Arginine radioactive

Our first attempt was the feeding of commercially available [guanido-l C]-L-arginine to the cultures of Gonyaulax tamarensis (Ipswich strain). The toxin fraction was isolated and further fractionated to the pure toxins (7). Figure 1 shows an example of the elution pattern of the toxins from a Bio-Rex 70 column. A good correlation between the toxicity and radioactivity was observed. 

Heath, T. G. Mooney, J. P. Broersma, R. 1997. Narrow-bore liquid chromatography-tandem mass spectrometry with simultaneous radioactivity monitoring for partially characterizing the biliary metabolites of an arginine fluoroalkyl ketone analog of D-MePhe-Pro-Arg, a potent thrombin inhibitor. J. Chromatgr. B Biomed. Sci. Appl., 688,281-289. 

The influence of three factors, namely pH, enzyme concentration and amino acid concentration, on the esterification of tRNA arginyl-tRNA synthetase is to be studied by counting the radioactivity of the final product, using 14C-labelled arginine. The higher is the count, the better are the conditions. 

Figure 2. Chromatography of preparations of ficin on CM-cellulose as performed in several laboratories. A (31) B (30) C (55). Solid line denotes protein as measured by absorbance at 280 nm. Dotted line denotes activity on benzoyl-mu-arginine-p-nitroanilide in A, casein in B, and radioactivity of C-14 carboxymethyl group in C.

NO has a short half-life (2-30 s) and therefore the direct measurement of NO production is impractical. In aqueous solutions, however, it rapidly reacts with oxygen to form the stable water-soluble metabolites nitrite and nitrate (Figure 1). The concentration of these ions, which can be measured via a variety of methods, is used as a measure of the tissue content of NO and/or the synthesis of NO by cultured cells (Hevel and Marietta, 1994 Archer, 1993). An alternative method used to quantify NOS activity is to directly measure the catalytic activity of a cell or tissue extract (i.e., the conversion of radioactive arginine to citrulline Hevel and Marietta, 1994 Archer, 1993). While both methods are sensitive measurements of the overall capacity of a cell or tissue extract to synthesize NO, neither one provides a true kinetic... 

Figure 6. Time course of the distribution of in amino adds extracted from A. cylindrica when fixation of [ N]N2 for 15 s was followed by evacuation of the label and then continued fixation of N e/CO (99 1, v/v) for 45, 105, and 285 s (12. The radioactivity of amino adds in methanolic extracts, subjected to electrophoresis, was quantitated by integration of peaks in radioscans, with corrections applied for decay (%) glutamine, (O) glutamate (plus a small fraction of aspartate after 45 s of chase), (A) dtrulline, (Wk) arginine and (D) an unknown substance that migrated between arginine and alanine.

When A. cylindrica was incubated for 120 s in the presence of and ImM azaserine, incorporation of into glutamate was inhibited over 98%, while formation of [ N]glutamine was reduced only 10% (13). radioactivity was not detected in a separate aspartate, citrulline, or arginine peak, when A. cylindrica was incubated with in the... 

Values are means ( standard deviation of the mean) of four experiments and were determined by integration and time correction of peaks of radioactivity from 13N in radioscans after electrophoresis at pH 9.2, in comparison with 13N02 or radioactivity added as determined by scintillation spectroscopy. Asp, i)ar-tate Glu, glutamate Gin, glutamine Cit, citrulline Ala, alanine Arg, arginine. 

Putrescine accumulation has been investigated in some detail and studies with radioactive precursors (see e.g.. Smith and Richards, 1%2 Smith, 1965) have established that it is synthesized from arginine (see Fig. 1). The mechanism underlying putrescine accumulation is uncertain although two of the biosynthetic enzymes, arginine decarboxylase, and iV-carbamyl pqtres-cine amidohydrolase exhibit two- to fourfold increases under conditions of K deficiency (Smith, 1%5). No increase was found to occur in the activity of agmatine iminohydrolase (Smith, 1969). 

Citrullinemia is a human disease caused by a deficiency of liver arginino-succinate synthetase. It is inherited as an autosomal recessive. A fibroblast cell line from the skin of an infant with citrullinemia could not ultilize citrulline (instead of arginine) in the medium, while control normal fibroblast could (Tedesco and Mellman, 1967). For mutational studies, it may be possible either to use selective medium in which arginine is replaced with citrulline or to apply radioactive citrulline in an autoradiographic assay. 

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