title: Salt-induced structural changes in nucleosomes.
abstract: Nucleosomes and oligonucleosomes were prepared by digestion of human placental nuclei with staphlococcal nuclease and fractionated by gel filtration chromatography. The effect of increasing salt on the structure of nucleosomes was examined in the presence and absence of 10 mM MgCl2. Nucleosomes and oligonucleosomes are insoluble over a broad range of salt concentration. Nucleosomes are insoluble in larger than or equal to 120 mM (NH4)2SO4 containing 10 mM MgCl2 allowing analyses of changes in nucleosomal DNA by C.D. spectroscopy. Nucleosomes are insoluble in less than or equal to 120 mM (NH4)2SO4 containing 10 mM MgCl2 as demonstrated by turbidity measurements. We conclude that the insolubility of nucleosomes accompanies salt-induced structural changes possibly due to individual particle condensation. As the salt concentration is increased the nucleosomes condense and then relax at higher salt concentrations.
mesh_terms: D000645:Ammonium Sulfate; D002467:Cell Nucleus / Q000032:analysis*; D055598:Chemical Phenomena; D002621:Chemistry; D002843:Chromatin / Q000032:analysis; D002942:Circular Dichroism; D004247:DNA; D005260:Female; D006801:Humans; D046911:Macromolecular Substances; D008274:Magnesium; D008836:Micrococcal Nuclease; D009994:Osmolar Concentration; D010920:Placenta / Q000032:analysis*; D011247:Pregnancy; D012995:Solubility
chemical_list: D002843:Chromatin; D046911:Macromolecular Substances; D004247:DNA; D008836:Micrococcal Nuclease; D008274:Magnesium; D000645:Ammonium Sulfate