This study shows that participation in course-based undergraduate research experiences (CUREs) improves students’ likelihood of graduating with a STEM degree and graduating within 6 years. These results support offering CUREs in place of standard lab courses as an effective strategy for producing additional college graduates with STEM degrees.

We demonstrate that the reduction of p-nitrophenol to p-aminophenol by NaBH4 is catalyzed by both monometallic and bimetallic nanoparticles (NPs). We also demonstrate a straightforward and precise method for the synthesis of bimetallic nanoparticles using poly(amido)amine dendrimers. The resulting dendrimer encapsulated nanoparticles (DENs) are monodisperse, and the size distribution does not vary with different elemental combinations. Random alloys of Pt/Cu, Pd/Cu, Pd/Au, Pt/Au, and Au/Cu DENs were synthesized and evaluated as catalysts for p-nitrophenol reduction. These combinations are chosen in order to selectively tune the binding energy of the p-nitrophenol adsorbate to the nanoparticle surface. Following the Brønsted–Evans–Polanyi (BEP) relation, we show that the binding energy can reasonably predict the reaction rates of p-nitrophenol reduction. We demonstrate that the measured reaction rate constants of the bimetallic DENs is not always a simple average of the properties of the constituent metals. In particular, DENs containing metals with similar lattice constants produce a binding energy close to the average of the two constituents, whereas DENs containing metals with a lattice mismatch show a bimodal distribution of binding energies. Overall, in this work we present a uniform method for synthesizing pure and bimetallic DENs and demonstrate that their catalytic properties are dependent on the adsorbate’s binding energy.

Meiotic recombination, an essential aspect of sexual reproduction, is initiated by programmed DNA double-strand breaks (DSBs). DSBs are catalyzed by the widely-conserved Spo11 enzyme; however, the activity of Spo11 is regulated by additional factors that are poorly conserved through evolution. To expand our understanding of meiotic regulation, we have characterized a novel gene, dsb-1, that is specifically required for meiotic DSB formation in the nematode Caenorhabditis elegans. DSB-1 localizes to chromosomes during early meiotic prophase, coincident with the timing of DSB formation. DSB-1 also promotes normal protein levels and chromosome localization of DSB-2, a paralogous protein that plays a related role in initiating recombination. Mutations that disrupt crossover formation result in prolonged DSB-1 association with chromosomes, suggesting that nuclei may remain in a DSB-permissive state. Extended DSB-1 localization is seen even in mutants with defects in early recombination steps, including spo-11, suggesting that the absence of crossover precursors triggers the extension. Strikingly, failure to form a crossover precursor on a single chromosome pair is sufficient to extend the localization of DSB-1 on all chromosomes in the same nucleus. Based on these observations we propose a model for crossover assurance that acts through DSB-1 to maintain a DSB-permissive state until all chromosome pairs acquire crossover precursors. This work identifies a novel component of the DSB machinery in C. elegans, and sheds light on an important pathway that regulates DSB formation for crossover assurance.

Course-based undergraduate research experiences (CUREs) provide a promising avenue to attract a larger and more diverse group of students into research careers. CUREs are thought to be distinctive in offering students opportunities to make discoveries, collaborate, engage in iterative work, and develop a sense of ownership of their lab course work. Yet how these elements affect students’ intentions to pursue research-related careers remain unexplored. To address this knowledge gap, we collected data on three design features thought to be distinctive of CUREs (discovery, iteration, collaboration) and on students’ levels of ownership and career intentions from ∼800 undergraduates who had completed CURE or inquiry courses, including courses from the Freshman Research Initiative (FRI), which has a demonstrated positive effect on student retention in college and in science, technology, engineering, and mathematics. We used structural equation modeling to test relationships among the design features and student ownership and career intentions. We found that discovery, iteration, and collaboration had small but significant effects on students’ intentions; these effects were fully mediated by student ownership. Students in FRI courses reported significantly higher levels of discovery, iteration, and ownership than students in other CUREs. FRI research courses alone had a significant effect on students’ career intentions.

Actin nucleation and branching by the Arp2/3 complex is tightly regulated by activating factors. However, the mechanism of Arp2/3 complex activation remains unclear. We used fluorescence resonance energy transfer (FRET) to probe the conformational dynamics of the Arp2/3 complex accompanying its activation. We demonstrate that nucleotide binding promotes a substantial conformational change in the complex, with distinct conformations depending on the bound nucleotide. Nucleotide binding to each Arp is critical for activity and is coupled to nucleation promoting factor (NPF) binding. The binding of Wiskott-Aldrich syndrome protein (WASP) family NPFs induces further conformational reorganization of the Arp2/3 complex, and the ability to promote this conformational reorganization correlates with activation efficiency. Using an Arp2/3 complex that is fused to the actin binding domain of WASP, we confirm that the NPF-induced conformational change is critical for activation, and that the actin and Arp2/3 binding activities of WASP are separable, but are independently essential for activity.

Monodisperse palladium nanoparticles consisting of 10−200 atoms were prepared using poly(amido)amine (PAMAM) dendrimer templates and were evaluated as catalysts using the model reduction of para-nitrophenol. The use of dendrimer templates allows for fine control of the average number of atoms per nanoparticle and systematic investigation of the effect of size on the catalytic activity of nanoparticles less than 2 nm in diameter. The palladium dendrimer-encapsulated nanoparticles (DENs) were found to be highly active for the hydrogenation of para-nitrophenol to para-aminophenol, with surface area-normalized rate constants ranging from 0.87 to 1.65 L s −1 m −2 (which is greater than any previously reported system). A near linear dependence of the observed rate constant on the synthetic Pd 2+ :dendrimer ratio was observed, suggesting that, within the size regime studied, most of the atoms lie on the surface of the nanoparticle and contribute to the catalytic activity. Interestingly, for Pd clusters containing between 10 and 50 atoms, the rate constant normalized on a per atom basis shows little variability, supporting the idea that all atoms lie on the surface of these clusters. However, for particles containing between 50 and 200 atoms, a decrease in per-atom activity is observed with increasing particle size, suggesting that in this size regime some atoms are located in the catalytically inactive core. Additionally, the generation of the PAMAM dendrimer template was found to have a significant effect on the observed rate constant due to steric crowding at the periphery (whereas the choice of an amine-or hydroxyl-termination on the dendrimer periphery did not).

Both scientists and the public would benefit from improved communication of basic scientific research and from integrating scientists into education outreach, but opportunities to support these efforts are limited. We have developed two low-cost programs—"Present Your PhD Thesis to a 12-Year-Old" and "Shadow a Scientist”—that combine training in science communication with outreach to area middle schools. We assessed the outcomes of these programs and found a 2-fold benefit: scientists improve their communication skills by explaining basic science research to a general audience, and students' enthusiasm for science and their scientific knowledge are increased. Here we present details about both programs, along with our assessment of them, and discuss the feasibility of exporting these programs to other universities.

Innovative models of teaching through research have broken the long-held paradigm that core chemistry competencies must be taught with predictable, scripted experiments. We describe here five fundamentally different, course-based undergraduate research experiences that integrate faculty research projects, accomplish ACS accreditation objectives, provide the benefits of an early research experience to students, and have resulted in publishable findings. The model detailed is the Freshman Research Initiative (FRI) at The University of Texas at Austin. While there are currently 30+ active FRI research groups, or “streams”, we focus this report on five different chemistry streams in these four areas (organic, inorganic, analytical, and biochemistry) to demonstrate how general chemistry laboratory skills are taught in the context of these varied research disciplines. To illustrate the flexibility of the FRI model for teaching first-year chemistry, we show how each stream teaches students three different skills within the context of their research: making (synthesis), measuring (UV-vis spectroscopy), and characterization. As a unifying example, all five chemistry streams describe using UV–vis spectroscopy to characterize new synthetic molecules, complexes, and compounds, followed by extensive quantitative collection, processing, and analysis of experimental data sets. The FRI model allows full integration of training in mandatory and accredited general chemistry skill sets with open-ended research experiences with unexpected outcomes in undergraduate science curricula. In turn, this model enables undergraduates to be productive contributors to new knowledge and scientific discovery at the earliest levels of the undergraduate experience.