Radioactive moiety

To confirm that the incorporated radioactive moiety was mono(ADP-ribose), the acid-insoluble fractions of SR vesicles incubated with labeled NAD in the presence and absence of poly L-lysine were treated with alkali and the respective supernatant was analyzed by reverse phase HPLC. In both cases, radioactive peaks co-eluted with authentic ADP-ribose and 5 AMP (data not shown). 

Application of [2- C]IAA to the cotyledon of etiolated 5-day-old broad been (Vicia faba L. cv Chukyo) seedlings resulted in accumulation of radioactive substances in the root primordia and in the stele of the basal part of the roots [24, 25]. Two metabolites being more polar than lAA-Asp accounted for 70-80% of total radioactivity in the root after 24-h treatment, and they were not extracted with ether in acid pH. After hydrolysis with 2 M HCl or 7 M NaOH, their radioactive moieties were extracted with ether, but they did not coincide with lAA. We purified the two substances from Vicia roots and identified them as 3-(0-)S-glucosyl)-2-indolone-3-acetylaspartic acid (Glc-DIA-Asp) and 3-hydroxy-2-indolone-3-acetylaspartic acid (DIA-Asp) [26, 27]. The DIA moiety is converted into 2-quinolone-4-carboxylic acid (QCA) by acid hydrolysis and the UV spectrum of QCA is quite different from that of DIA, which is in contrast with the conversion of OxIAA into l,2,3,4-tetrahydro-2-quinolone-4-carboxylic acid without accompanying large spectral change. 

Despite their extensive use, assays employing labeled analytes suffer from several disadvantages. First, analytes need to be conjugated to an enzyme, fluorophore or a radioactive moiety, which increases the cost of the assay. Second, assays that employ reporters typically require multiple washing and incubation steps and in most cases are end-point assays. Finally, in many instances, conjugation of reporters near the active site of the receptor can interfere with receptor-analyte binding. 

In contrast to the wealth of biogenetic speculation and model experimentation, none of which has direct bearing on actual biochemical events in the synthesis of /3-carbolines in their natural habitat, very few biosynthetic investigations have been carried out. As predicted, radioactivity from 2- C-tryptophan was incorporated into carbon atom-3 of the 1,2,3,4,4a,9a-hexahydro-)3-carboline moiety of ajmaUne and into carbon atom-3 of the jS-carbohnium segment... 

In the absence of phosphate or n-glucose-l-phosphate, the enzyme brings about a rapid equilibration between added radioactive free D-fruc-tose and the D-fructose moiety of sucrose.4 ... 

The downward systemic movement of ONCOL (structure given earlier), a new insecticide derived from carbofuran, has been observed (19). A significant amount of radioactivity was observed in the roots of cotton and bean plants treated topically at the base of bifoliate or trifoliated leaves with [carbamate carbonylONCOL. Downward movement of the radiolabeled material may be explained by hydrolytic degradation of the ethoxycarbonyl moiety in ONCOL to the carboxylic acid derivative, the acid function serving as a downward moving carrier. 

The major toxin, gonyautoxin-III was degraded to locate the radioactivity in the carbamoyl moiety. Thus gonyautoxin-III was converted to saxitoxin by treating with zinc and hydrochloric acid (8), which was then hydrolyzed with 6.7 N HCl to decarbamoylsaxitoxin and carbon dioxide (9). About one-third of the total activity (28%) was found to be associated with the released carbon dioxide and the rest with decarbamoylsaxitoxin (Scheme 2). The result seems to be in Scheme 2... 

A/-[3-(2-[ F]fluoropyridin-3-yloxy)-propyl]-2-bromoacetamide (p F]FPyBrA) was recently prepared by nucleophilic / eferoaromatic radiofluorination using a three-step radiochemical pathway and obtained in 20% overall non-decay-corrected yield in less than 85 min. In this reagent, the pyridinyl moiety carries the radioactive fluorine and the 2-bromoacetamide function ensures the alkylation of phosphorothioate monoester groups at the 3 - or 5 -end of a single-stranded oligonucleotide [18],... 

The radiosynthesis starts with the nucleophilic F-fluorination of 2-benzyloxy-4-formyl-A/,A/,A/-trimethylanilinium trifluoromethanesulfonate or 5-benzyloxy-2-nitrobenzaldehyde. Subsequent condensation with nitroethane yielded the corresponding 2-nitro-1-propanol derivatives. Reduction of the nitro moiety and deprotection provided the four stereoisomers of " F-labeled 2-amino-1-(4-fluoro-3-hydroxyphenyl)-1-propanol and 2-amino-1-(2-fluoro-5-hydroxyphe-nyl)-1-propanol, respectively. 4-p F]FMR was isolated from the 2-amino-1-(4-fluoro-3-hydroxyphenyl)-1-propanol stereoisomer mixture via semipreparative HPLC and additional chiral HPLC for enantiomeric resolution. In a similar manner enantiomeric pure 6-p F]FMR was obtained. From a synthetic point of view, 4-p F]FMR appeared to be the more promising candidate for PET investigations due to higher radiochemical yields. The main advantage of the nucleophilic approach over the electrophilic methods is the obtained high specific radioactivity (56-106 GBq/pmol) that is desired for safe use in humans with tracer doses far beyond the pharmacological level [173]. 

To make these substrates suitable for biological assays, the introduction of functional groups that can be traced with the proper analytical techniques is essential. The use of radio-, fluorescent-, and biotin-labeled lipidated peptides has been reported. The synthesis of fluorescent substrates is chemically straightforward and allows for production of larger quantities than the enzymatic synthesis used for radiolabeled peptides and is thus preferred over the use of radioactive compounds. [1 21] Common fluorescent probes can be introduced by conjugation to a free functional group present in the peptide. The fluorescent moiety is... 

The probe species is often radioactively labeled, or it may carry a fluorescent tag, or some other chemical or enzymatic moiety to generate a positional signal. For radioactive labeling, a common choice of radioisotope is phosphorus-32 (or 32P), because it can be incorporated as phosphate into DNA or RNA relatively easily, and it emits energetic beta particles that are easy to detect. The radioactivity on the membrane can be used to expose an adjacent x-ray film in a pattern corresponding to the radioactive spots on the membrane. After a suitable exposure time, one develops the film and studies the location and intensity of the images of the radioactive spots to deduce the position and degree of probe hybridization on the membrane. 

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