September 2023 NS&T Highlights
Research, program, and people/leadership achievements in the Nuclear Science & Technology directorate for the month of September.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
SEARCH · Engineering Papers
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Computational modeling highlights the role of the disordered Formin Homology 1 domain in profilin-actin transfer
Formins accelerate actin polymerization, assumed to occur through flexible Formin Homology 1 (FH1) domain-mediated transfer of profilin-actin to the barbed end. To investigate FH1 properties and address sequence effects, including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of a set of representative FH1 domains of formins: mouse mDia1 and mDia2, budding yeast Bni1 and Bnr1, and fission yeast Cdc12, For3, and Fus1. We discover that FH1 has flexible regions between high-propensity polyproline helix regions. A coarse-grained model retaining sequence specificity, assuming rigid polyproline segments, describes their size. Multiple bound profilins or profilin-actin complexes expand mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show that the leading FH1 can better transfer profilin or profilin-actin, with decreasing probability as the distance from FH2 increases.
59 BASIC BIOLOGICAL SCIENCES↗
Target highlights from the first post-PSI CASP experiment (CASP12, May–August 2016)
In this paper, the functional and biological significance of the selected CASP12 targets are described by the authors of the structures. Finally, the crystallographers discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP12 experiment.
59 BASIC BIOLOGICAL SCIENCES↗
Target highlights in CASP13: Experimental target structures through the eyes of their authors
The functional and biological significance of selected CASP13 targets are described by the authors of the structures. The structural biologists discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP13 experiment.
59 BASIC BIOLOGICAL SCIENCES↗
RNA target highlights in CASP15 : Evaluation of predicted models by structure providers
Abstract The first RNA category of the Critical Assessment of Techniques for Structure Prediction competition was only made possible because of the scientists who provided experimental structures to challenge the predictors. In this article, these scientists offer a unique and valuable analysis of both the successes and areas for improvement in the predicted models. All 10 RNA‐only targets yielded predictions topologically similar to experimentally determined structures. For one target, experimentalists were able to phase their x‐ray diffraction data by molecular replacement, showing a potential application of structure predictions for RNA structural biologists. Recommended areas for improvement include: enhancing the accuracy in local interaction predictions and increased consideration of the experimental conditions such as multimerization, structure determination method, and time along folding pathways. The prediction of RNA–protein complexes remains the most significant challenge. Finally, given the intrinsic flexibility of many RNAs, we propose the consideration of ensemble models.
59 BASIC BIOLOGICAL SCIENCES↗
Rearfoot Transcutaneous Oximetry is a Useful Tool to Highlight Ischemia of the Heel
PurposeTo demonstrate the usefulness of rearfoot transcutaneous oximetry to assess the peripheral arterial disease in diabetic patients with heel ulcer.MethodsFrom our database of 550 critical limb ischemia diabetic patients followed after a percutaneous transluminal angioplasty, we have selected patients with below the knee arterial disease. Patients were grouped according to the dorsal transcutaneous oximetry value (Group A < 30 mmHg; Group B ≥ 30 mmHg). Patients of Group B had a second oximetry performed at the rearfoot, close to the lesion localized in all cases at the heel. Finally, the analysis of the arterial pattern disease has been done.ResultsWe selected 191 patients: Group A (151 patients), dorsal transcutaneous oximetry of 11.8 ± 0.7 mmHg; Group B (40 patients), dorsal transcutaneous oximetry of 44.2 ± 10.1 mmHg. In Group B, rearfoot oximetry was 20.5 ± 5 mmHg, significantly lower than dorsal oximetry (p = 0.0179). The anterior tibial artery was involved in all patients of Group A. In Group B, the anterior tibial artery was involved in 15 subjects and never alone; the posterior tibial artery was involved in 20 subjects and in 11 cases alone. The peroneal artery was affected in 20 subjects and in 14 patients alone.ConclusionWhen a heel lesion is present and the transcutaneous oximetry recorded on the dorsum of the foot does not confirm the presence of critical limb ischemia (not ≤30 mmHg), a second oximetry recorded on the rearfoot is useful to point out ischemia of the peroneal artery and/or of the posterior tibial artery.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Pseudoaneurysm: Some Differences in its Character Between the Mesenteric vs. Uterine Artery Highlighting the Unique Feature of This Vascular Disorder
No abstract prepared.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Pseudoaneurysm: Some Differences in its Character Between the Mesenteric vs. Uterine Artery Highlighting the Unique Feature of This Vascular Disorder: Comments
No abstract prepared.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Genetic Screen for Cell Fitness in High or Low Oxygen Highlights Mitochondrial and Lipid Metabolism
Not Available
59 BASIC BIOLOGICAL SCIENCES↗
Separation of life stages within anaerobic fungi (Neocallimastigomycota) highlights differences in global transcription and metabolism
Anaerobic gut fungi of the phylum Neocallimastigomycota are microbes proficient in valorizing low-cost but difficult-to-breakdown lignocellulosic plant biomass. Characterization of different fungal life stages and how they contribute to biomass breakdown are critical for biotechnological applications, yet we lack foundational knowledge about the transcriptional, metabolic, and enzyme secretion behavior of different life stages of anaerobic gut fungi: zoospores, germlings, immature thalli, and mature zoosporangia. A Miracloth-based technique was developed to enrich cell pellets with zoospores - the free-swimming, flagellated, young life stage of anaerobic gut fungi. By contrast, fungal mats contained relatively more vegetative, encysted, mature sporangia that form films. Global gene expression profiles were compared from two sample types (zoospore-enriched cell pellets vs. mature mats) harvested from the anaerobic gut fungal strain Neocallimastix californiae G1. Despite cultures being grown on glucose, the fungal zoospore-enriched samples were transcriptionally primed to encounter plant matter substrate, as evidenced by upregulation of catabolic carbohydrate-active enzymes and putative carbohydrate transporters. Furthermore, we report significant differential gene expression for gene annotation groups, including putative secondary metabolites and transcription factors. Understanding global gene expression differences between the fungal zoospore-enriched cells and mature fungi aid in characterizing fungal development, unmasking gene function, and guiding cultivation conditions and engineering targets to promote enzyme secretion.
59 BASIC BIOLOGICAL SCIENCES↗
Theoretical estimates of equilibrium sulfur isotope effects in aqueous sulfur systems: Highlighting the role of isomers in the sulfite and sulfoxylate systems
We present theoretical calculations for all three isotope ratios of sulfur ( 33 S/ 32 S, 34 S/ 32 S, 36 S/ 32 S) at the B3LYP/6-31+G(d,p) level of theory for aqueous sulfur compounds modeled in 30–40H 2 O clusters spanning the range of sulfur oxidation state (S n , n = -2 to +6) for estimating equilibrium fractionation factors in aqueous systems. Computed 34 β values based on major isotope ( 34 S/ 32 S) reduced partition function ratios (RPFRs) scale to a first order with sulfur oxidation state and coordination, where 34 β generally increase with higher oxidation state and increasing coordination of the sulfur atom. Exponents defining mass dependent relationships based on β values ( x/34 κ = ln( x β)/ln( 34 β), x = 33 or 36) conform to tight ranges over a wide range of temperature for all aqueous compounds ( 33/34 κ ≈ 0.5148–0.5159, 36/34 κ ≈ 1.89–1.90 from T ≽ 0 °C). The exponents converge near a singular value for all compounds at the high temperature limit ( 33/34 κT→∞= 0.51587 ± 0.00003 and 36/34 κT→∞= 1.8905 ± 0.0002; 1 s.d. of all computed compounds), and typically follow trends based on oxidation state and coordination similar to those seen in 34 β values at lower temperatures. Theoretical equilibrium fractionation factors computed from these β-values are compared to experimental constraints for HSO 3 - T(aq)/SO 2(g, aq) , SO 2(aq) /SO 2(g) , H 2 S (aq) /H 2 S (g) , H 2 S (aq) /HS - (aq) , SO 4 2- (aq) /H 2 S T(aq) , S 2 O 3 2- (aq) (intramolecular), and S 2 O 3 2- (aq) /H 2 S T(aq) , and generally agree within a reasonable estimation of uncertainties. We make predictions of fractionation factors where other constraints are unavailable. Isotope partitioning of the isomers of protonated compounds in the sulfite and sulfoxylate systems depend strongly on whether protons are bound to either sulfur or oxygen atoms. The magnitude of the HSO 3 - T /SO 3 2- major isotope ( 34 S/ 32 S) fractionation factor is predicted to increase with temperature from 0 to 70 °C due to the combined effects of the large magnitude (HS)O 3 - /SO 3 2- fractionation factor (1000ln 34 α (HS)bisulfite-sulfite = 19.9‰, 25 °C) relative to the (HO)SO 2 - /SO 3 2- fractionation factor (1000ln 34 α (HO)bisulfite–sulfite = -2.2‰, 25 °C), and the increased stability of the (HS)O 3 - isomer with increasing temperature. Finally, we argue that isomerization phenomenon should be considered in models of the sulfur cycle, including models that describe the overall sulfur isotope fractionations associated with microbial metabolism (e.g., microbial sulfate reduction).
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Field-scale fault reactivation experiments by fluid injection highlight aseismic leakage in caprock analogs: Implications for CO 2 sequestration
Observations on tens-of-meter scale experiments of fault activation by fluid injection conducted in shales allow exploring how aseismic and seismic events may jeopardize the integrity of a sealing caprock overlying a CO 2 sequestration reservoir. We contrast the behavior of shale faults with another set of experiments conducted in carbonates. Significant fluid leakage occurs along the initially low-permeability shale faults when rupture is activated. Most of the leakage pathway closes when fluid injection ceases and fluid pressure drops. Dilatant slip on the fault plane alone does not explain the observed leakage behavior, which is also caused by fault opening favored by the softness of the shale, and by the structure of the fault zone that prevents fluids from diffusing into the adjacent damage zone. Experiments show a large amount of aseismic deformation. Small-magnitude seismicity (M w < -2.5) is observed outside the pressurized leakage patch. Stress transferred from this aseismic deformation patch can build up to stress-criticality and favor seismicity. Thus, in terms of fault activation in caprocks, aseismic fault slip leading to increased permeability and a loss of seal integrity is of great concern.
58 GEOSCIENCES↗
Treatment of Non-Small Cell Lung Cancer Patients With Proton Beam-Based Stereotactic Body Radiotherapy: Dosimetric Comparison With Photon Plans Highlights Importance of Range Uncertainty
Purpose: Proton beam radiotherapy has been proposed for use in stereotactic body radiotherapy (SBRT) for early-stage non-small-cell lung cancer. In the present study, we sought to analyze how the range uncertainties for protons might affect its therapeutic utility for SBRT. Methods and Materials: Ten patients with early-stage non-small-cell lung cancer received SBRT with two to three proton beams. The patients underwent repeat planning for photon SBRT, and the dose distributions to the normal and tumor tissues were compared with the proton plans. The dosimetric comparisons were performed within an operational definition of high- and low-dose regions representing volumes receiving >50% and <50% of the prescription dose, respectively. Results: In high-dose regions, the average volume receiving {>=}95% of the prescription dose was larger for proton than for photon SBRT (i.e., 46.5 cm{sup 3} vs. 33.5 cm{sup 3}; p = .009, respectively). The corresponding conformity indexes were 2.46 and 1.56. For tumors in close proximity to the chest wall, the chest wall volume receiving {>=}30 Gy was 7 cm{sup 3} larger for protons than for photons (p = .06). In low-dose regions, the lung volume receiving {>=}5 Gy and maximum esophagus dose were smaller for protons than for photons (p = .019 and p < .001, respectively). Conclusions: Protons generate larger high-dose regions than photons because of range uncertainties. This can result in nearby healthy organs (e.g., chest wall) receiving close to the prescription dose, at least when two to three beams are used, such as in our study. Therefore, future research should explore the benefit of using more than three beams to reduce the dose to nearby organs. Additionally, clinical subgroups should be identified that will benefit from proton SBRT.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Probing QCD and hadron physics: highlights of experimental results
The rich set of data collected from HERA, Tevatron and LHC collisions offer an extraordinary possibility to test different aspects of perturbative Quantum Chromodynamics. A selection of recent results illustrates the variety and precision of these tests. The comparison of the experimental data with the most recent theoretical predictions demonstrates the advances made in the theoretical field.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Molar Mass versus Polymer Solar Cell Performance: Highlighting the Role of Homocouplings
Explore the source record for details and available documents.
Vangerven, Tim↗