Isotop ically labelled

Preparation and characterization of the isotop-ically labelled hydrocarbons were described in two papers a third described a method for deter-... 

R 515 S.K. Straus, Recent Developments in Solid-State Magic-Angle Spinning, Nuclear Magnetic Resonance of Fully and Significantly Isotop-ically Labelled Peptides and Proteins , Philos.T.Roy.Soc. B, 2004,359, 997... 

The elucidation of the steps in the common part of the pathway from carbohydrate precursors to the formation of chorismate remains a classic example of the combined use of auxotrophic mutants, isotop-ically labelled precursors and finally enzyme studies to define a metabolic sequence. An auxotrophic mutant of an organism is a nutritional mutant. The genetic change in such mutant strains causes an inability to carry out one of the reactions in a biosynthetic pathway leading to one or more essential metabolites. Analysis of the sequence of steps in the biosynthetic pathway is facilitated by the fact that each mutant may accumulate in its culture fiuid the substrate for the enzymic reaction which is blocked and may utilise later members of the sequence to replace the required metabolites Davis S produced auxotrophic mutants of Escherichia coli, Aerobacter aerogenes. Bacillus subtilis and Salmonella typhitnurium by ultra-violet irradiation of a bacterial culture in a minimal medium of salts plus D-glucose. Selection of the mutant strains was dependent on the use of the observation that penicillin kills bacterial cells only... 

Since its introduction some 20 years ago, MALDI-MS has been established as a standard technique for a large variety of applications within the field of bioanalyt-ical mass spectrometry, ranging from protein identification to enzyme activity screening. Quantitative analysis has long been a challenge, but, with the use of isotopically labelled standards, it is steadily obtaining more attention. 

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