Abstract:
A living system is allowed to metabolize in the presence of tritiated water.3H protons are incorporated and eliminated at many points in the network of biological reactions which constitute the cells' metabolism. Thus, labelled compounds are formed whose identity implies the nature of the metabolism occurring in that organism.
There are three ways in which a tritium atom may be incorporated into a metabolite molecule:
1. As rapidly exchangeable hydrogen, e.g. the following groups: -OH, -SH, -NH2, =NH and -COOH which can become ionized. If placed in tritiated water these groups become labelled very quickly. Conversely, labelling is lost very rapidly if the specific activity of the surrounding water is reduced as, for example, during chromatography.
