83 resultados para C. Grandis L. Osbeck

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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本论文研究了从圆斑蛙蛇泰国亚种(Daboia russellii siamensis)蛇毒中纯化的C型凝集素样蛋白Dabocetin和L氨基酸氧化酶DRS一AO的理化性质、生物学活性和分子克隆。Dabocetin是分子量约为28扔。的异二聚体蛋白,它由分子量约为15.0kDa和14.5kDa的两个同源亚基以和p共价结合形成。N-末端氨基酸序列比较显示,Dabocetin与目前已知的蛇毒c型凝集素样蛋白有很高的同源性。即使在终浓度达50.0。叫而时,Dabocetin也不能直接诱导血小板聚集。此外,在终浓度为40.00μg/ml,Dabocetin几乎不能抑制由AdP,TMVA和stejnulxin诱导的血小板聚集。但是,Dabocetin呈剂量依赖地抑制瑞斯托霉素诱导的血小板凝集,其半数抑制率ICS。值为10.80ug/ml流式细胞仪分析表明,Dabocetin显著抑制单克隆抗体522与GPIba的结合,提示Dabocetin很可能是一个GPIb结合蛋白。从圆斑蛙蛇的毒腺中克隆到了7个编码不同蛇毒C型凝集素样蛋白亚基的七DNA(命名为DRs一1至DRs一7)。其中,DRsLS编码Dabocetin的a亚基,DRS一6编码Dabocetin的p亚基。DRs一1和DRS一2很可能是圆斑蛙蛇毒腺中表达的X因子激活剂的两条轻链LCZ和LCI的山NA。DRS一3,DRS毛4和DRSL7可能是圆斑蛙蛇毒腺中表达的C型凝集素样蛋白p亚基的。NA。DRsLAO是一个新的L氨基酸氧化酶,比活力为1.98U加噶。十二烷基磺酸钠一聚丙烯酞氨凝胶电泳(SDs-PAGE)分析显示,该酶在还原和非还原条件下均呈现一条蛋白带,表观分子量约为58kDa。N-末端氨基酸序列比较显示,DRS一AO与目前已知的蛇毒L氨基酸氧化酶有很高的同源性。该酶的最适底物为L亮氨酸,最适pH为8.8。DRs一Ao呈剂量依赖地抑制扔P和仆IvA诱导的血小板聚集,其半数抑制率ICS。值分别为32.8μg/ml32.3μg/mlDRS-LAO对金黄色葡萄球菌(灯Cc25923)和耐甲氧西林金黄色葡萄球菌有较强的抗菌作用。DRs一AO对金黄色葡萄球菌必Tcc25923)的最低抑菌浓度卿C和最低杀菌浓度耐甲氧西林金黄色葡萄球菌的孤CS。和呱Cg。值分别为18.。林留时和36.0μg/mlDRSLAo对耐甲氧西林金黄色葡萄球菌的MBC50和MBCg。值分别为36.0μg/ml72.0μg/ml通过对DRS一AO的分子克隆,得到了编码DRS-AO的部分cDNA序列。

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由于2酮L古龙酸还原酶(简称KGR)的存在,理论上造成了Vc合成前体2酮L古龙酸(简称2KLG)部分被还原成L艾杜糖酸[1,2],影响了Vc二步发酵的产率。而从L山梨糖到2酮L古龙酸的转化中,除被KGR催化的还原负反应外,均属...

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采用重稀土离子(Dy、Ho、Er、Tm、Yb)研究了水溶液中L-精氨酸的构象。结果表明,距稀土配位中心4个或4个键以上的配体核的接触位移都很小,在稀土离子附近的配体核具有显著的接触位移。通过对配体磁性核结构因子的实验值进行模拟,建立了水溶液中L-精氨酸的整体构象。在L-精氨酸稀土配合物中,配体的羧基与稀土离子配位,配体的骨架结构位于稀土离子的零偶极位移锥面的外侧。对于羧基的双齿配位模式,计算得到的RE~(3+)-O键长为0.21nm。在溶液中配体以伸展状态存在,分子骨架呈全反式构象。

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在维生素 C 二步发酵中,第二步发酵为混菌发酵。氧化葡萄糖酸杆菌为产酸菌,巨大芽孢杆菌为伴生菌。巨大芽孢杆菌和氧化葡萄糖酸杆菌纯化培养的生物学特性不同于其在混菌培养中的生物学特性。种子液的组成和生物量影响 2-酮基-L古龙酸的合成。在发酵过程中,采采取适宜的调控措施有利于产酸。Na~+和 H~+可诱导对数生长期的巨大芽孢杆菌发生自溶,Na~+诱导的自溶作用可被 Ca~++抑制。200mM Na~+ 可抑制 2-酮基-L古龙酸的合成。H~+可抑制稳定期的巨大芽孢杆菌衰亡。本文建立了简便易行的巨大芽孢杆菌的筛选模型,并获得两株耐低 pH 和 2-酮基-L古龙酸的突变株 Bn 和 B5,与氧化葡萄糖酸杆菌混合培养,发酵转化率可分别提高 4.1%和 3.8%。Bn和 B5 生长的最适 pH 值为 6.0~8.0,可促进氧化葡萄糖酸杆菌的生长,表现为延迟期缩短,稳定期延长。苏云金芽孢杆菌 B529 作为伴生菌与氧化葡萄糖酸杆菌组成的新混合菌系,具有抗污染、稳定高产的特性。B529 和巨大芽孢杆菌释放的分子量在 30~50kDa 和 >100kDa 的组份均可促进氧化葡萄糖酸杆菌产酸,其中 30~50kDa 的组份是促进产酸的关键物质。二菌所释放的活性物质经 Sephadex G-150 柱层析呈现不同的洗脱图谱,说明二菌释放的活性物质成分可能不同。B529 的培养上清液可增强氧化葡萄糖酸杆菌的细胞酶活力和 L山梨糖胶氢酶的活性。新混全菌系的最适发酵条件被确定,在4M~3 发酵罐中连续被批发酵,平均糖酸转化率提高了 6.4%,发酵周期缩短 7.3h。

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维生素C步发酵混菌生产中,第一步由单菌发酵将D-山梨醇转化为L-山梨糖,第二步由产酸菌氧化葡萄糖酸杆菌与伴生菌巨大牙孢杆菌混菌发酵将L-山梨糖转化为2-酮基-L-古龙酸(维生素C前体物).利用离子注入技术,采用N<'+>离子束为诱变源,诱变维生素C步混菌发酵中的产酸菌氧化葡萄糖酸杆菌.通过建立的维生素C产菌筛选方法,以2-酮基-L龙酸为筛选标记,获得一株维生素C产菌株D14,其与生产用伴生菌巨大牙孢杆菌组成维生素C混合菌系ND14,平均醇酸转化率比生产用混菌提高3.3个百分点.维生素C产菌株D14及维生素C混合菌系ND14生长特性及发酵特性为:维生素C产菌株D14生长能力明显增强;维生素C混合菌系D14于种子培养基中稳定期延长8-12小时,总生物量增加;在发酵过程中ND14生长明显快于CK,菌体总生物量增加.利用均匀设计的方法对新混合菌系ND14发酵培养基进行了优化,其结果为:最适玉米浆浓度为1.6%、最适尿素浓度为1.6%、最适MgSO<,4>浓度为0.03%、最适KH<,2>PO<,4>浓度为0.06%.

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该文对维生素C二步发酵法”第二步混合发酵中伴生菌对产酸菌——氧化葡萄糖酸杆菌作用机制进行了研究.除巨大芽孢杆菌外,还选用另外几种芽孢杆菌及酵母菌作为产酸菌的伴生菌.各伴生菌及其胞外液对产酸菌生长和2-酮基-L-古龙酸合成能力均有刺激作用,表明产酸菌的伴生菌具有广谱性.利用膜超滤浓缩、柱层析及电泳等技术,从伴生菌B2980胞外液中分离纯化出达电泳均一纯的高纯度活性蛋白质样品,并对其部分基本特性进行分析.结果表明:该活性物质是分子量为36300道尔顿,等电点为4.75的酸性蛋白质,并且是由一个亚基构成的单体蛋白.活性蛋白质的结晶呈规则的菱形形状,其水溶液显著提高产酸菌中SDH酶活性.试验中依伴生菌胞外液对产酸菌中SDH酶活性的作用,建立了该研究中目标活性物质的快速检测方法.

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本文利用分批培养数据构建了维生素C步发酵过程的数学模型关对模型方程中参数进行了估算。首先用2-酮基-L古龙酸产生株 2980(G.oxydan s 8c B. megaterium)在2.6L控发酵罐上进行了维生素C批发酵实验,并确认该发酵属于发酵动力学分类的Gaden第II型。在此基础上,提出了有关菌体增长(x)、基质消耗(s)和产物形成(p)的模型方程。然后,分别利用拟线性化方法及辨识方法对其中的参数进行估算。结果表明,拟线性化的方法只适合于求取参数的初值,需要利用其它估计方法进一步调整参数;而通过系统辨识求得的参数使模型仿真数据和实验数据符合得经较理想,基本反映了发酵过程中x. s和p的变化特征。

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采用有机溶剂沉淀方法去除J26发酵液中杂蛋白,通过离子交换、活性炭吸附去除发酵液中杂质,最后蒸发浓缩获得无色透明结晶。通过对所获晶体的红外光谱分析、熔点测定、纸层析鉴定,证明所获晶体确为维生素C体2-酮基-L古龙酸(2-KGA)。

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对新分离得到的能产生维生素C体2-酮基-L-古龙酸(2-KGA)的优良菌株蛭弧菌J26,进行了一系列摇瓶发酵条件试验,通过添加一些其它有机碳源或其它氮源,可使蛭弧菌J26摇瓶发酵产生2-KGA由50-60mg/ml升到70mg/ml上,采用SMA探针技术的流加发酵摇瓶试验产生2-KGA可以达到83.9-91.7mg/ml本文还对发酵时种子液的接种量、发酵初始精浓度、初始pH值等对产酸的影响,进行了比较研究,对摇瓶发酵全过程的单一菌体形态特征进行了电子显微镜观察。

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The failure of hydraulic structures in many estuaries and coastal regions around the world has been attributed to sediment transport and local scour. The sediment incipience in homogenous turbulence generated by oscillating grid is studied in this paper. The turbulent flow is measured by particle tracer velocimetry (PTV) technique. The integral length scale and time scale of turbulence are obtained. The turbulent flow near the wall is measured by local optical magnification. The sediment incipience is described by static theory. The relationship of probability of sediment incipience and the turbulent kinetic energy were obtained experimentally and theoretically. The distribution of the turbulent kinetic energy near the wall is found to obey the power law and the turbulent energy is further identified as the dynamic mechanism of sediment incipience.

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A ground-experiment study on the motions of solid particles in liquid media with vertical temperature gradient is performed in this paper. The movement of solid spheres toward the heating end of a close cell is observed. The behavior and features of the motions examined are quite similar to thermocapillary migration of bubbles and drops in a liquid. The motion velocities of particles measured are about 10(-3) to 10(-4) mm\s. The velocity is compared with the velocity of particles floated in two liquid media. The physical mechanism of motion is explored.

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An experimental investigation will be performed on the thermocapillary motion of two bubbles in Chinese return-satellite. The experiment will study the migration process of bubble caused by thermocapillary effect in microgravity environment, and their interaction between two bubbles. The bubble is driven by the thermocapillary stress on the surface on account on the variation of the surface tension with temperature. The interaction between two bubbles becomes significant as the separation distance between them is reduced drastically so that the bubble interaction has to be considered. Recently, the problem has been discussed on the method of successive reflections, and accurate migration velocities of two arbitrarily oriented bubbles were derived for the limit of small Marangoni and Reynolds numbers. Numerical results for the migration of the two bubbles show that the interaction between two bubbles has significant influence on their thermocapillary migration velocities with a bubble approaching another. However, there is a lack of experimental validate for the theoretic results. Now the experimental facility is designed for experimenting time after time. A cone-shaped top cover is used to expel bubble from the cell after experiment. But, the cone-shaped top cover can cause temperature uniformity on horizontal plane in whole cell. Therefore, a metal board with multi-holes is fixed under the top cover. The board is able to let the temperature distribution on the board uniform because of their high heat conductivity, and the bubble can pass through it. In the system two bubbles are injected into the test cell respectively by two sets of cylinder. And the bubbles sizes are controlled by two sets of step-by-step motor. It is very important problem that bubble can be divorced from the injecting mouth in microgravity environment. Thus, other two sets of device for injecting mother liquid were used to push bubble. The working principle of injecting mother liquid is to utilize pressure difference directly between test cell and reservoir