Modifications made for SOMAmer. The nucleotide triphosphate analogs were modified at the 5-UTR position (R) of uridine (dUTP), 5-benzylaminocarbonyl-dU(BndU); 5-naphthylmethylaminocarbonyl-dU (NapdU), 5-tryptaminocarbonyl-dU (TrpdU), and 5-isobutylaminocarbonyl-dU (iBudU) [8].