Abstract: Methods, compositions and kits are disclosed. The methods are directed to determining the presence or relative amounts of two or more components in a medium. A combination is provided comprising a medium suspected of containing the components, at least two sensitizer reagents and at least one reactive reagent activatable by singlet oxygen. The sensitizer reagents are capable of generating singlet oxygen and are distinguishable by wavelength of sensitization. The combination of sensitizer reagents and reactive reagents allows differential detection of the components. The sensitizer reagents are differentially activated. The amount of signal generated as a result of the activation of said reactive reagent is determined wherein the amount thereof is related to the amount of each of the components in the medium.

Abstract: Methods are disclosed for determining minute quantities of an analyte in a medium suspected of containing the analyte. One method comprises treating a medium suspected of containing an analyte under conditions such that the analyte, if present, causes a substrate having an oxidant cleavable linker and a photosensitizer to come into close proximity. The photosensitizer generates singlet oxygen which oxidatively cleaves the linker to form a product which can be detected in a sandwich detection assay such as LOCI. The amount of product detected is related to the amount of analyte in the medium. Compositions, kits, and compounds are also disclosed.

Abstract: Methods are disclosed for determining minute quantities of an analyte in a medium suspected of containing the analyte. One method comprises treating a medium suspected of containing an analyte under conditions such that the analyte, if present, causes a substrate having an oxidant cleavable linker and a photosenstizer to come into close proximity. The photosenstizer generates singlet oxygen which oxidatively cleaves the linker to form a product which can be detected in a sandwich detection assay such as LOCI. The amount of product detected is related to the amount of analyte in the medium. Compositions, kits, and compounds are also disclosed.

Abstract: Alpha-haloketones are useful alkylating agents for coupling to sulfhydryl-containing biomolecules. However, they react spontaneously with water, alkali and organic bases and therefore cannot be stored for extended periods of time in aqueous solutions, particularly in the presence of proteins at physiological pH. The present invention provides novel solutions to these problems, however, as novel compounds and compositions comprising protected haloketones are disclosed herein. Methods of preparing and using protected haloketones which are useful in a variety of applications—e.g., in assays and conjugation reactions—are also disclosed herein.