Hi All,
We routinely use HEK293 cells to produce recombinant proteins and antibodies in our facility and we observed that for a small portion of proteins/antibodies, there appear to be a non-protein type of aggregates that co-elute with the target protein/antibody during purification. Such aggregates can be visualized as precipitates that have a string-like appearance and can be removed by centrifugation. The removal of these aggregates doesn't alter the protein/antibody concentration and they will re-appear after 4C storage. I was wondering if anyone else might have faced a similar problem and I would appreciate any suggestions on how to remove or prevent such aggregates from forming.
P.S. We use a culture system similar to that of EXPi293.
I don't know how you're purifying your proteins/antibodies but a string-like precipitate immediately makes me think of genomic DNA. You could try treating with DNase to see if it goes away. Or if your samples are precious and you don't want to risk DNase contamination, then you could run a small amount of your sample on a Qubit or Bioanalyzer to test for the presence of gDNA.
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