Highly selective base-pair recognition makes DNA a suitable building block for orderly self-assembled structures. For some applications in nanotechnology DNA complexes need to be fixed onto surfaces. To fulfil this requirement on lipid membranes we have synthesised a thymidine monomer modified with a cholesterol moiety. Solution studies show that the melting temperature (Tm) of the duplex, with adjacent cholesterols on each strand, is much higher than that of the unmodified duplex.