A sample from a cell culture has some IgG and this is to be purified using protein A chromatography. Based on the chromatography handbook from GE-Healthcare/Cytiva, the protein sample should have "physiological" pH and conductivities. This corresponds to a pH between 6-8, but it is not clear what the conductivity sould be. Is there a ballpark value for this?
Also in general, the series of buffers for Protein A chromatography including a wash step looks something like this
- Binding buffer (physiological conditions) to equilibrate the column
- Protein sample to load the column
- Binding buffer (same as above) to wash impurities while retaining the protein
- Elution buffer to unload the column
Does the protein sample have to have the same pH and conductivity as the binding buffer? If so, it has to be adjusted after coming from a bioreactor. What happens if the solution from the bioreactor already has a very high conductivity above that of the binding buffer?