In the following, the first results on ultraviolet laser desorption (UVLD) of bioorganic compounds in the mass range above 10000 daltons are reported. Strong molecular ion signals were registered by use of an organic matrix with strong absorption at the wavelength used for controlled energy deposition and soft desorption (7)

Laser desorption ionization of proteins with molecular masses exceeding 10,000 daltons

DeJi~eitio, r Ge~e lrlt.~irm Much of tile attention and interest in modern molecular biology is fi~cussed on the regulation of gene expression. Factors influencing or mediating such regulation are often best studied using gene Alsions. Gene fusions can be defined its DNA constructions (perfi3rmed ill vitro or i~e Hvo) that result in the coding sequences from one gene (r@o,ter) being transcribed and/or translated under the direction of the controlling sequences of another gene (cmltrr Gene fusions can be of two general types, with many wtriatiuns within types. Transcriptional fusions are defined as fusions in which all protein coding sequences are derived from the reporter, with none from the cmm,//e~. Thus, although the m R N A produced may consist of sequences from both control/o and re/;o~ter, the protein synthesized will be encoded only by the reporter. Translational fusions, in contrast, are defined as those in which the polypeptide produced is the result of coding information provided by both copraoiler and reporter.

Assaying chimeric genes in plants: The GUS gene fusion system

First-generation glucose biosensors relied on the use of the natural oxygen cosubstrate and the production and detection of hydrogen peroxide and were much simpler, especially when miniaturized sensors are concerned. More sophisticated bioelectronic systems for enhancing the electrical response, based on patterned monolayer or multilayer assemblies and organized enzyme networks on solid electrodes, have been developed for contacting GOx with the electrode support. Electrochemical biosensors are well suited for satisfying the needs of personal (home) glucose testing, and the majority of personal blood glucose meters are based on disposable (screen-printed) enzyme electrode test strips, which are mass produced by the thick film (screen-printing) microfabrication technology. In the counter and an additional “baseline” working electrode, various membranes (mesh) are incorporated into the test strips along with surfactants, to provide a uniform sample coverage. Such devices offer considerable promise for obtaining the desired clinical information in a simpler, user-friendly, faster, and cheaper manner compared to traditional assays. Continuous ex-vivo monitoring of blood glucose was proposed in 1974 and the majority of glucose sensors used for in-vivo applications are based on the GOx-catalyzed oxidation of glucose by oxygen. The major factors that play a role in the development of clinically accurate in-vivo glucose sensors include issues related to biocompatibility, miniaturization, long-term stability of the enzyme and transducer, oxygen deficit, short stabilization times, in-vivo calibration, baseline drift, safety, and convenience.

Electrochemical Glucose Biosensors

The creation of core–shell particles is attracting a great deal of interest because of the diverse applicability of these colloidal particles; e.g., as building blocks for photonic crystals, in multi-enzyme biocatalysis, and in drug delivery. This review presents the state-of-the-art in strategies for engineering particle surfaces, such as the layer-by-layer deposition process (see Figure), which allows fine control over shell thickness and composition.

Nanoengineering of particle surfaces.

Application of conducting polymers to biosensors.

An enzyme electrode for the amperometric determination of glucose.

A urea-specific enzyme electrode.

Although soluble enzymes can be used as excellent reagents for the analysis of inorganic and organic compounds, they face a serious challenge when attempts are made to utilize them in complex matrices, like blood or crude water. Problems center about the effect of activators, inhibitors, other substrates, pH, and temperature on the soluble enzyme. However, upon immobilization most of these effects can be eliminated or minimized. For example, an enzyme with a narrow pH range of 4–6 can be transformed upon insolubilization to a more viable reagent with a broad pH range of 4–10. Also, following immobilization the enzymes are much more stable; they can be heated to 37, 40 or 50°C, with little loss of activity; and the activity persists after several thousand analysis are performed. However, the biggest advantage, analytically speaking, of immobilization, is that the insolubilized reagent becomes a much more selective reagent. No longer do many activators and inhibitors have an effect; only the most powerful can actually attack the enzyme.

Analytical Uses of Immobilized Enzymes

Practical fluorescence; theory, methods, and techniques,

The effect of fifteen different pesticides including carbamates, chlorinated hydrocarbons and organophosphurus compounds on cholinesterase from housefly, sugar boll weevll, fire ant and German cockroaches is reported. Since the cholinesterase from each source show different inhibition by various inhibitors, an increase in the specificity of enzyme systems for the determination of pesticides is possible.

George G. Guilbault

Papers

An enzyme electrode for the amperometric determination of glucose.

A urea-specific enzyme electrode.

Analytical Uses of Immobilized Enzymes

Practical fluorescence; theory, methods, and techniques,

Enzymatic methods of analysis