Isolation and characterization of photosystem II from the filamentous sporophyte of Porphyra yezoensis

Thylakoid membranes were isolated and purified from diploid filamentous sporophytes of Porphyra yezoensis Ueda using sucrose density gradient ultracentrifugation (SDGUC). After thylakoid membranes were solubilized with SDS, the phtosystem II (PSII) particles with high 2, 6-dichloroindophenol (DCIP) photoreduction activity were isolated by SDGUC. The absorption and fluorescence spectra, DCIP photoreduction activity and oxygen evolution activity of the thylakoid membranes and PSII particles were determined. The polypeptide composition of purified PSII particles was distinguished by SDS-PAGE. Results showed that PSII particles of sporophytes differed from the gametophytes in spectral properties and polypeptide composition. Apart from 55 kDa D1-D2 heterodimer, CP47, CP43, 33 kDa protein, D1, D2, cyt b559 and 12 kDa protein were identified from PSII particles from sporophytes; a new 102 kDa protein was also detected. However, cyt c-550, 20 kDa, 14 kDa and 16 kDa proteins found in PSII particles from gametophytes were not detected in the sporophytes.     

Cloning and functional characterization of an O-acetylserine(thiol)lyase-encoding gene in wild soybean (Glycine soja)

The terminal step of soybean cysteine synthesis is catalyzed by O-acetylserine(thiol)lyase (OAS-TL, EC 2.5.1.47). In this study, we isolated and characterized an OAS-TL gene from a wild soybean material (designated as GsOAS-TL1). GsOAS-TL1 cDNA sequence showed strict conservation at both nucleotide and amino acid levels compared with that from cultivated soybean. Genomic structure analysis of GsOAS-TL1 indicated that it contained 10 exons and 9 introns in the coding region with conserved exon sizes and intron locations compared with Arabidopsis thaliana OAS-TL-like genes. Among the complete GsOAS-TL1 cDNA and three part-deletion fragments, only expression of the full-length cDNA could rescue the NK3 cys⁻ Escherichia coli auxotroph, which was coherent with the assayed enzyme activity of purified fusion proteins. For RT-PCR analysis in different wild soybean tissues, GsOAS-TL1 showed lower expression in roots and developing seeds, whereas total OAS-TL activity of corresponding tissues showed significantly higher level in seeds than other tissues. To our knowledge, this is the first report on cloning and characterization of an OAS-TL gene from wild soybean. Our results are informative to further elucidate the function and evolution of OAS-TL in soybean.     

Molecular and kinetic characterization of two UDP-glucose pyrophosphorylases, products of distinct genes, from Arabidopsis

UDP-glucose pyrophosphorylase (UGPase) is an important enzyme in the production (and conversions) of UDP-glucose, a key precursor for carbohydrate biosynthesis. cDNAs corresponding to two UGPase isozymes in Arabidopsis were overexpressed in Escherichia coli and, subsequently, the recombinant proteins were purified and characterized. Both proteins were highly conserved, sharing 93% identity. Based on crystal structure-derived images, the main amino acid differences mapped to N- and C-termini domains, but not to central active site region. The two proteins existed mainly as monomers, and they had similar molecular masses of ca. 53 kDa. However, comparison of molecular masses of UGPases from Arabidopsis root and leaf extracts revealed that the root protein was slightly larger, suggesting a post-translational modification. Specific activity of the purified UGPase-1 was ca. 10-30% lower than that of UGPase-2, depending on direction of the reaction, whereas its K(m) values with all substrates in both directions of the reaction were consistently ca. twice lower than those of UGPase-2 (0.03-0.14 mM vs. 0.07-0.36 mM, respectively). Both proteins were "true" UGPases, and had no activity with ADP-glucose/ATP or galactose-1-P. Equilibrium constant for both proteins was ca. 0.3, suggesting preference for the pyrophosphorolysis direction of the reaction. The data are discussed with respect to potential roles of UGPase in carbohydrate synthesis/metabolism in Arabidopsis.     

NT-3 Expression in Spared DRG and the Associated Spinal Laminae as well as Its Anterograde Transport in Sensory Neurons Following Removal of Adjacent DRG in Cats

Neurotrophin-3 plays an important role in survival and differentiation of sensory and sympathetic neurons, sprouting of neurites, synaptic reorganization, and axonal growth. The present study evaluated changes in expression of NT-3 in the spinal cord and L6 dorsal root ganglion (DRG), after ganglionectomy of adjacent dorsal roots in cats. NT-3 immunoreactivity increased at 3 days post-operation (dpo), but decreased at 10 dpo in spinal lamina II after ganglionectomy of L1–L5 and L7–S2 (leaving L6 DRG intact). Conversely, NT-3 immunoreactivity decreased on 3 dpo, but increased on 10 dpo in the nucleus dorsalis. Very little NT-3 mRNA signal was detected in the spinal cord, despite the changes in NT-3 expression. The above changes may be related to changes in NT-3 expression in the DRG. Ganglionectomy of L1–L5 and L7–S2 resulted in increase in NT-3 immunoreactivity and mRNA in small and medium-sized neurons, but decreased expression in large neurons of L6 DRG at 3 dpo. It is possible that increased NT-3 in spinal lamina II is derived from anterograde transport from small- and medium-sized neurons of L6 DRG, whereas decreased NT-3 immunoreactivity in the nucleus dorsalis is due to decreased transport of NT-3 from large neurons in the DRG at this time. This notion is supported by observations on NT-3 distribution in the dorsal root of L6 after ligation of the nerve root. The above results indicate that DRG may be a source of neurotrophic factors such as NT-3 to the spinal cord, and may contribute to plasticity in the spinal cord after injury.     

Kinetic study of corn straw pyrolysis: comparison of two different three-pseudocomponent models

With heating rates of 20, 50 and 100 K min(-1), the thermal decomposition of corn straw samples (corn stalks skins, corn stalks cores, corn bracts and corn leaves) were studied using thermogravimetric analysis. The maximum pyrolysis rates increased with the heating rate increasing and the temperature at the peak pyrolysis rate also increased. Assuming the addition of three independent parallel reactions, corresponding to three pseudocomponents linked to the hemicellulose, cellulose and lignin, two different three-pseudocomponent models were used to simulate the corn straw pyrolysis. Model parameters of pyrolysis were given. It was found that the three-pseudocomponent model with n-order kinetics was more accurate than the model with first-order kinetics at most cases. It showed that the model with n-order kinetics was more accurate to describe the pyrolysis of the hemicellulose.     

Combustion characteristics of different parts of corn straw and NO formation in a fixed bed

Experiments with five samples of corn straw were carried out on a one-dimensional bench combustion test rig. The bed temperature distribution and the mass loss of fuel and gas components such as O2, CO, CO2 and NO were measured in the bed. The combustion of corn straw occurred in two stages, ignition front propagation and char oxidation. The average burning rate increased with an increase in the primary air flow until a critical point was reached, beyond which a further increase in the primary air flow resulted in a decreased burning rate. The mean concentration of NO reached a minimum value and then increased with increased primary air flow. The time taken for the drying front to reach the bottom of the bed was 800 s, 700 s, and 500 s; the temperatures in the high bed temperature zones were 900-935 degrees C, 800-850 degrees C and 700-743 degrees C; and the maximum concentrations of NO were 725 ppmv, 1287 ppmv, and 2730 ppmv, for whole corn stalks, hollow corn stalks and flaked corn stalks, respectively. The maximum concentrations of CO and NO were quite different between samples. There was only one peak in the distribution of NO concentration for sample B, but there were two peaks for whole corn stalks and sample A.     

Application of anaerobic ammonium-oxidizing consortium to achieve completely autotrophic ammonium and sulfate removal

The simultaneous ammonium and sulfate removal was detected in an anammox reactor, consisted of ammonium oxidization with sulfate deoxidization, and subsequently traditional anammox process, in via of middle medium nitrite with solid sulfur and N2 as the terminal products. The pure anammox bacteria offered a great biotechnological potential for the completely autotrophic reaction indicated by batch tests. Denaturing gradient gel electrophoresis (DGGE) analysis further revealed that a new organism belonging to Planctomycetales was strongly enriched in the defined niche: the redox of ammonium and sulfate. The new species "Anammoxoglobussulfate" was so considered as holding a critical role in the ammonium oxidization with sulfate deoxidization to nitrite. Afterwards, the Planctomyces existing in the bacteria community performed the anammox process together to achieve the complete nitrogen and sulfate removal. The potential use of sulfate as electron acceptor for ammonium oxidizing widens the usage of anammox bacteria.     

Substituted dipiperidine alcohols as potent CCR2 antagonists

The synthesis and biological evaluation of a series of substituted dipiperidine alcohols are described. Structure-activity relationship studies led to the discovery of potent CCR2 antagonists displaying IC(50) values in the nanomolar or subnanomolar range. The cinnamoyl compounds had higher binding affinities than the corresponding urea analogs.     

膜脂组成与植物抗冷性的关系及其分子生物学研究进展

植物的抗冷性与膜脂的组分和结构密切相关,与质膜中脂肪酸的不饱和度关系更为密切。膜脂不饱和脂肪酸含量越高,膜脂相变温度越低,植物的抗冷性提高。植物体内存在一些降低膜脂脂肪酸饱和程度的酶,如甘油3磷酸酰基转移酶,ω3脂肪酸去饱和酶等,它们能够催化膜中脂肪酸的去饱和反应,生成不饱和脂肪酸,从而提高植物的抗冷性。本文就低温对膜脂的影响、膜脂组成与植物抗寒性的关系及其分子生物学研究进展作一简单综述。