Aptamer beacons

Hamaguchi N, Ellington A, Stanton M. Aptamer beacons for the direct detection of proteins. Analytical Biochemistry 2001, 294, 126-131. 

Ii, J.J., Fang, X., Tan, W. (2002). Molecular aptamer beacons for real-time protein recognition. Biochem. Biophys. Res. Commun. 292, 31-40... 

Tan and colleagues also used the aptamer beacon strategy to develop realtime sensing of thrombin.In addition to using fluorescence quenching, they also used both FRET and excimer strategies that allowed for significant... 

Figure 34 A protein biosensor based on the aptamer beacon strategy. Thrombin shifts the DNA s conformational equilibrium to G-quadruplex and produces an increase in fluorescence as the donor-quencher groups get farther apart, compared to the stem-loop structure (See ref 63).

Some aptamer beacons using interactions between fluorescence and quenchers have been reviewed by Jayasena, 111). On the other hand, Hartig et al. 112) developed a ribozyme-based detection scheme where an external substrate labeled with a fluorescent molecule at its 5 end and a fluorescence quencher at its 3 end was cleaved, resulting in a fluorescence dequenching, enabling real-time monitoring of ribozyme activity. 

A farther electrochemical sensor platform development uses methylene bine connected to one end of the aptamer, which is fixed on the electrode surface by the other end as a redox marker for the detection of aptamer-binding reaction (Baker et al., 2006). The measuring principle is comparable to that of aptamer beacons with optical detection In the absence of target, the aptamer is thought to remain partially nnfolded with a greater distance between the redox marker and the electrode snrface in the presence of target, the aptamer presumably folds... 

Another method of detection of the thrombin-aptamer interaction was proposed by Bang et al. (2005). They immobilized aptamer beacon modified by an amino group to a self-assembled monolayer on a gold surface formed by... 

Figure 12.8 Two types of sensors with MB as a probe (A) aptamer-beacon approach (B) TREAS approach. [(A) From Bang et al. (2005) (B) from Li et al. (2007b).]...

Figure 12.11 Two approaches to designing POSFALF fluorescent aptasensors. The aptamer beacon approach contains two modes of signal-on (Al) (Yamamoto and Kumar, 2000 Hamaguchi et al., 2001) and signal-off/FRET (A2) (Li et al., 2002 Ueyama et al., 2002). The duplex-to-complex switching approach contains two signal-on modes B1 (Rupcich et al., 2005 Elowe et al., 2006) and B2 (Nutiu and Li, 2003).

In fact, aptamers selected capable of reporting domains are limited. Another series of fluorescent aptasensors take different routes and serve as complementary ways to make the PFSFALF more easily prepared and available for wider applications. This type of sensor is more similar to the POSFALF mode and can also be divided into two parts the aptamer beacon approach and the duplex-to-complex switching approach. 

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