Hello all!
I have a strange question today...I noticed that a few of my aliquotted 10x RIPA buffers that were in the -20 C had some kind of potential mold (white balls, some clusters, some with just one or two) sitting inside the frozen buffer. To me, this is really weird because it is usually difficult for something like mold to grow in such low temperatures and also these aliquots are handled with care. Has anyone had this happen before/know what it is?
Thank you!
RIPA buffer is prone to form aggregates. Most likely, your mold is not alive. This is the Additional Notes in the PDF from Cell Signaling:
"Aggregation may be present in this buffer upon arrival due to the high concentrations of reagents included at the supplied 10X formulation. At times, the aggregation persists despite warming to room temperature. We recommend warming the buffer to 37°C for 15 minutes and mixing to help eliminate the precipitate. Alternatively, diluting the 10X RIPA with ddH2O to at least 5X will yield a precipitate-free solution. Once diluted, it can be aliquoted and stored at -20°C for future use."
This usually happens because SDS tends to precipitate and the other detergents contained in RIPA buffer form aggregates. As the comment above suggests, you can warm your buffer to 37°C and it should return to normal (colorless). However, if it becomes white and the detergents don't dissolve properly, it is better to prepare new RIPA buffer.
I usually follow this very easy protocol from Biorad for its preparation:
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