Confocal microscopy showing a time course of lysis of fibrin clots formed using high and low thrombin concentrations in the presence of tPA-GFP. (A) The pattern of tPA binding and fibrin lysis as the fibrin front recedes for fibrin formed using 5nM thrombin (fibrin₅). (B) The same time course for fibrin formed at 100nM thrombin (fibrin₁₀₀). Images were taken at the indicated time after the addition of tPA-GFP, and the green channel components of the sequential frames were overlaid in a single image for presentation purposes. A characteristic granular pattern of fluorescence can be seen at the lysis front in fibrin₅, whereas in fibrin₁₀₀ the tPA-GFP is distributed more homogeneously.