Interactions of polyamines with the DNA octamers d(m(5)CG)(4) and d(GGAATTCC): A H-1-NMR investigation

The interaction of two DNA octamers, d(m(5)CG)(4) and d(GGAATTCC), with the polyamines spermine(4+) and spermidine(3+), has been studied by means of H -1-nmr nuclear Overhauser effect (NOE) difference measurements. The experim ents were performed at 10 degrees C and for a polyamine charge to DNA charg e (i.e., phosphate) ratio of 0.4, where the solution of d(m(5)CG)(4) contai ns about 50%' Z-form of the DNA. The results show that the polyamine intram olecular NOEs for the protons on the propyl chains are similarly negative w ith the two oligonucleotides, while those on the butyl chain show slightly more negative NOE with d(m(5)CG)(4) than with d(GGAATTCC). The fully N-meth ylated analogue of spermine (Me(10)Spn(4+)) and spermidine (Me(8)Spd(3+)) a s well as the diamines 1,3-diaminopropane (DAP(2+)) and 1,4-diaminobutane ( putrescine(2+)) have been studied for the ability to transform d(m(5)CG)(4) from the B- to the Z-form. H-1-nmr spectra showed the order spermine(4+) > spermidine(3+) > Me(10)Spn(4+) > Me(8)Spd(3+) > 1,3-diaminopropane(2+) > p utrescine(2+), with spermine showing the largest relative amount of Z-DNA. H-1-nmr pulsed-gradient self-diffusion measurements of the triamines showed a large difference in the interaction of Spd and Me,Spd with the two diffe rent duplexes. With the same duplex (either of the two), however, no differ ence between Spd and Me,Spd can be seen. Within a two-state model this is i nterpreted as a larger fraction of bound polyamines with d(m(5)CG)(4) than with d(GGAATTCC). (C) 1999 John Wiley & Sons, Inc.