The present invention provides compositions and methods for the optimization of cleavage of RNA species by RNase H. In some emboediments, the invention provides oligonucleotides that possess two or more regions of differing conformation, and at least one transitional nucleobase positioned between the regions that is capable of modulating transfer of the helical conformation characteristic of the region bound to the 3'hydroxy thereof, to the region bound to the 5' hydroxyl thereof.
