Human skin is home to a variety of commensal bacteria, including many species of coagulase-negative staphylococci (CoNS). While it is well established that the microbiota as a whole maintains skin homeostasis and excludes pathogens (i.e., colonization resistance), relatively little is known about the unique contributions of individual CoNS species to these interactions. Staphylococcus hominis is the second most frequently isolated CoNS from healthy skin, and there is emerging evidence to suggest that it may play an important role in excluding pathogens, including Staphylococcus aureus , from colonizing or infecting the skin.
The goal of this study was to evaluate the effectiveness of organic chemistry textbooks in developing student representational competence skills with eight representations of molecular structure (Lewis structures, Kekulé structures, condensed structures, electrostatic potential maps, skeletal structures, dash–wedge diagrams, Newman projections, and chair conformations). Five commonly used organic chemistry textbooks in the United States were deductively coded with Kozma and Russell’s representational competence framework. The analyses focused on identifying representational competence skills that are taught for each type of representation, as well as how consistently these skills are taught across text, worked examples, and practice problems within each textbook. We found that more representational competence skills are taught for some representations rather than others. In addition, all five textbooks may promote foundational representational competence skills, such as the ability to interpret, translate, and generate representations, but may fail to support learners in developing higher-level metarepresentational skills. Generally, more skills are taught in text, in comparison to the number of skills that are scaffolded in worked examples and assessed in practice problems. This means that the textbooks introduce various skills but do not provide as much support for students to develop and practice these skills. Finally, worked examples of some textbooks provide much more scaffolded explanations than others, allowing for a different amount of skill-building support.
The number of studies analyzing chemistry textbooks has steadily increased over the years and has notably surged in the past decade. In this literature review, we examine the research literature on chemistry textbooks. The review spans 40 years of research (from 1981 to 2021) and includes 79 studies published in over 20 different journals, analyzing secondary and postsecondary chemistry textbooks used in more than 17 countries. We synthesize the samples and methods used as well as the findings of the studies around chemistry textbooks. Based on this synthesis, we provide multiple concrete implications to improve the rigor of future studies of chemistry textbooks because most of the articles in our review lack a discussion of the limitations of their studies, half do not use any theoretical or analytical framework(s) to guide the design of their studies and the interpretation of findings, and a quarter do not specify the country of use for the textbooks in their samples. Additionally, we provide concrete recommendations for textbook developers to improve the quality of chemistry textbooks. Importantly, textbook developers need to ensure that their products are grounded in research and theory about student learning.
Botanical natural products have been widely consumed for their purported usefulness against COVID-19. Here, six botanical species from multiple sources and 173 isolated natural product compounds were screened for blockade of wild-type (WT) SARS-CoV-2 infection in human 293T epithelial cells overexpressing ACE-2 and TMPRSS2 protease (293TAT). Antiviral activity was demonstrated by an extract from Stephania tetrandra . Extract fractionation, liquid chromatography–mass spectrometry (LC-MS), antiviral assays, and computational analyses revealed that the alkaloid fraction and purified alkaloids tetrandrine, fangchinoline, and cepharanthine inhibited WT SARS-CoV-2 infection. The alkaloids and alkaloid fraction also inhibited the delta variant of concern but not WT SARS-CoV-2 in VeroAT cells. Membrane permeability assays demonstrate that the alkaloids are biologically available, although fangchinoline showed lower permeability than tetrandrine. At high concentrations, the extract, alkaloid fractions, and pure alkaloids induced phospholipidosis in 293TAT cells and less so in VeroAT cells. Gene expression profiling during virus infection suggested that alkaloid fraction and tetrandrine displayed similar effects on cellular gene expression and pathways, while fangchinoline showed distinct effects on cells. Our study demonstrates a multifaceted approach to systematically investigate the diverse activities conferred by complex botanical mixtures, their cell-context specificity, and their pleiotropic effects on biological systems.
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