Locked Nucleic Acid (LNA) was first described by Wengel and co-workers in 1998¹ as a novel class of conformationally restricted oligonucleotide analogues. LNA is a bicyclic nucleic acid where a ribonucleoside is linked between the 2’-oxygen and the 4’-carbon atoms with a methylene unit. Oligonucleotides containing LNA exhibit unprecedented thermal stabilities towards complementary DNA and RNA², which allows excellent mismatch discrimination. In fact the high binding affinity of LNA oligos allows for the use of short probes in, for example, SNP genotyping³, allele specific PCR and mRNA sample preparation. In fact, LNA is recommended for use in any hybridization assay that requires high specificity and/or reproducibility, e.g., dual labelled probes, in situ hybridization probes, molecular beacons and PCR primers. Furthermore, LNA offers the possibility to adjust T_m values of primers and probes in multiplex assays. As a result of these significant characteristics, the use of LNA-modified oligos in antisense drug development is now coming under investigation⁴, and recently the therapeutic potential of LNA has been reviewed.⁵ LNA can be mixed with DNA and RNA, as well as other nucleic acid analogues, modifiers and labels. LNA oligonucleotides are water soluble, and can be separated by gel electrophoresis and precipitated by ethanol.