Catalysis by small molecules (≤1000 Da, 10−9 m) that are capable of binding and activating substrates through attractive, noncovalent interactions has emerged as an important approach in organic and ...organometallic chemistry. While the canonical noncovalent interactions, including hydrogen bonding, ion pairing, and π stacking, have become mainstays of catalyst design, the cation–π interaction has been comparatively underutilized in this context since its discovery in the 1980s. However, like a hydrogen bond, the cation–π interaction exhibits a typical binding affinity of several kcal mol−1 with substantial directionality. These properties render it attractive as a design element for the development of small‐molecule catalysts, and in recent years, the catalysis community has begun to take advantage of these features, drawing inspiration from pioneering research in molecular recognition and structural biology. This Review surveys the burgeoning application of the cation–π interaction in catalysis.
Positive effects: This Review discusses the burgeoning role of the cation–π interaction in the small‐molecule catalysis of organic and organometallic reactions. An extensive survey of the state‐of‐the‐art research emphasizes how unexpected discoveries and systematic mechanistic studies have begun to enable rational applications of the cation–π interaction in catalyst design.
The objectives of this study were to determine: 1) the prevalence of frailty using Fried's phenotype method and the Short Performance Physical Battery (SPPB), 2) agreement between frailty assessment ...methods, 3) the feasibility of assessing frailty using Fried's phenotype method and the SPPB.
This cross-sectional study was conducted at a geriatric out-patient clinic in Hamilton, Canada. A research assistant conducted all frailty assessments. Patients were classified as non-frail, pre-frail or frail according to Fried's phenotype method and the SPPB. Agreement among methods is reported using the Cohen kappa statistic (standard error). Feasibility data included the percent of eligible participants agreeing to attempt the frailty assessments (criterion for feasibility: ≥90% of patients agreeing to the frailty assessment), equipment required, and safety considerations. A p-value of <0.05 is considered significant.
A total of 110 participants (92%) and 109 participants (91%) agreed to attempt Fried's phenotype method and SPPB, respectively. No adverse events occurred during any assessments. According to Fried's phenotype method, the prevalence of frailty and pre-frailty was 35% and 56%, respectively, and according to the SPPB, the prevalence of frailty and pre-frailty was 50% and 35%, respectively. There was fair to moderate agreement between methods for determining which participants were frail (0.488 0.082, p < 0.001) and pre-frail (0.272 0.084, p = 0.002).
Frailty and pre-frailty are common in this geriatric outpatient population, and there is fair to moderate agreement between Fried's phenotype method and the SPPB. Over 90% of the patients who were eligible for the study agreed to attempt the frailty assessments, demonstrating that according to our feasibility criteria, frailty can be assessed in this patient population. Assessing frailty may help clinicians identify high-risk patients and tailor interventions based on baseline frailty characteristics.
Following formative work in the 1970s, disappearance in the 1980s, and reemergence in the 1990s, a chronological review shows that the past decade has witnessed increasing interest in the study of ...urban metabolism. The review finds that there are two related, non-conflicting, schools of urban metabolism: one following Odum describes metabolism in terms of energy equivalents; while the second more broadly expresses a city’s flows of water, materials and nutrients in terms of mass fluxes. Four example applications of urban metabolism studies are discussed: urban sustainability indicators; inputs to urban greenhouse gas emissions calculation; mathematical models of urban metabolism for policy analysis; and as a basis for sustainable
urban design. Future directions include fuller integration of social, health and economic indicators into the urban metabolism framework, while tackling the great sustainability challenge of reconstructing cities.
This paper presents a chronological review of urban metabolism studies and highlights four areas of application.
Stephen Charles Gold MD FRCP 1915–2017 Kennedy, C.
British journal of dermatology (1951),
October 2017, 2017-10-00, 20171001, Volume:
177, Issue:
4
Journal Article
Wastewater-based epidemiology is an emerging tool for tracking the spread of SARS-CoV-2 through populations. However, many factors influence recovery and quantification of SARS-CoV-2 from wastewater, ...complicating data interpretation. Specifically, these factors may differentially affect the measured virus concentration, depending on the laboratory methods used to perform the test. Many laboratories add a proxy virus to wastewater samples to determine losses associated with concentration and extraction of viral RNA. While measuring recovery of a proxy virus is an important process control, in this piece, we describe the caveats and limitations to the interpretation of this control, including that it typically does not account for losses during RNA extraction. We recommend reporting the directly measured concentration data alongside the measured recovery efficiency, rather than attempting to correct the concentration for recovery efficiency. Even though the ability to directly compare SARS-CoV-2 concentrations from different sampling locations determined using different methods is limited, concentration data (uncorrected for recovery) can be useful for public health response.
An investigation of the mechanism of benzoic acid/thiourea co-catalysis in the asymmetric Pictet-Spengler reaction is reported. Kinetic, computational, and structure-activity relationship studies ...provide evidence that rearomatization via deprotonation of the pentahydro-β-carbolinium ion intermediate by a chiral thiourea·carboxylate complex is both rate- and enantioselectivity-determining. The thiourea catalyst induces rate acceleration over the background reaction mediated by benzoic acid alone by stabilizing every intermediate and transition state leading up to and including the final selectivity-determining step. Distortion-interaction analyses of the transition structures for deprotonation predicted using density functional theory indicate that differential π-π and C-H···π interactions within a scaffold organized by multiple hydrogen bonds dictate stereoselectivity. The principles underlying rate acceleration and enantiocontrol described herein are expected to have general implications for the design of selective transformations involving deprotonation of high-energy intermediates.
Molecular mechanisms underlying renal complications of diabetes remain unclear. We tested whether renal NADPH oxidase (Nox) 4 contributes to increased reactive oxygen species (ROS) generation and ...hyperactivation of redox-sensitive signaling pathways in diabetic nephropathy. Diabetic mice (db/db) (20 wk) and cultured mouse proximal tubule (MPT) cells exposed to high glucose (25 mmol/l, D-glucose) were studied. Expression (gene and protein) of Nox4, p22(phox), and p47(phox), but not Nox1 or Nox2, was increased in kidney cortex, but not medulla, from db/db vs. control mice (db/m) (P < 0.05). ROS generation, p38 mitogen-activated protein (MAP) kinase phosphorylation, and content of fibronectin and transforming growth factor (TGF)-β1/2 were increased in db/db vs. db/m (P < 0.01). High glucose increased expression of Nox4, but not other Noxes vs. normal glucose (P < 0.05). This was associated with increased NADPH oxidase activation and enhanced ROS production. Nox4 downregulation by small-interfering RNA and inhibition of Nox4 activity by GK-136901 (Nox1/4 inhibitor) attenuated d-glucose-induced NADPH oxidase-derived ROS generation. High d-glucose, but not l-glucose, stimulated phosphorylation of p38MAP kinase and increased expression of TGF-β1/2 and fibronectin, effects that were inhibited by SB-203580 (p38MAP kinase inhibitor). GK-136901 inhibited d-glucose-induced actions. Our data indicate that, in diabetic conditions: 1) renal Nox4 is upregulated in a cortex-specific manner, 2) MPT cells possess functionally active Nox4-based NADPH, 3) Nox4 is a major source of renal ROS, and 4) activation of profibrotic processes is mediated via Nox4-sensitive, p38MAP kinase-dependent pathways. These findings implicate Nox4-based NADPH oxidase in molecular mechanisms underlying fibrosis in type 2 diabetic nephropathy.
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