Search NASA⌕ Search

SEARCH · Search NASA

Results for “Spikes”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Machine Learning Reveals the Critical Interactions for SARS-CoV-2 Spike Protein Binding to ACE2

SARS-CoV and SARS-CoV-2 bind to the human ACE2 receptor in practically identical conformations, although several residues of the receptor-binding domain (RBD) differ between them. Herein, we have used molecular dynamics (MD) simulations, machine learning (ML), and free-energy perturbation (FEP) calculations to elucidate the differences in binding by the two viruses. Although only subtle differences were observed from the initial MD simulations of the two RBD–ACE2 complexes, ML identified the individual residues with the most distinctive ACE2 interactions, many of which have been highlighted in previous experimental studies. FEP calculations quantified the corresponding differences in binding free energies to ACE2, and examination of MD trajectories provided structural explanations for these differences. Lastly, the energetics of emerging SARS-CoV-2 mutations were studied, showing that the affinity of the RBD for ACE2 is increased by N501Y and E484K mutations but is slightly decreased by K417N.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

405 nm light microbicidal efficacy on Treponema pallidum spiked in ex vivo human platelets

Abstract Pathogen reduction technologies using chemicals and or UV light have been demonstrated to improve the safety of ex vivo platelets from infectious diseases. However, UV light exposure also may affect the treated products, depending on wavelength and exposure. Alternatively, visible spectra 405 nm violet-blue light has broad-spectrum microbicidal activity. Here we tested the effect of 405 nm light onTreponema pallidum, the bacterium that causes syphilis. We contaminated platelets stored in plasma with two treponemal concentrations (low and high titers) and treated an aliquot with 270 J/cm 2 dose (irradiance = 15 mW/cm 2 ) of 405 nm light while another aliquot remained untreated. Next, we inoculated intradermally an aliquot of both samples into rabbits. Rabbits inoculated with untreated samples developed syphilis while animals inoculated with light-treated samples did not. Thus, inactivation was demonstrated to the limit of detection of the bioassay. We estimated > 2 log 10 and > 4 log 10 reduction in the low and high dose studies, respectively. These results provide proof-of-concept that 405 nm light is effective in reducing syphilis risk in ex vivo platelets.

Science & Technology - Other Topics↗
DOE OSTI2022

Ultra-high SERS detection of consumable coloring agents using plasmonic gold nanostars with high aspect-ratio spikes

Solution-based SERS detection by using a portable Raman instrument has emerged as an important tool due to its simplicity, and flexibility for rapid and on-site screening of analyte molecules. However, this method has several shortcomings, including poor sensitivity especially for weak-affinity analyte molecules, where there is no close contact between the plasmonic metal surface and analyte molecule. Examples of weak-affinity molecules include pigment molecules that are commonly used as a consumable coloring agent, such as allura red (AR), and sunset yellow (SY). As high consumption of colorant agents has been shown to cause adverse effects on human health, there is a strong need to develop a simple and practical sensing system with high sensitivity for these agents. Here we present a novel, highly sensitive solution-based SERS detection method for AR, and SY by using CTAC capped gold nanostars (GNS) having different aspect ratios (GNS-2, GNS-4, and GNS-5) without utilizing any aggregating agents which can enhance SERS signal however it reduces batch to batch reproducibility. The influence of the aspect ratio of GNS on SERS properties was investigated. We have achieved a limit of detection (LOD) of AR and SY as low as 0.5 and 1 ppb, respectively by using GNS-5 with the advantages of minimal sample preparation by just mixing the analyte solution into a well plate containing GNS solution. In addition, excellent colloidal stability and reproducibility have further enhanced the applicability in real-world samples. Altogether, our results evidence that the solution-based SERS detection platform using high aspect-ratio GNS can be applied for practical application to detect pigment molecules in real samples with satisfactory results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Previous exposure to Spike-providing parental strains confers neutralizing immunity to XBB lineage and other SARS-CoV-2 recombinants in the context of vaccination

The emergence of SARS-CoV-2 recombinants is of particular concern as they can result in a sudden increase in immune evasion due to antigenic shift. Recent recombinants XBB and XBB.1.5 have higher transmissibility than previous recombinants such as “Deltacron.” We hypothesized that immunity to a SARS-CoV-2 recombinant depends on prior exposure to its parental strains. To test this hypothesis, we examined whether Delta or Omicron (BA.1 or BA.2) immunity conferred through infection, vaccination, or breakthrough infection could neutralize Deltacron and XBB/XBB.1.5 recombinants. We found that Delta, BA.1, or BA.2 breakthrough infections provided better immune protection against Deltacron and its parental strains than did the vaccine booster. None of the sera were effective at neutralizing the XBB lineage or its parent BA.2.75.2, except for the sera from the BA.2 breakthrough group. These results support our hypothesis. In turn, our findings underscore the importance of multivalent vaccines that correspond to the antigenic profile of circulating variants of concern and of variant-specific diagnostics that may guide public health and individual decisions in response to emerging SARS-CoV-2 recombinants.

59 BASIC BIOLOGICAL SCIENCES↗