Conformational Dynamics of metallo-β-lactamase CcrA during Catalysis Investigated by Using DEER Spectroscopy

Previous crystallographic and mutagenesis studies have implicated the role of a position-conserved hairpin loop in the metallo-β-lactamases in substrate binding and catalysis. In an effort to probe the motion of that loop during catalysis, rapid-freeze-quench double electron–electron resonance (RFQ-DEER) spectroscopy was used to interrogate metallo-β-lactamase CcrA, which had a spin label at position 49 on the loop and spin labels (at positions 82, 126, or 233) 20–35 Å away from residue 49, during catalysis. At 10 ms after mixing, the DEER spectra show distance increases of 7, 10, and 13 Å between the spin label at position 49 and the spin labels at positions 82, 126, and 233, respectively. In contrast to previous hypotheses, these data suggest that the loop moves nearly 10 Å away from the metal center during catalysis and that the loop does not clamp down on the substrate during catalysis. This study demonstrates that loop motion during catalysis can be interrogated on the millisecond time scale

University Chemistry Students’ Interpretations of Multiple Representations of the Helium Atom

Multiple chemistry education research studies at the secondary level have characterized students’ difficulties regarding a conceptual understanding of the quantum model of the atom. This research explores undergraduate students’ interpretations of multiple representations of the atom. Semi-structured interviews were conducted with first-year university chemistry students (n = 26) and second-semester physical chemistry students (n = 8) after they were taught and tested on the quantum model of the atom in their respective courses. During the interview, students were asked to interpret four representations of the atom (an electron cloud model, a probability representation, a boundary surface representation, and the Bohr model) and to rank each of the representations from most preferred to the least preferred. Nearly two-thirds of the students ranked the electron cloud and Bohr-model as their two most preferred representations. Students invoked ideas from classical mechanics to interpret the electron cloud model and used probabilistic language to describe the Bohr model of the atom

Students\u27 use of chemistry core ideas to explain the structure and stability of DNA

Students tend to think of their science courses as isolated and unrelated to each other, making it difficult for them to see connections across disciplines. In addition, many existing science assessments target rote memorization and algorithmic problem-solving skills. Here, we describe the development, implementation, and evaluation of an activity aimed to help students integrate knowledge across introductory chemistry and biology courses. The activity design and evaluation of students\u27 responses were guided by the Framework for K-12 Science Education as the understanding of core ideas and crosscutting concepts and the development of scientific practices are essential for students at all levels. In this activity, students are asked to use their understanding of noncovalent interactions to explain (a) why the boiling point differs for two pure substances (chemistry phenomenon) and (b) why temperature and base pair composition affects the stability of DNA (biological phenomenon). The activity was implemented at two different institutions (N = 441) in both introductory chemistry and biology courses. Students\u27 overall performance suggests that they can provide sophisticated responses that incorporate their understanding of noncovalent interactions and energy to explain the chemistry phenomenon, but have difficulties integrating the same knowledge to explain the biological phenomenon. Our findings reinforce the notion that students should be provided with opportunities in the classroom to purposefully practice and support the use and integration of knowledge from multiple disciplines. Students\u27 evaluations of the activity indicated that they found it to be interesting and helpful for making connections across disciplines

Impact of Ocean Acidification on Shelled Organisms: Supporting Integration of Chemistry and Biology Knowledge through Multidisciplinary Activities

Students often experience difficulty in connecting knowledge from different college courses to solve complex problems such as ocean acidification, a pressing concern within the ongoing climate crisis. Here, we introduce a multidisciplinary activity in which students use their chemistry knowledge of change and stability in chemical systems through Le Chatelier’s principle and equilibrium of coupled reactions to explain the biological phenomenon of how changes in CO2 concentrations can impact shelled organisms and ecosystems more broadly in the ocean. In this activity, we build on prior literature and emphasize Three-Dimensional Learning (3DL) to support students in developing a deeper understanding of this complex problem. This Ocean Acidification activity asks students to explain (1) the relationship between CO2 concentration and ocean pH and (2) how and why changes in ocean pH could weaken shelled organisms. Among 136 students in a second-semester general chemistry course at a large institution, 93% were able to correctly predict the relationship between CO2 and pH (chemistry-biology connection). Additionally, 43% of the students were able to then further apply this knowledge correctly to explain an unfamiliar situation in which the decreased pH could lead to less available carbonate ion for the shells (biological phenomenon). This result highlights that while some students were able to correctly explain the biological phenomenon and make meaningful connections, others would require additional in-class scaffolding and student-instructor interaction to be able to integrate their knowledge to explain this unfamiliar complex biological phenomenon. Implications for teaching and future implementations are also discussed

“Big Ideas” of Introductory Chemistry and Biology Courses and the Connections between Them

Introductory courses are often designed to cover a range of topics with the intent to offer students exposure to the given discipline as preparation to further their study in the same or related disciplines. Unfortunately, students in these courses are often presented with an overwhelming amount of information that may not support their formation of a usable coherent network of knowledge. In this study we conducted a mixed-method sequential exploratory study with students co-enrolled in General Chemistry II and Introductory Biology I to better understand what students perceived to be the “take-home” messages of these courses (i.e., core ideas) and the connections between these courses. We found that students identified a range of ideas from both courses; further analysis of students’ explanations and reasoning revealed that, when students talked about their chemistry ideas, they were more likely to talk about them as having predictive and explanatory power in comparison with reasons provided for their biology big ideas. Furthermore, students identified a number of overlapping ideas between their chemistry and biology courses, such as interactions, reactions, and structures, which have the potential to be used as a starting place to support students building a more coherent network of knowledge

Fabrication of Core–Shell Nanoparticles via Controlled Aggregation of Semiflexible Conjugated Polymer and Hyaluronic Acid

Fabrication of Core–Shell Nanoparticles via Controlled Aggregation of Semiflexible Conjugated Polymer and Hyaluronic Aci