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21.
α淀粉酶广泛应用于粮食加工、食品、酿造、发酵、纺织品和医药工业[1].由于固定化酶的优点,国内外研究人员对固定化糖化酶[2,3]和固定化α淀粉酶[4]的制备及在淀粉酶法生产葡萄糖方面的应用作了大量的研究,显示了工业应用前景.然而,迄今为止,用磁性载体固定化α淀粉酶尚未见报道.我们用磁性聚乙二醇胶体粒子作载体,制备出具有磁响应性强、稳定性强、活力高的固定化α淀粉酶.由于具有磁响应性,可借助外部磁场方便简单地回收酶,为该酶工业化生产葡萄糖提供了一种新的途径.而且,由于磁性的优点,也为该酶在食品、医药、纺织… 相似文献
22.
以聚丙烯酰胺凝胶电泳方法测定了331例辽宁满族新生儿脐带血血红蛋白F中Gγ/Aγ比值。结果显示:高Gγ(>80%)者4例,占1.21%,其基因频率(f)为0.00604,低Gγ(30-48%)者6例,占1.81%,其基因频率为0.00906,其余正常,Gγ平均值为65.23±6.38%。未发现AγT链。对其中八例异常者(4例高Gγ值,4例低Gγ值)的染色体DNA进行了基因图谱分析,确定4例高Gγ值者基因型有两种:Gγ-Gγ/Gγ-Aγ二例,Gγ-AGγ-Aγ/Gγ-Aγ二例;4例低Gγ值者基因型有二种,分别为:Aγ-Aγ/Gγ-Aγ二例和-GAγ/Gγ-Aγ二例。其中Aγ-Aγ基因型在中国人群中未见报道过。 相似文献
23.
Qingxi Fu Naiyong Gao Jixu Yu Guozhao Ma Yifeng Du Fumin Wang Quanping Su Fengyuan Che 《Neurochemical research》2014,39(7):1313-1321
The aggregation and accumulation of amyloid-β (Aβ) plays a significant role in the pathogenesis of Alzheimer’s disease. Aβ is known to increase free radical production in neuronal cells, leading to oxidative stress and cell death. Diazoxide (DZ), a highly selective drug capable of opening mitochondrial ATP-sensitive potassium channels, has neuroprotective effects against neuronal cell death. However, the mechanism through which DZ protects cholinergic neurons against Aβ-induced oxidative injury is still unclear. The present study was designed to investigate the effects of DZ pretreatment against Aβ1–42 induced oxidative damage and cytotoxicity. Through measures of DZ effects on Aβ1–42 induced cellular damage, reactive oxygen species (ROS) and MDA generation and expressions of gp91phox and p47phox in cholinergic neurons, new insights into the neuroprotective mechanisms can be derived. Aβ1–42 significantly decreased 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide levels and increased ROS and MDA production; all effects were attenuated by pretreatment with DZ or diphenyleneiodonium chloride (a NOX2 inhibitor). Pretreatment with DZ also attenuated the upregulation of NOX2 subunits (gp91phox and p47phox) induced by Aβ1–42. Since NOX2 is one of the main sources of free radicals, these results suggest that DZ can counteract Aβ1–42 induced oxidative stress and associated cell death by reducing the level of ROS and MDA, in part, by alleviating NOX2 expression. 相似文献
24.
The effects of dissolved organic matter (DOM), water soluble organic matter derived from sewage sludge, on the sorption of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine) by soils were studied using a batch equilibrium technique. Six paddy soils, chosen so as to have different organic carbon contents, were experimented in this investigation. Atrazine sorption isotherms on soils were described by the linear equation, and the distribution coefficients without DOM (Kd) or with DOM (Kd*) were obtained. Generally, the values of Kd*/Kd initially insoil-solution system form. Critical concentrations of DOM (DOMnp) were obtained where the value of Kd* was equal to Kd. The presence of DOM with concentrations lower than DOMnp promoted atrazine sorption on soils (Kd* > Kd), whereas the presence of DOM with concentrations higher than DOMnp tended to inhibit atrazine sorption (Kd* < Kd). Interestingly, DOMnp for tested soils was negatively correlated to the soil organic carbon content, and the maximum of Kd*/Kd (i.e.Kmax) correlated positively with the maximum of DOM sorption on soil (Xmax). Further investigations showed that the presence of hydrophobic fraction of DOM evidently promoted the atrazine sorption on soils, whereas the presence of hydrophilic DOM fraction obviously tended to inhibit the atrazine sorption. Interactions of soil surfaces with DOM and its fractions were suggested to be the major processes determining atrazine sorption on soils. The results of this work provide a reference to the agricultural use of organic amendment such as sewage sludge for improving the availability of atrazine in soils. 相似文献
25.
Combinatorial signals of activin/nodal and bone morphogenic protein regulate the early lineage segregation of human embryonic stem cells 总被引:2,自引:0,他引:2
Wu Z Zhang W Chen G Cheng L Liao J Jia N Gao Y Dai H Yuan J Cheng L Xiao L 《The Journal of biological chemistry》2008,283(36):24991-25002
Cell fate commitment of pre-implantation blastocysts, to either the inner cell mass or trophoblast, is the first step in cell lineage segregation of the developing human embryo. However, the intercellular signals that control fate determination of these cells remain obscure. Human embryonic stem cells (hESCs) provide a unique model for studying human early embryonic development. We have previously shown that Activin/Nodal signaling contributes to maintaining pluripotency of hESCs, which are derivatives of the inner cell mass. Here we further demonstrate that the inhibition of Activin/Nodal signaling results in the loss of hESC pluripotency and trophoblast differentiation, similar to BMP4-induced trophoblast differentiation from hESCs. We also show that the trophoblast induction effect of BMP4 correlates with and depends on the inhibition of Activin/Nodal signaling. However, the activation of BMP signaling is still required for trophoblast differentiation when Activin/Nodal signaling is inhibited. These data reveal that the early lineage segregation of hESCs is determined by the combinatorial signals of Activin/Nodal and BMP. 相似文献
26.
水稻体细胞杂交研究进展 总被引:2,自引:0,他引:2
水稻是世界重要的粮食作物,全世界约有120个国家种植水稻。水稻的近缘或远缘种具有一些优良性状,如抗病、抗虫、抗逆等。将这些性状导入水稻,是科学家们所希望的,但因用普通杂交方法存在交配系统的不亲和性等难题而进展不大。随着组织培养技术的发展,特别是植物原生质体培养技术的日趋成熟,使得人类能够在细胞水平通过体细胞杂交方法实现遗传信息的重组。 相似文献
27.
cⅠ857基因的体外定位同义突变陈南春,高辉,陈苏民,杨萍,刘新平(西安第四军医大学分子生物学研究所,西安710032)外源基因要在大肠杆菌中获得高表达,需要合适的SD序列和可调控的强启动子[1]。PL启动子在原核启动子中属强启动子,它受cⅠ基因产物... 相似文献
28.
29.
Effects of Cadmium on Root Growth, Cell Division and Nucleoli in Root Tip Cells of Garlic 总被引:3,自引:0,他引:3
The effects of different concentrations (10−7 to 10−2 M) of cadmium chloride on root growth, cell division and nucleoli in root tip cells of Allium sativum L. were investigated. At lower concentrations of Cd2+ (10−7 to 10−6 M), Cd2+ did not influence the root growth, even had a stimulation effects during a short treatment. The results showed that the rate
of root growth per day at the treatment groups (10−4 to 10−2 M Cd2+) decreased with increasing duration of the treatment and increasing Cd2+ concentration. Cd2+ induced c-mitosis, anaphase bridges, chromosome stickiness and on nucleoli, causing some particles of similar silver-stained
material scattered in the nuclei and making the silver staining reaction at the periphery of the nucleolus weaker.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
30.
Nitric oxide production, nitric oxide synthase (NOS) and mitochondrial nitrite-reducing activities in roots, leaves and stems
of different developmental stages were investigated, using potted 3-year-old apple (Malus domestica Borkh.) trees. The arginine-dependent NOS activity is sensitive to NOS inhibitor L-NAME and aminoguanidine (AG), with L-NAME
being more effective than AG. Endogenous NO production, NOS and mitochondrial nitrite-reducing activities are predominately
presented in young leaves and especially in young white roots and young stems. Root and stem mitochondria can reduce nitrite
to nitric oxide at the expense of NADH, however, this mitochondrial nitrite-reducing activity is absent in leaves. 相似文献