期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1974
卷号：71
期号：7
页码：2740-2743
DOI：10.1073/pnas.71.7.2740
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Calf-thymus chromatin was fractionated by ion-exchange chromatography on ECTHAM-cellulose and sucrose gradient sedimentation. [ECTHAM-cellulose is a cationic adsorbent prepared by coupling tris(hydroxymethyl)aminomethane to cellulose with epichlorohydrin.] The capacity of these fractionated chromatins to support RNA synthesis by DNA-dependent RNA polymerase of Escherichia coli was examined, using procedures that permit measurement of binding site frequency. Unfractionated calf thymus chromatin has 5-10% as many binding sites as protein-free DNA. By combination of the two fractionation methods, chromatin samples were obtained containing as few as 2% and as many as 47% of the number of binding sites found on protein-free DNA.
