Impact of Energy-related Pollutants On Chromosome Structure. Progress Report, January 1-december 31, 1980. Iquid Column Chromatography; Absorption Spectra; Computer Codes; Dichroism; Equipment Interfaces; Microprocessors; Spectrophotometers; ; Carbon 13;

摘要

Methods for rapidly analyzing methylated and ethylated nucleosides and bases by high pressure liquid chromatography were investigated. Deoxyribonucleotides were alkylated with alkyl iodides and dialkyl sulfates. Several unreported products of the reactions of methyl and ethyl iodide in dimethylsulfoxide were found and are being characterized. The Cary 219 UV-Vis spectrophotometer was interfaced to a microcomputer and several utility programs were written. Preliminary absorption and circular dichroism studies of the binding of ethidium to DNA and nucleosome cores showed binding to cores to be quite different from binding to DNA. Free radical and additional reactions of bisulfite with DNA in chromatin were examined. Free radical attack was minimal. Some conversion of cytosine to uracil was noted, but protein crosslinking to DNA was not detected. The first valid natural abundance /sup 13/C nmr spectra of double-stranded DNA and double-stranded DNA complexed with ethidium were obtained. These spectra suggested that DNA undergoes considerable internal motion. The data show that 13-C nmr studies of the conformational and motional properties of native DNA and of complexes of native DNA with small molecules are practical and promising. Studies of subnucleosomes derived from nucleosomes were completed. Based on these studies, a model of the linear arrangement of histone C-terminal and N-terminal chain regions along nucleosome DNA was proposed. The use of staphylococcal protease to probe histone conformations in nucleosomes was explored. Preliminary data indicate that H3 is much more susceptible to protease than other core histones, and is cleaved in its hydrophobic domain. A procedure for fractionating chromatin was alos developed. (ERB)