The phenomenon of the migration of charged particle in the influence of electrical field is termed as Electrophoresis. It is one the powerful means of separating proteins and other bio-molecules such as DNA, RNA etc.
When a potential difference is applied across the electrodes , a potential gradient will be generated which is equal to the ratio of potential difference and the difference the two electrodes.
V = Volatage applied.
f = Distance between the two electrode.
If potential difference of 100 V is applied and the distance between the two electrode is 20 cm then:
Potential Gradient = 100 / 20 = 5 V/cm
When potential gradient is applied , the force acting upon the charged molecule having charge q will be:
F = E.q
So, the charge molecule will move with this force, but there is some frictional resistance that slow down the movement of this charge molecule i.e. size and shape of this charge molecule , pore size of the medium in which electrophoresis taking place and the viscosity of the buffer. . . . velocity of charged particle in an electrical field = F/f
= E.q /f
Now, the current in the solution between the electrodes is conducted mainly by the buffer ions.
Than according to Ohm’s law:
R = V / I
or applied voltage is directly proportional to flow of current.
Above statement demonstrate that it is possible to accelerate an electrophoratic separation by increasing the applied voltage , which will result in a corresponding increase in the current flow.
The distance migrated will be proportional to both current and time.
However, increasing the voltage will cause generation of heat which have the following effects:
For exp. – DNA samples will migrate faster in 0.8 % gel compared to a 1% gel likewise. Samples will migrate faster in a 20 ml (6 mm thick ) gel verses a 30 ml (8 mm thick ) gel with the same 7 × 7 centimeter dimension.
T5) his technique is simple, rapid to perform and capable of resolving fragments of DNA that can not be separated adequately by other procedures, as density gradient centrifugation.