Abstract: A homogeneous assay that utilizes molecular beacons as the reporter and nucleic acid ligands as the sensor is described. This assay, called the ligand beacon assay, is for the detection of target molecules in a test mixture. The concept of the ligand beacon assay was tested using several proteins to which high affinity and specific nucleic acid ligands are available. The assay specifically detects the molecular target that binds the nucleic acid ligand with high affinity and specificity. The range of the assay is dictated by the concentration of the nucleic acid ligand/ligand beacon pair used in the assay. Target proteins were detected in buffer as well as in plasma, expanding its applicability to clinical use. This is a simple to use and fast assay format with the potential for automation for high throughput screening applications.

Abstract: The invention provides method for producing nucleic acid ligands that generate a signal, or cause a decrease in the level of a signal, in the presence of a target molecule or an environmental stimulus. The methods of the instant invention are collectively termed Conditional SELEX. The nucleic acid ligands of the instant invention are useful in any application where it is desirable to measure the concentration of a target molecule or detect and quantitate an environmental stimulus.

Abstract: A Nucleic acid ligand “Biochip” is disclosed, consisting of a solid support to which one or more specific Nucleic acid ligands is attached in a spatially defined manner. Each Nucleic acid ligand binds specifically and avidly to a particular Target molecule contained within a Test mixture, such as a Bodily fluid. The Target molecules include, but are not limited to, proteins (cellular, viral, bacterial, etc.) hormones, sugars, metabolic byproducts, cofactor, and intermediates, drugs, and toxins. In principle, the Biochip could be used to test any chemically complex mixture provided that Nucleic acid ligands to components suspected of being present in the mixture are attached to the Biochip. Thus, the Nucleic acid ligand Biochip will have a wider use in environmental testing, etc.