I have a 6X His Tag protein that is secreted from 293 EBNA cells and is purified nicely using an antibody specific for the protein we work with that is fused to the His tag. We elute from the column using DEA pH 11.5 and neutralize with Sodium Phosphate pH 5.6
The problem we are having is concentrating the protein using various concentrators from Millipore and Centricon. I lose over half of the protein after using the concentrator and it appears the protein precipitates out of solution while concentrating. Has anyone had this problem and if so I would really appreciate any suggestions and hints he/she can provide.
Thanks in advance!!