The structure is an open one, and its water content is rather high. At lower water contents we would expect the bases to tilt so that the structure could become more compact.
The novel feature of the structure is the manner in which the two chains are held together by the purine and pyrimidine bases. The planes of the bases are perpendicular to the fibre axis. They are joined together in pairs,a single base from the other chain,so that the two lie side by side with identical z-co-ordinate. One of the pair must be a purine and the other a pyrimidine for bonding to occur. The hydrogen bond made as follows: purine position 1 to pyrimidine position 1;purine position 6to pyrimidine position 6.