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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The first crystal structure of a xylobiose-bound xylobiohydrolase with high functional specificity from the bacterial glycoside hydrolase family 30, subfamily 10

Xylobiose is a prebiotic sugar that has applications in functional foods. This report describes the first X-ray crystallographic structure models of apo and xylobiose-bound forms of a xylobiohydrolase (XBH) from Acetivibrio clariflavus. This xylan-active enzyme, a member of the recently described glycoside hydrolase family 30 (GH30), subfamily 10, phylogenetic clade has been shown to strictly release xylobiose as its primary hydrolysis product. Inspection of the apo structure reveals a glycone region X-2-binding slot. When X-2 binds, the non-reducing xylose in the -2 subsite is highly coordinated with numerous hydrogen bond contacts while contacts in the -1 subsite mostly reflect interactions typical for GH30 and enzymes in clan A of the carbohydrate-active enzymes database (CAZy). This structure provides an explanation for the high functional specificity of this new bacterial GH30 XBH subfamily.

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

Crystal Structure of an i‐Motif from the HRAS Oncogene Promoter

Abstract An i‐motif is a non‐canonical DNA structure implicated in gene regulation and linked to cancers. The C‐rich strand of the HRAS oncogene, 5′‐CG CCC GTG CCC TGCG CCC GCAA CCC GA‐3′ (herein referred to as iHRAS), forms an i‐motif in vitro but its exact structure was unknown. HRAS is a member of the RAS proto‐oncogene family. About 19 % of US cancer patients carry mutations in RAS genes. We solved the structure of iHRAS at 1.77 Å resolution. The structure reveals that iHRAS folds into a double hairpin. The two double hairpins associate in an antiparallel fashion, forming an i‐motif dimer capped by two loops on each end and linked by a connecting region. Six C−C + base pairs form each i‐motif core, and the core regions are extended by a G−G base pair and a cytosine stacking. Extensive canonical and non‐canonical base pairing and stacking stabilizes the connecting region and loops. The iHRAS structure is the first atomic resolution structure of an i‐motif from a human oncogene. This structure sheds light on i‐motifs folding and function in the cell.

Li, Kevin S.↗
DOE OSTI2023

Crystal Structure of an i‐Motif from the HRAS Oncogene Promoter

Abstract An i‐motif is a non‐canonical DNA structure implicated in gene regulation and linked to cancers. The C‐rich strand of the HRAS oncogene, 5′‐CG CCC GTG CCC TGCG CCC GCAA CCC GA‐3′ (herein referred to as iHRAS), forms an i‐motif in vitro but its exact structure was unknown. HRAS is a member of the RAS proto‐oncogene family. About 19 % of US cancer patients carry mutations in RAS genes. We solved the structure of iHRAS at 1.77 Å resolution. The structure reveals that iHRAS folds into a double hairpin. The two double hairpins associate in an antiparallel fashion, forming an i‐motif dimer capped by two loops on each end and linked by a connecting region. Six C−C + base pairs form each i‐motif core, and the core regions are extended by a G−G base pair and a cytosine stacking. Extensive canonical and non‐canonical base pairing and stacking stabilizes the connecting region and loops. The iHRAS structure is the first atomic resolution structure of an i‐motif from a human oncogene. This structure sheds light on i‐motifs folding and function in the cell.

Li, Kevin S.↗
DOE OSTI2022

Synthesis, Crystal Structure, and Physical Properties of BaSnS 2

Phase-pure BaSnS 2 , with space group P2 1 /c, is synthesized, and the structural and physical properties are investigated. We report thermal properties and optical measurements are reported for the first time. The Debye temperature and Sommerfeld coefficient are obtained from temperature-dependent heat capacity measurements, the latter indicating that BaSnS 2 is an electrical insulator. A direct bandgap of 2.4 eV is obtained from diffuse reflectance and photoluminescence spectroscopy. The findings herein lay the foundation for understanding the physical properties of this material and are part of a continuing effort to investigate previously unexplored ternary chalcogenides.

semiconductors↗