Influence of polypeptides and proteins on electrofusion of human cancer cells

The electrofusion of human cancer U937 and K562 cells was studied under the influence of a selected group of polypeptides and proteins adsorbed at the ir membranes. For poly-1-lysine, we found that the higher the molecular mas s (M-m) the higher the relative fusion yield (F-r), whereas poly-l-arginine and poly-1-ornithine showed toxicity. As recently measured for barley prot oplast fusion, the same rule of dependence on the isoelectric point (pI) co uld be verified: pI > 8 --> F-r > 1 pI similar to 7 --> F-r similar to 1 pI < 6 --> F-r < 1, which means 0.5 < F-r < 4 in 0.3 M mannitol solution (pH 6). If the pH of t he 0.3 M mannitol solution is the same as the pi of the protein, its influe nce on the membrane nearly disappears. Bridging by Ca ions increases F-r fr om 0.5 (bovine serum albumin) to F-r <similar to> 1 by charge compensation. The value of F-r is commensurate with the pore resealing time tau -determi ned by trypan blue staining-in such a way that for pI > 8, tau is longer an d for pi < 6, <tau> is shorter than the control without protein content. Qu alitatively, plant and animal membranes studied show equal behavior. Accord ing to our technique, the adsorption of biopolymers and other substances ca n be detected by this bioelectrochemical method, which is also a tool for a nalysis of electric stress mechanisms.