Alpha Screen

Von, L.A., Kumpf, R., Menzel, S., Reulle, D., Griebel, R., Valler, M.J., and Buttner, F.H., Miniaturization and validation of a high-throughput serine kinase assay using the alpha screen platform, /. Biomol. Screen., 9, 719, 2004. 

Radioactivity in environmental waters can originate from both natural and artificial sources. The natural or background radioactivity usuaUy amounts to <100 mBq/L. The development of the nuclear power industry as weU as other industrial and medical uses of radioisotopes (qv) necessitates the deterrnination of gross alpha and beta activity of some water samples. These measurements are relatively inexpensive and are useful for screening samples. The gross alpha or beta activity of an acidified sample is deterrnined after an appropriate volume is evaporated to near dryness, transferred to a flat sample-mounting dish, and evaporated to dryness in an oven at 103—105°C. The amount of original sample taken depends on the amount of residue needed to provide measurable alpha or beta activity. 

The experiment conducted by Rutherford and his co-workers involved bombarding gold foil with alpha particles, which are doubly charged helium atoms. The apparatus used in their experiment is shown in Figure 14-9. The alpha particles are produced by the radioactive decay of radium, and a narrow beam of these particles emerges from a deep hole in a block of lead. The beam of particles is directed at a thin metal foil, approximately 10,000 atoms thick. The alpha particles are delected by the light they produce when they collide with scintilltaion screens, which are zinc sulfide-covered plates much like the front of the picture tube in a television set. The screen... 

Luminescent screen to detect scattered alpha particles... 

As for GRAPH but a graph is produced on the screen terminal using alpha-numeric characters. 

DOE. 1995a. Assays and screening of alpha contaminated soils using low-resolution alpha spectroscopy of thick soil samples. Washington, DC U.S. Department of Energy. NTIS/DE95008969. 

Amplified Luminescence Proximity Homogeneous Assay (AlphaS-creen ) technology have been reported [50,51]. With an HTS methodology in hand and orthogonal assays previously developed [47-49], nonpeptide antagonists of methyl lysine binding should appear from diversity screening approaches in the near future. 

Each serie of measurements consisted of two parallel samples with counting during and after sampling, one with the screen diffusion battery and the second as the reference sample, so that the fractional free radon daughters could be calculated. The radon daughters are collected on a membrane filter (filter diameter 25 mm, pore diameter 1.2 ym) and the decays of Po-218 and Po-214 are counted by means of alpha spectrometry with a surface barrier detector (area 300 mn ). 

Reineking, A. and J. Porstendorfer, High-volume Screen Diffusion Batteries and the Alpha Spectroscopy for Measurements of the Radon Daughter Activity Size Distributions in the Environment, J. of Aerosol Science 17 (1986) (accepted for publication). 

In order to determine the efficiency of the screens, the front-to-back ratio (F/B) of activities and a loss factor (SL) by which one multiplies to correct for loss in the screens (the alpha particles absorbed in a screen that cannot be detected either during the front or back measurements, see figure 1) have to be determined. Experimentally, this was accomplished by two methods ... 

Leonardi, A., Barlocco, D., Montesano, F., Cignarella, G., Motta, G., Testa, R., Poggesi, E., Seeber, M. et fli. (2004) Synthesis, screening, and molecular modeling of new potent and selective antagonists at the alpha Id adrenergic receptor. Journal of Medicinal Chemistry, 47, 1900-1918. 

As a follow-up to the RGS4 primary screen, the GPC spin column/ESI-MS methodology was applied to a selected series of seven RGS4 drug candidates to identify those compounds that bind non-covalently to RGS4 and not to G alpha [24]. Three ESI-MS experiments were performed with each of the compounds. 

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