Fed-batch cultivation of recombinant escherichia coli JM103 and production of the fusion protein SPA::EcoRI in a 60-L working volume airlift tower loop reactor

SPA::EcoRI fusion protein was produced by Escherichia coli JM103 carrying the multicopy expression plasmid pMTC48, the multicopy repressor plasmid pRK248, and the multicopy protection plasmid pEcoR4 in a 60-L working volume airlift tower loop reactor on M9 minimal medium with glucose. Cell mass concentration, total cell count, number of colony-forming units, specific growth rate, yield coefficient, and metabolite (acetate, pyruvate, succinate, lactate, ethanol) concentrations were monitored during the growth phase and gene expression. Gene expression was induced by temperature shift or chemically by isopropyl-thiogalactosidase in the airlift tower loop reactor (ALTR) at constant cultivation time and in a small stirred tank reactor at different cultivation times. During induction, the cultivation medium was supplemented with concentrated Luria-Bertani (LB) medium. The intracellular enzyme activity was evaluated as a function of the time after the start of the induction. It was found that the reduction of the glucose concentration and increase of the dissolved oxygen concentration reduced the acetate produced and increased the intracellular enzyme activity. (c) 1993 John Wiley & Sons, Inc.     

盐酸胍诱导的α淀粉酶去折叠与再折叠

利用蛋白质内源荧光和酶活性两种信号以及荧光偏振,HPLC和停流等方法研究了盐酸胍诱导的α淀粉酶去折叠与重折叠的平衡转变和动力学。实验结果表明α淀粉酶去折叠与重折叠是两个不同的过程;变性与复性过程中可能伴有聚集体生成;去折叠与重折叠均为双相过程,重折叠大约始于2秒之后。     

五种高山藏医药用植物茎叶的结构特征研究

通过对青藏高原东北部３８００ｍ至５１００ｍ处生长的五种高山藏医药用植物茎叶的解剖观察发现,这些植物的叶表皮单层,气孔不下陷,但叶肉中的栅栏细胞多层,有的叶表面密被表皮毛、角质膜厚,茎叶中普遍形成发达的通气组织。这些特征是高寒地区空气稀薄、气温低、日照辐射强等外界条件长期作用的结果。     

猫纹状皮层神经元整合野亚区结构和亚区间的空间总合特性

用正弦调制的光栅图形研究了猫纹状皮层神经元传统感受野外区域(整合野)的亚区结构,整合野不同亚区的作用可表现为抑制或易化。根据端区和侧区的作用性质,整合野有4种不同的结构形式。在端区和侧区的内部以及在这两个区域之间,空间总合显示非线性特性。其非线性程度随刺激面积的增加而变大,表明在整合野的亚区内和亚区间存在着相互抑制。     

A NEW SPECIES OF GENUS HABROPHLEBIODES ULMER (EPHEMEROPTERA: LEPTOPHLEBIIDAE)

Abstract  The present paper deals with a new species Habrophlebiodes zijinensis sp. nov. collected in Nanjing, Jiangsu Povince, China.     

Uptake by central nervous tissues as a mechanism for the regulation of extracellular adenosine concentrations

The various facets of the uptake of adenosine by central nervous tissues are described. The uptake process includes the transport of nucleoside across neuronal and glial plasma membranes and its metabolism within the cell. Much of the transported adenosine is phosphorylated into adenosine nucleotides. Inhibitors of adenosine uptake increase extracellular levels of adenosine and can thus potentiate its pharmacological actions. This may be an important component in the actions of various groups of psychoactive drugs.     

The shape of myosin subfragment-1. A equivalent oblate ellipsoid model based on hydrodynamic properties

The molecular weights of the two heads of myosin subfragment-1, S-1(A1) and S-1(A2), based on sedimentation equilibrium are 120 000 and 110 000. Hydrodynamically, the two heads are indistinguishable, with intrinsic viscosity, [eta], of 0.064-0.065 dL/g and sedimentation coefficient, s(0)20,w, of 5.8 S.Together with the rotational correlation time taken from the literature (235 ns), all three hydrodynamic properties can be better fitted with an equivalent oblate ellipsoid of revolution than a prolate model. The width of the equatorial axis of the ellipsoid is about 135 A (the axial ratio is about 6). Probably, the S-1(A1) and S-1(A2) molecules have a half-doughnutlike or a flattened pearlike shape rather than an elongated one.