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Background Preclinical murine infection models lack inter-laboratory uniformity, complicating result comparisons and data reproducibility. The European Innovative Medicines initiative-funded consortium (COMBINE) has developed a standardized murine neutropenic pneumonia protocol to address these concerns. While model methods have been standardized, a major obstacle to consistent results is the lack of available bacteria with defined viability and variability. Herein, we establish a diverse challenge set of Klebsiella pneumoniae and Pseudomonas aeruginosa suitable for use in the COMBINE protocol to further minimize experimental inconsistency and improve the interpretability of data generated among differing laboratories. Materials and methods Sixty-six K. pneumoniae and 65 P. aeruginosa were phenotypically profiled against tigecycline (K. pneumoniae only), levofloxacin, meropenem, cefiderocol and tobramycin. Fifty-nine isolates were introduced into the COMBINE model to assess the sufficiency of the starting bacterial inoculation, resultant baseline bacterial burden, achievement of ≥1 log10cfu/lung growth at 24 h, time to and percentage mortality. Forty-five isolates displaying desirable minimum inhibitory concentration profiles were subjected to replicate in vivo testing to assess target parameters. Results 83% of K. pneumoniae reached the prerequisite growth at 24 h using a starting bacterial burden ≥7 log10cfu/lung. P. aeruginosa isolates grew well in the model: 90% achieved the growth target with a starting bacterial burden of 6 log10cfu/lung. Mortality was negligible for K. pneumoniae but high for P. aeruginosa. Poor or inconsistent achievement of the 24 h growth target was seen in 11/59 isolates. Conclusions With this diverse cache of viable isolates established in the COMBINE pneumonia model, future translational studies can be undertaken to set efficacy benchmarks among laboratories. [ABSTRACT FROM AUTHOR]

Background Lack of uniformity in infection models complicates preclinical development. The COMBINE protocol has standardized the murine neutropenic pneumonia model. Herein we provide benchmark efficacy data of humanized exposures of tigecycline and levofloxacin in plasma and epithelial lining fluid (ELF) against a collection of Klebsiella pneumoniae and Pseudomonas aeruginosa. Methods Following the COMBINE protocol, plasma and ELF human-simulated regimens (HSRs) of tigecycline 100 mg followed by 50 mg q12h and levofloxacin 750 mg once daily were developed and confirmed in the murine neutropenic pneumonia model. Tigecycline HSRs were tested against seven K. pneumoniae isolates. Levofloxacin HSRs were assessed against 10 K. pneumoniae and 9 P. aeruginosa. The change in cfu/lung over 24 h for each treatment was calculated. Each isolate was tested in duplicate against both the plasma and ELF HSRs on separate experiment days. Results Tigecycline 1.8 and 3 mg/kg q12h achieved humanized exposures of serum and ELF, respectively. Levofloxacin 120 and 90 mg/kg q8h led to f AUC exposures in plasma and ELF similar to in humans. Both tigecycline regimens were ineffective across the MIC range. Levofloxacin regimens achieved multilog kill against susceptible isolates, and no appreciable cfu/lung reductions in isolates with an MIC of ≥32 mg/L. Differences in cfu/lung were evident between the levofloxacin plasma and ELF HSRs against isolates with MICs of 4 and 8 mg/L. Conclusions Administering HSRs of tigecycline and levofloxacin based on both serum/plasma and ELF in the COMBINE pneumonia model resulted in cfu/lung values reasonably aligned with MIC. These data serve as translational benchmarks for future investigations with novel compounds. [ABSTRACT FROM AUTHOR]

The development of proficiency in the practices used by scientists and engineers is considered an important student outcome of laboratory instruction. We developed tasks to assess students' use and development of selected scientific and engineering practices in the general chemistry laboratory using an adapted evidence-centered design approach. In this paper, we provide a detailed description of the process of development and validation of these assessment tasks, using one of our tasks to illustrate the process. The tasks show strong evidence of validity and reliability for revealing students' understanding of scientific and engineering practices within the research context.

Inquiry-style laboratory courses, in which students engage in open-ended projects rather than a prescribed set of experimental steps ("cookbooks"), are becoming increasingly popular at the undergraduate level. Reformed curricula require reforms in training teachers; in the case of large universities, laboratory instructors are typically graduate teaching assistants (TAs). The General Chemistry Laboratory courses at a large, public, research-intensive university in the Midwestern region of the United States recently underwent a transformation from a "cookbook" to a project-based lab, and despite efforts to improve training, TAs continue to express difficulty teaching the course. To determine the source of these difficulties, we conducted multiple video observations and semi-structured interviews with seven TAs throughout one semester. We report TAs' beliefs about what is expected of them, their philosophical alignment to perceived expectations, and a comparison of the Lab Coordinator's expectations to TAs' actual teaching practices. We found that the TAs generally agreed with behaviors they were expected to perform, but responses to actions they were not supposed to do indicated that they were unsure of what the Lab Coordinator expected and personally believed that an ideal TA would perform those actions. This work highlights a need to clearly communicate the aims and expectations in a course and the rationale for those choices.

In recent years, much of the emphasis for transformation of introductory STEM courses has focused on "active learning", and while this approach has been shown to produce more equitable outcomes for students, the construct of "active learning" is somewhat ill-defined and is often used as a "catch-all" that can encompass a wide range of pedagogical techniques. Here we present an alternative approach for how to think about the transformation of STEM courses that focuses instead on what students should know and what they can do with that knowledge. This approach, known as three-dimensional learning (3DL), emerged from the National Academy's "A Framework for K-12 Science Education", which describes a vision for science education that centers the role of constructing productive causal accounts for phenomena. Over the past 10 years, we have collected data from introductory biology, chemistry, and physics courses to assess the impact of such a transformation on higher education courses. Here we report on an analysis of video data of class sessions that allows us to characterize these sessions as active, 3D, neither, or both 3D and active. We find that 3D classes are likely to also involve student engagement (i.e. be active), but the reverse is not necessarily true. That is, focusing on transformations involving 3DL also tends to increase student engagement, whereas focusing solely on student engagement might result in courses where students are engaged in activities that do not involve meaningful engagement with core ideas of the discipline. [ABSTRACT FROM AUTHOR]

Monte Carlo statistical mechanics simulations were conducted on the complexation of halide ions in chloroform by the bis(phenylurea) p-tert-butylcalix[4]arene. The findings indicate that the gas-phase optimized structures of the complexes are generally maintained in chloroform solution. Moreover, the results demonstrate that complexation of F- by two water molecules would be sufficient to overcome complexation by the bis-urea host.

Monte Carlo simulations with an all-atom force field analyze the structural and binding free energies related to complexes of pyrazine, quinoxaline and pyridine with Rebek's acridine diacid in chloroform. The study allows flexibility into the host and the resulting structures have two-point binding for the diazene guests. Quinoxalilne has greater binding affinity than pyridine and pyrazine.

Calculation of free energy profiles for the approach of area and guanidinium ion (Gdm+) to benzene and of urea to naphtalene in water, is used to explore the proabability of straightforward interactions between protein denaturants and aromatic hydrocarbons in water. The presence of straightforward chaotrope arene interactions is confirmed. These interactions are probably important to the process of protein denaturation enhanced by the chaotropes.

Gas-phase abinitio and solution-phase statistical mechanics studies probe into the effects of solvation on rotational freedom about the carbonyl C-N bond in N,N-dimethylacetamide. Calculated free energies of activation are found to correlate well with available experimental values. Monte Carlo simulations, using refined solute-solvent potential functions, reproduce observed changes inactivation energy in going from aqueous to aprotic solvents, but yield a very low rise in isomerization barrier in going from carbon tetrachloride to the gasphase. The discrepancy is attributed to amide aggregation and interphase parameter differences.

The infrared predissociation spectra of the mass-selected electrocatalytic water oxidation intermediate [Ru(tpy)(bpy)(OH)]2+(H2O)0-4 are reported. The [Ru(tpy)(bpy)(OH)]2+ species is generated by passing a solution of [Ru(tpy)(bpy)(H2O)](ClO4)2 through an electrochemical flow cell held at 1.2 V and is immediately introduced into the gas phase via electrospray ionization (ESI). The microsolvated clusters are formed by reconstructing the water network in a cryogenic ion trap. Details of the hydrogen bonding network in these clusters are revealed by the infrared predissociation spectra in the OH stretch region. This improved method for capturing microsolvated clusters yielded colder complexes with much better resolved IR features than previous studies. The analysis of these spectra, supported by electronic structure calculations and compared to previous results on [Ru(tpy)(bpy)(H2O)]2+(H2O)0-4 clusters, reveals the nature of the Ru-OH bond and the effect of hydrogen bonding on facilitating the subsequent oxidation to [Ru(tpy)(bpy)(O)]2+ in the proposed catalytic cycle. Particularly, the hydrogen bonding interaction in [Ru(tpy)(bpy)(OH)]2+(H2O)1 is much weaker than that in the corresponding [Ru(tpy)(bpy)(H2O)]2+(H2O)1 and thus is less effective at activating the hydroxyl ligand for further oxidation via proton coupled electron transfer (PCET). Furthermore, the results here reveal that the Ru-OH bond, though formally described as an Ru3+/OH- interaction, has more covalent bond character than ionic bond character. [ABSTRACT FROM AUTHOR]

Mass spectrometry coupled with an in-line electrochemical electrospray ionization source is used to capture some of the reaction intermediates formed in the [Ru(bpy)(tpy)(H2O)]2+ (bpy=2,2'-bipyridine, tpy=2,2':6',2"-terpyridine) catalyzed water oxidation reaction. By controlling the applied electrochemical potential, we identified the parent complex, as well as the first two oxidation complexes, identified as [Ru(bpy)-(tpy)(OH)]2+ and [Ru(bpy)(tpy)(O)]2+. The structures of the parent and first oxidation complexes are probed directly in the mass spectrometer by using infrared predissociation spectroscopy of D2-tagged ions. Comparisons between experimental vibrational spectra and density functional theory calculations confirmed the identity and structure of these two complexes. Moreover, the frequency of the O-H stretching mode in [Ru(bpy)(tpy)(OH)]2+ shows that this complex features a Ru-OH interaction that is more covalent than ionic. [ABSTRACT FROM AUTHOR]

The infrared spectraof gas-phase mass-selected [Ru(bpy)(tpy)(H2O)]2+·(H2O)0–4clusters (bpy = 2,2′-bipyridine;tpy = 2,2′:6,2″-terpyridine)in the OH stretching region are reported. These species are formedby bringing the homogeneous water oxidation catalyst [Ru(bpy)(tpy)(H2O]2+from solution into the gas phase via electrosprayionization (ESI) and reconstructing the water network at the activesite by condensing additional water onto the complex in a cryogenicion trap. Infrared predissociation spectroscopy is used to probe thestructure of these clusters via their distinctive OH stretch frequencies,which are sensitive to the shape and strength of the local hydrogen-bondingnetwork. The analysis of the spectra, aided by electronic structurecalculations, highlights the formation of strong hydrogen bonds betweenthe aqua ligand and the solvating water molecules in the first solvationshell. These interactions are found to propagate through the subsequentsolvation shells and lead to the stabilization of asymmetric solvationmotifs. Electronic structure calculations show that these strong hydrogenbonds are promoted by charge transfer from the H atom of the aqualigand to the Ru–OH2bond. [ABSTRACT FROM AUTHOR]

Issues concerning the examination of the properties of over two hundred organic solutes in aqueous solution using Monte Carlo (MC) statistical mechanics simulations are discussed. Comparisons are made between the results of these studies and gas to liquid free solvation energies in hexadecane, octanol and water showing the greater hydrogen-bond-donating ability of water.