Keeping Plant Tissue Slices Attached to the Slide During Harsh Extraction of PoIysaccharide

During extraction of hemicellulose and noncellulose polysaccharides from plant histological slices of plants the morphological integrity of the slices may be disturbed if the reagents extracting hemicellulose and noncellulose polysaccharides are rinsed away by water. Removing the reagents by delicate suction rather than removing the glass tray from the staining dish, followed by desiccation and a rinse in 95% ethanol terminates the treatment without altering the morphology of the tissues.     

Colocalization of aldolase and FBPase in cytoplasm and nucleus of cardiomyocytes

The protein exchange method, immunocytochemistry and the nuclear import of fluorophore-labeled enzymes were used to investigate the colocalisation of aldolase and FBPase in cardiomyocytes. The results indicate in vivo interaction of these two enzymes. In the cardiomyocyte cytoplasm, these enzymes were found to colocalise at the Z-line and on intercalated discs. The translocation of both enzymes through the nuclear pores was also investigated. The immunocytochemistry revealed the colocalisation of aldolase and FBPase in the heterochromatin region of cardiomyocyte nuclei. The Pearson's correlation coefficients, which represent the degree of colocalisation were 0.47, 0.52 and 0.66 in the sarcomer, the intercalated disc and the nucleus, respectively. This is the first report on aldolase and FBPase colocalisation in cardiomyocytes. Interaction of aldolase with FBPase, which results in heterologous complex formation, is necessary for glyconeogenesis to proceed. Therefore, this metabolic pathway in the sarcomer, in the intercalated disc as well as in the nucleus might be expected.     

Influence of operational variables on properties of piroxicam pellets prepared by extrusion-spheronization: A technical note

Summary and Conclusion  The processing conditions has a pronounced effect on the pellet properties. Drying conditions influenced the mean size and the drug release of the pellets. Because of the shrinking of the pellets upon drying at higher temperatures, the pellets also showed increased densities. Freeze drying almost prevented shrinking and thus led to the highest drug release. With an increase in the temperature of drying, the drug release rate decreased. Both spheronization time and spheronization speed affected the shapes of pellets, and the changes in shapes then affected the pellet flow properties. Within the studied range, the circularity of the pellets was affected more by the spheronization time than by the spheronization speed. Drying conditions influenced pellet friability, which decreased with an increase in drying temperature, indicating the formation of more dense structures at higher temperatures. The same result was obtained with spheronization time. With an increase in spheronization time, the friability decreased, because of the formation of more compact masses at higher spheronization time. Mean size was not affected by spheronization time or spheronization speed. Published: March 9, 2007     

Formulation and optimization of porous osmotic pump-based controlled release system of oxybutynin

The aim of the current study was to design a porous osmotic pump-based drug delivery system for controlled release of oxybutynin. The porous osmotic pump contains pore-forming water-soluble additives in the coating membrane, which after coming in contact with water, dissolve, resulting in an in situ formation of a microporous structure. The dosage regimen of oxybutynin is one 5-mg tablet 2 to 3 times a day. The plasma half-life ranges from ∼2 to 3 hours. Hence, oxybutynin was chosen as a model drug with an aim to develop a controlled release system for a period of 24 hours. Linear and reproducible release similar to that of Ditropan XL was achieved for optimized formulation (f2>50) independent of hydrodynamic conditions. The effect of different formulation variables, namely, ratio of drug to osmogent, membrane weight gain, and level of pore former on the in vitro release was studied. Cellulose acetate (CA) was used as the semipermeable membrane. It was found that drug release rate increased with the amount of osmogent because of the increased water uptake, and hence increased driving force for drug release. Oxybutynin release was inversely proportional to the membrane weight gain; however, directly related to the level of pore former, sorbitol, in the membrane. This system was found to deliver oxybutynin at a zero-order rate for 20 hours. The effect of pH on drug release was also studied. The optimized formulations were subjected to stability studies as per International Conference on Harmonisation (ICH) guidelines and formulations were stable after a 3 month study. Published: July 13, 2007     

Architecture of the Cellulose Synthase Outer Membrane Channel and Its Association with the Periplasmic TPR Domain

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1株大熊猫肠道纤维素降解菌的分离鉴定及其酶学性质

以羧甲基纤维素钠为唯一碳源,利用刚果红染色法,从大熊猫粪便内筛选具有降解纤维素能力的菌株,并研究其酶学特性。分离获得1株酶活力较高的菌株A1,通过形态学和BD PhoenixTM-100全自动细菌鉴定仪鉴定为蜡样芽胞杆菌(Bacillus cereus)。菌株A1最适生长条件和酶活力测定表明,其最适生长温度为37℃,Na Cl浓度为0.5%,p H值为7.0,内切葡聚糖苷酶、外切葡聚糖苷酶、β-葡萄糖苷酶和总酶活的最大值分别为0.139、0.074、0.126、0.108 5 IU/m L。丰富了大熊猫肠道纤维素降解菌的种类,为后续研究大熊猫如何消化利用竹纤维提供了菌源。     

宿主遗传背景对重组酿酒酵母木糖共发酵影响的研究进展

木糖是纤维素原料水解液中最主要的五碳糖成分,由于野生的酿酒酵母缺乏有效的木糖利用途径,将外源木糖代谢途径整合至酿酒酵母中使其具有发酵木糖生产乙醇的能力是构建纤维素乙醇发酵菌株的关键。国内外学者的研究表明,同一木糖代谢途径导入不同酿酒酵母菌株中,所得到的重组菌发酵性能存在明显差异,表明宿主的遗传背景对菌株利用木糖能力和发酵性能具有重要的影响。就酿酒酵母宿主对重组菌株的木糖发酵性能的影响进行了综述,分析了产生宿主差异的内在机理,为进一步选育高效木糖共发酵菌种提供借鉴。     

One-step immobilization of antibodies for α-1-fetoprotein immunosensor based on dialdehyde cellulose/ionic liquid composite

A novel immunosensor for α-1-fetoprotein based on dialdehyde cellulose/ionic liquid composite film as a matrix has been developed. Microcrystalline cellulose was activated by sodium metaperiodate to produce dialdehyde cellulose. Antibodies can be immobilized on the electrode by a one-step method through covalent bonding of the aldehyde groups of dialdehyde cellulose with the amino groups of antibodies, in which no additional chemical cross-linking step is required. Moreover, ionic liquid added can improve the conductivity of the sensing interface and, therefore, can enhance the electrochemical signal. In this work, α-1-fetoprotein was detected within the range from 0.1 to 60 ng ml⁻¹ with a detection limit of 0.07 ng ml⁻¹ (signal/noise = 3). The proposed immunosensor had good specificity and reproducibility. It was used to determine real samples with satisfactory results.     

Combined Crystal Structure of a Type I Cohesin: MUTATION AND AFFINITY BINDING STUDIES REVEAL STRUCTURAL DETERMINANTS OF COHESIN-DOCKERIN SPECIFICITIES*

Cohesin-dockerin interactions orchestrate the assembly of one of nature''s most elaborate multienzyme complexes, the cellulosome. Cellulosomes are produced exclusively by anaerobic microbes and mediate highly efficient hydrolysis of plant structural polysaccharides, such as cellulose and hemicellulose. In the canonical model of cellulosome assembly, type I dockerin modules of the enzymes bind to reiterated type I cohesin modules of a primary scaffoldin. Each type I dockerin contains two highly conserved cohesin-binding sites, which confer quaternary flexibility to the multienzyme complex. The scaffoldin also bears a type II dockerin that anchors the entire complex to the cell surface by binding type II cohesins of anchoring scaffoldins. In Bacteroides cellulosolvens, however, the organization of the cohesin-dockerin types is reversed, whereby type II cohesin-dockerin pairs integrate the enzymes into the primary scaffoldin, and type I modules mediate cellulosome attachment to an anchoring scaffoldin. Here, we report the crystal structure of a type I cohesin from B. cellulosolvens anchoring scaffoldin ScaB to 1.84-Å resolution. The structure resembles other type I cohesins, and the putative dockerin-binding site, centered at β-strands 3, 5, and 6, is likely to be conserved in other B. cellulosolvens type I cohesins. Combined computational modeling, mutagenesis, and affinity-based binding studies revealed similar hydrogen-bonding networks between putative Ser/Asp recognition residues in the dockerin at positions 11/12 and 45/46, suggesting that a dual-binding mode is not exclusive to the integration of enzymes into primary cellulosomes but can also characterize polycellulosome assembly and cell-surface attachment. This general approach may provide valuable structural information of the cohesin-dockerin interface, in lieu of a definitive crystal structure.