The chemical ionization mass spectrometric analysis of phenylthiohydantoin and 2-anilino-5-thiazolinone amino acids obtained from the Edman degradation of proteins and peptides

Using the ability of ammonia to form complexes with several compounds, we have developed a method for visualization and fixation of urease (EC 3.5.1.5) activity in polyacrylamide gels. In this method lead acetate was used alone or in combination with a pH-sensitive indicator to detect the enzyme activity. Results indicated a fairly linear relationship between the urease concentration (from 0.6 to 3.0 IU) and the amount of lead precipitate formed. Further, this method appears to be more sensitive than staining with pH indicator alone. It can also be effectively used to detect the enzyme activity in crude protein extracts. In addition, lead acetate-stained gels can be stored either wet or dry indefinitely with no visual loss in the activity profiles.