Electrophoresis
From Wikipedia, the free encyclopedia
- For specific types of electrophoresis (for example, the process of administering medicine, iontophoresis), see electrophoresis (disambiguation).
Electrophoresis is the movement of an electrically charged substance under the influence of an electric field. This movement is due to the Lorentz force, which may be related to fundamental electrical properties of the body under study and the ambient electrical conditions by the equation given below. F is the Lorentz force, q is the charge carried by the body, E is the electric field [1]:
- <math>\bar F_e\ = q \bar E\ </math>.
The resulting electrophoretic migration is countered by forces of friction such that the rate of migration is constant in a constant and homogeneous electric field:
- <math>F_f\ =\ vf </math>
Where v is the velocity and f is the frictional coefficient.
- <math>q \bar E\ = vf </math>
The electrophoretic mobility <math>\mu</math> is defined as followed.
- <math>\mu = {v \over E} = {q \over f}</math>
The expression above applied only to ions at a concentration approaching 0 and in a non-conductive solvent. Polyionic molecules are surrounded by a cloud of counterions which alter the effective electric field applied on the ions to be separated. This renders the previous expression a poor approximation of what really happens in an electrophoretic apparatus.
The mobility depends on both the particle properties (e.g., surface charge density and size) and solution properties (e.g., ionic strength, electric permittivity, and pH). For high ionic strengths, an approximate expression for the electrophoretic mobility is given by the Smoluchowski equation,
- <math>\mu_e = \frac{\epsilon\epsilon_0\zeta}{\eta}</math>,
where <math>\epsilon</math> is the dielectric constant of the liquid, <math>\epsilon_0</math> is the permitivitty of free space, <math>\eta</math> is the viscosity of the liquid, and <math>\zeta</math> is the zeta potential (i.e., surface potential) of the particle.
[edit] Applications
Gel electrophoresis is used in biology to compare the protein profiles or DNA profiles of different organisms and thereby estimate their relatedness (e.g. Jahn et al. 1986, Khattak and Matthews 1993).
Electrophoretic displays (EPD's) are a class of information display that form images by electrophoretic motion of charged, colored pigment particles. Products incorporating electrophoretic displays include the Sony Librie electronic book reader, and the iRex iLiad e-newspaper tablet, both of which use electrophoretic films manufactured by E Ink Corporation.
[edit] References
- John R. Taylor, Chris D. Zafiratos, and Michael A. Dubson, "Modern Physics for Scientists and Engineers," Prentice Hall, Upper Saddle River, 2004.
- http://gslc.genetics.utah.edu/units/activities/electrophoresis/
- W.B. Russel, D.A. Saville, and W.R. Schowalter, "Colloidal Dispersions," Cambridge University Press, Cambridge UK, 1989.
- Voet and Voet, Biochemistry, John Whiley & sons. 1990.
- Jahn, G. C., Hall, D.W., and Zam, S. G. 1986. A comparison of the life cycles of two Amblyospora (Microspora: Amblyosporidae) in the mosquitoes Culex salinarius and Culex tarsalis Coquillett. J. Florida Anti-Mosquito Assoc. 57, 24–27.
- Khattak MN, Matthews RC. Genetic relatedness of Bordetella species as determined by macrorestriction digests resolved by pulsed-field gel electrophoresis. Int J Syst Bacteriol. 1993 Oct;43(4):659-64.
[edit] See also
de:Elektrophorese eo:Elektroforezo es:Electroforesis fa:الکتروفورز fr:Électrophorèse id:Elektroforesis su:éléktroforésis fi:Elektroforeesi sv:elektrofores vi:Điện di
