IN-VITRO SELECTION OF A DNA-LIGAND THAT SELECTIVELY BINDS TO THE ANTICANCER AGENT METHOTREXATE

A DNA ligand that selectively binds to the anticancer agent methotrexa te was identified using the in vitro selection method. A pool of singl e-stranded DNAs consisting of random sequences was incubated with a me thotrexate-immobilized agarose gel; bound DNAs were then collected and amplified using the polymerase chain reaction (PCR). This selection p rocess was repeated six times. The selected DNAs were cloned and were found to contain two common sequences. One of these selected DNA clone s selectively bound to the methotrexate-immobilized gel and showed a h igh level of discrimination against the gel immobilized with folic aci d, which has a similar chemical structure to methotrexate. In the sele ction process, a buffer solution was used for DNA binding to the metho trexate-immobilized gel and water was used for elution from the gel. U ltraviolet absorption measurement showed that the conformation of the DNA ligand in the binding buffer was different from that in elution wa ter.