Enzyme-aptamer complex

To demonstrate a way of the use of aptamers in design of biomimetic sensors, two examples will be cited from the recent literature. The piezoelectric sensor for protein IgE has been developed with the use of commercially available anti-IgE aptamer oligonucleotide.167 The obtained sensor shows specificity and sensitivity equivalent to these of immunosensor, but for aptamer-based sensor a less decrease of sensitivity after consecutive cycles of analyte binding and regeneration, as well as relative heat resistance and stability over several weeks was shown. A more complex mechanism of sensing was employed in adenosine aptamer-based sensor.168 Detection was based on enzymatic activity measurements by fluorescence polarization with the use of aptameric enzyme subunit, which was a DNA aptamer composed of enzyme-inhibiting aptamer and adenosine-binding aptamer. 

While selection for RNA aptamers that bind transition state analogues have not yet yielded catalysts, researchers have found many RNAs that specifically bind amino acids [21], as well as other small molecules. It seems possible that RNAs that bind amino acids, for example, may have evolved to catalyse peptide bond formation. Subtle mutations that conferred less binding to reactants or products may have led to transition state stabilisation and subsequent product formation. As enzymes (nucleic acid or otherwise) developed diverse catalytic strategies, biological complexity would have increased. 

---