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.     

Preparation and characterization of a silica gel-based substrate activated with a doubly attached chlorotriazine

It is shown that trichloro-1,3,5-triazine can be attached to aminated silica gel at two sites. This method of activating the silica gel for immobilization of analytical reagents is considered in relation to the typical single-site method of attachment. Diffuse-reflectance infrared and ultraviolet spectroscopic results are presented to confirm the nature of the attachment. 2,2′,4-Trihydroxyazobenzene is used as a model reagent to illustrate that better control of the immobilization reaction results from the second site of attachment of the triazine linkage to the substrate.     

Microelectronic array devices and techniques for electric field enhanced DNA hybridization in low-conductance buffers

A variety of electronic DNA array devices and techniques have been developed that allow electric field enhanced hybridization to be carried out under special low-conductance conditions. These devices include both planar microelectronic DNA array/chip devices as well as electronic microtiter plate-like devices. Such "active" electronic devices are able to provide controlled electric (electrophoretic) fields that serve as a driving force to move and concentrate nucleic acid molecules (DNA/RNA) to selected microlocation test-sites on the device. In addition to ionic strength, pH, temperature and other agents, the electric field provides another controllable parameter that can affect and enhance DNA hybridization. With regard to the planar microelectronic array devices, special low-conductance buffers were developed in order to maintain rapid transport of DNA molecules and to facilitate hybridization within the constrained low current and voltage ranges for this type of device. With regard to electronic microtiter plate type devices (which do not have the low current/voltage constraints), the use of mixed buffers (low conductance upper chamber/high conductance lower chamber) can be used in a unique fashion to create favorable hybridization conditions in a microzone within the test site location. Both types of devices allow DNA molecules to be rapidly and selectively hybridized at the array test sites under conditions where the DNA in the bulk solution can remain substantially denatured.