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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

β-Hydroxyacyl-acyl Carrier Protein Dehydratase (FabZ) from Francisella tularensis and Yersinia pestis : Structure Determination, Enzymatic Characterization, and Cross-Inhibition Studies

The bacterial system for fatty acid biosynthesis (FAS) contains several enzymes whose sequence and structure are highly conserved across a vast array of pathogens. This, coupled with their low homology and difference in organization compared to the equivalent system in humans, makes the FAS pathway an excellent target for antimicrobial drug development. To this end, we have cloned, expressed, and purified the β-hydroxyacyl-acyl carrier protein dehydratase (FabZ) from both Francisella tularensis (FtFabZ) and Yersinia pestis (YpFabZ). We also solved the crystal structures and performed an enzymatic characterization of both enzymes and several mutant forms of YpFabZ. Additionally, we have discovered two novel inhibitors of FabZ, mangostin and stictic acid, which show similar potencies against both YpFabZ and FtFabZ. Lastly, we selected several compounds from the literature that have been shown to be active against single homologues of FabZ and tested them against both YpFabZ and FtFabZ. These results have revealed clues as to which scaffolds are likely to lead to broad-spectrum antimicrobials targeted against FabZ as well as modifications to existing FabZ inhibitors that may improve potency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Water Promotion (or Inhibition) of Condensation Reactions Depends on Exposed Cerium Oxide Catalyst Facets

Nanoparticles with well-defined facets enable quantitative correlations between surface features and catalytic activity. In this work, we explore the role of geometric and acid–base properties in the mechanism of aldol condensation catalyzed by ceria nanoshapes. In the crucial C–C coupling step, the two carbonyl adsorbates are bound to two adjacent cations. On the CeO 2 (110) plane, all atoms lie on the same layer, favoring the interaction between adsorbates and facilitating the bimolecular C–C coupling. Thus, the initial unimolecular deprotonation is rate-limiting. In contrast, the (100) and (111) planes have an open structure with O on the top layer and Ce on the layer below. The former O layer interferes between adsorbates linked to Ce sites, making the C–C coupling rate-limiting. Water helps in overcoming this spatial hindrance by remote bond polarization via H-bonds. Therefore, water promotion is only observed on those planes for which the bimolecular step is rate-limiting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗