Patent ID: 7067324

Claim:
A system for fluorescence assays, comprising: a) a source of excitation light, for fluorescent excitation; b) a detector, for measuring emission; and c) an aqueous reagent mixture, comprising; i) a plurality of living cells in contact with a solid surface, ii) a first reagent, comprising a photon producing agent, iii) a second reagent comprising a photon reducing agent, wherein said photon reducing agent is substantially impermeant to a plasma membrane of a living mammalian cell, wherein said photon reducing agent does not specifically bind to said membrane compartment, wherein said photon reducing agent has an absorption spectrum that overlaps with the absorption, emission or excitation spectrum of said photon producing agent, and wherein said photon reducing agent is present in said aqueous reagent mixture at an amount sufficient to reduce light emitted from said aqueous reagent mixture by at least 10% compared to the light emitted from said aqueous reagent mixture in the absence of said photon reducing agent.