Reversal of polyamine selectivity for DNA and RNA by steric hindrance

The polyamines known until today generally bind better to double-stranded RNA than to DNA, as shown in significantly higher melting point increases with RNA. We report that large and bulky polyamines with three or four positively charged nitrogen centers connected via flexible or rigid linkers to either a benzene or an adamantane core show high affinities and are large enough to exhibit a strong preference for double-stranded DNA (polydApolydT) in comparison to RNA (polyApolyU), which differs by its smaller and deeper groove.