It is sometimes the case that the signal for some probes may saturate in some wells. Perhaps the gain settings were too high, or the target was expressed at a higher level than expected. In some cases, these data sets can be rescued by using an alternative color channel. Bleed from the target channel into another channel can give a signal which is proportional to target, but which is lower than target and does not saturate when target does. Depending on gain settings and filter overlaps, either red2 or yellow may be suitable.
The extended range plot can be generated by double-clicking a well in expert mode. Choose a well with a high level of signal, for instance, the highest well of a standard curve. Try each channel to see if a good correlation between target and an alternative channel is found, similar to the figure below.
The X axis is the target channel. It saturates at a level of 10,000 in this example. The Y axis is the red2 channel. It is proportional to target up to the point where target saturates. Beyond that value, its level can be used to extrapolate what target signal would have been had it not saturated.
A suitable channel must satisfy several criteria
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