Electrophoresis
Definition and meaning of Electrophoresis in chemistry.
Electrophoresis is the migration of charged particles or molecules through a fluid or gel medium under an applied electric field, with cations moving toward the cathode and anions toward the anode. The rate of migration depends on the particle's net charge, size, and shape.
In more detail
In gel electrophoresis, a porous matrix such as agarose or polyacrylamide acts as a molecular sieve, so smaller molecules thread through the pores faster than larger ones, allowing separation by size in addition to charge. This makes electrophoresis a core technique in biochemistry and molecular biology for resolving mixtures of DNA, RNA, or proteins. The migration speed per unit field strength is called electrophoretic mobility, and it depends on the applied voltage, buffer ionic strength, and gel pore size.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Driving force | Applied DC electric field |
| Common media | Agarose gel, polyacrylamide gel (PAGE), buffer solution |
| Key parameter | Electrophoretic mobility, μ = v/E |
In agarose gel electrophoresis, DNA fragments are loaded into wells and a voltage is applied; because the phosphate backbone gives DNA a net negative charge, all fragments migrate toward the anode, with smaller fragments traveling farther through the gel than larger ones in a given time.
Frequently asked questions
Why does DNA migrate toward the anode during electrophoresis?
DNA's sugar-phosphate backbone carries negatively charged phosphate groups, so DNA molecules are net negatively charged in solution and move toward the positive electrode (anode).
How is electrophoresis different from electrolysis?
Electrophoresis uses an electric field to separate charged particles by mobility through a medium, generally without a net chemical reaction, while electrolysis uses electric current to drive a nonspontaneous redox reaction at the electrodes.