I want to assess the effect a certain compound in the macromolecular biosynthesis of bacteria, for that I intended to use tritiated-thymidine and uridine labelled with phosphorus-32. Can I add both isotopes at the same sample and measure the radiation by liquid scintillation counting?
Yes, of course. The beta energies of these two radioisotopes differ considerably. 3-H emits the lowest, 32-P the highest energy of tracers used in biology. Your instrument will almost certainly be able to measure in different energy windows. The manual will tell you more. In any case you are always able to measure 32-P completely separated from 3H (high energy window), whereas it might be possible to detect some 32P in the 3-H (low energy window), too. This depends on quenching behaviour of your samples. Quenching substances that shift the energy to lower channels and thus affect your counting results are: water and phenol and many coloured substances. The best sample is dried and bound to a lass fiber or nitrocellulose filter. In any case: All samples in one experiment must have the same composition. So, if there is water in your samples, make sure it's the same amount in all vials. It is also helpful to have the same amout of cell extract in all vials.
Please read the manual of your conter for settings, and you will see, with some easy precautions, things are far from being difficult.
Yes, of course. The beta energies of these two radioisotopes differ considerably. 3-H emits the lowest, 32-P the highest energy of tracers used in biology. Your instrument will almost certainly be able to measure in different energy windows. The manual will tell you more. In any case you are always able to measure 32-P completely separated from 3H (high energy window), whereas it might be possible to detect some 32P in the 3-H (low energy window), too. This depends on quenching behaviour of your samples. Quenching substances that shift the energy to lower channels and thus affect your counting results are: water and phenol and many coloured substances. The best sample is dried and bound to a lass fiber or nitrocellulose filter. In any case: All samples in one experiment must have the same composition. So, if there is water in your samples, make sure it's the same amount in all vials. It is also helpful to have the same amout of cell extract in all vials.
Please read the manual of your conter for settings, and you will see, with some easy precautions, things are far from being difficult.
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