Cerenkov counting

The immobilized immunoprecipitates are washed twice with lysis buffer containing 0.5 MNaCl and twice with buffer A. The beads are resuspended in 20 /il of kinase buffer also containing the appropriate concentration of the specific peptide. Reactions should also be set up without peptide as a negative control for nonspecific or self-incorporation of radiolabel. To start the reactions, 5 /il of ATP is added (final concentration 0.1 mM unlabeled ATP, 1 /iCi [7 -32P]ATP (per assay) in kinase buffer). The assays are allowed to proceed for 15 to 30 min at 30° with constant shaking at 900 rpm, and stopped by spotting 20 /il of the sample (slurry) onto a square (1.5 X 1.5 cm) of phosphocellulose (P81) paper. The P81 papers are immediately immersed in 500 ml of 1% (v/v) orthophosphoric acid, and then washed 3 times with the same solution (to remove the excess ATP). The washes therefore contain almost all of the radiolabel and must be handled carefully and disposed of appropriately. The papers are briefly rinsed in ethanol and air-dried. The incorporation of 32P-label is measured by Cerenkov counting. 

Rao, D.D., Sudheendren, V., Baburajan, A., Chandramouh, S., Hegde, A.G., Mishra, U.C. Measurement of high energy gross beta and K by Cerenkov counting in liquid scintillation analyzer. J. Radioanal. Nucl. Chem 243(3), 651-655 (2000)... 

Blackburn, R., Al-Masri, M.S. Determination of radon-222 and radium-226 in water samples by Cerenkov counting. Analyst 118, 873-876 (1993)... 

High energy / emitters, particularly 32P, can be counted directly in aqueous solutions without recourse to stintillation cocktails, since electrons with energies > 0.5 MeV excite water molecules to emit blue light which can be observed by the photomultiplier. This, so-called Cerenkov counting method, has an efficiency of about 40 %. 

Scintillation measurements are usually carried out using 20 ml standard vials, or 6 ml mini-vials equipped with screw caps. Disposable vials are available in polypropylene, polyester or polycarbonate. Glass vials, which must be of low potassium content because the naturally occurring 40K isotope is a /S emitter, can be re-used. Care should be taken that tbey do not get scratched. Cerenkov counting is usually carried out in 1 ml, 500 pi or 250 pi Eppendorf vials, placed either in special adaptors or in 20 ml standard vials. For accurate and reliable measurements, the positioning of the vials must all be the same, to ensure that the counting geometry with respect to the photomultiplier tube is identical. 

The quantity of radioactive strontium is typically determined by gas-flow proportional, liquid scintillation, and Cerenkov counting techniques (Scarpitta et al. 1999). The standard EPA analytical... 

Pietra, R.. Sabbioni, E. and Girardi, F. (1975). Determination of Ca. Mg. Ni and Si in biological materials by neutron activation analysis and Cerenkov counting. Radiochem. Radioanal. Lett. 22, 243-250. 

Prefractioiation, Postlabeling and Ininuncprecipitation). The ordinate means radToactivity determined by Cerenkov-counting. The abscissa is the amount of 0 -Et-3 -TMP in an assay tube. 

Assay of radioactivity. Assay all 8 eluants by Cerenkov counting in a Beckman LS7(K)0 liquid scintillation counter (or equivalent) at settings. 

Investigation of Cerenkov Counting of Environmental Strontium-90 S. A. REYNOLDS and J. S. ELDRIDGE... 

Count the all of the fractions by Cerenkov counting, and plot the results. You should see two distinct peaks. 

The recovery of radioactivity should be monitored at every step by Cerenkov counting in a scintillation counter to ensure that the majority of the radioactivity ends up in the final sample. 

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