Methanol fixation is normally carried out at -20oC but I am having difficulty devising a method to get the methanol onto the cells inside an apparatus at that temperature. One proposed method is to cool the methanol with dry ice and pump it into the apparatus hoping that the temperature will be below -20 when it hits the cells. There is of course the possibility that the methanol will arrive at some temperature well below -20 and if enough is pumped into the apparatus it will eventually get near -78oC once the apparatus starts cooling down.
Can anyone think of any reasons that I would not want to allow the temperature to get much below -20oC?
The simplest solution is to prechill Coplin jars with methanol in a -20C. Have your cells or tissue attached to slides or coverslips, and drop them into the jars, and then immediately return the jar(s) to the -20C freezer for the desired fixation period.
In practice, I've performed methanol fixation for nuclear proteins in tissue culture cells using the above method or simply incubating on ice at the bench, with similar outcomes. So the absolute temperature of fixation, provided it is
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