Tackling Teaching: Understanding Commonalities among Chemistry, Mathematics, and Physics Classroom Practices.

Abstract: Education research in chemistry, mathematics, and physics tends to focus on issues inherent to the discipline, most notably content. At this time, little literature evidence exists that documents fruitful collaborations between education specialists across the STEM disciplines. This work seeks to unite the disciplines by investigating a common task: teaching. This study explores how discipline-specific practices influence the common act of reformed teaching pedagogy with a focus on the use of inquiry. We seek to identify commonalities among classroom teaching practices in these disciplines and contribute to the development of analytical tools to study STEM teaching

Characterizing illusions of competence in introductory chemistry students

The Dunning–Kruger effect is a cognitive bias that plagues a particular population of students – the unskilled. This population suffers from illusory competence, as determined by inaccurate ratings of their own ability/performance. These mistakenly high self-ratings (i.e. “illusions of competence”) are typically explained by a metacognitive deficiency of the unskilled – they simply can\u27t recognize their own mistakes. This work, involving more than a thousand students, nine course sections, and sampling multiple time points over a semester, established the Dunning–Kruger effect as a robust phenomenon in university-level introductory chemistry. Using a combination of graphical analyses and hierarchical linear modeling, we confirmed that low-performing students tend to overestimate their own performance while high-performing students tend to underestimate their performance. We also observed a clear difference between female and male students with regard to these miscalibrations. Lastly, we demonstrated that student miscalibrations are invariant over time, a result that has profound implications for the types of instructor feedback conventionally provided in introductory chemistry courses

Assessing the relation between language comprehension and performance in general chemistry

Few studies have focused specifically on the role that language plays in learning chemistry. We report here an investigation into the ability of language comprehension measures to predict performance in university introductory chemistry courses. This work is informed by theories of language comprehension, which posit that high-skilled comprehenders hold a cognitive advantage over the low-skilled because of a heightened ability to inhibit contextually irrelevant details and utilize prior knowledge to effectively bridge conceptual gaps when comprehending new information. Over a two-year period, data on comprehension ability, math ability, prior chemistry knowledge, and course performance were obtained in multiple general chemistry courses. Regression analyses and hierarchical linear models (HLMs) were utilized to establish relationships between predictor variables and course performance and to determine if comprehension ability could potentially compensate for low prior knowledge, a phenomenon predicted by theories of comprehension ability. Results indicate that comprehension ability correlates with general chemistry performance; it also contributes comparable information about course performance when compared to math ability and prior knowledge. In addition, we found that comprehension skill partially compensates for deficits in prior knowledge. Therefore, efforts to prepare students for success in general chemistry should include both content and the development of language comprehension skill

The Testing Effect: An Intervention on Behalf of Low-Skilled Comprehenders in General Chemistry

Past work has demonstrated that language comprehension ability correlates with general chemistry course performance with medium effect sizes. We demonstrate here that language comprehension’s strong cognitive grounding can be used to inform effective and equitable pedagogies, namely, instructional interventions that differentially aid low-skilled language comprehenders. We report the design, implementation, and assessment of such an intervention strategy. Guided by two models of comprehension, we predicted that a multiple pre-testing strategy would differentially aid low-skilled comprehenders in a general chemistry class. We also explored the effect of two question types (multiple choice and elaborative interrogation) on this intervention strategy. A within-subjects, learning-goals driven design was used to build the intervention into two semesters of the course; data generated by this approach were analyzed with hierarchical linear models. We found that the achievement gap between low- and high-skilled comprehenders was partially abated by repeated testing prior to course examinations. We also found that the differential benefits of repeated testing could be accounted for entirely by multiple-choice questions, while elaborative interrogation questions had a statistically significant, but negative, impact. The implication of this work for all levels of chemistry teaching is clear: testing can be used to enhance (not just to assess) student learning, and this act affects different groups of students in different ways

The interaction of mitochondrial iron with superoxide dismutase

Superoxide dismutase 2 (SOD2) is one of the rare mitochondrial enzymes evolved to use manganese as a cofactor over the more abundant element iron. Although mitochondrial iron does not normally bind SOD2, iron will misincorporate into Saccharomyces cerevisiae Sod2p when cells are starved for manganese or when mitochondrial iron homeostasis is disrupted by mutations in yeast grx5, ssq1, and mtm1. We report here that such changes in mitochondrial manganese and iron similarly affect cofactor selection in a heterologously expressed Escherichia coli Mn-SOD, but not a highly homologous Fe-SOD. By x-ray absorption near edge structure and extended x-ray absorption fine structure analyses of isolated mitochondria, we find that misincorporation of iron into yeast Sod2p does not correlate with significant changes in the average oxidation state or coordination chemistry of bulk mitochondrial iron. Instead, small changes in mitochondrial iron are likely to promote iron-SOD2 interactions. Iron binds Sod2p in yeast mutants blocking late stages of iron-sulfur cluster biogenesis (grx5, ssq1, and atm1), but not in mutants defective in the upstream Isu proteins that serve as scaffolds for iron-sulfur biosynthesis. In fact, we observed a requirement for the Isu proteins in iron inactivation of yeast Sod2p. Sod2p activity was restored in mtm1 and grx5 mutants by depleting cells of Isu proteins or using a dominant negative Isu1p predicted to stabilize iron binding to Isu1p. In all cases where disruptions in iron homeostasis inactivated Sod2p, we observed an increase in mitochondrial Isu proteins. These studies indicate that the Isu proteins and the iron-sulfur pathway can donate iron to Sod2p

The Interaction of Mitochondrial Iron with Manganese Superoxide Dismutase*

Superoxide dismutase 2 (SOD2) is one of the rare mitochondrial enzymes evolved to use manganese as a cofactor over the more abundant element iron. Although mitochondrial iron does not normally bind SOD2, iron will misincorporate into Saccharomyces cerevisiae Sod2p when cells are starved for manganese or when mitochondrial iron homeostasis is disrupted by mutations in yeast grx5, ssq1, and mtm1. We report here that such changes in mitochondrial manganese and iron similarly affect cofactor selection in a heterologously expressed Escherichia coli Mn-SOD, but not a highly homologous Fe-SOD. By x-ray absorption near edge structure and extended x-ray absorption fine structure analyses of isolated mitochondria, we find that misincorporation of iron into yeast Sod2p does not correlate with significant changes in the average oxidation state or coordination chemistry of bulk mitochondrial iron. Instead, small changes in mitochondrial iron are likely to promote iron-SOD2 interactions. Iron binds Sod2p in yeast mutants blocking late stages of iron-sulfur cluster biogenesis (grx5, ssq1, and atm1), but not in mutants defective in the upstream Isu proteins that serve as scaffolds for iron-sulfur biosynthesis. In fact, we observed a requirement for the Isu proteins in iron inactivation of yeast Sod2p. Sod2p activity was restored in mtm1 and grx5 mutants by depleting cells of Isu proteins or using a dominant negative Isu1p predicted to stabilize iron binding to Isu1p. In all cases where disruptions in iron homeostasis inactivated Sod2p, we observed an increase in mitochondrial Isu proteins. These studies indicate that the Isu proteins and the iron-sulfur pathway can donate iron to Sod2p

Ferrous human cystathionine b-synthase loses activity during enzyme assay due to a ligand switch process

Cystathionine β-synthase (CBS) is a pyridoxal-5‘-phosphate-dependent enzyme that catalyzes the condensation of serine and homocysteine to form cystathionine. Mammalian CBS also contains a heme cofactor that has been proposed to allosterically regulate enzyme activity via the heme redox state, with FeII CBS displaying approximately half the activity of FeIII CBS in vitro. The results of this study show that human FeII CBS spontaneously loses enzyme activity over the course of a 20 min enzyme assay. Both the full-length 63-kDa and truncated 45-kDa form of CBS slowly and irreversibly lose activity upon reduction to the FeII form. Additionally, electronic absorption spectroscopy reveals that FeII CBS undergoes a heme ligand exchange to FeII CBS424 when the enzyme is incubated at 37 °C and pH 8.6. The addition of enzyme substrates or imidazole has a moderate effect on the rate of the ligand switch, but does not prevent conversion to the inactive species. Time-dependent spectroscopic data describing the conversion of FeII CBS to FeII CBS424 were fitted to a three-state kinetic model. The resultant rate constants were used to fit assay data and to estimate the activity of FeII CBS prior to the ligand switch. Based on this fit it appears that FeII CBS initially has the same enzyme activity as FeIII CBS, but FeII CBS loses activity as the ligand switch proceeds. The slow and irreversible loss of FeII CBS enzyme activity in vitro resembles protein denaturation, and suggests that a simple regulatory mechanism based on the heme redox state is unlikely

Writing-to-teach: A new pedagogical approach to elicit explanative writing in undergraduate chemistry students

Contemporary strategies in STEM education focus on developing pedagogies that more actively engage students in their own learning. A method that has proven effective to this end has been peer instruction and discussion, particularly those in which participating students must organize information in such a way as to be able to verbally articulate it to others. The success of peer learning raises the question of what other communicative activities could lead to similar learning gains. Writing is a reasonable choice for such an activity, as there is strong historical evidence of the value of writing in facilitating student learning. Presented here is “writing-to-teach”; a fusion of writing and peer instruction that is rooted in the theories of meaningful learning and situated cognition as well as research on student-generated explanatory knowledge. Writing-to-teach activities were designed and implemented in an introductory physical chemistry course and evaluated using student surveys. In addition, a novel expert-ranking methodology was employed to evaluate the quality of explanatory writing produced by students engaging in writing-to-teach activities. Lastly, suggestions are given on how writing-to-teach can be implemented more broadly in other STEM classrooms

Porphyrin-cored polymer nanoparticles: Macromolecular models for heme iron coordination

Porphyrin-cored polymer nanoparticles (PCPNs) were synthesized and characterized to investigate their utility as heme protein models. Created using collapsible heme-centered star polymers containing photodimerizable anthracene units, these systems afford model heme cofactors buried within hydrophobic, macromolecular environments. Spectroscopic interrogations demonstrate that PCPNs display redox and ligand-binding reactivity similar to that of native systems and thus are potential candidates for modeling biological heme iron coordination. © 2016 American Chemical Society