Nucleotide rigidity.

It is show that in aqueous solution the backbone conformation of adenosine is as much flexible as that of 3'-AMP, 5'-AMP and 3', 5'-ADP indicating that nucleotides are not any more rigid than nucleosides. The flexible conformation of the monomeric components is conserved in the nucleotidyl units of destacked ApA, ApApA and poly(A), but it is not conserved in base stacked conditions. The findings are extended to guanosine, uridine and cytidine systems. It is projected that in aqueous solution, conformations of the individual nucleotidyl units of yeast tRNAhe are confined to the classically stable domains in the base stacked region and non-rigid flexible structures populate in the unstacked region comprising D16, D17, G20, U47 and A76.