A lab technician who I work with got both pure protein and wanted protein
with two contaminating bands, both of which molecular weight is higher than
the molecular weight of the wanted protein, from different batches of
protein purification. The molecular weights of the contaminating bands are
not high enough to account for different oligomerization states of the
The two contaminating protein bands hang on really tightly with the wanted
protein and we have not been able to get rid of them.
I dont know what is the difference between purifications which produce pure
protein and the purifications which don't, but I suspect that at least
there has been differences at how long the cells have been growing since
they were harvested.
This leads me to my question that I want to ask from you:
Have you ever had problems with contaminating proteins (stable
proteins/chaperons hanging along, modifications of the wanted protein ?)
when S.cerevisae cells have been in a certain growth phase ?