Interaction between the left-handed Z-DNA and polyamine. The crystal structure of the d(CG)3 and N-(2-aminoethyl)-1,4-diamino-butane complex.

The DNA fragment d(CG)3 was co-crystallized with N-(2-aminoethyl)-1,4-diaminobutane (PA(24], a chemically synthesized polyamine. The complex crystal contained one polyamine, 3 magnesium cations and one sodium cation per duplex of d(CG)3, and well diffracted the X-ray intensities up to 1.0 A resolution. The d(CG)3 took a left-handed Z-DNA conformation, and the PA(24) molecule electrostatically interacted with the phosphate groups of the d(CG)3 duplex.