The theory of planned behavior (TPB) has been used to understand a variety of different wildlife-related behaviors for more than two decades. Since its introduction, a large body of research ...involving this theory has allowed for a critical look at the concept to develop. This opinion piece is designed to give researchers and professionals in the field a holistic perspective on TPB, including the merits of using the theory, the criticisms of the theory, why TPB is likely to see continued use in human dimensions research, and directions for future exploration. Collectively, readers will better understand the strengths and weaknesses of TPB and how they can contribute to its utility moving forward.
The synthesis of unsymmetrical cyclobutanes by controlled heterodimerization of olefins remains a substantial challenge, particularly in an enantiocontrolled fashion. Shown herein is that chiral ...Lewis acid catalyzed triplet sensitization enables the synthesis of highly enantioenriched diarylcyclobutanes by photocycloaddition of structurally varied 2′‐hydroxychalcones with a range of styrene coupling partners. The utility of this reaction is demonstrated through the direct synthesis of a representative norlignan cyclobutane natural product.
Cross‐products: Lewis acid catalyzed triplet sensitization enables the highly enantioselective crossed cycloaddition of chalcones and styrenes to forge cyclobutane cores. These cores are found in multiple bioactive natural products.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recently identified coronavirus that causes the respiratory disease known as coronavirus disease 2019 (COVID-19). Despite the urgent ...need, we still do not fully understand the molecular basis of SARS-CoV-2 pathogenesis. Here, we comprehensively define the interactions between SARS-CoV-2 proteins and human RNAs. NSP16 binds to the mRNA recognition domains of the U1 and U2 splicing RNAs and acts to suppress global mRNA splicing upon SARS-CoV-2 infection. NSP1 binds to 18S ribosomal RNA in the mRNA entry channel of the ribosome and leads to global inhibition of mRNA translation upon infection. Finally, NSP8 and NSP9 bind to the 7SL RNA in the signal recognition particle and interfere with protein trafficking to the cell membrane upon infection. Disruption of each of these essential cellular functions acts to suppress the interferon response to viral infection. Our results uncover a multipronged strategy utilized by SARS-CoV-2 to antagonize essential cellular processes to suppress host defenses.
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•NSP16 binds mRNA recognition domains of U1/U2 snRNAs and disrupts mRNA splicing•NSP1 binds in the mRNA entry channel of the ribosome to disrupt protein translation•NSP8 and NSP9 bind the signal recognition particle and disrupt protein trafficking•These disruptions of protein production suppress the interferon response to infection
SARS-CoV-2 proteins directly engage host RNAs to dysregulate essential steps of protein production and suppress the interferon response.
Relatively few catalytic systems are able to control the stereochemistry of electronically excited organic intermediates. Here we report the discovery that a chiral Lewis acid complex can catalyze ...triplet energy transfer from an electronically excited photosensitizer. We applied this strategy to asymmetric 2 + 2 photocycloadditions of 2'-hydroxychalcones, using tris(bipyridyl) ruthenium(ll) as a sensitizer. A variety of electrochemical, computational, and spectroscopic data rule out substrate activation by means of photoinduced electron transfer and instead support a mechanism in which Lewis acid coordination dramatically lowers the triplet energy of the chalcone substrate. We expect that this approach will enable chemists to more broadly apply their detailed understanding of chiral Lewis acid catalysis to stereocontrol in reactions involving electronically excited states.
Methods for the highly stereoselective and regiodivergent hydrosilylation of 1,3‐disubstituted allenes have been developed. The synthesis of E allylsilanes is accomplished with palladium NHC ...catalysts, and trisubstituted Z alkenylsilanes are accessed with nickel NHC catalysts. Unsymmetrically substituted allenes are well tolerated with nickel catalysis and afford Z alkenylsilanes. Evidence for a plausible mechanism was obtained through an isotopic double‐labeling crossover study.
Silanes with a choice: The hydrosilylation of 1,3‐disubstituted allenes, which have presented a notorious challenge for regioselective additions, can now be accomplished with outstanding levels of regio‐ and stereocontrol. By altering the metal catalyst and ligand structure, access to trisubstituted Z alkenylsilanes or trans allylsilanes is provided in a simple catalytic operation.
Visitation to parks and protected areas is a common COVID-19 coping strategy promoted by state and national public health officials and political leadership. Crowding and congestions in parks has ...been a perennial problem and the ability to socially distance within them is an unproven assumption. Is it possible to socially distance in a busy national park that has been designed to concentrate use?
An observational study was conducted in July 2020 at the outside foyer of the Visitor Center of Arches National Park. Motion sensor cameras were placed to record one-minute videos when a person entered the field of view. Number of groups, group size, facial coverings and encounters within 6 feet (1.83 meters) of other groups were recorded. Groups were smaller on average than recorded in previous studies. Approximately 61% of the visitors wore masks. Most groups (69%) were able to experience the visitor center with no intergroup encounters. We model the probability of intergroup encounters and find as group size and number of groups increases, the probability of encounters rises. With four groups present, the probability of one or more encounters ranges from 19% to 40% for common group sizes, while if eight groups are present, the probability of one or more encounters increases from 34% to 64% for common group sizes.
Under conditions in which park visitors have the physical space to avoid close encounters with other groups they are taking advantage of the opportunity. Visitors are minimizing group size, wearing masks, and remaining socially distant. However, encounters increase as the number or the size of the groups increases. In other areas of the parks this ability to avoid encounters may not be as possible. We recommend that park managers continue to appeal for compliance with CDC guidelines, especially the wearing of masks and encouraging visitors to split up into small groups when visiting.
Highlights • The Salmonellae PhoPQ virulence system is a major regulator of outer membrane (OM) lipids and proteins. • Lipopolysaccharide (LPS) regulation increases bacterial resistance to host ...killing. • PhoPQ regulates modification to LPS phosphates and controls acylation of lipid A. • PhoPQ promotes pamitoylation of phosphatidylglycerol (PG) and increases cardiolipin content of the OM. • The PhoPQ-regulated OM palmitoyltransferase, PagP, transfers palmitoyl groups to PG and lipid A within the OM of S. Typhimurium.
Advances in hydroarylation have been achieved by the development of a one-pot regioselective allene hydrosilylation/Pd(0)-catalyzed cross-coupling protocol. The regioselectivity is primarily governed ...by N-heterocyclic carbene (NHC) ligand identity in the hydrosilylation step and is preserved in the subsequent cross-coupling reaction. This methodology affords streamlined access to functionalized 1,1-disubstituted alkenes with excellent regiocontrol.
Metal-Cation-Based Anion Exchange Membranes Zha, Yongping; Disabb-Miller, Melanie L; Johnson, Zachary D ...
Journal of the American Chemical Society,
03/2012, Letnik:
134, Številka:
10
Journal Article
Recenzirano
Here we present the first metal-cation-based anion exchange membranes (AEMs), which were synthesized by copolymerization and cross-linking of a norbornene monomer functionalized with a water-soluble ...bis(terpyridine)ruthenium(II) complex and dicyclopentadiene. Each ruthenium complex has two associated counteranions, unlike most ammonium- and phosphonium-based membranes with single cation–anion pairs. The resulting AEMs show anion conductivities and mechanical properties comparable to those of traditional quaternary-ammonium-based AEMs as well as good alkaline stability and methanol tolerance. These results suggest that metal-cation-based polymers hold promise as a new class of materials for anion-conducting applications.
Gram-negative bacteria have two lipid membranes separated by a periplasmic space containing peptidoglycan. The surface bilayer, or outer membrane (OM), provides a barrier to toxic molecules, ...including host cationic antimicrobial peptides (CAMPs). The OM comprises an outer leaflet of lipid A, the bioactive component of lipopolysaccharide (LPS), and an inner leaflet of glycerophospholipids (GPLs). The structure of lipid A is environmentally regulated in a manner that can promote bacterial infection by increasing bacterial resistance to CAMP and reducing LPS recognition by the innate immune system. The gastrointestinal pathogen, Salmonella Typhimurium, responds to acidic pH and CAMP through the PhoPQ two-component regulatory system, which stimulates lipid A remodeling, CAMP resistance, and intracellular survival within acidified phagosomes. Work here demonstrates that, in addition to regulating lipid A structure, the S. Typhimurium PhoPQ virulence regulators also regulate acidic GPL by increasing the levels of cardiolipins and palmitoylated acylphosphatidylglycerols within the OM. Triacylated palmitoyl-PG species were diminished in strains deleted for the PhoPQ-regulated OM lipid A palmitoyltransferase enzyme, PagP. Purified PagP transferred palmitate to PG consistent with PagP acylation of both lipid A and PG within the OM. Therefore, PhoPQ coordinately regulates OM acidic GPL with lipid A structure, suggesting that GPLs cooperate with lipid A to form an OM barrier critical for CAMP resistance and intracellular survival of S. Typhimurium.
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