Protein research. Close-up of bands produced by protein samples on a polyacrylamide gel electrophoresis (PAGE) plate. PAGE is a technique used for separating samples of proteins (or nucleic acids, such as DNA). The samples are placed in a gel across which an electric field is applied. This causes the charged fragments to migrate towards one of the electrodes. The rate at which the fragments move depends on their charge and their mass, thus identical fragments move the same distance across the plate. The technique is widely used in biotechnology for sample identification and DNA sequencing or fingerprinting.