In Vitro Selection of a DNA Aptamer Binding to Thyroxine

A DNA aptamer that selectively binds to a hormone, thyroxine, was isolated using the in vitro selection method. A pool of single-stranded DNAs consisting of random sequences was incubated with the thyroxine-immobilized agarose gel; bound DNAs were then collected and amplified by the polymerase chain reaction. This selection process was repeated nine times. The selected DNAs were cloned and sequenced. Some of the cloned DNA contained a consensus sequence. Several DNAs containing the sequence were chemically synthesized and the binding ratios to the thyroxine-immobilized gel were determined. Among them a DNA containing 14 nucleotides was found to bind selectively to thyroxine.