The crystallographic study of left-handed Z-DNA d(CGCGCG)2 and thermine complexes crystallized at various temperatures and at various concentration of cations.

In crystals of complexes of thermine and d(CGCGCG)2 molecules grown at 4, 10, and 20 degrees C, the numbers of thermine molecules connected to the DNA molecule were dependent on the temperature of the crystallization. Two molecules of thermine and one Mg2+ ion were connected to DNA molecule when thermine and d(CGCGCG)2 were co-crystallized at 4 and at 20 degrees C. When an increased concentration of magnesium and thermine molecules were co-crystallized with d(CGCGCG)2 molecules at 10 degrees C, three Mg2+ ions and only one thermine molecule were bound with a d(CGCGCG)2 molecule.

The rare crystallographic structure of d(CGCGCG)(2): the natural spermidine molecule bound to the minor groove of left-handed Z-DNA d(CGCGCG)(2) at 10 degrees C.

Several crystal structure analyses of complexes of synthetic polyamine compounds, including N(1)-(2-(2-aminoethylamino))ethyl)ethane-1,2-diamine PA(222) and N(1)-(2-(2-(2-aminoethylamino)ethylamino)ethyl)ethane-1,2-diamine PA(2222), and left-handed Z-DNA d(CGCGCG)(2) have been reported. However, until now, there have been no examples of naturally occurring polyamines bound to the minor groove of the left-handed Z-DNA of d(CGCGCG)(2) molecule. We have found that spermidine, a natural polyamine, is connected to the minor groove of left-handed Z-DNA of d(CGCGCG)(2) molecule in a crystalline complex grown at 10 degrees C.

Measurement of circular dichroism and structural chemical research of d(CG)6 and d(TA)6.

It was known that d(CG)(6) became left-handed Z-DNA by a theoretical calculation. We carried out a CD measurement of d(CG)(6) at room temperature. B-Z transition was occurred when I raised the concentration of Mg salt.