Patent ID: 7223538

Claim:
In a nucleic acid expression assay, comprising (1) performing in vitro transcription of target nucleic acid template to generate cRNA, (2) contacting said cRNA with a probe immobilized on a microarray under conditions that allow hybridization between said cRNA and said probe, and (3) detecting hybridized cRNA to assay expression of said target nucleic acid template, the improvement comprising, (a) during said performing step, incorporating in said cRNA at least one phosphorothioate moiety; and (b) labeling said cRNA by conjugating a reporter molecule to said phosphorothioate moiety wherein said labeling step comprises reacting said target nucleic acid with a conjugating moiety that specifically reacts with said phosphorothioate moiety, followed by reaction with a labeling moiety that specifically reacts with said conjugating moiety.