Performance evaluation of activated carbon sorbents for indoor air purification during normal and wildfire events.

Volatile organic compounds (VOCs) are a significant class of indoor air pollutants and are known for their adverse effects on health. A common strategy to reduce indoor VOC levels is to use sorbents, including activated carbons (ACs). The amount of activated carbon is critical to achieving a reasonable AC filter lifetime in an air purification device.

DNA Polymerase λ Active Site Favors a Mutagenic Mispair between the Enol Form of Deoxyguanosine Triphosphate Substrate and the Keto Form of Thymidine Template: A Free Energy Perturbation Study.

Human DNA polymerase λ is an intermediate fidelity member of the X family, which plays a role in DNA repair. Recent X-ray diffraction structures of a ternary complex of a loop-deletion mutant of polymerase λ, a deoxyguanosine triphosphate analogue, and a gapped DNA show that guanine and thymine form a mutagenic mispair with an unexpected Watson-Crick-like geometry rather than a wobble geometry. Hence, there is an intriguing possibility that either thymine in the DNA or guanine in the deoxyguanosine triphosphate analogue may spend a substantial fraction of time in a deprotonated or enol form (both are minor species in aqueous solution) in the active site of the polymerase λ mutant.

Redox chemistry and metal-insulator transitions intertwined in a nano-porous material.

Metal-organic frameworks are nano-porous adsorbents of relevance to gas separation and catalysis, and separation of oxygen from air is essential to diverse industrial applications. The ferrous salt of 2,5-dihydroxy-terephthalic acid, a metal-organic framework of the MOF74 family, can selectively adsorb oxygen in a manner that defies the classical picture: adsorption sites either do or do not share electrons over a long range. Here we propose, and then justify phenomenologically and computationally, a mechanism.

Ab initio carbon capture in open-site metal-organic frameworks.

During the formation of metal-organic frameworks (MOFs), metal centres can coordinate with the intended organic linkers, but also with solvent molecules. In this case, subsequent activation by removal of the solvent molecules creates unsaturated 'open' metal sites known to have a strong affinity for CO(2) molecules, but their interactions are still poorly understood. Common force fields typically underestimate by as much as two orders of magnitude the adsorption of CO(2) in open-site Mg-MOF-74, which has emerged as a promising MOF for CO(2) capture.

Selective binding of O2 over N2 in a redox-active metal-organic framework with open iron(II) coordination sites.

The air-free reaction between FeCl(2) and H(4)dobdc (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) in a mixture of N,N-dimethylformamide (DMF) and methanol affords Fe(2)(dobdc)·4DMF, a metal-organic framework adopting the MOF-74 (or CPO-27) structure type. The desolvated form of this material displays a Brunauer-Emmett-Teller (BET) surface area of 1360 m(2)/g and features a hexagonal array of one-dimensional channels lined with coordinatively unsaturated Fe(II) centers. Gas adsorption isotherms at 298 K indicate that Fe(2)(dobdc) binds O(2) preferentially over N(2), with an irreversible capacity of 9.

Chemistry of fast electrons.

A chemicurrent is a flux of fast (kinetic energy approximately > 0.5-1.3 eV) metal electrons caused by moderately exothermic (1-3 eV) chemical reactions over high work function (4-6 eV) metal surfaces.

Assessment of Density Functionals for Predicting One-Bond Carbon-Hydrogen NMR Spin-Spin Coupling Constants.

We benchmark the performance of 20 approximate density functionals for the calculation of one-bond carbon-hydrogen NMR spin-spin coupling constants (SSCCs). These functionals range from the simplest local-spin density approximation to novel meta-generalized gradient approximation and hybrid density functionals. Our testing set consists of 72 diverse molecules that represent multiple types of hybridization of the carbon atom corresponding to 96 experimentally measured one-bond carbon-hydrogen SSCCs.

Current-dependent extension of the Perdew-Burke-Ernzerhof exchange-correlation functional.

The probability current density is used in addition to the electron density and its gradient as a variable in the construction of an exchange-correlation functional. Starting from the Perdew-Burke-Ernzerhof generalized gradient approximation, we employ exact conditions to build a nonempirical exchange functional. Matching the correlation functional to that for exchange yields a current-dependent approximation for correlation.