The influence of Mn2+ on DNA structure in the presence of Na+ ions: a Raman spectroscopic study

The influence of Mn(2+) ions on the structure of natural calf thymus DNA was studied by Raman spectroscopy. Measurements were done at room temperature and pH 6.2±0.2, in the presence of the physiological concentration of 150 mM Na+ ions, and in the presence of Mn(2+) concentrations that varied between 0 and 600 mM. No condensation of DNA was observed at any of the Mn(2+) concentrations. At 5 mM Mn(2+) and 150 mM Na(+) no significant influence of Mn(2+) ions on the DNA structure can be observed. Compared with our previous results obtained at 10 mM Na(+) ions, binding of Mn(2+) ions to charged phosphate groups and to DNA bases is inhibited in the presence of 150 mM Na(+) ions. DNA backbone conformational changes were not observed in the whole concentration range of Mn(2+) ions as judging from the Raman spectra. No evidence for DNA melting was identified. A high Mn(2+) affinity for binding to guanine N7 and possibly, in a much lesser extent, to adenine have been found

Raman microspectroscopic study of effects of Na(I) and Mg(II) ions on low pH induced DNA structural changes

In this work a confocal Raman microspectrometer is used to investigate the influence of Na+ and Mg2+ ions on the DNA structural changes induced by low pH. Measurements are carried out on calf thymus DNA at neutral pH (7) and pH 3 in the presence of low and high concentrations of Na+ and Mg2+ ions, respectively. It is found that low concentrations of Na+ ions do not protect DNA against binding of H+. High concentrations of monovalent ions can prevent protonation of the DNA double helix. Our Raman spectra show that low concentrations of Mg2+ ions partly protect DNA against protonation of cytosine (line at 1262 cm-1) but do not protect adenine and guanine N(7) against binding of H+ (characteristic lines at 1304 and 1488 cm-1, respectively). High concentrations of Mg2+ can prevent protonation of cytosine and protonation of adenine (disruption of AT pairs). By analyzing the line at 1488 cm-1, which obtains most of its intensity from a guanine vibration, high magnesium salt protect the N(7) of guanine against protonation. A high salt concentration can prevent protonation of guanine, cytosine, and adenine in DNA. Higher salt concentrations cause less DNA protonation than lower salt concentrations. Magnesium ions are found to be more effective in protecting DNA against binding of H+ as compared with calcium ions presented in a previous study. Divalent metal cations (Mg2+, Ca2+) are more effective in protecting DNA against protonation than monovalent ions (Na+)

Mn2+-DNA interactions in aqueous systems: A Raman spectroscopic study

Interaction of natural calf thymus DNA with Mn2+ ions was studied by means of Raman spectroscopy. Spectra of DNA in 10 mM Na-cacodylate buffer, pH 6.2, 10 mM NaCl and in buffer containing Mn2+ ions were measured at room temperature. Mn2+ concentrations varied between 0 and 0.6 M. DNA backbone conformational changes and DNA denaturation were not observed in the concentration range 0 and 0.5 M, however, DNA condensation was observed at a critical concentration of 100 mM Mn2+ that prevented the measurement of Raman spectra. Binding of Mn2+ to the charged phosphate groups of DNA is indicated in the spectra. A high affinity of Mn2+ for guanine N7 was obvious, and binding to adenine was barely suggested

DNA structure at low pH values, in the presence of Mn2+ ions: a Raman study

Raman spectra of calf thymus DNA were measured in the pH interval 6.4 to 3.45 in the presence of divalent manganese ions. pH-dependent protonation of AT and GC base pairs and conformational changes were indicated in the spectra. Protonation of adenine residues becomes obvious at pH 4.4 and continues upon lowering the pH to 3.45. Adenine protonation is connected with the disruption of AT base pairs. Protonation of GC base pairs is indicated at somewhat lower pH than that of AT base pairs, namely at pH 3.8, and continues upon lowering the pH to 3.45. At pH 3.8 unstacking of thymine residues is indicated, and spectral markers for the unstacking of adenine and cytosine were found at pH 3.45. Changes of the DNA backbone are indicated by spectral changes of conformational marker bands at 898 and 1423 cm-1

Raman microspectroscopic study on low-pH-induced DNA structural transitions in the presence of magnesium ions

Low-pH-induced DNA structural changes were investigated in the pH range 6.8-2.10 by Raman microspectroscopy. Measurements were carried out on calf thymus DNA in the presence of low concentrations of Mg2+ ions. Vibrational spectra are presented in the wavenumber region 500-1650 cm-1. Large changes in the Raman spectra of calf-thymus DNA were observed on lowering the pH value. These are due to protonation and unstacking of the DNA bases during DNA melting and also to changes in the DNA backbone conformation. The intensities of the Raman bands of guanine (681 cm-1), adenine (728 cm-1), thymine (752 cm-1) and cytosine (785 cm-1), typical of the C2-endo-anti conformation of B-DNA, are discussed. The B-form marker near 835 cm-1 and the base vibrations in the higher wavenumber region (1200-1680 cm-1) are analysed. Effects of low pH value upon the protonation mechanism of opening AT and changing the protonation of GC base pairs in DNA are discussed

The Genome Sequence of Taurine Cattle:A Window to Ruminant Biology and Evolution

To understand the biology and evolution of ruminants, the cattle genome was sequenced to about sevenfold coverage. The cattle genome contains a minimum of 22,000 genes, with a core set of 14,345 orthologs shared among seven mammalian species of which 1217 are absent or undetected in noneutherian (marsupial or monotreme) genomes. Cattle-specific evolutionary breakpoint regions in chromosomes have a higher density of segmental duplications, enrichment of repetitive elements, and species-specific variations in genes associated with lactation and immune responsiveness. Genes involved in metabolism are generally highly conserved, although five metabolic genes are deleted or extensively diverged from their human orthologs. The cattle genome sequence thus provides a resource for understanding mammalian evolution and accelerating livestock genetic improvement for milk and meat production.Fil: Bovine Genome Sequencing and Analysis Consortium. Bovine Genome Sequencing And Analysis Consortium; Estados UnidosFil: Amadio, Ariel Fernando. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Poli, Mario Andres. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentin