Search for: All records

Abstract Integral and interacting membrane proteins (IIMPs) constitute a vast family of biomolecules that perform essential functions in all forms of life. However, characterizing their interactions with lipid bilayers remains limited due to challenges in purifying and reconstituting IIMPs in vitro or labeling IIMPs without disrupting their function in vivo. Here, we report cell-free transcription-translation in a quartz crystal microbalance with dissipation (TXTL-QCMD) to dynamically characterize interactions between diverse IIMPs and membranes without protein purification or labeling. As part of TXTL-QCMD, IIMPs are synthesized using cell-free transcription-translation (TXTL), and their interactions with supported lipid bilayers are measured using a quartz crystal microbalance with dissipation (QCMD). TXTL-QCMD reconstitutes known IIMP-membrane dependencies, including specific association with prokaryotic or eukaryotic membranes, and the multiple-IIMP dynamical pattern-forming association of theE. colidivision-coordinating proteins MinCDE. Applying TXTL-QCMD to the recently discovered Zorya anti-phage system that is unamenable to labeling, we discovered that ZorA and ZorB integrate within the lipids found at the poles of bacteria while ZorE diffuses freely on the non-pole membrane. These efforts establish the potential of TXTL-QCMD to broadly characterize the large diversity of IIMPs. 

Abstract A key issue in the development of theory and models for plasma propulsion devices is to describe the instabilities and fluctuations of the devices. It has been widely recognized that many Hall effect thrusters (HETs) exhibit oscillations at frequencies in the range of ∼ 20 kHz. These ionization-related oscillations are generally referred to as Breathing Mode oscillations and have been the subject of considerable research. Here, for the first time, we report direct temporally resolved measurements of the ground state neutral density variation during the period of the oscillation. We used the laser-based Two-Photon Absorption Laser Induced Fluorescence (TALIF) technique to measure neutrals within the plume of a 1.5 kW HET operating on krypton (Kr). Our TALIF scheme employs a frequency-doubled, pulsed dye laser operating at ∼ 212 nm to probe ground state Kr atoms. A novel phase-binning approach is used to recover the time-dependent signal by assigning the timing of each collected TALIF signal (laser shot) relative to the phase of the discharge current. We find that the neutral density fluctuates quite strongly over the period of the oscillation, and that this fluctuation leads the current fluctuation as expected. 

Abstract Efforts to discourage academic misconduct in online learning environments frequently include the use of remote proctoring services. While these services are relatively commonplace in undergraduate science courses, there are open questions about students’ remote assessment environments and their concerns related to remote proctoring services. Using a survey distributed to 11 undergraduate science courses engaging in remote instruction at three American, public, research-focused institutions during the spring of 2021, we found that the majority of undergraduate students reported testing in suboptimal environments. Students’ concerns about remote proctoring services were closely tied to technological difficulties, fear of being wrongfully accused of cheating, and negative impacts on mental health. Our results suggest that remote proctoring services can create and perpetuate inequitable assessment environments for students, and additional research is required to understand the efficacy of their intended purpose to prevent cheating. We also advocate for continued conversations about the broader social and institutional conditions that can pressure students into cheating. While changes to academic culture are difficult, these conversations are necessary for higher education to remain relevant in an increasingly technological world. 

Abstract The new generation of cell-free gene expression systems enables the prototyping and engineering of biological systems in vitro over a remarkable scope of applications and physical scales. As the utilization of DNA-directed in vitro protein synthesis expands in scope, developing more powerful cell-free transcription–translation (TXTL) platforms remains a major goal to either execute larger DNA programs or improve cell-free biomanufacturing capabilities. In this work, we report the capabilities of the all-E. coli TXTL toolbox 3.0, a multipurpose cell-free expression system specifically developed for synthetic biology. In non-fed batch-mode reactions, the synthesis of the fluorescent reporter protein eGFP (enhanced green fluorescent protein) reaches 4 mg/ml. In synthetic cells, consisting of liposomes loaded with a TXTL reaction, eGFP is produced at concentrations of >8 mg/ml when the chemical building blocks feeding the reaction diffuse through membrane channels to facilitate exchanges with the outer solution. The bacteriophage T7, encoded by a genome of 40 kb and ∼60 genes, is produced at a concentration of 1013 PFU/ml (plaque forming unit/ml). This TXTL system extends the current cell-free expression capabilities by offering unique strength and properties, for testing regulatory elements and circuits, biomanufacturing biologics or building synthetic cells. 

To investigate patterns of gender-based performance gaps, we conducted a meta-analysis of published studies and unpublished data collected across 169 undergraduate biology and chemistry courses. While we did not detect an overall gender gap in performance, heterogeneity analyses suggested further analysis was warranted, so we investigated whether attributes of the learning environment impacted performance disparities on the basis of gender. Several factors moderated performance differences, including class size, assessment type, and pedagogy. Specifically, we found evidence that larger classes, reliance on exams, and undisrupted, traditional lecture were associated with lower grades for women. We discuss our results in the context of natural science courses and conclude by making recommendations for instructional practices and future research to promote gender equity. 

National efforts to improve equitable teaching practices in biology education have led to an increase in research on the barriers to student participation and performance, as well as solutions for overcoming these barriers. Fewer studies have examined the extent to which the resulting data trends and effective strategies are generalizable across multiple contexts or are specific to individual classrooms, institutions, or geographic regions. To address gaps in our understanding, as well as to establish baseline information about students across contexts, a working group associated with a research coordination network (Equity and Diversity in Undergraduate STEM, EDU-STEM) convened in Las Vegas, Nevada, in November of 2019. We addressed the following objectives: 1) characterize the present state of equity and diversity in undergraduate biology education research; 2) address the value of a network of educators focused on science, technology, engineering, and mathematics equity; 3) summarize the status of data collection and results; 4) identify and prioritize questions and interventions for future collaboration; and 5) construct a recruitment plan that will further the efforts of the EDU-STEM research coordination network. The report that follows is a summary of the conclusions and future directions from our discussion. 

Abstract A multi-agency succession of field campaigns was conducted in southeastern Texas during July 2021 through October 2022 to study the complex interactions of aerosols, clouds and air pollution in the coastal urban environment. As part of the Tracking Aerosol Convection interactions Experiment (TRACER), the TRACER- Air Quality (TAQ) campaign the Experiment of Sea Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) and the Convective Cloud Urban Boundary Layer Experiment (CUBE), a combination of ground-based supersites and mobile laboratories, shipborne measurements and aircraft-based instrumentation were deployed. These diverse platforms collected high-resolution data to characterize the aerosol microphysics and chemistry, cloud and precipitation micro- and macro-physical properties, environmental thermodynamics and air quality-relevant constituents that are being used in follow-on analysis and modeling activities. We present the overall deployment setups, a summary of the campaign conditions and a sampling of early research results related to: (a) aerosol precursors in the urban environment, (b) influences of local meteorology on air pollution, (c) detailed observations of the sea breeze circulation, (d) retrieved supersaturation in convective updrafts, (e) characterizing the convective updraft lifecycle, (f) variability in lightning characteristics of convective storms and (g) urban influences on surface energy fluxes. The work concludes with discussion of future research activities highlighted by the TRACER model-intercomparison project to explore the representation of aerosol-convective interactions in high-resolution simulations.