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181.
Effects of different sugars on pullulan production, UDP-glucose level, and activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glucosyltransferase in Aureobasidium pullulans Y68 were examined. It was found that more pullulan was produced when the yeast strain was grown in the medium containing glucose than when it was cultivated in the medium supplementing other sugars. Our results demonstrate that when more pullulan was synthesized, less UDP-glucose was left in the cells of A. pullulans Y68. However, it was observed that more pullulan was synthesized, the cells had higher activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glycosyltransferase. Therefore, high pullulan yield is related to high activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glucosyltransferase in A. pullulans Y68 grown on different sugars. A pathway of pullulan biosynthesis in A. pullulan Y68 was proposed based on the results of this study and those from other researchers. This study will be helpful to metabolism-engineer the yeast strain to further enhance pullulan yield. 相似文献
182.
Nucleobindin-1 (NUCB1) and nucleobindin-2 (NUCB2) are multifunctional proteins that interact with Ca(2+), nucleic acids and various regulatory proteins in different signaling pathways. So far, our understanding of the regulation of the biological functions of nucleobindins remains limited. In our proteome-wide selection for downstream caspase substrates, both NUCB1 and NUCB2 are found to be the downstream substrates of caspases. We report here the detailed analyses of the cleavage of nucleobindins by caspases. Significantly, the caspase cleavage sites are located exactly at one of the Ca(2+)-binding EF-hand motifs. Our results suggest that the functions of nucleobindins could be modulated by caspase-mediated cleavage in apoptosis. 相似文献
183.
ATP-induced Changes in Energy Status and Membrane Integrity of Harvested Litchi Fruit and its Relation to Pathogen Resistance 总被引:6,自引:0,他引:6
C. Yi H. X. Qu Y. M. Jiang J. Shi X. W. Duan D. C. Joyce Y. B. Li 《Journal of Phytopathology》2008,156(6):365-371
Litchi is a subtropical fruit of high commercial value on the international market but the fruit deteriorates rapidly after harvest due to rot development caused by Peronophythora litchii. To investigate the role of energy metabolism during disease development on harvested litchi fruit, fruits were dipped into solutions of either 0 or 1.0 mm adenosine triphosphate (ATP) for 3 min before being inoculated with Peronophythora litchii or not. Fruit were then stored for 6 days at 25°C and 90–100% relative humidity. Significant reductions in pericarp browning and disease severity and significant delays in membrane permeability and malondialdehyde (MDA) content were found in ATP‐treated and P. litchii‐inoculated fruit. Higher ATP concentrations and adenylate energy charge (EC) were observed in ATP‐treated fruit. In addition, lower activities of phospholipase D, acid phosphatase and lipoxygenase enzymes involved in membrane lipid peroxidation and hydrolysis were recorded in ATP‐treated fruit. Thus, treatment with ATP maintained higher energy levels, inhibited activities of the membrane hydrolysis‐related enzymes, reduced membrane lipid peroxidation and helped maintain membrane integrity of the harvested litchi fruit at the early stage of storage, which could account for the inhibition of disease development of P. litchii‐inoculated fruit. 相似文献
184.
Sun JB Duan JH Dai SL Ren J Guo L Jiang W Li Y 《Biotechnology and bioengineering》2008,101(6):1313-1320
Bacterial magnetosomes (BMs) are commonly used as vehicles for certain enzymes, nucleic acids and antibodies, although they have never been considered drug carriers. To evaluate the clinical potential of BMs extracted from Magnetospirillum gryphiswaldense in cancer therapy, doxorubicin (DOX) was loaded onto the purified BMs at a ratio of 0.87 +/- 0.08 mg/mg using glutaraldehyde. The DOX-coupled BMs (DBMs) and BMs exhibited uniform sizes and morphology evaluated by TEM. The diameters of DBMs and BMs obtained by AFM were 71.02 +/- 6.73 and 34.93 +/- 8.24 nm, respectively. The DBMs released DOX slowly into serum and maintained at least 80% stability following 48 h of incubation. In vitro cytotoxic tests showed that the DBMs were cytotoxic to HL60 and EMT-6 cells, manifested as inhibition of cell proliferation and suppression in c-myc expression, consistent with DOX. These observations depicted in vitro antitumor property of DBMs similar to DOX. The approach of coupling DOX to magnetosomes may have clinical potential in anti-tumor drug delivery. 相似文献
185.
Efficient production of biodiesel from high free fatty acid-containing waste oils using various carbohydrate-derived solid acid catalysts 总被引:3,自引:0,他引:3
In the present study, such carbohydrate-derived catalysts have been prepared from various carbohydrates such as d-glucose, sucrose, cellulose and starch. The catalytic and textural properties of the prepared catalysts have been investigated in detail and it was found that the starch-derived catalyst had the best catalytic performance. The carbohydrate-derived catalysts exhibited substantially higher catalytic activities for both esterification and transesterification compared to the two typical solid acid catalysts (sulphated zirconia and Niobic acid), and gave markedly enhanced yield of methyl esters in converting waste cooking oils containing 27.8wt% high free fatty acids (FFAs) to biodiesel. In addition, under the optimized reaction conditions, the starch-derived catalyst retained a remarkably high proportion (about 93%) of its original catalytic activity even after 50 cycles of successive re-use and thus displayed very excellent operational stability. Our results clearly indicate that the carbohydrate-derived catalysts, especially the starch-derived catalyst, are highly effective, recyclable, eco-friendly and promising solid acid catalysts that are highly suited to the production of biodiesel from waste oils containing high FFAs. 相似文献
186.
Ramarao MK Shen MW Murphy EA Duan W Zhao Y McKew J Lee KL Thakker P Behnke ML Clark JD 《Analytical biochemistry》2008,383(2):217-225
Cytosolic phospholipase A2 alpha (cPLA2α, type IVA phospholipase) acts at the membrane surface to release free arachidonic acid, which is metabolized into inflammatory mediators, including leukotrienes and prostaglandins. Thus, specific cPLA2α inhibitors are predicted to have antiinflammatory properties. However, a key criterion in the identification and development of such inhibitors is to distinguish between compounds that bind stoichiometrically to cPLA2α and nonspecific membrane perturbants. In the current study, we developed a method employing isothermal titration calorimetry (ITC) to characterize the binding of several distinct classes of cPLA2α inhibitors. Thermodynamic parameters and the binding constants were obtained following titration of the inhibitor to the protein at 30 °C and pH 7.4. The compounds tested bound cPLA2α with a 1:1 stoichiometry, and the dissociation constant Kd of the inhibitors calculated from the ITC experiments correlated well with the IC50 values obtained from enzymatic assays. Interestingly, binding was observed only in the presence of a micellar surface, even for soluble compounds. The site of binding of these inhibitors within cPLA2α was analyzed by testing for binding in the presence of methyl arachidonyl fluorophosphonate (MAFP), an irreversible active site inhibitor of cPLA2α. Lack of binding of inhibitors in the presence of MAFP suggested that the compounds tested bound specifically at or near the active site of the protein. Furthermore, the effect of various detergents on the binding of certain inhibitors to cPLA2α was also tested. The results are discussed with reference to thermodynamic parameters such as changes in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG). The data obtained from these studies provide not only structure-activity relationships for compounds but also important information regarding mechanism of binding. This is the first example of ITC used for studying inhibitors of enzymes with interfacial kinetics. 相似文献
187.
188.
A linear (1-->3)-alpha-D-glucan was isolated from the spores of Ganoderma lucidum (Fr.) Karst. Six different functionalized derivatives of the (1-->3)-alpha-D-glucan-aminopropylated, hydroxyethylated, sulfated, carboxymethylated, carboxymethylated and sulfated, and benzylamidated-carboxymethylated-with varying degrees of substitution were synthesized. The structural features and physicochemical properties of all derivatives were investigated by means of chemical and spectral analyses, and their effects on lymphocyte proliferation and antibody production were tested in vitro and in vivo. In general, the structural and physicochemical properties, and lymphocyte proliferation activity of all samples varied with the functionalized groups and the degree of substitution. The results of immunological assays indicated that some modified derivatives had potent stimulating effects on lymphocyte proliferation and antibody production and the introduction of carboxymethyl group with low degree of substitution (DS<0.28) was the best choice on the improvement of the immunostimulating activity. 相似文献
189.
J. Enjalbert X. Duan T. Giraud D. Vautrin C. De Vallavieille‐Pope M. Solignac 《Molecular ecology resources》2002,2(4):563-565
We report the characterization of 12 microsatellite markers in the biotrophic fungus Puccinia striiformis f.sp. tritici, responsible for yellow rust on wheat. An enrichment protocol was used to isolate microsatellite loci, and polymorphism was explored with 96 isolates from natural populations collected from several French and Chinese locations. Eight primers (67%) showed cross‐amplification when tested with eight isolates of P. triticina. 相似文献
190.
Xi Wang Bai-Ren Wang Xiao-Li Duan Ping Zhang Yu-Qiang Ding Yi Jia Xi-Ying Jiao Gong Ju 《The journal of histochemistry and cytochemistry》2002,50(12):1677-1684
One of the unsolved key questions in neuroimmunomodulation is how peripheral immune signals are transmitted to the brain. It has been reported that the vagus might play a role in this regard. The underlying mechanism for this immune system-to-brain communication route is related to the binding of cytokines, such as interleukin (IL)-1beta originating from activated immune cells, to their receptors in glomus cells of the vagal paraganglia. The existence of IL-1 receptor type I (IL-1RI) in vagal paraganglia has been proved. On the basis of these studies, a hypothesis is raised that the carotid body, as the largest paraganglion, might play a similar role to that of its abdominal partner. In this study we examined the distribution of IL-1RI in the carotid body by immunohistochemistry (IHC) and Western blotting techniques. The IHC results showed that almost all glomus cells in the carotid body displayed strong IL-1RI immunoreactivity. The IL-1RI-immunoreactive products were localized in the cytoplasm, nucleus, and cell membrane of the glomus cells. The Western blotting results also confirmed the existence of IL-1RI in both membranous and cytoplasmic elements of the carotid body. These results imply that the carotid body not only serves as a chemoreceptor for modulation of cardiorespiratory performance, as traditionally recognized, but also acts as a cytokine chemorereceptor for sensing immune signals. 相似文献