Chromatin ionic atmosphere analyzed by a mesoscale electrostatic approach

Hin Hark Gan, Tamar Schlick

Research output: Contribution to journalArticle

Abstract

Characterizing the ionic distribution around chromatin is important for understanding the electrostatic forces governing chromatin structure and function. Here we develop an electrostatic model to handle multivalent ions and compute the ionic distribution around a mesoscale chromatin model as a function of conformation, number of nucleosome cores, and ionic strength and species using Poisson-Boltzmann theory. This approach enables us to visualize and measure the complex patterns of counterion condensation around chromatin by examining ionic densities, free energies, shielding charges, and correlations of shielding charges around the nucleosome core and various oligonucleosome conformations. We show that: Counterions, especially divalent cations, predominantly condense around the nucleosomal and linker DNA, unburied regions of histone tails, and exposed chromatin surfaces; ionic screening is sensitively influenced by local and global conformations, with a wide ranging net nucleosome core screening charge (56-100e); and screening charge correlations reveal conformational flexibility and interactions among chromatin subunits, especially between the histone tails and parental nucleosome cores. These results provide complementary and detailed views of ionic effects on chromatin structure for modest computational resources. The electrostatic model developed here is applicable to other coarse-grained macromolecular complexes.

Original languageEnglish (US)
Pages (from-to)2587-2596
Number of pages10
JournalBiophysical Journal
Volume99
Issue number8
DOIs
StatePublished - Oct 20 2010

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Static Electricity
Atmosphere
Chromatin
Nucleosomes
Histones
Macromolecular Substances
Divalent Cations
Osmolar Concentration
Ions
DNA

ASJC Scopus subject areas

  • Biophysics

Cite this

Chromatin ionic atmosphere analyzed by a mesoscale electrostatic approach. / Hark Gan, Hin; Schlick, Tamar.

In: Biophysical Journal, Vol. 99, No. 8, 20.10.2010, p. 2587-2596.

Research output: Contribution to journalArticle

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