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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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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Cardiac troponin T N-domain variant destabilizes the actin interface resulting in disturbed myofilament function

Missense variant Ile79Asn in human cardiac troponin T (cTnT-I79N) has been associated with hypertrophic cardiomyopathy and sudden cardiac arrest in juveniles. cTnT-I79N is located in the cTnT N-terminal (TnT1) loop region and is known for its pathological and prognostic relevance. A recent structural study revealed that I79 is part of a hydrophobic interface between the TnT1 loop and actin, which stabilizes the relaxed (OFF) state of the cardiac thin filament. Given the importance of understanding the role of TnT1 loop region in Ca 2+ regulation of the cardiac thin filament along with the underlying mechanisms of cTnT-I79N-linked pathogenesis, we investigated the effects of cTnT-I79N on cardiac myofilament function. Transgenic I79N (Tg-I79N) muscle bundles displayed increased myofilament Ca 2+ sensitivity, smaller myofilament lattice spacing, and slower crossbridge kinetics. These findings can be attributed to destabilization of the cardiac thin filament’s relaxed state resulting in an increased number of crossbridges during Ca 2+ activation. Additionally, in the low Ca 2+ -relaxed state (pCa8), we showed that more myosin heads are in the disordered-relaxed state (DRX) that are more likely to interact with actin in cTnT-I79N muscle bundles. Dysregulation of the myosin super-relaxed state (SRX) and the SRX/DRX equilibrium in cTnT-I79N muscle bundles likely result in increased mobility of myosin heads at pCa8, enhanced actomyosin interactions as evidenced by increased active force at low Ca 2+ , and increased sinusoidal stiffness. These findings point to a mechanism whereby cTnT-I79N weakens the interaction of the TnT1 loop with the actin filament, which in turn destabilizes the relaxed state of the cardiac thin filament.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Mechanisms of a novel regulatory light chain–dependent cardiac myosin inhibitor

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the heart characterized by thickening of the left ventricle (LV), hypercontractility, and impaired relaxation. HCM is caused primarily by heritable mutations in sarcomeric proteins, such as β myosin heavy chain. Until recently, medications in clinical use for HCM did not directly target the underlying contractile changes in the sarcomere. Here, we investigate a novel small molecule, RLC-1, identified in a bovine cardiac myofibril high-throughput screen. RLC-1 is highly dependent on the presence of a regulatory light chain to bind to cardiac myosin and modulate its ATPase activity. In demembranated rat LV trabeculae, RLC-1 decreased maximal Ca2+-activated force and Ca2+ sensitivity of force, while it increased the submaximal rate constant for tension redevelopment. In myofibrils isolated from rat LV, both maximal and submaximal Ca2+-activated force are reduced by nearly 50%. Additionally, the fast and slow phases of relaxation were approximately twice as fast as DMSO controls, and the duration of the slow phase was shorter. Structurally, x-ray diffraction studies showed that RLC-1 moved myosin heads away from the thick filament backbone and decreased the order of myosin heads, which is different from other myosin inhibitors. In intact trabeculae and isolated cardiomyocytes, RLC-1 treatment resulted in decreased peak twitch magnitude and faster activation and relaxation kinetics. In conclusion, RLC-1 accelerated kinetics and decreased force production in the demembranated tissue, intact tissue, and intact whole cells, resulting in a smaller cardiac twitch, which could improve the underlying contractile changes associated with HCM.

Physiology↗
DOE OSTI2024

Calcium has a direct effect on thick filament activation in porcine myocardium

Sarcomere activation in striated muscle requires both thin filament–based and thick filament–based activation mechanisms. Recent studies have shown that myosin heads on the thick filaments undergo OFF to ON structural transitions in response to calcium (Ca2+) in permeabilized porcine myocardium in the presence of a small molecule inhibitor that eliminated active force. The changes in X-ray diffraction signatures of OFF to ON transitions were interpreted as Ca2+ acting to activate the thick filaments. Alternatively, Ca2+ binding to troponin could initiate a Ca2+-dependent crosstalk from the thin filament to the thick filament via interfilament connections such as the myosin binding protein-C. Here, we exchanged native troponin in permeabilized porcine myocardium for troponin containing the cTnC D65A mutation, which disallows the activation of troponin through Ca2+ binding to determine if Ca2+-dependent thick filament activation persists in the absence of thin filament activation. After the exchange protocol, over 95% of the Ca2+-activated force was eliminated. Equatorial intensity ratio increased significantly in both WT and D65A exchanged myocardium with increasing Ca2+ concentration. The degree of helical ordering of the myosin heads decreased by the same amount in WT and D65A myocardium when Ca2+ concentration increased. These results are consistent with a direct effect of Ca2+ in activating the thick filament rather than an indirect effect due to Ca2+-mediated crosstalk between the thick and thin filaments.

Physiology↗
DOE OSTI2023

Single-trial classification of evoked responses to auditory tones using OPM- and SQUID-MEG

Abstract Objective. Optically pumped magnetometers (OPMs) are emerging as a near-room-temperature alternative to superconducting quantum interference devices (SQUIDs) for magnetoencephalography (MEG). In contrast to SQUIDs, OPMs can be placed in a close proximity to subject’s scalp potentially increasing the signal-to-noise ratio and spatial resolution of MEG. However, experimental demonstrations of these suggested benefits are still scarce. Here, to compare a 24-channel OPM-MEG system to a commercial whole-head SQUID system in a data-driven way, we quantified their performance in classifying single-trial evoked responses. Approach. We measured evoked responses to three auditory tones in six participants using both OPM- and SQUID-MEG systems. We performed pairwise temporal classification of the single-trial responses with linear discriminant analysis as well as multiclass classification with both EEGNet convolutional neural network and xDAWN decoding. Main results. OPMs provided higher classification accuracies than SQUIDs having a similar coverage of the left hemisphere of the participant. However, the SQUID sensors covering the whole helmet had classification scores larger than those of OPMs for two of the tone pairs, demonstrating the benefits of a whole-head measurement. Significance. The results demonstrate that the current OPM-MEG system provides high-quality data about the brain with room for improvement for high bandwidth non-invasive brain–computer interfacing.

Iivanainen, Joonas (ORCID:0000000160344604)↗
DOE OSTI2020

Understanding effects of printhead geometry in aerosol jet printing

Aerosol jet printing offers a versatile, high-resolution digital patterning capability broadly relevant to flexible and printed electronic systems. Despite its promise and numerous demonstrations, the theoretical principles driving process outputs have not been thoroughly explored. In this study, a custom-built, modular printing system is developed to provide a head-to-head comparison of two print nozzle geometries to better understand the technology. Print resolution data from a range of process parameters are analyzed using a support vector machine framework. The linear deposition rate is identified as a key variable, which can confound careful studies of printing performance. Taking this into account, a clear difference is observed between the printheads, corresponding to a difference in resolution of 57% ± 11% under typical conditions. Models to understand differences in aerodynamic and mass transport effects identify enhanced drying within the NanoJet printhead as a likely cause of this difference. Overall, this study provides improved understanding of the aerosol jet printing process, including valuable insight to inform process optimization, robust data analysis, ink formulation, and printer geometric design.

42 ENGINEERING↗
DOE OSTI2023

Structure of the Ndc80 complex and its interactions at the yeast kinetochore–microtubule interface

The conserved Ndc80 kinetochore complex, Ndc80c, is the principal link between mitotic spindle microtubules and centromere-associated proteins. We used AlphaFold 2 (AF2) to obtain predictions of the Ndc80 ‘loop’ structure and of the Ndc80 : Nuf2 globular head domains that interact with the Dam1 subunit of the heterodecameric DASH/Dam1 complex (Dam1c). The predictions guided design of crystallizable constructs, with structures close to the predicted ones. The Ndc80 ‘loop’ is a stiff, α-helical ‘switchback’ structure; AF2 predictions and positions of preferential cleavage sites indicate that flexibility within the long Ndc80c rod occurs instead at a hinge closer to the globular head. Conserved stretches of the Dam1 C terminus bind Ndc80c such that phosphorylation of Dam1 serine residues 257, 265 and 292 by the mitotic kinase Ipl1/Aurora B can release this contact during error correction of mis-attached kinetochores. We integrate the structural results presented here into our current molecular model of the kinetochore–microtubule interface. The model illustrates how multiple interactions between Ndc80c, DASH/Dam1c and the microtubule lattice stabilize kinetochore attachments.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Glass Additive and Subtractive Manufacturing of a Fiber Optic Rotary Encoder for Downhole Pressure Sensing

This article presents a fiber optic rotary encoder-based pressure sensor for downhole applications. The rotary encoder, which is composed of an encoding pad and an all-glass optical fiber sensing head, converts the rotation angles of a pressure transducer to digital codes. The optical fiber only serves as the telemetry channel to directly transmit the data in digital format such that the environmental temperature influence and the long-time drift are minimized. The glass additive and subtractive manufacturing (ASM) techniques are used to embed the multichannel optical fibers into a bulk-fused silica glass substrate. Because the fused silica glass shares a similar material property to the optical fiber (e.g., thermal expansion coefficient), the optical fiber sensing head is well sealed and fixed even at an elevated temperature. The picosecond laser blackening technique is used to fabricate the high reflectivity contrast encoding pad with high accuracy. Here, the proposed pressure sensor was manufactured and experimentally verified to have a signal-to-noise ratio (SNR) of 23 dB and a linear pressure response with a root-mean-square error (RMSE) of 0.37. During the 400-h 250 °C long-term stability test, there was no digital code variation. In addition, a mathematical model to study the relationships between the sensor’s performances and design parameters was established. According to the model, a 12-bit encoder (0.02% pressure sensitivity) can be achieved with a radius of 20 mm.

02 PETROLEUM↗
DOE OSTI2025

Cooling Design and Thermal Analysis for Thermal Shields of a Cryocooler-Cooled Superconducting ECR Ion Source MARS-D Magnet

Here, a demonstrative NbTi based Mixed Axial and Radial field System (MARS-D) is being developed for a next-Generation Electron Cyclotron Resonance Ion Source (ECRIS) at Lawrence Berkeley National Laboratory (LBL), which employs a novel closed-loop coil design scheme that more efficiently utilizes conductor fields and extend the application of NbTi for high frequency (up to 45 GHz) ECR operation. The NbTi MARS-D magnet consists of a single hexagonally shaped closed-loop coil and a set of auxiliary solenoids. A cryostat for cooling the MARS-D magnet is under design at LBL. The MARS-D magnet working around 4.2 K will be bath-cooled in liquid helium using multiple two-stage cryocoolers. An intermediate temperature thermal radiation shield is adopted to reduce the heat leakage imposed on 4.2 K coil cold mass from room temperature. The thermal shield is conduction-cooled by the first-stage cold heads of four two-stage cryocoolers and the cold head of a single-stage cryocooler shared with nine binary leads. The temperature in the area of the shield that warm ends of HTS leads are mounted on is expected no higher than 60 K, which is limited by maximum allowable working temperature of HTS leads. The paper presents thermal analysis on the thermal radiation shield including heat loads and effects of eddy current induced during quench on its material selection.

ECRIS↗
DOE OSTI2020

A Data-Driven Pivot-Point-Based Time-Series Feeder Load Disaggregation Method

The load profile at a feeder-head is usually known to utility engineers while the nodal load profiles are not. However, the nodal load profiles are increasingly important for conducting time-series analysis in distribution systems. Therefore, in this paper, we present a pivot-point based, two-stage feeder load disaggregation algorithm using smart meter data. The two stages are load profile selection (LPS) and load profile allocation (LPA). In the LPS stage, a random load profile selection process is first executed to meet the load diversity requirement. Then, a few pairs of pivot points are selected as the matching targets. After that, a matching algorithm will run repetitively to select one load profile at a time for matching the reference load profile at the pivot points. In the LPA stage, the LPS selected load profiles are allocated to each load node on the feeder considering distribution transformer loading limits, load composition, and square-footage. The proposed method is validated using actual data collected in a North Carolina service area. Finally, simulation results show that the proposed method can generate a unique load shape for each load node while match the shape of their aggregated profile with the actual feeder head load profile.

42 ENGINEERING↗
DOE OSTI2020

Novel animal model of multiple sclerosis: The glial connexin gap junction as an environmental tuner for neuroinflammation

Abstract Connexins, which comprise gap junctions (GJs) via homotypic/heterotypic oligomerization, act as channels to connect opposing cells, mainly in solid organs such as the skin, liver, heart, and central/peripheral nervous system. Connexins are synthesized in the endoplasmic reticulum, assembled in the Golgi apparatus as hexamers, and inserted into the cell membrane as hemichannels. These hemichannels are closed under normal conditions until they combine to form clusters and connect to neighboring cells via GJs in a head‐to‐head configuration. Opening of hemichannels, which depends on the intra‐ or extracellular environment, allows various bioactive molecules to enter into or be released from the host cells. Recent pathological studies on human demyelinating diseases have revealed alterations of connexin expression patterns in demyelinating lesions. To elucidate the molecular mechanisms of connexins in the pathomechanisms of inflammatory demyelination, we induced experimental autoimmune encephalomyelitis (EAE) in connexin 30 (Cx30)‐deficient mice, oligodendroglia‐specific Cx47‐ablated mice, and astroglia‐specific Cx43‐ablated mice. We found that both astroglial‐Cx30‐deficient mice and Cx43‐ablated mice showed amelioration of the clinical course of EAE, while oligodendroglial‐Cx47‐ablated mice showed aggravation. These findings indicate the distinct role of connexins expressed in different cell types and the substantial contribution of connexin‐mediated pathology to demyelinating disorders. The imbalance in connexin expression, which is caused by the inflammatory environment, results in an increase in hemichannels in glial cells. The release of proinflammatory molecules induced by the increase in hemichannels on activated glial cells is a crucial mechanism of demyelinating disorders.

Yamasaki, Ryo↗
DOE OSTI2021

Measured influence of overhead HVAC on exposure to airborne contaminants from simulated speaking in a meeting and a classroom

Tracer gas experiments were conducted in a 158 m 3 room with overhead supply diffusers to study dispersion of contaminants from simulated speaking in physically distanced meeting and classroom configurations. The room was contained within a 237 m 3 cell with open plenum return to the HVAC system. Heated manikins at desks and a researcher operating the tracer release apparatus presented 8-9 thermal plumes. Experiments were conducted under conditions of no forced air and neutral, cooled, or heated air supplied at 980-1100 cmh, and with/out 20% outdoor air. CO 2 was released at the head of one manikin in each experiment to simulate small (< 5 µm diameter) respiratory aerosols. The metric of exposure relative to perfectly mixed (ERM) is introduced to quantify impacts, based on measurements at manikin heads and at three heights in the center and corners of the room. Chilled or neutral supply air provided good mixing with ERMs close to one. Thermal stratification during heating produced higher ERMs at most manikins: 25% were ≥ 2.5 and the highest were > 5× perfectly mixed conditions. Operation of two within-zone air cleaners together moving ≥400 cmh vertically in the room provided enough mixing to mitigate elevated exposure variations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Influence of oxygen vacancies on the domain wall stability in BiFeO 3

Oxygen vacancy is the most common type of point defects in functional oxides, and it is known to have profound influence on their properties. This is particularly true for ferroelectric oxides since their interaction with ferroelectric polarization often dictates the ferroelectric responses. Here, we study the influence of the concentration of oxygen vacancies on the stability of ferroelectric domain walls (DWs) in BiFeO 3 , a material with a relatively narrow bandgap among all perovskite oxides, which enables strong interactions among electronic charge carriers, oxygen vacancies, and ferroelectric domains. It is found that the electronic charge carriers in the absence of oxygen vacancies have essentially no influence on the spatial polarization distribution of the DWs due to their low concentrations. Upon increasing the concentration of oxygen vacancies, charge-neutral DWs with an originally symmetric polarization distribution symmetric around the center of the wall can develop a strong asymmetry of the polarization field, which is mediated by the electrostatic interaction between polarization and electrons from the ionization of oxygen vacancies. Strongly charged head-to-head DWs that are unstable without oxygen vacancies can be energetically stabilized in the off-stoichiometric BiFeO 3–δ with δ ~ 0.02 where ionization of oxygen vacancies provides sufficient free electrons to compensate the bound charge at the wall. Our results delineate the electrostatic coupling of the ionic defects and the associated free electronic charge carriers with the bound charge in the vicinity of neutral and charged DWs in perovskite ferroelectrics.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Sorghum SbGhd7 is a major regulator of floral transition and directly represses genes crucial for flowering activation

Molecular genetic understanding of flowering time regulation is crucial for sorghum development. GRAIN NUMBER, PLANT HEIGHT AND HEADING DATE 7 (SbGhd7) is one of the six classical loci conferring photoperiod sensitivity of sorghum flowering. However, its functions remain poorly studied. The molecular functions of SbGhd7 were characterized. The gene regulatory network controlled by SbGhd7 was constructed and validated. The biological roles of SbGhd7 and its major targets were studied. SbGhd7overexpression (OE) completely prevented sorghum flowering. Additionally, we show thatSbGhd7is a major negative regulator of flowering, binding to the promoter motif TGAATG(A/T)(A/T/C) and repressing transcription of the major florigen FLOWERING LOCUS T 10(SbFT10) and floral activators EARLY HEADING DATE(SbEhd1),FLAVIN-BINDING,KELCH REPEAT,F-BOX1(SbFKF1) and EARLY FLOWERING 3(SbELF3). Reinforcing the direct effect ofSbGhd7,SbEhd1OE activated the promoters of three functional florigens (SbFT1,SbFT8andSbFT10), dramatically accelerating flowering. Here our studies demonstrate that SbGhd7 is a major repressor of sorghum flowering by directly and indirectly targeting genes for flowering activation. The mechanism appears ancient. Our study extends the current model of floral transition regulation in sorghum and provides a framework for a comprehensive understanding of sorghum photoperiod response.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Evaluation of Potential Impacts of Free Chlorine during Washing of Fresh-Cut Leafy Greens on Escherichia coli O157:H7 Cross-Contamination and Risk of Illness

Addition of chlorine-based antimicrobial substances to fresh-cut leafy green wash water is done to minimize microbial cross-contamination during processing. We developed the FDA Leafy Green Risk Assessment Model (FDA-LGRAM) to quantify the impact of free chlorine concentration in wash water during fresh-cut lettuce processing on the extent of water-mediated cross-contamination between shredded lettuce and the associated risk of illness due to exposure to Escherichia coli O157:H7. At different contamination prevalence and levels of E. coli O157:H7 on incoming lettuce heads, the model compared the predicted prevalence of contaminated fresh-cut lettuce packages and the risk of illness per serving between: (1) a scenario where fresh-cut lettuce was packaged without washing; and (2) scenarios involving washing fresh-cut lettuce with different levels of free chlorine (0 ppm, 5 ppm, 10 ppm, 15 ppm, and 20 ppm) prior to packaging. Our results indicate that the free chlorine level in wash water has a substantial impact on the predicted prevalence of contaminated fresh-cut lettuce packages and the risk of illness associated with E. coli O157:H7 in fresh-cut lettuce. Results showed that the required level of free chlorine that can minimize water-mediated cross-contamination and reduce the corresponding risk of illness depended on contamination prevalence and levels of E. coli O157:H7 on incoming lettuce heads. Our model also indicated that the pathogen inactivation rate in wash water via free chlorine was a key model parameter that had a significant impact on the extent of cross-contamination during washing and the predicted associated risk of illness.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Development and Validation of Passive Yaw in the Open-Source WEC-Sim Code

A passive yaw implementation is developed, validated, and explored for the WEC-Sim, an open-source wave energy converter modeling tool that works within MATLAB/Simulink. The Reference Model 5 (RM5) is selected for this investigation, and a WEC-Sim model of the device is modified to allow yaw motion. A boundary element method (BEM) code was used to calculate the excitation force coefficients for a range of wave headings. An algorithm was implemented in WEC-Sim to determine the equivalent wave heading from a body’s instantaneous yaw angle and interpolate the appropriate excitation coefficients to ensure the correct time-domain excitation force. This approach is able to determine excitation force for a body undergoing large yaw displacement. For the mathematically simple case of regular wave excitation, the dynamic equation was integrated numerically and found to closely approximate the results from this implementation in WEC-Sim. A case study is presented for the same device in irregular waves. In this case, computation time is increased by 32x when this interpolation is performed at every time step. To reduce this expense, a threshold yaw displacement can be set to reduce the number of interpolations performed. A threshold of 0.01° was found to increase computation time by only 22x without significantly affecting time domain results. Similar amplitude spectra for yaw force and displacements are observed for all threshold values less than 1°, for which computation time is only increased by 2.2x.

50 EE - Wind and Water Power Program - Water (EE-4↗
DOE OSTI2023

Post Irradiation Examination of Pressurized Water Reactor Stainless Steel Internal Components

Internal structural components of pressurized water reactors (PWR), such as baffle former bolts, are subjected to significant neutron irradiation and mechanical stresses at elevated temperatures during plant operation. Over the long operation of the power plant, these conditions lead to potential degradation and reduced load-carrying capacity of these bolts. To understand property degradation more fully, to confirm the results of experimental irradiation programs, and to predict operational lifetime performance of structural materials in internal components, post irradiation examination of harvested materials from operating nuclear reactors is required. In this work, two high fluence 316 stainless steel baffle former bolts were retrieved from a commercial Westinghouse two-loop downflow type PWR and then sectioned for analysis via mechanical testing and microstructural characterization. The irradiation damage fluctuated along the bolt length with damage levels from 15 to 41 displacements per atom with the bolt head receiving approximately twice the neutron damage levels as that of the bolt thread section. Mechanical testing evaluations showed extensive irradiation hardening and a sharp decrease in fracture toughness in all parts of the bolt, though with limited variation along the bolt length. Microstructural characterization using analytical scanning transmission electron microscopy and atom probe tomography showed significant radiation induced precipitation, segregation, and dislocation loop and cavity formation. However, unlike the mechanical behavior, there was considerable variation along the bolt length but opposite of what may be expected, with more precipitation and cavity formation in the bolt thread where the neutron radiation dose is less than in the bolt head where the neutron radiation dose is higher. The cause of this variation is likely due to gradients in temperature, neutron energy spectra, and gamma irradiation.

Lach, Tim↗
DOE OSTI2023

Towards a new generation long trace profiler LTP-2020: optical design of pencil beam interferometry sensor

Improvements in the quality of synchrotron beamline x-ray optics required for next-generation light sources (e.g. the ALS Upgrade project) drive the need to improve the performance of the metrology instrumentation used to measure these components. The Long Trace Profiler (LTP) that is in use at many synchrotron metrology laboratories around the world has some known issues that affect the accuracy of its measurements. The main error source is optical path difference (OPD) phase error introduced into the probe beam by inhomogeneities in the glass components used in the optical head. We have developed a new optical head design, LTP-2020, that replaces the cube polarizing beamsplitter (PBS) with a thin wedge plate polarizing beamsplitter (WPBS) and replaces the cemented doublet lens with an aspheric singlet. Both of these components significantly reduce the glass volume traversed by the laser probe beam. Careful attention to ghost ray interference produced by back reflection from optical surfaces is necessary to minimize distortion in the primary image that translates into systematic error in the slope angle measurement. We make extensive use of a commercial raytracing program to model the back reflections and adjust component parameters as necessary to minimize distortion. Deliberate misalignment of components is necessary to make the system perform correctly. Stringent requirements are placed on the 45◦ incidence coatings on the WPBS and on the normal incidence coatings on the lens and camera window elements. We encourage our colleagues who wish to upgrade their current LTP systems to join us in the procurement of these custom optical components.

Takacs, Peter Z.↗
DOE OSTI2020

Pre–T cell receptors topologically sample self-ligands during thymocyte β-selection

Self-discrimination, a critical but ill-defined molecular process programmed during thymocyte development, requires myriad pre–T cell receptors (preTCRs) and αβTCRs. Using x-ray crystallography, we show how a preTCR applies the concave β-sheet surface of its single variable domain (Vβ) to “horizontally” grab the protruding MHC α2-helix. By contrast, αβTCRs purpose all six complementarity-determining region (CDR) loops of their paired VαVβ module to recognize peptides bound to major histocompatibility complex molecules (pMHCs) in “vertical” head-to-head binding. Additionally, the preTCR topological fit ensures that CDR3β reaches the peptide’s featured C-terminal segment for pMHC sampling, establishing the subsequent αβTCR canonical docking mode. “Horizontal” docking precludes germline CDR1β- and CDR2β-MHC binding to broaden β-chain repertoire diversification before αβTCR-mediated selection refinement. Thus, one subunit successively attunes the recognition logic of related multicomponent receptors.

59 BASIC BIOLOGICAL SCIENCES↗