CDNA probes characteristics

Probes may also consist of DNA copied from mRNA. This is known as cDNA and is also widely used to determine indirectly the sequences of mRNA molecules. Messenger RNA may be isolated from the total cellular RNA by affinity chromatography on bound poly (dT) or poly (U). These materials selectively hold RNA with the poly (A) tails characteristic of most eukaryotic mRNA (see Chapter 28). Another source of mRNA is polyribosomes (polysomes), which are "reading" mRNA and actively making proteins. 

A recent paper by Chauret et al. described the discovery of a novel fluorescent probe that is selectively metabolized by CYP3A in human liver microsomes (32). This probe, DFB [3-[(3,4-difhiorobenzyl)oxy]-5,5-dimethyl-4-[4-(methylsulfonyl) phenyl] furan-2(5F/)-one], is metabolized to DFH [3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl)phenyl]furan-2(5//)-one], which has fluorescent characteristics (Fig. 7). In vitro CYP reaction phenotyping studies (cDNA-expressed CYP proteins and immunoinhibition experiments with highly selective anti-CYP3A4 antibodies) demonstrated that DFB was metabolized primarily by CYP3A4 (Fig. 8). Furthermore, metabolism studies performed with human liver microsomes obtained from different donors indicated that DFB dealkylation and testosterone 6P-hydroxylation correlated well (Fig. 9). 

Microarray A microscopic, ordered array of nucleic acids, proteins, small molecules, cells, or other substances that enables parallel analysis of complex biochemical samples. The term microarray originally referred to spotted cDNA arrays, but now others and we use it for any hybridization-based array. The major characteristics of microarrays are that they have a glass or plastic slide as a matrix, and are created with robots that deposit probes on the slides. 

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