with respect to the size of RNA or DNA that can be Transfection of satellite cells from dog muscle (myoencapsidated efficiently, the fact that retroviruses inblasts) in primary culture has been optimized with refect only dividing cells (they are used mainly in ex vivo spect to the position of the cholesteryl moiety along approaches), and that adenoviruses can provoke an imthe polyamine chain of spermidine or spermine. Spermune response which limits their efficiency upon readmidine or spermine were derivatized with cholesterministration in vivo and may reduce persistence of ylchloroformate giving rise to three isomers in the transgene expression (2-4). This has led to a very accase of spermidine and two isomers for spermine that tive search for alternative ways to deliver nucleic acids were separated by reversed-phase high-performance using synthetic molecules. Among synthetic comliquid chromatography (rp-HPLC). The position of the pounds that have shown promise as vectors for DNA cholesteryl moiety was assigned by 13 C-NMR and codelivery, cationic lipids hold a prominent position. Nuelution with synthetic isomers of defined structure. merous derivatives have been synthesized and evalu-The isomeric cationic lipids were evaluated for their ated for their capacity to promote the entry of nucleic transfection activity in myoblasts from dog muscle and acids into cells (reviewed in 5-7). Synthetic cationic