Figure 1
Protein content of residual Pap test fluid. (A) The protein concentration of residual Pap test fluid from 72 randomly selected SurePathTM samples was measured using the BCA protein assay in duplicate. Error bars show standard deviation. (B) The protein composition of the cell-free Pap test fluid from 16 individuals randomly selected from the samples in (A) was visualized by silver staining of SDS-PAGE gels. Five micrograms of protein was loaded per lane. MW, molecular weight standards. (C) Five micrograms of protein from serum (lane 6; S) or 5 different individuals’ SurePathTM samples (lanes 1–5) with varying protein concentrations (0.1–0.5 mg/ml) were visualized by silver stained SDS-PAGE. (D) In a parallel experiment, the SDS-PAGE gels was transferred to a PVDF membrane and probed by Western immunoblot with a polyclonal antibody recognizing human serum albumin. In (C) and (D), the protein concentration of the individual’s Pap test sample is listed above each lane. The large arrow indicates the individual’s Pap test sample with the highest protein concentration (lane 2; 0.5 mg/ml), and the small arrow indicates the individual’s Pap test sample with the lowest serum albumin content as detected by Western immunoblotting (lane 4).