L Scale (l + scale)

Distribution by Scientific Domains

Selected Abstracts

Large-scale expression and thermodynamic characterization of a glutamate receptor agonist-binding domain

FEBS JOURNAL, Issue 13 2000
Dean R. Madden
The ionotropic glutamate receptors (GluR) are the primary mediators of excitatory synaptic transmission in the brain. GluR agonist binding has been localized to an extracellular domain whose core is homologous to the bacterial periplasmic binding proteins (PBP). We have established routine, baculovirus-mediated expression of a complete ligand-binding domain construct at the 10-L scale, yielding 10,40 milligrams of purified protein. This construct contains peptides that lie outside the PBP-homologous core and that connect the domain core to the transmembrane domains of the channel and to the N-terminal ,X'-domain. These linker peptides have been implicated in modulating channel physiology. Such extended constructs have proven difficult to express in bacteria, but the protein described here is stable and monomeric. Isothermal titration calorimetry reveals that glutamate binding to the domain involves a substantial heat capacity change and that at physiological temperatures, the reaction is both entropically and enthalpically favorable. [source]

Mesomixing in semi-batch reaction crystallization and influence of reactor size

AICHE JOURNAL, Issue 12 2004
Marika Torbacke
Abstract Experiments on semibatch reaction crystallization of benzoic acid are reported, in which hydrochloric acid was fed into an agitated solution of sodium benzoate. The influence of mixing and the influence of reactor size are examined on the product crystal mean size. The product mean size increases with increasing stirring rate and with decreasing feed rate. At low feed rates, the mean size increases at decreasing feed pipe diameter. At high feed rates the influence of the feed pipe diameter is more complex. Micromixing is of some importance in most experiments, but the rate of mesomixing especially governs the process. Mesomixing seems to be adequately described by the inertial-convective disintegration mechanism. In many aspects experimental results cannot be described by the turbulent-dispersion mechanism. The product mean size does not exhibit a clear dependence on reactor size, but depends more strongly on other parameters. Results from experiments from 1 L scale to 200 L scale can be correlated fairly well against a dimensionless number defined as the ratio of the total time of reactant feeding to the time constant of mixing. The best representation of the mixing time constant is obtained by making it directly proportional to the ratio of the feed pipe diameter and the linear velocity of the bulk flow passing the feed pipe. The proportionality constant can be calculated from turbulence data over the bulk flow at the feed point. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3107,3119, 2004 [source]

Electrochemical Deodorization and Disinfection of Hog Manure

Dorin Bejan
Abstract Electrolysis of liquid hog manure under direct current achieved amelioration of odour, in terms of both odour quality and odour intensity, and simultaneously reduced the population of odour-causing bacteria by two orders of magnitude. A comparison of anode materials indicated that hydroxyl radical-forming anodes (boron-doped diamond and Ebonex) were the most effective, but unfortunately these materials are not yet available commercially in large size format. Dimensionally stable anodes composed of Ti/IrO2 were found to be satisfactory; lead-based anodes leached unacceptable quantities of inorganic lead into the treated manure, and graphite anodes tended to disintegrate on long-term use. The mechanism of action of the bactericidal effect involves a combination of toxicity by O2 that is released at the anode and hypochlorination due to the chloride ion that is present in manure. The proposed technology was shown to be successful at the 27 L scale in an on-farm demonstration. L'électrolyse du purin de porc liquide avec un courant continu a permis d'améliorer l'odeur, tant en qualité qu'en intensité, et simultanément, de réduire la population de bactéries à l'origine de l'odeur de deux ordres de grandeur. Une comparaison des matériaux anodiques indique que les anodes formant des radicaux libres d'hydroxyle (diamant amélioré au bore et Ebonex) sont les plus efficaces, mais malheureusement ces matériaux ne sont pas encore disponibles en grand quantité dans le commerce. On a trouvé que des anodes dimensionnellement stables composées de Ti/IrO2 étaient satisfaisantes, tandis que les anodes à base de plomb ont donné des quantités inacceptables de plomb lixivié non organique dans le purin traité et les anodes graphites tendent à se désintégrer avec une utilisation prolongée. Le mécanisme d'action de l'effet bactéricide implique une combinaison de toxicité par l'O2 qui est libéré à l'anode et par l'hypochloruration à cause de l'ion de chlorure présent dans le purin. On montre que la technologie proposée est un succès dans une démonstration à l'échelle de 27 L dans une ferme [source]

Development of a system for the on-line measurement of carbon dioxide production in microbioreactors: Application to aerobic batch cultivations of Candida utilis

Michiel van Leeuwen
Abstract We developed and applied a conductometric method for the quantitative online measurement of the carbon dioxide (CO2) production during batch cultivations of Candida utilis on a 100-,L scale. The applied method for the CO2 measurement consisted of absorption of the produced CO2 from the exhaust gas of the microbioreactor in an alkali solution, of which the conductivity was measured on-line. The measured conductivity change of the alkali solution showed a linear relation with the total amount of CO2 absorbed. After calibration of the CO2 measurement system, it was connected to a well of a 96-well microtiter plate. The mixing in the well was achieved by a magnetic stirrer. Using online measurement of the CO2 production during the cultivation, we show reproducible exponential batch growth of C. utilis on a 100-,L scale. The CO2 production measurements obtained from the microcultivation were compared with the CO2 production measurement in a 4-L bioreactor equipped with a conventional off-gas analyzer. The measurements showed that on-line measurement of the CO2 production rate in microbioreactors can provide essential data for quantitative physiological studies and provide better understanding of microscale cultivations. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]