NAPPA uses DNA template that has already been immobilized onto the same protein capture surface. The DNA template is biotinylated and is bound to avidin that is pre-coated onto the protein capture surface. Newly synthesized proteins which are tagged with GST are then immobilized next to the template DNA by binding to the adjacent polyclonal anti-GST capture antibody that is also pre-coated onto the capture surface. The main drawback of this method is the extra and tedious preparation steps at the beginning of the process: (1) the cloning of cDNAs in an expression-ready vector; and (2) the need to biotinylate the plasmid DNA but not to interfere with transcription. Moreover, the resulting protein array is not ‘pure’ because the proteins are co-localized with their DNA templates and capture antibodies.