title: Serum proteins are extracted along with monolayer cells in plasticware and interfere with protein analysis.
abstract: Washing and lysing monolayer cells directly from cell culture plasticware is a commonly used method for protein extraction. We found that multiple protein bands were enriched in samples with low cell numbers from the 6-well plate cultures. These proteins contributed to the overestimation of cell proteins and led to the uneven protein loading in Western blotting analysis. In Coomassie blue stained SDS-PAGE gels, the main enriched protein band is about 69 kDa and it makes up 13.6% of total protein from 104U251n cells. Analyzed by mass spectrometry, we identified two of the enriched proteins: bovine serum albumin and bovine serum transferrin. We further observed that serum proteins could be extracted from other cell culture plates, dishes and flasks even after washing the cells 3 times with PBS. A total of 2.3 mg of protein was collected from a single well of the 6-well plate. A trace amount of the protein band was still visible after washing the cells 5 times with PBS. Thus, serum proteins should be considered if extracting proteins from plasticware, especially for samples with low cell numbers.
authors.affiliation: Department of Neurosurgery, Henry Ford Health System, Detroit, Michigan 48202, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Hong
authors.affiliation: Department of Neurosurgery, Henry Ford Health System, Detroit, Michigan 48202, USA.
authors.forename: Yuling
authors.initials: Y
authors.lastname: Meng
authors.affiliation: Department of Neurosurgery, Henry Ford Health System, Detroit, Michigan 48202, USA.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Kalkanis
keywords: bovine serum protein; cell culture; protein adsorption; protein extraction; serum albumin