Four new DNA letters double life's alphabet

Studies on the structure and chirality of A-motif in adenosine monophosphate nucleotide metal coordination complexes

Structure and chirality of A-motif.

New Insights into the Structure and Reactivity of Uracil Derivatives in Different Solvents-A Computational Study

Ab initio calculations were carried out to understand the reactivity and stability of some uracil derivatives, cytosine, 1-methyl cytosine, and cytidine in solvents, water, dimethyl sulfoxide (DMSO), n-octanol, and chloroform. Geometries were fully optimized at MP2 and B3LYP using the 6-31+G(d,p) basis set by applying the Solvation Model on Density (SMD) in solvent systems. The syn conformer of cytidine (cytidine II) is the most stable conformer in the gas phase, while the anticonformer (cytidine IV) is most stable in all of the solvents. Solvation free energy and polarizability values in different solvents decrease in the order water > DMSO > n-octanol > chloroform, while dipole moment, first-order hyperpolarizability, and HOMO-LUMO energy gap values follow the order of polar protic solvent (water and n-octanol) > polar aprotic solvent (DMSO) > nonpolar solvent (chloroform). The solvation free energy, dipole moment, polarizability, and first-order hyperpolarizability values also follow the order of cytosine > 1-methyl cytosine > cytidine. To illustrate that the molecular properties correlate well with the reactivity of the molecules, ab initio calculations were carried out for the reaction of uracil derivatives with Br2 in the gas phase, water, DMSO, n-octanol, and chloroform. All ground and transition state geometries were fully optimized at B3LYP/6-31+G(d,p), and energies were also calculated at G3MP2 for cytosine and 1-methyl cytosine. For cytosine and 1-methyl cytosine, Gibbs energies of activation decrease with the polarity of the solvent that is chloroform > n-octanol > DMSO > water, while the Gibbs energies of activation for the reaction with cytidine decrease in the order of water > DMSO > n-octanol > chloroform. These results suggest that solvent polarity is very important for the stability and reactivity of uracil derivatives. Hydrogen bonding may also play an important role mainly for cytidine. Free energies of activation decrease with the size of the molecule, i.e., cytosine > 1-methyl cytosine > cytidine.

Strengthening Security for Gene Synthesis: Recommendations for Governance

Since the inception of gene synthesis technologies, there have been concerns about possible misuse. Using gene synthesis, pathogens-particularly small viruses-may be assembled "from scratch" in the laboratory, evading the regulatory regimes many nations have in place to control unauthorized access to dangerous pathogens. Progress has been made to reduce these risks. In 2010, the US Department of Health and Human Services (HHS) published guidance for commercial gene synthesis providers that included sequence screening of the orders and customer screening. The industry-led International Gene Synthesis Consortium (IGSC) was formed in 2009 to share sequence and customer screening methods, and it now includes the major international gene synthesis providers among its members. Since the 2010 HHS Guidance was released, however, there have been changes in gene synthesis technologies and market conditions that have reduced the efficacy of these biosecurity protections, leading to questions about whether the 2010 HHS Guidance should be updated, what changes could make it more effective, and what other international governance efforts could be undertaken to reduce the risks of misuse of gene synthesis products. This article describes these conditions and recommends actions that governments should take to reduce these risks and engage other nations involved in gene synthesis research.