期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 97, 期 1, 页码 127-132出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.97.1.127
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资金
- NIGMS NIH HHS [R01 GM032543, R37 GM032543, GM-32543] Funding Source: Medline
Single chicken erythrocyte chromatin fibers were stretched and released at room temperature with force-measuring laser tweezers. In low ionic strength, the stretch-release curves reveal a process of continuous deformation with little or no internucleosomal attraction. A persistence length of 30 nm and a stretch modulus of approximate to 5 pN is determined for the fibers. At forces of 20 pN and higher, the fibers are modified irreversibly, probably through the mechanical removal of the histone cores from native chromatin. In 40-150 mM NaCl, a distinctive condensation-decondensation transition appears between 5 and 6 pN. corresponding to an internucleosomal attraction energy of approximate to 2.0 kcal/mol per nucleosome. Thus, in physiological ionic strength the fibers possess a dynamic structure in which the fiber locally interconverting between open and closed states because of thermal fluctuations.
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