We have been doing [35S]methionine labeling in wheat germ extract in vitro translation.
(1) Some months a go, it suddenly happened that labeling efficiency of Promega WGE/ [35S]Met from American Radiolabeled Chemicals became 10% or so of before.
(2) We did parallel experiments using this new batch and more-than-half-decayed old batch with Promega and "home-made" WGE. The old batch worked much better for both Promega and home-made WGE.
(3) We then tried [35S]Met from Hungarian Acad Sci. It worked OK for that time, but the next batch did not work well.
(2) tells that something is wrong with [35S]Met. But it should be rare that two different source have the same problem.
Do anyone out there experienced/experiencing similar trouble?