Facet-specific adsorption of tripeptides at aqueous au interfaces: open questions in reconciling experiment and simulation

YesThe adsorption of three homo-tripeptides, HHH, YYY, and SSS, at the aqueous Au interface is investigated, using molecular dynamics simulations. We find that consideration of surface facet effects, relevant to experimental conditions, opens up new questions regarding interpretations of current experimental findings. Our well-tempered metadynamics simulations predict the rank ordering of the tripeptide binding affinities at aqueous Au(111) to be YYY > HHH > SSS. This ranking differs with that obtained from existing experimental data which used surface-immobilized Au nanoparticles as the target substrate. The influence of Au facet on these experimental findings is then considered, via our binding strength predictions of the relevant amino acids at aqueous Au(111) and Au(100)(1 × 1). The Au(111) interface supports an amino acid ranking of Tyr > HisA ≃ HisH > Ser, matching that of the tripeptides on Au(111), while the ranking on Au(100) is HisA > Ser ≃ Tyr ≃ HisH, with only HisA showing non-negligible binding. The substantial reduction in Tyr amino acid affinity for Au(100) vs Au(111) offers one possible explanation for the experimentally observed weaker adsorption of YYY on the nanoparticle-immobilized substrate compared with HHH. In a separate set of simulations, we predict the structures of the adsorbed tripeptides at the two aqueous Au facets, revealing facet-dependent differences in the adsorbed conformations. Our findings suggest that Au facet effects, where relevant, may influence the adsorption structures and energetics of biomolecules, highlighting the possible influence of the structural model used to interpret experimental binding data.Air Office of Scientific Research, Grant No. FA9550-12-1-022

INSTRUCTIONAL VIDEOS, CONCEPTUAL UNDERSTANDING AND SELF-EFFICACY IN THE TIME OF COVID-19

Advances in technology offer new opportunities for teaching. Many students engage with online videos that enable them to watch, and re-watch these support materials flexibly and at their own pace. In our large-enrolment introductory first-year physics unit, many students find the content very challenging. To support their learning, we have developed short videos of 4-7 minutes explaining concepts and providing demonstrations of the problem-solving process. Our study was originally designed to evaluate and compare the effect on conceptual understanding and self-efficacy of students engaging with two different types of videos: screencasts (e.g. Khan Academy style) and lightboard videos, where the teacher presents direct to the camera on a writable transparent board (the image is then inverted to be the right way round). Then COVID struck, and all our learning was moved online. Thus, in the second semester of the study, we only used screencasts, and focused our research on exploring the relationship between online engagement, self-efficacy and conceptual understanding of students. We found that students preferred lightboards, and that both semesters’ average survey scores on self-efficacy and conceptual understanding were generally stable or increased only slightly. This is at odds with other studies of similar cohorts. However, the small number of paired responses in our study meant that a self-selection bias may have skewed results. Scores on the conceptual understanding were weakly correlated with assessment performance, suggesting the presence of other contributing variables. Initial self-efficacy scores did not predict subsequent engagement. Instead, missing multiple early assessments was identified as a stronger predictor of failing to pass the subject