I am working on Knock out cells and after protein purification their concentration seems to be good (ranging from ~0.185-0.191mg/ml) however, once I do the buffer change and do the Nanodrop the concentration drops down giving me in negatives or very low such as 0.006. It seems to be the patterns for every protein in that KO cell. The surprise is when I ran the post-CBB gel it would give me a signal but a very weak one. Does any one know what is exactly going on here? Thanks!