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Full-Text Articles in Physics
Solution Scattering And Fret Studies Of Nucleosomes Reveal Dna: Unwrapping Effects Of H3 And H4 Tail Removal, Kurt Andresen, Isabel Jimenez-Useche, Steven C. Howell, Chongli Yuan, Xiangyun Qiu
Solution Scattering And Fret Studies Of Nucleosomes Reveal Dna: Unwrapping Effects Of H3 And H4 Tail Removal, Kurt Andresen, Isabel Jimenez-Useche, Steven C. Howell, Chongli Yuan, Xiangyun Qiu
Physics and Astronomy Faculty Publications
Using a combination of small-angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET) measurements we have determined the role of the H3 and H4 histone tails, independently, in stabilizing the nucleosome DNA terminal ends from unwrapping from the nucleosome core. We have performed solution scattering experiments on recombinant wild-type, H3 and H4 tail-removed mutants and fit all scattering data with predictions from PDB models and compared these experiments to complementary DNA-end FRET experiments. Based on these combined SAXS and FRET studies, we find that while all nucleosomes exhibited DNA unwrapping, the extent of this unwrapping is increased for nucleosomes …
Ion Competition In Condensed Dna Arrays In The Attractive Regime, Xiangyun Qiu, John Giannini, Steven C. Howell, Qi Xia, Fuyou Ke, Kurt Andresen
Ion Competition In Condensed Dna Arrays In The Attractive Regime, Xiangyun Qiu, John Giannini, Steven C. Howell, Qi Xia, Fuyou Ke, Kurt Andresen
Physics and Astronomy Faculty Publications
Physical origin of DNA condensation by multivalent cations remains unsettled. Here, we report quantitative studies of how one DNA-condensing ion (Cobalt3+ Hexammine, or Co3+Hex) and one nonDNA-condensing ion (Mg2+) compete within the interstitial space in spontaneously condensed DNA arrays. As the ion concentrations in the bath solution are systematically varied, the ion contents and DNA-DNA spacings of the DNA arrays are determined by atomic emission spectroscopy and x-ray diffraction, respectively. To gain quantitative insights, we first compare the experimentally determined ion contents with predictions from exact numerical calculations based on nonlinear Poisson-Boltzmann equations. Such calculations …
Elucidating Internucleosome Interactions And The Roles Of Histone Tails, Steven C. Howell, Kurt Andresen, Isabel Jimenez-Useche, Chongli Yuan, Xiangyun Qiu
Elucidating Internucleosome Interactions And The Roles Of Histone Tails, Steven C. Howell, Kurt Andresen, Isabel Jimenez-Useche, Chongli Yuan, Xiangyun Qiu
Physics and Astronomy Faculty Publications
The nucleosome is the first level of genome organization and regulation in eukaryotes where negatively charged DNA is wrapped around largely positively charged histone proteins. Interaction between nucleosomes is dominated by electrostatics at long range and guided by specific contacts at short range, particularly involving their flexible histone tails. We have thus quantified how internucleosome interactions are modulated by salts (KCl, MgCl2) and histone tail deletions (H3, H4 N-terminal), using small-angle x-ray scattering and theoretical modeling. We found that measured effective charges at low salts are ∼1/5th of the theoretically predicted renormalized charges and that H4 tail deletion …