Explanatory Modeling in Science Through Text-Based Investigation: Testing the Efficacy of the Project READI Intervention Approach

This article reports the results of a randomized control trial of a semester-long intervention designed to promote ninth-grade science students’ use of text-based investigation to create explanatory models of biological phenomena. The main research question was whether the student participants in the intervention outperformed the students in the control classes, as assessed by several measures of comprehension and application of information to modeling biological phenomena not covered in the instruction. A second research question examined the impact on the instructional practices of the teachers who implemented the intervention. Multilevel modeling of outcome measures, controlling for preexisting differences at individual and school levels, indicated significant effects on the intervention students and teachers relative to the controls. Implications for classroom instruction and teacher professional development are discussed

Synthesis and structure of mono-, bi- and trimetallic amine-bis(phenolate) cobalt(II) complexes

A series of cobalt(II) amine-bis(phenolate) complexes has been prepared and characterized. The protonated tripodal tetradentate ligand precursors; dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methylphenol), H2[O2NN¢]BuMeNMe2, dimethylaminoethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol), H2[O2NN¢]BuBuNMe2, diethylaminoethylamino-N,N-bis(2-methylene-4,6-di-tert-amylphenol), H2[O2NN¢]AmAmNEt2 and 2-pyridylamino-N,N-bis(2-methylene-4,6-di-tert-amylphenol), H2[O2NN¢]AmAmPy; were reacted with cobaltous acetate tetrahydrate under varying conditions to afford a range of monometallic, bimetallic and trimetallic species. An unusual four coordinate complex Co[O2NN¢]AmAmNEt2 containing CoII in a trigonal monopyramidal environment was structurally characterized, whereas using a less sterically demanding ligand a series of five coordinate complexes Co[O2NN¢]BuBuNMe2(L) (L = H2O, CH3OH, (CH3)2C=O, propylene oxide) containing CoII in a trigonal bipyramidal environment was prepared. A new angular structural parameter related to t is defined, where t¢ may be used to compare complexes with trigonal monopyramidal structures. In contrast, ligands containing a pendant pyridyl donor afford dimeric species including {Co(m-CH3OH)[O2NN¢]AmAmPy}2. In the absence of base and in the presence of excess cobaltous acetate, trimetallic complexes were isolated containing a central CoII in an octahedral environment coordinated to four CH3OH and two bridging acetate ligands between two Co[O2NN¢] fragments with CoII in a trigonal bipyramidal setting. The paramagnetic CoII complexes reported were also characterized by UV-vis spectroscopy, mass spectrometry, cyclic voltammetry and magnetic measurements

Reproducibility of fluorescent expression from engineered biological constructs in E. coli

We present results of the first large-scale interlaboratory study carried out in synthetic biology, as part of the 2014 and 2015 International Genetically Engineered Machine (iGEM) competitions. Participants at 88 institutions around the world measured fluorescence from three engineered constitutive constructs in E. coli. Few participants were able to measure absolute fluorescence, so data was analyzed in terms of ratios. Precision was strongly related to fluorescent strength, ranging from 1.54-fold standard deviation for the ratio between strong promoters to 5.75-fold for the ratio between the strongest and weakest promoter, and while host strain did not affect expression ratios, choice of instrument did. This result shows that high quantitative precision and reproducibility of results is possible, while at the same time indicating areas needing improved laboratory practices.Peer reviewe