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The NadABC pathway is involved in the biosynthesis of nicotinamide adenine dinucleotide (NAD) and is a dominant pathway in bacteria. The conversion of l-aspartate to quinolinic acid is initiated by the l-aspartate oxidase NadB, which catalyzes the formation of iminoaspartate that is used by quinolinate synthase NadA in a condensation reaction with dihydroxyacetone phosphate to produce quinolinic acid. NadA is a [4Fesingle bond4S] cluster-containing enzyme that is indispensable in the production of NAD. In B. subtilis, the cysteine sulfurtransferase nifS gene is located in genomic proximity to the nad genes, and its expression is regulated by NadR based on the availability of nicotinic acid. Inactivation of nifS leads to inactivation of the NAD pathway and, consequently, nicotinic acid auxotrophy. In this study, we explored the hypothesis that NifS’ involvement in NAD biosynthesis is associated with its role in the maturation of NadA [4Fesingle bond4S] cluster. We showed through in vitro reconstitution experiments that NifS is catalytically competent in promoting cluster assembly onto apo-NadA and that the rate of reactivation depends on the rate of sulfur mobilization. Furthermore, the activity of NifS in sulfur mobilization is modulated by Apo-NadA. Under conditions of cluster synthesis, apo-NadA enhances the turnover rate of NifS. This phenomenon is not observed for YrvO, NifZ, and SufSU, the other three cysteine sulfurtransferases in B. subtilis. This work provides biochemical evidence for the requirement of a dedicated cysteine desulfurase in the maturation of specialized Fesingle bondS enzymes. 

The “Heliophysics Big Year” was an extended “year” when major solar events engaged the public. NASA and the National Science Foundation (NSF) funded several projects to educate the public on the science of the heliosphere and safe observing practices. In response to this initiative, we worked with other teams to create and disseminate accurate yet engaging information. We expanded our eclipse website (https://space.rice.edu/eclipse/) with activities, citizen science projects, resources, training videos, suggested equipment, and links to other compendia. We directed the Citizen CATE 2024 project, and trained state coordinators and their teams to use the specialized equipment and procedures. We trained teachers at local, regional, national, and international workshops, providing eclipse viewing cards, lenses for making “solar cup projectors,” a pattern for a safe viewing screen, and additional materials. With other teams, we gave presentations to the media at SciLine in San Antonio and hosted public events to demonstrate safe eclipse viewing techniques. The most lasting and impactful product was our planetarium show “Totality,” which was distributed free of license fees. More than 180,000 views of the show and its animations have been documented. We improved our space weather forecasting site (https://mms.rice.edu) and used our email lists (14,000+) to send out real-time warnings about the major solar storm of 10–11 May 2024. In total, we provided nearly two million people with heliophysics information. In summary, the federal/private/business partnerships meant that the events of this “year” were a fun, safe, learning experience for tens of millions of Americans. 

Low-molecular-weight (LMW) thiols play critical roles in maintaining redox buffer systems required for normal biological function. Glutathione (GSH) represents the most common LMW thiol found in Nature, but Gram-positive bacteria utilize bacillithiol (BSH) or mycothiol (MSH). Nitroxyl (HNO) can influence bacterial transcription through persulfide formation, a biological phenomenon that prompts the examination of the reactions of HNO with these LMW thiols. The development and application of colorimetric and enzymatic (Bacillus subtilis thioredoxin assay) methods combined with mass spectrometry of reaction products show the unique reactivity of BSH to favor sulfinamide adduct formation upon equimolar reaction with HNO. The reaction profile with GSH results in nearly equal distribution between sulfinamide:disulfide, whereas reaction with MSH only yields disulfide. These varied results led to the preparation of a group of BSH and MSH analogs, and their reactions with HNO reveal the requirement for a free amine group for sulfinamide formation. The thiol and amine group pKa's appear critical for sulfinamide generation, with the thiolate acting as a nucleophile to attack HNO and the ammonium donating a proton to facilitate water loss from the N-hydroxysulfenamide intermediate. Furthermore, the B. subtilis thioredoxin system efficiently reduces BSSB with a calculated KM_BSSB = 34 ± 3 μM and Vmax = 152 ± 3.4 nmol/min/nmol TrxR (kcat = 2.5 s−1), but does not reduce bacillithiol sulfinamide. Similarly, this thioredoxin reduces MSSM with a calculated KM_MSSM of 9 ± 2.1 μM and Vmax of 103 ± 7.1 nmol/min/nmol TrxR (kcat = 1.7 s−1). Bacillithiol possesses a unique structure that allows a rapid reaction with HNO to form a stable product that may provide a basis for antibiotic development or clues for further biological roles of nitroxyl. 

In professional development (PD), who the learners are becomes a central feature that influences not only their learning, but also that of those around them. Participant identities, expectations, and teaching philosophies all influence the success of PD. In 2019, Zagallo and colleagues developed a set of personas to characterize how instructors show up in these settings. We are expanding on this prior study to include instructors from diverse institution types participating in a different PD context. To validate the existing personas and generate potential new personas, we followed Zagallo's stepwise procedure that included the collection of multiple types of data (interview transcripts, PD observations, meeting observations) over a 2-y period, qualitative analysis and triangulation of data, creation of skeletons that could be further developed into personas, description and refinement of skeletons into personas, and validation of the personas. Themes from the original study were also captured in this study: knowledge of students, teaching values, approaches to innovations, and perceived barriers. Four personas from the original paper were refined, and two new personas (Riley the Rookie and Ash the Advocate) were identified; both arose from institutional contexts not present in the prior research. 

Little research explores the effect of heat on the isotopic composition of ostrich eggshell (OES), though several studies use stable isotopes in OES to assist in paleoclimatic reconstruction. Archaeological OES often shows signs of heat exposure, though distinguishing lower-temperature exposure remains challenging. This controlled study uses modern OES heated in an electric kiln to examine if exposure to low through high degrees of heat shifts δ13C, δ15N, and δ18O values in the organic and mineral components of ostrich eggshell. Results indicate that the total organic portion of the shell conserves original isotopic signatures with exposure below ~220 ◦C, while the mineral portion conserves signatures up to 500 ◦C. Additionally, the study provides C:N ratios as a reliability criterion for the organic portion of archaeological OES. Data produced in this study allows for a more discriminating selection of archaeological samples for paleoclimatic reconstructions. 

This research-to-practice full paper describes a cohort-based undergraduate research program designed to improve STEM retention through structured mentoring and community building. Drawing on the Affinity Research Group (ARG) model, the program fosters faculty-student research collaboration and integrates faculty mentorship training, student-led peer mentoring, and structured interventions, such as research skills workshops and networking events. Each year, faculty from biology, chemistry, computer science, environmental science, and mathematics lead small-group research projects with recruited students who may participate for up to three years. Faculty and students receive ARG training to promote consistent mentoring practices. A credit-bearing, major-specific first-year orientation course supports recruitment and reinforces students’ scientific identity. Faculty also engage in professional development workshops to strengthen student-centered mentoring approaches. Data collection includes surveys, interviews, retention tracking, and weekly journaling to assess STEM identity, belonging, and skill development. External evaluators reviewed the faculty focus groups to assess mentoring effectiveness. Initial findings show strong faculty engagement with the ARG model, with many adopting adaptive mentoring strategies that enhance student support. Students report increased confidence and belonging within their disciplines. However, cross-disciplinary collaboration remains limited, highlighting the need for more intentional networking within the cohort. Students also emphasized the value of peer collaboration alongside faculty mentorship. These results suggest that undergraduate research can serve as a powerful tool for building community and supporting persistence in STEM. Ongoing efforts will focus on expanding networking opportunities, strengthening peer collaboration, and evaluating long-term impacts on student retention. 

Abstract The San Fernando Valley (SFV), part of the Los Angeles metropolitan area, is a seismically active urban environment. Large-magnitude earthquakes, such as the 1994 Mw 6.7 Northridge event that occurred on a blind fault beneath the valley, caused significant infrastructure damage in the region, underscoring the need for enhanced seismic monitoring to improve the identification of buried faults and hazard evaluation. Currently, the Southern California Earthquake Data Center operates four broadband instruments within the valley; however, the network’s ability to capture small earthquakes beneath the region may be limited. To demonstrate how this data gap can be filled, we use recordings from the SFV array, comprised of 140 nodal instruments with interstation distances ranging from 0.3 to 2.5 km that recorded for one month. High-anthropogenic noise levels in urbanized areas tend to conceal earthquake signals; therefore, we applied a previously developed machine learning model fine-tuned on similar waveforms to detect events and pick seismic phases. In a two-step event association workflow, isolated phase picks were first culled, which eliminated false positive detections and reduced computational runtime. We located 62 events within a 209 km radius of our array with magnitudes ranging from ML 0.13 to 4, including 36 new events that were undetected by the regional network. One event cluster reveals a previously unidentified (5.3 km × 4 km) blind fault zone located ∼5 km beneath the southern part of the valley. Seismicity from this zone is rare in the regional catalog (<3 events per year), despite producing a Mb 4.4 event in 2014. Our results highlight the benefits of detecting small-magnitude seismicity for hazard estimation. Temporary nodal arrays can identify critical gaps in regional monitoring and guide site selection for permanent stations. In addition, our workflow can be applied to complement seismic monitoring in other urban settings. 

The biological synthesis of iron–sulfur (Fe–S) clusters requires dedicated pathways involved in the recruitment and activation of Fe and S for cluster assembly with subsequent transfer of preformed clusters to acceptor proteins. Several pathways have been described that include various numbers and types of biosynthetic components, although all of them share the same basic principles for [Fe–S] cluster formation and delivery to target proteins. The NifUS system was discovered and first described in studies involving the model diazotroph Azotobacter vinelandii . It has a dedicated role in serving as the starting point for the activation of [Fe–S] cluster-containing proteins specifically involved in biological nitrogen fixation. NifS is a pyridoxal-5′-phosphate containing l -cysteine-dependent sulfur transferase that delivers activated sulfur to the three-domain NifU, which not only serves as a scaffold for the construction of [2Fe–2S] and [4Fe–4S] clusters but also participates in their delivery to various target proteins involved in nitrogen fixation. Interestingly, analysis of sequenced genomes reveals that the three-domain NifU and NifU-like encoded proteins are not limited to diazotrophs, suggesting a broader role for this system in [Fe–S] cluster biogenesis in other organisms. The colocalization of adjacent nifU and nifS encoding sequences in most of these genomes also provides a strong indication for the involvement of the NifU–NifS [Fe–S] cluster assembly and delivery toolkit for activation of [Fe–S] cluster-containing proteins in a variety of organisms that do not fix nitrogen. 

Rates and directions of crustal extension in a continental rift vary in time and space as the rift evolves, and these geologic records are often preserved along fault planes. Some fault-kinematic studies have been undertaken in the central to northern segments of the Rio Grande rift, but similar studies from the southern part of the Rio Grande rift of western Texas, USA, and northern Mexico are fewer. We present new fault-kinematic data from six locations in the southern Rio Grande rift of Trans-Pecos Texas, combined with U-Pb dating of calcite slickenlines, to constrain the directions and time scales of extension. All locations preserve NE-SW−oriented extension, and locations within the Sunken Block graben preserve a more complex kinematic history of multiple extension directions. Four U-Pb ages range from 30.1 ± 3.1 Ma to 13.7 ± 0.9 Ma. Combined with fault-kinematic data and assuming a constant stress regime between 30 Ma and 14 Ma, these data support the interpretation that earliest extension in the southern rift was oriented NE-SW, and extension rotated clockwise to E-W and NW-SE after 13.7 ± 0.9 Ma. Based on available data, this rotation was broadly coincident with rotation in the extension direction in the southern Española basin and in the Basin and Range Province. These differences suggest that extension in the Rio Grande rift responded to the evolving western boundary of the North American plate but included initial underlying driving forces that were supplanted by lateral forces as the transform margin lengthened. Additionally, geochronologic and kinematic data across the Sunken Block graben of the southern Rio Grande rift indicate that the locus of rifting concentrated with time toward the center of this basin; such structural narrowing has previously been demonstrated in the northern segment of the rift. This study provides a much-needed comparison between the southern and northern segments of the rift but highlights the need for more collection of combined kinematic and geochronologic data. 

Abstract The San Fernando Valley (SFV), a densely populated region in Southern California, has high earthquake hazard due to a complex network of active faults and the amplifying effects of the sedimentary basin. Since the devastating 1994 Mw 6.7 Northridge earthquake, numerous studies have examined its structure using various geological and geophysical datasets. However, current seismic velocity models still lack the resolution to accurately image the near-surface velocity structure and concealed or blind faults, which are critical for high-frequency wavefield simulations and earthquake hazard modeling. To address these challenges, we develop a 3D high-resolution shear-wave velocity model for the SFV using ambient noise data from a dense array of 140 seismic nodes and 10 Southern California Seismic Network stations. We also invert gravity data to map the basin geometry and integrate horizontal-to-vertical spectral ratios and aeromagnetic data to constrain interfaces and map major geological structures. With a lateral resolution of 250 m near the basin center, our model reveals previously unresolved geological features, including the detailed geometry of the basin and previously unmapped structure of faults at depth. The basin deepens from the Santa Monica Mountains in the south to approximately 4 km near its center and 7 km in the Sylmar sub-basin at the basin’s northern margin. Strong velocity contrasts are observed across major faults, at the basin edges, and in the basin’s upper 500 m, for which we measure velocities as low as 200 m/s. Our high-resolution model will enhance ground-motion simulations and earthquake hazard assessments for the SFV and has implications for other urban areas with high seismic risk.