Free solution mobility of DNA molecules containing variable numbers of cationic phosphoramidate internucleoside linkages

The free solution electrophoretic mobility of an 118-base pair DNA fragment containing zero, three, six or nine cationic phosphoramidate internucleosi de linkages has been measured by capillary electrophoresis. The electrophor etic mobility decreases with the increasing number of cationic phosphoramid ate linkages, as expected because of the reduced negative charge on the DNA molecules. The decrease in mobility is approximately linear for DNA molecu les containing three and six cationic phosphoramidate linkages, but begins to level off when nine cationic phosphoramidate linkages have been added. T he mobility also varies somewhat depending on whether the modified phosphor amidate linkages are located at the 5'- or 3'-end of the DNA molecule. (C) 2000 Elsevier Science B.V. All rights reserved.