quantum chemistry. The chemistry of irradiation is complex and biological consequences are significant. This includes cell death, mutations, carcinogenic transformations, etc. In the proposal we theoretically modeled several elemental processes related to the radiolysis of components of the nucleic… more
Date: April 30, 1996
Creator: Adamowicz, Ludwik
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
Back to Top of Screen