RESUMO
The process of fractionation of total calf thymus DNA using a step precipitation of DNA by means of increasing concentrations of the homologous histone KAP was investigated. In addition to the known fractions three so far undescribed ones/in thymus/,characterized by buoyant densities in CsCl equal 1.692, 1.706 and 1.728 g/ccm, were identified. Considerable amounts of preparations seriously enriched in individual satellite fractions were obtained. The ability of GC-rich satellite DNAs to form more soluble complexes with histone KAP is suggested as reason for the observed fractionation.
Assuntos
DNA , Timo/análise , Animais , Bovinos , Centrifugação com Gradiente de Concentração , Fenômenos Químicos , Físico-Química , DNA/isolamento & purificação , Histonas , Temperatura Alta , Cinética , Lisina , Substâncias Macromoleculares , Métodos , Desnaturação de Ácido Nucleico , Ligação Proteica , Espectrofotometria UltravioletaRESUMO
It was found that fractionation of calf thymus DNA on homologous histtone KAP covalently bound to CNBr activated Sepharose 4B depends on the molecular weight of DNA. The maximum of elution of high molecular DNA (m. wt. above 5 x 10(6)) was observed at 0.56 M NaCl and that of degraded DNA (m. wt. 0.8 x 10(6)) at 0.52 M NaCl. Significant differences in melting temperatures and melting intervals were observed among fractions obtained from low molecular DNA as a result of enrichment of some fractions in satellite DNAs. These differences were very small in DNA of m. wt. above 5 x 10(6). The results are discussed in terms of specific areas which may exist on calf thymus DNA molecules playing the role of loci, where lysine-rich histone KAP is preferentially bound.
