Electrophoresis
Definition and meaning of Electrophoresis in chemistry.
Electrophoresis is a laboratory technique used to move charged particles through a fluid or gel. An externally applied electric field drives this controlled migration across the medium. Positively charged cations naturally move toward the negatively charged cathode. Negatively charged anions migrate toward the positively charged anode.
In more detail
Gel electrophoresis is a highly common variation used in modern science laboratories. It uses a porous matrix made of materials like agarose or polyacrylamide. This spongy gel acts as a highly effective microscopic sieve for chemical molecules.
Smaller molecules thread through the tiny microscopic pores very quickly and easily. Larger molecules get tangled in the matrix and move at a much slower pace. This physical barrier allows scientists to separate molecules by both size and electrical charge.
Researchers rely on this method daily to resolve complex mixtures of DNA or proteins. The migration speed of a particle per unit of electric field is called electrophoretic mobility. This specific mobility depends heavily on several adjustable experimental factors in the laboratory.
The applied voltage directly controls the overall driving force acting on the particles. The buffer solution ionic strength affects the electrical conductivity of the entire system. The chosen gel pore size determines the amount of physical resistance the molecules face.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Driving force | Applied direct current electric field |
| Common media | Agarose gel, polyacrylamide gel (PAGE) |
| Key parameter | Electrophoretic mobility, μ = v/E |
| Typical targets | DNA, RNA, and protein mixtures |
| Separation factors | Particle net charge, physical size, and overall shape |
In standard agarose gel electrophoresis, a scientist pipettes DNA fragments into small wells. These small wells sit at the negative end of a rectangular gel slab. The scientist then applies a strong direct voltage across the entire gel structure. The chemical phosphate backbone gives every single DNA molecule a net negative charge. Because opposite charges attract, all DNA fragments actively migrate toward the positive anode. Smaller DNA fragments slip easily through the agarose pores and travel quite far. Larger DNA fragments experience more physical drag and lag behind near the starting wells. A special fluorescent dye later reveals distinct bands representing the different fragment sizes.
Frequently asked questions
Why does DNA migrate toward the positive anode during gel electrophoresis?
DNA contains a sugar-phosphate backbone packed with negatively charged chemical phosphate groups. This gives the DNA a net negative charge in solution. Because opposites attract, the DNA moves steadily toward the positive electrode.
How is an electrophoresis experiment physically different from a chemical electrolysis process?
Electrophoresis simply moves intact charged particles through a physical medium to separate them by size. Electrolysis actively uses an electric current to force a nonspontaneous chemical reaction that breaks chemical compounds apart.
Why do chemists use a thick gel instead of just a simple liquid bath?
A plain liquid allows particles to move based entirely on their electrical charge. A gel adds a physical barrier filled with tiny microscopic pores. This extra physical barrier lets scientists separate complex molecules by their physical size.