Which radioisotope should you choose?
Here are a few issues you need to consider when choosing a radiolabel:
Specific activity & radiochemical stability
Higher specific activities are required when the chemical concentration of the tracer is low.
Stability is both a function of the molecule, the isotope and the position of labeling.
General stability of the isotopes are:
carbon-14> tritium> iodine
Radionuclide properties
The inherent nature of radioisotopes will affect the timing and course of your experiment.
Half-life
Routinely used as tracers (eg phosphorus-32, iodine-125, tritium, carbon-14) have half-lives ranging from several days to thousands of years.
Such half-lives, and the related specific activities of these radionuclides make them ideally suited to applications such as DNA synthesis studies, radioimmunoassays, binding studies, drug screening and ADME work.
In contrast, when the half-life of a radionuclide is very short, any compound labeled with it will be difficult to prepare, use and measure within the time of decay. |
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New to custom labeling?
The Custom Label Service offers numerous labeling methods, from simple techniques such as tritiated water exchange to carbon-14 core labelling of a molecule.
If you're new to custom labeling it may seem like there is a wide variety of labels that you can use to label your compound of interest. There are many aspects to consider such as the properties of the radionuclide itself, to the performance of this in your experimental conditions.
Begin by considering the basic properties of the radioisotope and then determine how it will perform in your individual experimental conditions.
Carbon-14 labeling
This is the isotope of choice for labelled products in most pharmakinetic and agrochemical studies. It allows core labeling, rather than peripheral labeling of the molecule of interest, thus ensuring integrity of the label during your investigation.
Tritium-labeled
These isotopes have uses in screening, discovery and ADME. They offer a higher specific activity than carbon-14 and a longer half-life than Iodine-125.
Iodine-125 labeled
These Isotpoes are mostly used for protein and peptides, However it is used in screening and occasionally in ADME. Iodine-125 offers a high specific activity, but a short half-life. Molecules are often modified during labeling, which can change the binding properties of a compound.
Stable Isotopes
Are used as mass spec standards for ADME studies, Isotopic abundance is critical.
Carbon-14, iodine, stable or tritium-labeling? Find out which label is suitable for you
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