Novel reagents are provided along with methods for their use in nucleic acid hybridization assays for detecting target nucleic acids in samples. The most preferred reagent is a mixture of guanidinium thiocyanate and tetramethylammonium:Trifluoracetate and possesses many properties for facilitating hybridization between target nucleic acid and nucleic acid probes capable of binding thereto and surprisingly results in the phenomenon of superstoichiometric labeling.