Gene site saturation mutagenesis (GSSM) technology is applied for the directed evolution of a nitrilase. The nitrilase effectively catalyzes the desymmetrization of the prochiral substrate 3-hydroxyglutaronitrile to afford (R)-4-cyano-3-hydroxybutyric acid, a precursor to the valuable cholesterol-lowering drug Lipitor. The discovered wild-type enzyme effectively performs the reaction at the industrially relevant 3 M substrate concentration but affords a product enantiomeric excess of only 87.6% ee. Through GSSM, a mutagenesis technique that effects the combinatorial saturation of each amino acid in the protein to each of the other 19 amino acids, combined with a novel high-throughput mass spectroscopy assay, a number of improved variants were identified, the best of which is the Ala190His mutant that yields product enantiomeric excess of 98.5% at 3 M substrate loading and a volumetric productivity of 619 g L-1 d-1.
The development of an efficient catalyst for formic acid electrocatalytic oxidation reaction (FAEOR) is of great significance to accelerate the commercial application of direct formic acid fuel cells (DFAFC). Herein, palladium phosphide (Pd x P y ) porous nanotubes (PNTs) with different phosphide content (i.e., Pd 3 P and Pd 5 P 2 ) are prepared by combining the self-template reduction method of dimethylglyoxime-Pd(II) complex nanorods and succedent phosphating treatment.During the reduction process, the self-removal of the template and the continual inside-outside Ostwald ripening phenomenon are responsible for the generation of the one-dimensional hollow and porous architecture. On the basis of the unique synthetic procedure and structural advantages, Pd 3 P PNTs with optimized phosphide content show outstanding electroactivity and stability for FAEOR. Importantly, the strong electronic effect between Pd and P promotes the direct pathway of FAEOR and inhibits the occurrence of the formic acid decomposition reaction, which effectively enhances the FAEOR electroactivity of Pd 3 P PNTs. In view of the facial synthesis, excellent electroactivity, high stability, and unordinary selectivity, Pd 3 P PNTs have the potential to be an efficient anode electrocatalyst for DFAFC.
Abscisic acid (ABA) glucose conjugation mediated by uridine diphosphate glucosyltransferases (UGTs) is an important pathway in regulating ABA homeostasis. In the present study, we investigated three tomato SlUGTs that are highly expressed in fruit during ripening, and these SlUGTs were localized to the cytoplasm and cell nucleus. Among these three UGTs, SlUGT75C1 catalyzes the glucosylation of both ABA and IAA in vitro; SlUGT76E1 can only catalyze the conjugation of ABA; and SlUGT73C4 cannot glycosylate either ABA or IAA. Therefore, SlUGT75C1 was selected for further investigation. SlUGT75C1 RNA interference significantly up-regulated the expression level of SlCYP707A2, which encodes an ABA 8'-hydroxylase but did not affect the expression of SlNCED1, which encodes a key enzyme in ABA biosynthesis. Suppression of SlUGT75C1 significantly accelerated fruit ripening by enhancing ABA levels and promoting the early release of ethylene. SlUGT75C1-RNAi altered the expression of fruit ripening genes (genes involved in ethylene release and cell wall catabolism). SlUGT75C1-RNAi seeds showed delayed germination and root growth compared with wild-type as well as increased sensitivity to exogenous ABA. SlUGT75C1-RNAi plants were also more resistant to drought stress. These results demonstrated that SlUGT75C1 plays a crucial role in ABA-mediated fruit ripening, seed germination, and drought responses in tomato.
The term remote sensing became common after 1962 and generally refers to nonintrusive Earth observation using electromagnetic waves from a platform some distance away from the object of the study. After more than five decades of development, humankind can now use different types of optical and microwave sensors to obtain large datasets with high precision and high resolution for the atmosphere, ocean, and land. The frequency of data acquisition ranges from once per month to once per minute, the spatial resolution ranges from kilometer to centimeter scales, and the electromagnetic spectrum covers wavebands ranging from visible light to microwave wavelengths. Technological progress in remote sensing sensors enables us to obtain data on the global scale, remarkably expanding humanity's understanding of its own living environment from spatial and temporal perspectives, and provides an increasing number of data resources for Digital Earth. This chapter introduces the developments and trends in remote sensing satellites around the world. Keywords Remote sensing • Digital Earth • Satellite • Earth observation 3.1 Development of Remote Sensing Remote sensing is a core technology for Earth observation. It covers information collection, in-orbit processing, information storage and transmission, ground reception, processing for applications, calibration, verification, applied research, and basic research, providing fundamental data resources for Digital Earth (Guo 2012).
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