testable, single-value assessment of the relationship between the stained protein
pairs. The ratio of the number of positive values to the total number of pixel
pairs is first computed, and then the ICQ is determined by subtracting 0.5 from
this value to distribute the quotients in the range 0.5 to þ0.5. With random
(or mixed) staining, ICQ 0; with dependent staining, 0 < ICQ # þ0:5; and
for segregated staining, 0 > ICQ $ 0:5 [65]. The intensity correlation ICQ
analysis allows identification of potential low-affinity protein complexes while
retaining information on the cellular and subcellular locations.
12.7.4 Fluorescence Ratio Imaging (RI)
In fluorescence imaging, ratio imaging has three major applications: combina-
torial ratio labeling, comparative ...