Radioactive—nonradioactive detection systems

Presently, nonradioactive probes, especially biotin or digoxigenin, are favored because they are less hazardous to work with, can be more rapidly developed, and provide better spatial resolution. Thus, introduction of nonradioactive detection systems has made ISH, using formalin-fixed and paraffin-embedded tissues, more accessible for application to molecular cell biology and diagnostic pathology. However, radioactive detection systems are more sensitive than nonradioactive probes, especially oligonucleotide probes used instead of cRNA probes (Sperry et al., 1996). 

Enzymes useful for detection purposes in ELISA techniques (Chapter 26) also can be employed in the creation of highly sensitive DNA probes for hybridization assays. The attached enzyme molecule provides detectability for the oligonucleotide through turnover of substrates that can produce chromogenic or fluorescent products. Enzyme-based hybridization assays are perhaps the most common method of nonradioactive detection used in nucleic acid chemistry today. The sensitivity of enzyme-labeled probes can approach or equal that of radiolabeled nucleic acids, thus eliminating the need for radioactivity in most assay systems. 

The liquid radioactive waste system is designed to collect, process, store and dispose of liquid radioactive waste generated as the result of normal operation, including anticipated operational occurrences such as reactor coolant system level reduction for refuelling. Nonradioactive secondary system waste is not processed by the liquid radioactive waste system however, if significant radioactivity is detected in secondary-side systems, blowdown or a portion of the blowdown may be diverted to the liquid radwaste system for processing and disposal. 

Generally, radioactive probes are used for the detection of RNA, notably for rare transcripts. However, several powerful nonradioactive systems, such as DIG-labeled probes, have been developed to eliminate health hazards, probe instability and cost. Nonradioactive systems are unlikely to work if it takes longer than 36-48 h with a P-probe to obtain a signal. 

A radioactive tracer is a very small amount of radioactive isotope added to a chemical, biological, or physical system to study the system. The advantage of a radioactive tracer is that it behaves chemically just as a nonradioactive isotope does, but it can be detected in exceedingly small amounts by measuring the radiations emitted. 

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