Storage of B-gal staining buffer

[Matt Springer]

In case anyone's curious...

(I'm posting this because SUMIT CHANDA told me to...)

Since some people store their B-gal yellow staining solution cold, some
store it in the dark, some store it on the bench in the light, and some
make it up fresh each time, I decided to compare them all.  I made up 
a batch of the stuff and split it into several bottles.  One was kept 
dark at 4 degrees, one was on the bench in a brown glass bottle, one
was on the bench covered with foil, and one was on the bench in a clear
glass bottle.  Two months later, I stained LacZ expressing C2C12 
myoblasts with all of the above solutions and also with a freshly  
made batch.  The results, amusingly, were that all gave identical 
staining except for one; the FRESH batch gave inferior staining.
Which shows two things: (1) there can be batch to batch variability
depending on the alignment of the planets, and more importantly,
(2) storage in the light at room temperature is just fine over 2 months.

I think I'll try it again in about half a year...

(Staining solution was 5 mM K ferricyanide, 5 mM K ferrocyanide, 
2 mM magnesium chloride in PBS pH 7.4.  X-gal was added fresh to 
1 mg/ml.  Cells were fixed in 4% formaldehyde/0.25% glutaraldehyde
for 4 min before staining.)

-Matt Springer