Abstract: Nucleic acids and sequences therefor are disclosed that are characterized by a reduction or lack of internal secondary structure, are capable of hybridizing with a complementary nucleic acid and do not hybridise with non-complementary nucleic acids (eg. do not cross-hybridise or form dimers) under low stringency hybridisation conditions. In particular, the nucleotide sequences enable use of these nucleic acids, without reduction in target hybridisation efficiency with increasing nucleic acid length. The nucleic acids may be used with analyte capture systems, for example medical, veterinary and agricultural diagnostic applications. In particular, the nucleic acid may be used as irrelevant binding pairs in an analyte capture system, such as an array or lateral flow assay.