23 research outputs found
The contribution of phosphate–phosphate repulsions to the free energy of DNA bending
DNA bending is important for the packaging of genetic material, regulation of gene expression and interaction of nucleic acids with proteins. Consequently, it is of considerable interest to quantify the energetic factors that must be overcome to induce bending of DNA, such as base stacking and phosphate–phosphate repulsions. In the present work, the electrostatic contribution of phosphate–phosphate repulsions to the free energy of bending DNA is examined for 71 bp linear and bent-form model structures. The bent DNA model was based on the crystallographic structure of a full turn of DNA in a nucleosome core particle. A Green's function approach based on a linear-scaling smooth conductor-like screening model was applied to ascertain the contribution of individual phosphate–phosphate repulsions and overall electrostatic stabilization in aqueous solution. The effect of charge neutralization by site-bound ions was considered using Monte Carlo simulation to characterize the distribution of ion occupations and contribution of phosphate repulsions to the free energy of bending as a function of counterion load. The calculations predict that the phosphate–phosphate repulsions account for ∼30% of the total free energy required to bend DNA from canonical linear B-form into the conformation found in the nucleosome core particle
Approaches to lowering the cost of large space telescopes
New development approaches, including launch vehicles and advances in
sensors, computing, and software, have lowered the cost of entry into space,
and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat)
missions. To bring about a similar transformation in larger space telescopes,
it is necessary to reconsider the full paradigm of space observatories. Here we
will review the history of space telescope development and cost drivers, and
describe an example conceptual design for a low cost 6.5 m optical telescope to
enable new science when operated in space at room temperature. It uses a
monolithic primary mirror of borosilicate glass, drawing on lessons and tools
from decades of experience with ground-based observatories and instruments, as
well as flagship space missions. It takes advantage, as do large launch
vehicles, of increased computing power and space-worthy commercial electronics
in low-cost active predictive control systems to maintain stability. We will
describe an approach that incorporates science and trade study results that
address driving requirements such as integration and testing costs,
reliability, spacecraft jitter, and wavefront stability in this new
risk-tolerant "LargeSat" context.Comment: Presented at SPIE, Optics+Photonics 2023, Astronomical Optics:
Design, Manufacture, and Test of Space and Ground Systems IV in San Diego,
CA, US
Structure and binding of Mg(II) ions and di-metal bridge complexes with biological phosphates and phosphoranes
Accurate Proton Affinity and Gas-Phase Basicity Values for Molecules Important in Biocatalysis
Multilevel and Density Functional Electronic Structure Calculations of Proton Affinities and Gas-Phase Basicities Involved in Biological Phosphoryl Transfer â€
Proton-Coupled Electron Transfer in a Biomimetic Peptide as a Model of Enzyme Regulatory Mechanisms
Birds of Cimarron National Grassland /
"August 1996."Includes bibliographical references (p. 107-108).Mode of access: Internet