Crystallography of Biological Macromolecules

Cyclohexene nucleic acids (CeNA) contain a cyclohexene ring instead of the normal -D-2’-deoxyribose. The cyclohexene oligonucleotide GTGTACAC was synthesized using phosphoramidite chemistry and standard protecting groups [1]. CeNA is stable against enzymatic degradation and induces RNaseH activity. CeNA also forms more stable duplexes with RNA than its natural analogues [2] [3]. Crystals of GTGTACAC were obtained at 289K by the hangingdrop vapour-diffusion technique. The crystals diffract to 1.7 Å resolution and belong to the trigonal space group R3 with unit-cell parameters a = 41.434 and c = 66.735 Å. The structure of a fully modified GTGTACAC sequence with left handed CeNA building blocks is presented. Particular interests concern the puckering of the sugar moiety, helical parameters and the hydration of the double helix.