Electron cryomicroscopy methods.

Electron cryomicroscopy methods comprise a rapidly expanding field providing insights into the structure and function of biological macromolecules and their supramolecular assemblies. The 3.8 A resolution structure of the membrane protein aquaporin, a view of the herpesvirus capsid at 8.5 A and the 10 A resolution structure of the spliceosomal U1 small nuclear ribonucleoprotein complex are three outstanding examples emphasizing the versatility of this technique.     

New gene transfer methods.

The intentional introduction of recombinant DNA molecules into a living organism can be achieved in many ways. Viruses have been making a living by practicing gene transfer for millennia. Recently, man has gotten into the act. The paradigm employed is fairly straightforward. First, a way must be found to move genetic information across biological membrane barriers. Then, presumably, DNA repair mechanisms do the rest. The array of methods available to move DNA into the nucleus provides the flexibility necessary to transfer genes into cells as physically diverse as sperm and eggs. Some of the more promising alternative strategies such as sperm-mediated gene transfer, restriction enzyme-mediated integration, metaphase II transgenesis, and a new twist on retrovirus-mediated gene transfer will be discussed, among other methods.     

Advanced methods for bioreactor characterization.

Bioreactors are characterized by the transport capacities they provide to optimally supply the microorganisms during production process. The transport is performed by flows induced in their cultivation media. In order to understand the extremely complex mixing, mass and heat transfer phenomena encountered, and to perceive their influences on bioreactor performance, sophisticated measuring techniques are required. This review compiles the developments currently in progress to surmount today's shortage of reliable measuring techniques. Measuring techniques are distinguished which can be used on different scales and their application spectra are illustrated by recently obtained results. Several new measuring techniques, which can be employed to resolve the flow structures, are discussed in detail. Only those techniques are considered which can be used to advantage during real cultivations in industrial-scale reactors.     

Specificity controls for immunocytochemical methods.

Immunocytochemistry is used for antibody localization of proteins in cells and tissues. The specificity of the results depends on two independent criteria: the specificity of the antibody and of the method used. The antibody specificity is best determined by immunoblot and or immunoprecipitation. Absorption of the antibody with a protein does not determine that the antibody would have bound to the same protein in the tissue, and therefore is not a good control for antibody specificity. The specificity of the method is best determined by both a negative control, replacing the primary antibody with serum, and a positive control, using the antibody with cells known to contain the protein. With the increasing use of immunocytochemistry, it is important to be aware of the appropriate controls needed to show specificity of the labeling. (J Histochem Cytochem 48:163-165, 2000)