Double-strand breaks in DNA induced by the K-shell ionization of calcium atoms.

A calcium (Ca)-DNA complex in a buffered aqueous solution was irradiated with monochromatic x-rays at around the K-shell absorption edge of the Ca atom. The energies were 4.030 and 4.071 keV, which correspond to slightly below and above the K-shell absorption edge of Ca (4.047 keV). The number of double-strand breaks (DSB) and single-strand breaks (SSB) per one molecule of Col E1 DNA was calculated using Povirk's equation after the electrophoretic separation of three forms of plasmid DNA (forms I, II and III, which are supercoiled closed circular, open circular and linear, respectively). In a solution with Ca ions, the DSB yield in DNA irradiated with 4.071 keV x-rays is 1.27 times higher than that with 4.030 keV x-rays. In contrast, in the absence of Ca ions, the DSB yield is the same at both the x-ray energies. The SSB yields are also independent of the x-ray energy in the presence and absence of Ca ions. A reference experiment regarding irradiation with 60Co gamma-rays shows that the ratio of the DSB yield to the SSB yield upon irradiation with 4.071 keV x-rays is higher (factor of 3.2) than that with 60Co gamma-rays.

[1]  K. Hieda,et al.  Uracil-DNA glycosylase produces excess lethal damage induced by an Auger cascade in BrdU-labelled bacteriophage T1. , 1993, International journal of radiation biology.

[2]  N. Munakata,et al.  Inactivation action spectra of Bacillus subtilis spores with monochromatic soft X rays (0.1-0.6 nm) of synchrotron radiation. , 1992, Radiation research.

[3]  M. Sasaki,et al.  Induction of chromosome aberrations by monochromatic X-rays with resonance energy of phosphorus K-shell absorption edge. , 1992, International journal of radiation biology.

[4]  K. Suzuki,et al.  Mutagenic and transforming effects of soft-X-rays with resonance energy of phosphorus K-absorption edge. , 1992, International journal of radiation biology.

[5]  K. Hieda,et al.  Effects of K-shell X-ray absorption of intracellular phosphorus on yeast cells. , 1991, International journal of radiation biology.

[6]  K. Hieda,et al.  Biological effects of Auger processes of bromine on yeast cells induced by monochromatic synchrotron X-rays. , 1991, International journal of radiation biology.

[7]  K. Baverstock,et al.  DNA damage by auger emitters , 1988 .

[8]  T. Mori,et al.  Effects of monoenergetic X-rays with resonance energy of bromine K-absorption edge on bromouracil-labelled E. coli cells. , 1988, International journal of radiation biology and related studies in physics, chemistry, and medicine.

[9]  K. Shinohara,et al.  Enhanced killing of HeLa cells pre-labeled with 5-bromodeoxyuridine by monochromatic synchrotron radiation at 0.9 A: an evidence for Auger enhancement in mammalian cells. , 1985, Journal of radiation research.

[10]  J. H. Hubbell,et al.  Photon mass attenuation and energy-absorption coefficients , 1982 .

[11]  H. Stuhrmann.  Uses of synchrotron radiation in biology , 1982 .

[12]  R. Lloyd,et al.  Bleomycin-specific fragmentation of double-stranded DNA. , 1978, Biochemistry.

[13]  L. Povirk,et al.  DNA double-strand breaks and alkali-labile bonds produced by bleomycin. , 1977, Nucleic acids research.

[14]  H. Triebel,et al.  Conformation and reactivity of DNA. IV. Base binding ability of transition metal ions to native DNA and effect on helix conformation with special references to DNA–Zn(II) complex , 1974, Biopolymers.

[15]  R. M. Izatt,et al.  Sites and thermodynamic quantities associated with proton and metal ion interaction with ribonucleic acid, deoxyribonucleic acid, and their constituent bases, nucleosides, and nucleotides. , 1971, Chemical reviews.