Mixed backbone oligonucleotides (MBOs) which contain segments of prima
ry phosphoramidate linkages (PO-NH2) in conjunction,with either phosph
oric diesters (PO), or phosphorothioates (PS) were prepared. Thermal d
enaturation of the duplexes with RNA and DNA reveal that they form sta
ble duplexes which display cooperative melting profiles. Preliminary s
tability studies reveal that the PO-NH2 linkage is resistant to serum
nucleases. Thus, these MBOs represent novel antisense molecules. Copyr
ight (C) 1996 Elsevier Science Ltd