Fig. 7. Non-classically secreted GFP is not fluorescent. Untransfected (CHO) and GFP-transfected CHO cells (CHO+GFP) were washed and incubated in fresh medium for 6 hours. (A) The cell lysate (C) and media (M) were immunoprecipitated with anti-GFP antibodies, separated by SDS-PAGE and immunoblotted with anti-GFP antibodies. (B) The fluorescence was measured from 200 µl aliquots of the cell lysate and the media harvested as above. The graph shows the relative fluorescence units (RFU) per ml for the samples. The fluorescence was also measured from the lysate of GFP-expressing cells diluted 1:1 in fresh medium or PBS (CHO+GFP lysate diluted). Each bar on the graph represents the average value derived from at least three independent samples. (C) CHO cells expressing GFP were lyzed in medium supplemented with 1x Triton X-100. The fluorescence was measured from 200 µl aliquots of the medium after 0, 3 and 6 hours of incubation at 37°C. The values are plotted as RFU per ml.