Parallel or antiparallel, homologous or complementary binding of nucleic acids or analogues thereof to form duplex, triplex or quadruplex complexes

A method for assaying a target, said method comprising:

• providing a sample comprising said target containing a heteropolymeric target sequence of nucleic acids or nucleic acid analogues;
• providing a probe containing a heteropolymeric probe sequence of nucleic acids or nucleic acid analogues;
• providing a hybridization mixture comprising said target, said probe, water, and a buffer;
• incubating said hybridization mixture for an incubation time effective to bind said heteropolymeric target sequence to said heteropolymeric probe sequence to provide a complex;
• and
• detecting a signal correlated with binding affinity between said probe and said target to assay said target,
• wherein said heteropolymeric probe sequence is bonded to said heteropolyrmeric target sequence by Watson-Crick complementary base interaction or by homologous base interaction free of Hoogsteen bonding, provided that when said complex is a duplex and said heteropolymeric probe sequence is antiparallel to said heteropolymeric target sequence, said heteropolymeric probe sequence is bonded to said heteropolymeric target sequence by homologous base interaction, and provided that when said complex is a triplex, said complex is free of recombination protein.