It is not the heat used to dissolve paraformaldehyde that causes
>  autofluorescence, it is caused by aldehyde induced autofluorescence when the
>  PFA crosslinks proteins.  There are places to buy PFA in liquid form to
>  avoid having to weigh and dissolve.  We never bother to add NaOH if we heat,
>  and we also buy our paraformaldehyde from Sigma.
>
>  We always heat our PFA but never exceeding 60C.  It will go into solution
>  around 56C, with stirring in approx 15 minutes or so.

We have two protocols for making 4% PFA and I always wondered why one
called for a temperature of 65C and the other just about boiling water
when adding the PFA.  Why would it matter which temperature is used to
make the solution if, in the end, the PFA is dissolved?  Does heating
PFA about 65C cause damage to the solution?


Emily
-- 
People aren't like chocolates. People are bastards. Bastards with
bastard coating and bastard filling.

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