Molecules show their aptitude
In a review of the history
and applications of aptamers, David H.J. Bunka and Peter G. Stockley of the University
of Leeds in the UK note that photonics techniques have improved the process of selecting
aptamers, which are RNA and DNA that interact with small molecules. They also state
that aptamers have been used for biological detection.
The process of selecting aptamers involves
mixing nucleic acids and target molecules and eluting the nucleic acids that bind
the most tenaciously. The partitioning efficiency of this technique has been improved
through the use of surface plasmon resonance. Furthermore, researchers have developed
variations on the selection technique that include UV-induced cross-linking of aptamers
to their targets, resulting in aptamers with increased binding affinity.
Aptamers can serve as reagents for
microarrays, Förster resonance energy transfer experiments and fluorescence
quenching experiments. These applications are based on ligand-induced conformational
changes. For example, researchers have used a dye that binds only the signaling
domain of an aptamer. Upon ligand binding to the recognition domain of that aptamer,
the signaling domain binds the dye. In addition, researchers have bound multiple
copies of an aptamer to a quantum dot, pairing each to a complementary strand carrying
a quencher. Ligand binding displaces the complementary strand, leading to large
increases in fluorescence emission. These quantum dots may be used to rapidly detect
cell damage or death.
Others have invented a colorimetric
assay that employs aptamers bound to gold nanoparticles. Ligand binding induces
a conformational change that causes the aggregated nanoparticles to disassemble.
These assays may be used to detect illegal drugs or biological and chemical weapons.
(Nature Reviews Microbiology, August 2006, pp. 588-596.)
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