Electrophoresis is an analytical method frequently used in molecular biology and medicine.
It is applied for the separation and characterization of proteins, nucleic acids and subcellular-sized particles like viruses and small organelles. Its principle is that the charged particles of a sample migrate in an applied electrical field. If conducted in solution, samples are separated according to their surface net charge density. The presence of such a matrix adds a sieving effect so that particles can be characterized by both charge and size. Additives are not necessary for nucleic acids which have a similar surface charge irrespective of their size.