DNA chain flexibility and the structure of chromatin V.bodies

Abstract

The persistence length of high-molecular-weight, monodisperse-bihelical DNA has been evaluated from low-shear flow birefringence and viscosity data at several temperatures in 2.0 M NaCl neutral pH buffer. At these solvent conditions, both the DNA and histone components of chromatin v-bodies have structural features similar to those in the intact nucleohistone complex at low ionic strength. The theory of Landau and Lifshitz is used to relate the experimental results to the thermodynamic functions for bending 140 nucleotide pairs of DNA into a plausible model structure: per v-body, ΔGb = 43.8 ± 5.3 kcal/mole, ΔHb = 45.7 ± 3.7 kcal/mole, and ΔSb = 6.2 ± 12.4 entropy units. This bending free energy is comparable to or less than that estimated to be required for a kinked DNA configuration and appears to be well within the range of estimated electrostatic free energies available from DNA-histone interactions in a v-body assembly. © 1997 Information Retrieval Limited.