Microelectrophoresis and auxilary micromethods

In this retrospect of approximately 30 years of work with micromethods, some of them developed in our own laboratory, their principles and application to different separation problems are described, such as one- and two-dimensional microelectrophoresis in capillaries and microslab gels, isoelectric focusing in capillaries or microslab gels, microchromatography, microphotometry, and microfluorometry for qualitative and quantitative evaluation of separation patterns. In addition, some useful auxiliary methods are also described, e.g., a method for quantitative protein determination in a microliter volume when neither the volume nor the protein content in that volume are known, and methods for the determination of glycoproteins, amino acids, and sugars in the picomole range.

Amino acid transport across the human blood-CSF barrier. An evaluation graph for amino acid concentrations in cerebrospinal fluid

The correlation of cerebrospinal fluid (CSF)/serum concentration quotients was used as a method for identification of amino acids which are transported by a common carrier system across the blood-CSF barrier. Isoleucine, leucine, valine, phenylalanine, tyrosine and lysine were found to compete for the same carrier system. This group of amino acids in man was found to be different from the system described as a neutral amino acid carrier at the blood-brain barrier in rats. In man, methionine and tryptophan do not compete with the other neutral amino acids for the same carrier system. In contrast, lysine as a basic amino acid is found to be correlated with the same transport system as the five neutral amino acids. A graph for the evaluation of pathological amino acid concentrations in CSF is presented. Patients with a blood-CSF barrier dysfunction for proteins showed partly normal, partly increased, CSF/serum concentration quotients for the amino acids. Hydroxyproline could be identified as a constituent of the amino acid pool in CSF. For proline and hydroxyproline a special control system has to be suggested because of their smaller biological variance in CSF than in blood. Contrary to the other amino acids proline and hydroxyproline have a smaller biological variation in CSF than in serum.

In vitro experiments on the metabolism, uptake and release of 5-hydroxytryptamine in bovine retina

The accumulation, metabolism and potassium-induced release of 5-hydroxytryptamine (5-HT) in bovine retinae was studied. When isolated retina pieces were incubated at 37 degrees C in a medium containing [14C]5-HT, tissue:medium ratios of about 5 were obtained after only 10 min. Within this time the accumulated amine is hardly metabolized and even after a 60 min period, only approximately 12% of the amine is metabolized to form 5-hydroxyindoleacetic acid. The process responsible for this accumulation showed properties of an active transport system: it was temperature-sensitive, sodium-dependent and inhibited in particular by Lilly 110140, chlorimipramine and desimipramine. The uptake of [14C]5-HT was saturated with increasing 5-HT concentrations and could be accounted for by two saturable processes; a high-affinity system with a Km1 of 1.3 X 10(-7) M and Vmax1 of 0.65 pmol/mg/10 min, and a low affinity system with a Km2 of 1.2 X 10(-5) and Vmax2 of 29 pmol/mg/10 min. A rapid efflux of [14C]5-HT from tissue loaded with [14C]amine was observed when exposed to 70 mM KCl. This release was inhibited when the calcium content in the medium was replaced by sucrose. Cobalt ions added to the incubation medium also counteracted the effect of KCl, while chlorimipramine added to the medium enhanced the release of 5-HT caused by KCl. Bovine retinae also possess the enzymes necessary to produce 5-HT from tryptophan. These data generally support the idea that 5-HT is a transmitter in the retina, although as this study shows, the amine is present only in minute quantities.

[Purification by affinity chromatography and properties of the acetylcholinesterase of formosan cobra (Naja naja atra) venom (author's transl)]

The acetylcholinesterase was purified by CM-Sephadex chromatography and affinity chromatography on Sepharose bound m-[6-(6-aminocaproylamino)caproylamino]phenyltrimethylammonium bromide. The purified enzyme was obtained with a specific activity of 5470 U/mg (1160-fold purification) and a 89% yield. The molecular weight of the native enzyme was estimated to be 144,000. The enzyme is split into two subunits of approximately equal molecular weight (Mr 69,000) by SDS treatment. It is a glycoprotein and can be resolved by disc gel electrophoresis into seven and by isoelectric focusing into more than ten multiple forms. The N-terminal amino acid is serine.

Simultaneous quantitation of twenty-two amino acids in nanolitre samples of biological fluid

The technique of thin-layer chromatography and 14C-dansylation has been used for simultaneous measurements of 22 individual amino acids, taurine, serotonin, and gamma-aminobutyric acid in nanolitre samples of glomerular and renal tubule fluid. Standard curves of each amino acid mixture containing all the others showed excellent linearity at amounts ranging from 5.7.10(-13) to 1.45.10(-11) mole (regression coefficients all greater than 0.95). With careful standardization of dansylation conditions, the technique permits highly reproducible measurement of less than 1 pmole of an amino acid.