Background color/signal/noise

The sensitivity that is achievable in staining is determined by (1) the amount of stain that binds to the proteins, (2) the intensity of the coloration, and (3) the difference in coloration between stained proteins and the residual, background coloration in the body of the gel (signal-to-noise ratio). With all of the common stains, unbound stain molecules can be washed out of the bodies of the gels without removing much stain from the proteins. 

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