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921.
This study describes acid-catalyzed production of 3,6-anhydro-D-galactose (D-AnG) from κ-carrageenan, a sulfated polysaccharide with an alternating backbone consisting of D-AnG and D-galactose (D-Gal). We analyzed four hydrolysis products (D-AnG, 5-hydroxymethylfurfural (HMF), levulinic acid (LA), and D-Gal) and reducing sugar contents during acid hydrolysis. Acid screening was carried out using seven acid catalysts which have different acidity. The catalysts showing high D-AnG production and high selectivity were chosen for subsequent experiments. We selected four acid catalysts (HCOOH, CH3COOH, HNO3, and HCl), and studied the effects of catalyst acidity, hydrolysis temperature T, and reaction time t on the production of D-AnG and other hydrolysis products. The optimal condition for maximum production of D-AnG by κ-carrageenan hydrolysis was T = 100°C and t = 30 min using 0.2 M HCl. Under this condition, 2.81 g/L D-AnG (33.5% of theoretical maximum) could be obtained from 2% (w/v) κ-carrageenan. In general, the maximum values of D-AnG, D-Gal, and the sum of two by-products (HMF and LA) increased with the acidity of catalysts. However, HNO3 was an exception in that the maximum production levels of HMF and LA were unusually low compared with other acid catalysts. D-AnG was successfully purified from acid hydrolysates using silica gel chromatography and the product was nearly 100% pure. This effective D-AnG production could facilitate future studies on the conversion of D-AnG to biofuels and biochemicals. 相似文献
922.
Kyeoung Rok Kim Young Hoon Song Jeong Hyun Seo Dong Gyun Kang Chang Sup Kim 《Biotechnology and Bioprocess Engineering》2016,21(4):502-507
Specific whole cell activity strongly affects sensitivity and detection limit of whole cell-based biosensors. Previously, we developed recombinant Escherichia coli coexpressing periplasmic organophosphorus hydrolase (OPH) and cytosolic chaperone GroEL-GroES (GroEL/ES). In present work, we investigated the effect of culture conditions on whole cell OPH activity. Especially, the whole cell OPH activity was significantly affected by the concentration of tetracycline that is an inducer for chaperone GroEL/ES. When cultured at 20°C for 31 h in M9 medium containing 1 mM IPTG, 50 ng/mL tetracycline, and 500 µM CoCl2, the recombinant E. coli exhibited a specific whole cell OPH activity (U/OD600) of ~0.55, which is 2.6-fold higher than that of recombinant E. coli cultured as previously described conditions. In addition, recombinant cells showed adequate storage stability for 1 week with 100% of original response. Finally, the improved activity and adequate stability in the whole cell biocatalyst will contribute to sensitivity, detection time, and stability of a whole cell-based biosensor for the detection of toxic organophosphates. 相似文献
923.
Helicobacter pylori Activates IL‐6‐STAT3 Signaling in Human Gastric Cancer Cells: Potential Roles for Reactive Oxygen Species
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924.
James C. Campbell Jeong Joo Kim Kevin Y. Li Gilbert Y. Huang Albert S. Reger Shinya Matsuda Banumathi Sankaran Todd M. Link Keizo Yuasa John E. Ladbury Darren E. Casteel Choel Kim 《The Journal of biological chemistry》2016,291(11):5623-5633
Membrane-bound cGMP-dependent protein kinase (PKG) II is a key regulator of bone growth, renin secretion, and memory formation. Despite its crucial physiological roles, little is known about its cyclic nucleotide selectivity mechanism due to a lack of structural information. Here, we find that the C-terminal cyclic nucleotide binding (CNB-B) domain of PKG II binds cGMP with higher affinity and selectivity when compared with its N-terminal CNB (CNB-A) domain. To understand the structural basis of cGMP selectivity, we solved co-crystal structures of the CNB domains with cyclic nucleotides. Our structures combined with mutagenesis demonstrate that the guanine-specific contacts at Asp-412 and Arg-415 of the αC-helix of CNB-B are crucial for cGMP selectivity and activation of PKG II. Structural comparison with the cGMP selective CNB domains of human PKG I and Plasmodium falciparum PKG (PfPKG) shows different contacts with the guanine moiety, revealing a unique cGMP selectivity mechanism for PKG II. 相似文献
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Junghwa Chang Ho Jeong Kwon 《Journal of industrial microbiology & biotechnology》2016,43(2-3):221-231
Natural products are valuable resources that provide a variety of bioactive compounds and natural pharmacophores in modern drug discovery. Discovery of biologically active natural products and unraveling their target proteins to understand their mode of action have always been critical hurdles for their development into clinical drugs. For effective discovery and development of bioactive natural products into novel therapeutic drugs, comprehensive screening and identification of target proteins are indispensable. In this review, a systematic approach to understanding the mode of action of natural products isolated using phenotypic screening involving chemical proteomics-based target identification is introduced. This review highlights three natural products recently discovered via phenotypic screening, namely glucopiericidin A, ecumicin, and terpestacin, as representative case studies to revisit the pivotal role of natural products as powerful tools in discovering the novel functions and druggability of targets in biological systems and pathological diseases of interest. 相似文献
930.
Hyun Min Kim Jeong Hwan Lee Ah-Young Kim Se Hee Park Sang Hoon Ma Sanghyeob Lee Young Hee Joung 《Molecular breeding : new strategies in plant improvement》2016,36(6):71
Flowering time in members of the Solanaceae plant family, such as pepper (Capsicum spp.) and tomato (Solanum lycopersicum), is an important agronomic trait for controlling shoot architecture and improving yield. To investigate the feasibility of flowering time regulation in tomato, an RNA-binding protein (RBP) encoding gene homologous to human Nucleolar protein interacting with the forkhead-associated (FHA) domain of pKI-67 (NIFK), CaRBP, was isolated from hot pepper. The function of CaRBP was determined in transgenic tomato. The deduced amino acid sequence includes an RNA recognition motif (RRM) and showed most similarity to the RRM present in a putative RBP encoded by human NIFK. CaRBP was highly expressed in the vegetative and reproductive tissues, such as leaves and fruits, respectively. Subcellular localization analysis indicated that CaRBP is a nucleolar protein. Heterologous expression of CaRBP under 35S promoter in tomato plants induced severe alteration of flowering with additional defects of vegetative organs. This floral retardation was associated with the alteration of SFT/SP3D and SlSOC1s as floral integrators. Furthermore, CaRBP reduces the expression levels of SlCOLs/TCOLs via changes in the expression of SlCDF3, SlFBHs, and SlFKF1s. This indicates a repressive effect of CaRBP on the regulation of flowering time in tomato. Overall, these results suggest that alteration in CaRBP expression levels may provide an effective means of controlling flowering time in day-neutral Solanaceae. 相似文献