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Updated: Aug 24, 2026

Sequential Salt Extractions for the Analysis of Bulk Chromatin Binding Properties of Chromatin Modifying Complexes
Published on: October 2, 2017
Physical properties of a genomic condensed chromatin fragment
Rodolfo Ghirlando1, Michael D Litt, Marie-Noëlle Prioleau
1Department of Health and Human Services, Laboratory of Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
We have studied the physical properties of a segment of condensed chromatin that lies upstream of the chicken beta-globin locus. This segment can be excised from an avian erythroleukemia cell line by restriction enzyme digestion and released from the nucleus as an essentially homogeneous fragment about 15.5 kbp long. Because of this homogeneity we could measure its sedimentation coefficient quite accurately by a combination of sucrose gradient and analytical ultracentrifugation. By measuring additionally the buoyant density of the cross-linked particle in CsCl we could deduce the total mass of the particle, hence its frictional coefficient, f, directly related to its shape. The measured value of f is consistent with a rod-like particle of the approximate length and diameter proposed earlier for the 30 nm chromatin fiber. The method is generally applicable to homogeneous particles of unique sequence at genomic abundance.
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