PREPARATION OF LABELED MOLECULES BY EXCHANGE WITH O-18 WATER

This chapter discusses the synthesis of 18O-labeled molecules to equilibrium exchange reactions with H2180. Several functional groups containing oxygen have the property of undergoing exchange of their oxygen atoms with water and these reactions can be catalyzed by both chemical and enzymatic means. Examples of such moieties are carboxylic acids, ketones, phenols, and phosphate esters, and it should be noted that the rates of 18O exchange differ for each of the functional groups. The combined use of stable isotope-labeled molecules and mass spectrometry has been a powerful means to address numerous problems in chemistry and biochemistry which had been difficult or impossible to probe by other techniques. Molecules labeled with 18O have been used in numerous mass spectrometric studies from the classic determination of the fate of the carboxyl oxygen atoms in ester hydrolysis, mechanistic studies of gas-phase ion decompositions, internal standards for quantitative mass spectrometric analysis, and detailed studies of chemical and biochemical reaction mechanisms. © 1990, Elsevier Inc. All rights reserved.