As an addendum, ABI told us on a recent course that red rain is also at
least
partly attributable to dirty plates. People who degas thoroughly but had
been
experiencing red rain were (reportedly) able to get rid of it by a 0.1M
NaOH wash
followed by a 0.1M HCl wash, presumably because dirty plates exacerbate
any tendency
of the gel to form bubbles, possibly by allowing local heating by the
laser.
Personally, I suffered from red rain with degassed gels (I use a similar
setup
to Bruce's), but solved it not by an alkaine wash but by lowering the run
temperature from 51 to 48C.
Anthony.
