Fluorescence resonance energy transfer reporters

Following previous work, Hagiwara and collaborators [71] recently prepared 5 -terminal acridone-labeled DNAs, using the succinimidyl ester 24 of the acridone acetic acid 23 reported before [69], and evaluated their use as donors for a fluorescence resonance energy transfer (FRET) system in combination with 3 -dabcyl-tagged DNA... 

Fluorescence-based detection methods are the most commonly used readouts for HTS as these readouts are sensitive, usually homogeneous and can be readily miniaturised, even down to the single molecule level.7,8 Fluorescent signals can be detected by methods such as fluorescence intensity (FI), fluorescence polarisation (FP) or anisotropy (FA), fluorescence resonance energy transfer (FRET), time-resolved fluorescence resonance energy transfer (TR-FRET) and fluorescence intensity life time (FLIM). Confocal single molecule techniques such as fluorescence correlation spectroscopy (FCS) and one- or two-dimensional fluorescence intensity distribution analysis (ID FID A, 2D FIDA) have been reported but are not commonly used. 

Since the initial paper by Fields and Song, there have been significant technical improvements in the method. DNA-binding domains and transcription activation domains have been optimized to reduce false positives and increase the transcription read-out. A variety of reporter plasmids have been engineered to detect a broad range of protein-protein interactions. Much more is understood about the nature of false positives and how to rout them out. Moreover, in response to the utility of this approach, several laboratories have begun to develop transcription-based assays that can be carried out in bacteria, or protein-protein interaction assays based on alternate readouts such as enzyme complementation or fluorescence resonance energy transfer (FRET). 

Figure 37-24 Common probes and dyes for real-time PCR. f/J Double-stranded DNA dyes show a significant increase in fluorescence when bound to DNA (hv = excitation light). (2) Adjacent hybridization probes. Fluorescence resonance energy transfer (FRET) is illustrated between a donor and acceptor fluorophore.The x indicates phosphorylation of the 3 terminus of the probe to prevent polymerase extension. (3) FRET between a labeled primer and a single hybridization probe. (4) Hydrolysis probes are cleaved between the reporter and quencher, resulting in increased fluorescence. (5) Hairpin probes are quenched in the native conformation, but increase in fluorescence when hybridized. (6) Hairpin primers retain their native, quenched conformation until they are incorporated into a double-stranded product (Modified with permission of the publisher from Pritham GH, Wittwer CT Continuous f/uorescent monitoring of PCR.J Clin Ug Assay 1998, 21 404-412. 1998 Clinical Ligand Assay Society, Inc.)...

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