A highly simplified horizontal electrophoretic apparatus including a handmade power supply and its application

Abstract

An extremely simplified electrophoretic apparatus and power supply have been introduced for horizontal (flat-bed) electrophoresis and isoelectrofocusing. The electrophoretic apparatus consisted of a buffer tray with a plastic food container in which a gel glass plate attached to two removable bar electrodes with rubber bands was submerged. The removable bar electrode consisted of an acrylic bar plate containing holes to which platinum wire was attached. The power supply simply contained a bridge diode, fuse, capacitor, and output terminals which were also assembled in a small plastic food container. Since the output electric potential of the power supply was constant pulse dc 90 V (in the absence of a capacitor) or 140 V (in the presence of a capacitor) at 100 V ac input, the following equation was experimentally derived to control the electrophoretic current: I (mA) = aD + b, I (mA) = kF. In these, I, a, D, k, and F were electrophoretic current, constant, distance between positive and negative electrodes, constant, and dilution factor of the electrophoretic buffer which was proportional to buffer concentration, respectively. These equations indicate that electrophoretic current can be controlled by the changes of electrode distance and buffer dilution. The latter equation was theoretically derived from the theory of electrolyte conductance and Ohm's law and was simulated with a microcomputer. With the apparatus and power supply, agarose gel electrophoresis of DNA and discontinuous polyacrylamide gel electrophoresis of protein samples were successfully carried out. The construction and assembly of the system can be easily carried out in a laboratory without any special tools and machines. The high cost performance, compactness, and simplicity were superior points of this system. The applicability of the equation I = kF to tube gel and vertical slab gel electrophoresis was tested. The rheostat usage made it easy for the power supply to change dc-output potential without spoiling its cost performance. A convenient sample slot-former and gel preparation with it are also described.