Protein fingerprinting using flat-surface electrophoresis

Developments in the field of proteomics are highly encouraging for medical researchers. While gel electrophoresis offers a successful means for protein recognition, it requires the use of a relatively large system and a rather long period of time. Here, a protocol is developed for electrophoresis of proteins using flat surfaces based on the principles of electrophoresis of DNA on flat surfaces. By further adapting this system, it is hoped to create a portable device for protein electrophoresis. Droplets of fluorescently tagged proteins such as albumin, casein, poly-L-lysine and their mixtures were placed on glass surfaces in an electrophoretic cell and allowed to dry. TBE buffer was added to the cell and the migration of the salt complexes was monitored using confocal microscopy. We show that different protein -salt complexes have different mobilities on a flat surface. The shape and size distributions of the protein-salt complexes and their mixtures on surfaces were also studied using atomic force microscopy and were found to be dependent upon the proteins. It is observed that the native charge of the proteins play a dominant role in the migration of the protein-salt complexes in the electrophoretic cell. From the morphology of the protein droplets it is observed that large aggregates are formed when oppositely charged proteins are mixed. Light scattering measurements and zeta potential measurements confirm the difference in the size and shape of the aggregates in solution leading to different mobilities of the protein-salt aggregates during electrophoresis.