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Molecular Biology Problem Solver 45

Molecular Biology Problem Solver 45. Sách được nhiều nhà khoa học có uy tín, nhiều kinh nghiệm trong nghiên cứu thực nghiệm trình bày những vấn đề thường hay phát sinh trong phòng thí nghiệm. Do vậy mà sách không trình bày các protocol hay quy trình như các sách khác, thay vào đó các tác giả sẽ trình bày các vấn đề nhằm giúp giúp đọc giả: Tự nâng cao khả năng chẩn đoán nguyên nhân khi gặp các vấn để về kỹ thuật, quy trình, hóa chất, thuốc thử trong quá trình thực nghiệm trong phòng thí. | composite signal consisting of radioactive and photon emissions. Exposure at -70 C is essential a photon of light will generate only a single unstable silver atom in a silver halide crystal that will rapidly revert to a silver ion. -70 C stabilizes a single silver atom long enough to allow hits by additional photons of light producing stable silver atoms and hence visible grains on the film. Fluorographic chemicals are also utilized for indirect autoradiography. A fluorographic reagent is a solution organic or aqueous containing fluors which will soak into a gel or accrete onto a membrane Laskey and Mills 1975 Chamberlain 1979 . When dried the gel or membrane will have an even layer of fluors impregnated onto the surface. The fluors that are in proximity to the radioactivity fixed on the matrix will be activated by the radiation. These fluors give off light upon being activated enhancing the signal coming from the radioactive sample. Fluorography requires film exposure at -70 C for the same reason as required by intensifying screens. The additional sensitivity provided by intensifying screens is offset by a loss of resolution because the signals generated from the screen disperse laterally. In addition the use of screens and fluorographic reagents also compromises the quantitative response of the film. Two or more silver atoms within a silver halide crystal are required to generate a visible grain on film but a photon of light will generate only a single unstable silver atom that will rapidly revert to a silver ion. Because larger quantities of radioactivity are more likely than smaller quantities to produce sufficient photons to generate stable silver atoms lesser amounts of radioactivity are under-represented when working with screens and flours. When working with radioactive labels this problem can be corrected by a combination of exposure at -70 C and sensitizing the film with a controlled pre-flash of light of the appropriate duration and wavelength Laskey and