Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

The absorption of carbon dioxide in solutions of monoethanolamine

Infrared, thermogravimetric and analytical results are presented that establish that the ethanolamine salt of 2-hydroxyethylcarbamic acid is formed when carbon dioxide is absorbed in solutions of ethanolamine.     

Computable error bounds for pointwise derivatives of a Neumann problem

In this paper we discuss the recovery of derivatives and thecomputation of rigorous and useful upper bounds for the pointwiseerror in the recovered derivatives, for finite element approximationsof the Laplace equation with Neumann boundary conditions, especiallyat points close to or on a smooth, curved boundary. We analyzethe dipole image technique for the case of curved boundaries,and show how to compute reliable recovered derivatives and errorbounds even in the limiting case of points lying on the curvedboundary. Numerical experiments show reasonably tight errorbounds for points both close to and away from a curved boundary.     

A titrimetric method for the rapid determination of carbon in steel with an aqueous titrant

It is demonstrated that the addition of 5% of water to the non-aqueous solvent for the titrimetric determination of carbon in steel improves the performance of the titration. Modifications to the procedure are proposed which allow the normal titrant, tetra-n-butylammonium hydroxide dissolved in benzene-methanol, to be replaced by an aqueous solution of potassium hydroxide. The proposed procedure has been applied to the analysis of a wide range of standard steel samples.     

Coulometric titration of acids in isopropanol-II Electrode reactions with lithium chloride and tetraethylammonium bromide as supporting electrolytes

Cathodic reactions in methanol and isopropanol have been investigated in the presence of both lithium chloride and tetraethylammonium bromide as supporting electrolytes. A side-reaction in lithium chloride medium leads to the formation of insoluble lithium hydroxide but base is generated stoichiometrically in tetraethylammonium bromide by reduction of solvent, oxygen and traces of water. Tetraethylammonium bromide is recommended as supporting electrolyte for the coulometric titration of acids in isopropanol.     

Acoustic field positioning for containerless processing

The non-contact positioning of materials in a space processing chamber is accomplished using a new type of acoustic levitator. Liquid and solid materials are positioned using a single source of sound. Fine control of position may be obtained by motion of an acoustical reflector. The electrical power required is usually less than 100 watts. The system operates satisfactorily at high and low temperatures and is adaptable as an “add-on” feature to existing space experiments. Containerless melting and solidification can be performed and a freely suspended liquid can be shaped to the contour of the sound field. Experiments are described in which aluminium, glass and plastic materials are melted and solidified in the containerless state. The system has applications to containerless crystal growth, melting and related processes.