Free radical scavengers useful for reducing autoflourescence in fixed cells

An in situ fluorimetric process which process comprises the steps of:

• (a) contacting a biological entity with a solution comprising a fluorescent probe that binds to a target molecule in or on said biological entity, said contacting performed in a manner such that said fluorescent probe binds to said target molecule so as to make said fluorescent probe a biological entity-bound probe,
• (b) contacting the biological entity with a solution comprising a free radical scavenger selected from the group consisting of Vitamin E, thiophenol and 2,2,6,6,-tetramethyl-piperidine-N-oxyl for a period of time of not less than 5 minutes and not more than 16 hours,
• (c) causing the biological entity-bound probe to absorb light of wavelengths that are fluorescent absorption wavelengths of said biological entity-bound probe, and
• (d) detecting light of a wavelengths that are fluorescent emission wavelengths of said biological entity-bound probe;
• wherein step (a) takes place before step (b), after step (b),or during step (b),
• wherein said biological entity is a cell or a virus, and
• wherein the autofluorescence that contributes to the light detected during step (d) is less in the presence of said free radical scavenger than in the absence of said free radical scavenger.