Photosynthesis: Molecular biology and bioenergetics

Book Review

Photosynthesis: Molecular biology and bioenergeticsG.S. Singhal, J. Barber, R.A. Dilley, Govindjee, R. Haselkorn and P. Mohanty (Eds), Proceedings of the International Workshop on Application of Molecular Biology and Bioenergetics of Photosynthesis. Berlin, Heidelberg, New York, London, Paris, Tokyo, Hong Kong and Narosa: Springer-Verlag, 1989. xiv+441 pages. DM 148,00. ISBN 3-540-50451-6     

Plant protoplasts and genetic engineering II

Book Review

Plant protoplasts and genetic engineering IIY.P.S. Bajaj (Ed.), (Biotechnology in Agriculture and Forestry, Vol. 9). Berlin: Springer-Verlag, 1989. 510 pages. DM398.00. ISBN 3-540-50789-2     

Dye-promoted precipitation of serum proteins. Mechanism and application.

Immobilized dyes have been used primarily for purification of nucleotide dependent enzymes and proteins from plasma and other sources. Due to their low costs, high protein binding capacity and resistance to degradation dyes bear the potential as ligand for affinity separation of proteins on a large scale. In this paper dyes have been used for precipitation of proteins. Using albumin, prealbumin, alpha 1-acid glycoprotein and immunoglobulin G as model proteins we could demonstrate that dye-promoted precipitation depends on several factors which include the structure of the dye, the pH of the solution, the dye/protein molar ratio and the intrinsic properties of the proteins. It revealed that most of the dyes tested were endowed with the precipitating potential. The efficacy of precipitation was found to increase with the complexity of the dye structure. However, the amount of a dye required for total precipitation was found to be different for a given protein. Electrostatic as well as hydrophobic forces are involved in the mechanism of precipitation. It was demonstrated that by optimizing the conditions, mixtures of proteins can be resolved by dye-promoted precipitation. The high sensitivity of the reaction offers the possibility of using this method for rapid concentration of very diluted protein solutions.     

Enzyme sensor-FIA-system for on-line monitoring of glucose, lactate and glutamine in animal cell cultures.

Enzyme sensors for glucose, lactate and glutamine were connected via flow-injection analysis (FIA) devices to two different bioprocesses. They were used for on-line process control of perfused bioreactor systems containing mammalian cell lines producing a monoclonal antibody and recombinant interleukin-2. The biosensor system gives direct access to important process data which can be used as control parameters for long term cell cultivation systems.     

Mouse Chromosome 7

Chair of Committee for Mouse Chromosome 7     

Parthenogenetic stem cells in postnatal mouse chimeras.

The ability of parthenogenetic (pg) cells to contribute to proliferating stem cell populations of postnatal aggregation chimeras was investigated. Using DNA in situ analysis, pg participation was observed in highly regenerative epithelia of various regions of the gastrointestinal tract, e.g., stomach, duodenum and colon, in the epithelia of tongue and uterus and in the epidermis. Pg cells also contributed to the epithelium of the urinary bladder, which is characterized by a relatively slow cellular turnover. Using a sensitive proliferation marker to determine division rate of pg and normal (wt) cells in tissues of a 24-day-old chimera, no significant differences between pg and fertilized cells were observed. However, in colon and uterus of a pg <==> wt chimera aged 101 days, a significant loss of proliferative capacity of pg cells was found. In the colon, this loss of proliferative potential was accompanied by an altered morphology of pg crypts. In general, they were situated at the periphery of the epithelium and lacked access to the lumen, with consequent cystic enlargement and flattened epithelium. No obvious morphological changes were observed in the pg-derived areas of the uterine epithelium of this chimera. Our results provide evidence that pg cells can persist as proliferating stem cells in various tissues of early postnatal chimeras. They suggest that pg-derived stem cells may cease to proliferate in restricted areas of the gastrointestinal tract and in the uterine epithelium of pg <==> wt chimeras of advanced age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mediated amperometric determination of xylose and glucose with an immobilized aldose dehydrogenase electrode.

An enzyme electrode was constructed for amperometric determination of xylose and glucose. The electrode is based on the PQQ-dependent membrane-bound aldose dehydrogenase (ALDH) from Gluconobacter oxydans. ALDH was covalently immobilized on a graphite electrode. Immobilized dimethylferrocene, soluble ferrocene carboxylic acid and phenazine methosulphate were used as electron transfer mediators. When xylose was measured electrochemically using an electrode modified with ALDH and dimethylferrocene, the linear measurement range extended to 100 mM. For glucose measurement the linear measurement range was about one-tenth of that for xylose. The electrode showed fairly good stability; 50% of the original electrode response was still obtained after 5 days of intermittent use. The effect of possible leakage of adsorbed mediator was determined by measuring the response of an electrode with soluble mediator as a function of time. The reproducibility of the electrode was good, the standard deviation of the electrode response in ten measurements with the same electrode being only 2.7%.     

Tubulin structure and biochemistry.

In the past year, much has been learned about structure-function correlations in the tubulin molecule, and specifically about the nature and roles of post-translational modifications and tubulin isotypes. The interactions between tubulin and its ligands--both microtubule-associated proteins and anti-mitotic drugs--are becoming clearer at the molecular level.     

A quartz crystal biosensor for measurement in liquids.

The detection of anti-human immunodeficiency virus (HIV) antibodies by means of synthetic HIV peptide immobilized on a piezoelectric quartz sensor is demonstrated. The measurement set-up consists of an oscillator circuit, a suitably modified AT-cut thickness-shear-mode quartz crystal with gold electrodes, which is housed in a special reaction vessel, and a computer-controlled frequency counter for the registration of the measured frequency values. The quartz crystal is adapted for a steady operation in liquids at a frequency of 20 MHz. In phosphate-buffered saline solution the oscillator reaches a stability of about 0.5 Hz within a few seconds, of about 2 Hz within 10 min and about 30 Hz within 1 h. The frequency shift due to the adsorption of various proteins to the uncoated sensor surface has been investigated. It can be shown that a stable adsorptive binding of proteins to an oscillating gold surface is feasible and can be used for the immobilization of a receptor layer (e.g. HIV peptide). Specific binding of the anti-HIV monoclonal antibody to the HIV peptide immobilized on the quartz sensor is demonstrated. Control experiments show, however, additional unspecific binding. According to the experiments, the Sauerbrey formula gives a sufficiently accurate value for the decrease of the resonant frequency due to adsorption or binding of macromolecular proteins on the quartz crystal surface.