Screening methods bioassays

Figure 1 Examples of fragment hit identification (showing fragment and target, bioassay activity and screening method).

Bosveld ATC, van den Berg M (1994), Fresenius J. Anal. Chem. 348 106-110. Biomarkers and bioassays as alternative screening methods for the presence and effects of PCDD, PCDF and PCB ... 

The mouse bioassay, which is still the ofircial method used for some natural toxins present in the marine enviromnent, has been used as a routine screening method for a few years, but this method has been recently replaced in maty laboratories worldwide with a more sensitive method such as an enzyme-linked-immrmosorbent assay (Nagata 1995). Protein phosphatase assays (Metcalf 2001) have been also used but more details on these methods will be discussed later. 

The characterizations are necessarily incomplete since only the major components were determined. Knowledge of the composition of a given fraction allows us to assess the need of further fractionation or to devise appropriate methods for the detection and measurement of minor components. This approach is essential in order to obtain useable information from bioassay screening tests. 

Interestingly, the results obtained analyzing the ACNA soil samples with DNA biosensor were confirmed by other bioassays, hence this kind of biosensor can be very useful as a rapid screening method of analysis. 

In summary, GC-0 techniques should be seen as screening methods to gain an insight into important contributors to a characteristic aroma (7,71). GC-O performed as Charm analysis and Osme have also been claimed as quantitative bioassays (10,77). However, more time is needed for training of assessors and verification using statistical means. 

Numerous testing systems and protocols have been used to study 5-LO inhibitors in different laboratories, complicating attempts to compare compounds and series. In vitro, a variety of both cell-free and cellular preparations have been employed as primary screens. The most commonly used cell-free system is the crude cytosolic fraction from broken RBL-1 cells [25] various broken neutrophil preparations are also used, and more recently purified enzymes have occasionally been employed. The formation of 5-LO products is generally determined by radioimmunoassay or (in older work) HPLC or bioassay methods. 

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