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211.
Andrei Ogonkov Cora L. Dieterich Dr. Roy A. Meoded Prof. Jörn Piel Dr. Amy E. Fraley Prof. Severin Sasso 《Chembiochem : a European journal of chemical biology》2023,24(18):e202300209
Type I fatty acid synthases (FASs) are known from higher eukaryotes and fungi. We report the discovery of FasT, a rare type I FAS from the cyanobacterium Chlorogloea sp. CCALA695. FasT possesses an unusual off-loading domain, which was heterologously expressed in E. coli and found to act as an α-oxoamine synthase (AOS) in vitro. Similar to serine palmitoyltransferases from sphingolipid biosynthesis, the AOS off-loading domain catalyzes a decarboxylative Claisen condensation between l -serine and a fatty acyl thioester. While the AOS domain was strictly specific for l -serine, thioesters with saturated fatty acyl chains of six carbon atoms and longer were tolerated, with the highest activity observed for stearoyl−coenzyme A (C18). Our findings suggest a novel route to α-amino ketones via the direct condensation of iteratively produced long-chain fatty acids with l -serine by a FAS with a cis-acting AOS off-loading domain. 相似文献
212.
Teresa Liberto Maria Chiara Dalconi Gregorio Dal Sasso Maurizio Bellotto Agathe Robisson 《Journal of the American Ceramic Society》2023,106(9):5187-5202
Understanding the mechanisms controlling the early (fresh) and long-term (hardened) hydration of one-part alkali-activated slags (AAS) is key to extend their use as low CO2 substitutes for ordinary Portland cement (OPC). Their “just add water” use makes them easier and less hazardous to manipulate than the more studied two-part ones. This is due to the absence of liquid alkaline activators, which are environmentally and energy demanding. In this work, numerous experimental techniques have been linked to obtain a comprehensive physico-chemical characterization of a one-part AAS activated with Na2CO3 and Ca(OH)2 powders at several water to solid ratios (w/s). Calorimetry and pH/conductivity measurements describe the functioning of the activators immediately after contact with water. Early reactivity is characterized through in situ X-ray powder diffraction (XRPD) and small amplitude oscillatory shear (SAOS) rheology, which reveal a rapid precipitation of nanometric hydration products (nano-C-A-S-H), which results in a continuous increase in the paste cohesivity until setting. Moreover, SAOS shows that rejuvenating the paste by means of shearing (performed externally to the rheometer in this study) is enough to restore the initial cohesion (i.e., workability) for long time spans until setting occurs. The long-term hydration is characterized by ex situ XRPD on aged AAS pastes, in parallel with mechanical testing on AAS mortar. A correlation can be observed between the amount of nano-C-A-S-H and the increase in compressive strength. Overall, this formulation shows satisfactory fresh and solid properties, demonstrating suitability for low- and normal-strength applications. 相似文献