We report the use of modified RNA, in which the 2'-OH group of pyrimid
ines is replaced by a 2'-amino (2'-NH2) group to identify high affinit
y ligands specific for human neutrophil elastase (HNE) by in vitro sel
ection. Compared to unmodified RNA the P'-NH2-modified RNA ligands sho
w enhanced stability in human serum and urine. Use of RNase T1 cleavag
e data in the presence of K+ and Li+ ions suggests that the modified R
NA ligands selected for HNE form an intermolecular G-quartet structure
.