Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 4 of 4

Full-Text Articles in Physical Sciences and Mathematics

Competitive Halide Binding By Halogen Versus Hydrogen Bonding: Bis-Triazole Pyridinium, Binod Nepal, Steve Scheiner Jul 2015

Competitive Halide Binding By Halogen Versus Hydrogen Bonding: Bis-Triazole Pyridinium, Binod Nepal, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The binding of F-, Cl-, Br-, and I- anions by bis‐triazole‐pyridine (BTP) was examined by quantum chemical calculations. There is one H atom on each of the two triazole rings that chelate the halide via H bonds. These H atoms were replaced by halogens Cl, Br, and I, thus substituting H bonds by halogen bonds. I substitution strongly enhances the binding; Br has a smaller effect, and Cl weakens the interaction. The strength of the interaction is sensitive to the overall charge on the BTP, rising as the binding agent becomes singly and then doubly positively charged. The strongest preference …


Multiple-Time Step Ab Initio Molecular Dynamics Based On Two-Electron Integral Screening, Shervin Fatehi, Ryan P. Steele Jan 2015

Multiple-Time Step Ab Initio Molecular Dynamics Based On Two-Electron Integral Screening, Shervin Fatehi, Ryan P. Steele

Chemistry Faculty Publications and Presentations

A multiple-timestep ab initio molecular dynamics scheme based on varying the two-electron integral screening method used in Hartree–Fock or density functional theory calculations is presented. Although screening is motivated by numerical considerations, it is also related to separations in the length- and timescales characterizing forces in a molecular system: Loose thresholds are sufficient to describe fast motions over short distances, while tight thresholds may be employed for larger length scales and longer times, leading to a practical acceleration of ab initio molecular dynamics simulations. Standard screening approaches can lead, however, to significant discontinuities in (and inconsistencies between) the energy and …


Substrate-Assisted And Enzymatic Pretransfer Editing Of Nonstandard Amino Acids By Methionyl-Trna Synthetase, Grant B. Fortowsky, Daniel J. Simard, Mohamed M. Aboelnga, James W. Gauld Jan 2015

Substrate-Assisted And Enzymatic Pretransfer Editing Of Nonstandard Amino Acids By Methionyl-Trna Synthetase, Grant B. Fortowsky, Daniel J. Simard, Mohamed M. Aboelnga, James W. Gauld

Chemistry and Biochemistry Publications

Aminoacyl-tRNA synthetases (aaRSs) are cen- tral to a number of physiological processes, including protein biosynthesis. In particular, they activate and then transfer their corresponding amino acid to the cognate tRNA. This is achieved with a generally remarkably high fidelity by editing against incorrect standard and nonstandard amino acids. Using docking, molecular dynamics (MD), and hybrid quantum mechanical/molecular mechanics methods, we have inves- tigated mechanisms by which methionyl-tRNA synthetase (MetRS) may edit against the highly toxic, noncognate, amino acids homocysteine (Hcy) and its oxygen analogue, homo- serine (Hse). Substrate-assisted editing of Hcy-AMP in which its own phosphate acts as the mechanistic …


Computational Chemistry In Rational Material Design For Organic Photovoltaics, Andrew Hoffman Jan 2015

Computational Chemistry In Rational Material Design For Organic Photovoltaics, Andrew Hoffman

Western Libraries Undergraduate Research Award

The acceleration in global population growth, combined with worldwide economic development, have together dramatically increased the demand for energy. This demand has been filled by fossil fuels. The reliance on fossil fuels as a cheap and convenient means of energy is leading to adverse, and perhaps irreversible, ramifications for the entire planet. Many potential alternative energy sources have been explored to alleviate the dependence upon fossil fuels. The use of solar energy as a renewable energy source has been a key area of investigation to many scientists and engineers looking to solve this problem. Among current solar cell design paradigms, …