Abstract: The present invention relates to a population of nucleic acids, said population comprising a first population of nucleic acids of the same length, said length being in the range of 5-15 nucleotides or units, said first population representing at least 1% of the possible different nucleic acid sequences for nucleic acids of said length, at least one nucleic acid in the first population being an LNA (Locked Nucleoside Analogues) oligomer. The population of oligonucleotides is preferably bonded to a solid support. The pluralities of nucleic acids are particularly useful in methods relating to the capture of target nucleic acids, or as probes, e.g. PCR probes. The invention also features LNA oligomers wherein the LNA units have SBC (Selective Binding Complementary) nucleobases.