NMR Solution Structure of a Parallel LNA Quadruplex

The soln. structure of a locked nucleic acid (LNA) quadruplex, formed by the oligomer d(TGGGT), contg. only conformationally restricted LNA residues is reported. NMR and CD spectroscopy, as well as mol. dynamics and mechanic calcns., has been used to characterize the complex. The mol. adopts a parallel stranded conformation with a 4-fold rotational symmetry, showing a right-handed helicity and the guanine residues in an almost planar conformation with three well-defined G-tetrads. The thermal stability of Q-LNA has been found to be comparable with that of [r(UGGGU)]4, while a Tm increment of 20° with respect to the corresponding DNA quadruplex structure [d(TGGGT)]4 has been obsd. The structural features of the LNA quadruplex reported here may open new perspectives for the biol. application of LNAs as novel versatile tools to design aptamer or catalyst oligonucleotides.