HS competent cells in -20 - are they still usable (Nov/15/2006 )
Last year I made a stock of heat shock competent cells for myself. During my holiday, someone has taken them out of the -80 and put them in the -20. I think they are standing in -20 now for 3 or 4 weeks.
Can I still use them or can I better just throw them away and make new ones?
I never tried, but you could try to transform one aliquot with a plasmid, just to see.
i would reprepare a new stock. Mine were submitted during misclosing to -80 --> -30° --> -80° and they begun bad