Oligonucleotides of the formula (I): 5'-(U)n-3' in which U is an identical or different radical of a natural or a synthetic nucleoside and n is a number from 2 to 200 comprising at least one structural unit of two consecutive nucleosides wherein one of the nucleotides is substituted in the 2'-position or wherein the nucleotides are substituted differently in their 2'-position, and wherein the backbone is modified.
