Nucleic acid molecules capable of distinguishing the isoforms PrPc and PrPSc of prion proteins and processes for their production

A process for the identification and isolation of nucleic acid molecules which are capable of distinguishing between the isoforms PrPc and PrPSc of prion proteins associated with transmissible spongiform encephalopathies comprising the steps of

• (i) incubating a prion protein isoform or peptide fragment or derivative of this prion protein isoform with a pool of nucleic acid molecules comprising different sequences;
• (ii) selecting and isolating those nucleic acid molecules which are capable of binding to said prion protein isoform or fragment or derivative thereof;
• (iii) optionally, amplifying the isolated nucleic acid molecules and repeating steps (i) and (ii);
• and
• (iv) determining the binding specificity of the isolated nucleic acid molecules for the PrPc and PrPSc isoforms of prion proteins.