Grazing incidence X-Ray diffraction: identifying the dominant facet in copper foams that electrocatalyze the reduction of carbon dioxide to formate.

Copper foams have been shown to electrocatalyze the carbon dioxide reduction reaction (CO2RR) to formate (HCOO-) with significant faradaic efficiency (FE) at low overpotentials. Unlike the CO2RR electrocatalyzed at copper foils, the CO2RR electrocatalyzed at porous copper foams selects for HCOO- essentially to the exclusion of hydrocarbon products. Formate is an environmentally friendly organic acid with many applications such as food preservation, textile processing, de-icing, and fuel in fuel cells. Thus, HCOO- is an attractive product from the CO2RR if it is produced at an overpotential lower than that at other electrocatalysts. In this study, grazing incidence X-ray diffraction (GIXRD) was used to identify the dominant surface facet of porous copper foams that accounts for its selectivity for HCOO- during the CO2RR. Included are data from the CO2RR at different temperatures using copper foams as the electrocatalyst. Under optimal reaction conditions at 2 °C, the FE for converting CO2 to HCOO- at Cu foams approaches 50% while the FE for hydrogen gas (H2) falls below 40%, a significant departure from that obtained at polycrystalline Cu foils. Computational studies by others have proposed (200) and (111) facets of Cu foils thermodynamically favour methane and other hydrocarbons, CO, HCOO- from the CO2RR. Results from the GIXRD studies indicate Cu foams are dominated by the (111) facet, which accounts for the selectivity of Cu foams toward HCOO- regardless of temperature used for the CO2RR.

Two DNA vaccines protect against severe disease and pathology due to SARS-CoV-2 in Syrian hamsters.

The SARS-CoV-2 pandemic is an ongoing threat to global health, and wide-scale vaccination is an efficient method to reduce morbidity and mortality. We designed and evaluated two DNA plasmid vaccines, based on the pIDV-II system, expressing the SARS-CoV-2 spike gene, with or without an immunogenic peptide, in mice, and in a Syrian hamster model of infection. Both vaccines demonstrated robust immunogenicity in BALB/c and C57BL/6 mice. Additionally, the shedding of infectious virus and the viral burden in the lungs was reduced in immunized hamsters. Moreover, high-titers of neutralizing antibodies with activity against multiple SARS-CoV-2 variants were generated in immunized animals. Vaccination also protected animals from weight loss during infection. Additionally, both vaccines were effective at reducing both pulmonary and extrapulmonary pathology in vaccinated animals. These data show the potential of a DNA vaccine for SARS-CoV-2 and suggest further investigation in large animal and human studies could be pursued.

Enhanced CO2 electroreduction efficiency through secondary coordination effects on a pincer iridium catalyst.

An iridium(III) trihydride complex supported by a pincer ligand with a hydrogen bond donor in the secondary coordination sphere promotes the electrocatalytic reduction of CO2 to formate in water/acetonitrile with excellent Faradaic efficiency and low overpotential. Preliminary mechanistic experiments indicate formate formation is facile while product release is a kinetically difficult step.

"Strange kinetics" in the temperature dependence of methionine ligand rebinding dynamics in cytochrome c.

The temperature dependence of methionine ligand dissociation and rebinding dynamics in cytochrome c in aqueous solution has been studied using classical molecular dynamics simulation. Results are compared with previous study of rebinding dynamics at 300 K in water in order to understand how the change of protein environment and the underlying protein energy landscape influence the dynamics. Rebinding dynamics at 77, 180, and 300 K exhibits changes in both time scale and mechanism as the protein and solvent undergo a dynamic "glass transition". At each temperature, the rebinding dynamics yields a subset of trajectories that undergo fast rebinding as well as a subset of trajectories that undergo slower rebinding. At 300 K in water, both a fast (4.0 ps) and slow (14.6 ps) rebinding is observed. While fast rebinding occurs from a "downward" (heme pointing) substate of the methionine, the slow rebinding involves interconversion between an "upward" substate, from which rebinding cannot occur, and the downward substate. At lower temperatures (77 and 180 K), the upward dissociated substate was not observed due to the high barrier imposed by the "frozen" protein structure. However, a slow rebinding phase is observed at both 77 and 180 K and is associated with a process of trapping in downward but "binding forbidden" substates with subsequent slow dynamical conversion to "binding competent" substates from which rebinding is relatively rapid. Distinctive rebinding dynamics at 77 and 180 K suggest that different rebinding time scales are predetermined by the protein and solvent structural arrangement prior to photodissociation, which causes either fast rebinding (about 2 ps) or slow (>50 ps) rebinding. Suggestions for future experiments to further probe the role of dynamic heterogeneity in the kinetics of methionine ligand binding in cytochrome c protein are proposed.