Three basically different electrophoretic separation methods are performed in practice nowadays

 Electrophoresis, sometimes called Zone Electrophoresis (ZE) GE

 Isotachophoresis (ITP) SDS PAGE

Isoelectric focusing (IEF).

TLS Online TPP Program

#Id: 2921

#Unit 13. Methods in Biology

RCF units are therefore dimensionless (denoting multiples of g) and revolutions per
minute are usually abbreviated as r.p.m.

TLS Online TPP Program

#Id: 2922

#Unit 13. Methods in Biology

Nomograph for the determination of the relative centrifugal fi eld for a given rotor
speed and radius.

TLS Online TPP Program

#Id: 2927

#Unit 13. Methods in Biology

The rate of sedimentation is dependent not only upon the applied centrifugal field, but
also on the nature of the particle, i.e., its density and radius, and also the viscosity of the
surrounding medium. Stokes’ Law describes these relationships for the sedimentation of a
rigid spherical particle:

TLS Online TPP Program

#Id: 2928

#Unit 13. Methods in Biology

Nomograph for the determination of the relative centrifugal fi eld for a given rotor
speed and radius. The three columns represent the radial distance (in mm), the relative
centrifugal fi eld and the rotor speed rpm (in min-1).

TLS Online TPP Program

#Id: 2929

#Unit 13. Methods in Biology

The time of sedimentation (in seconds) for a spherical particle is (Please see the picture below)
where t is the sedimentation time, is the viscosity of medium, R hydro is the
hydrodynamic radius of the particle, r b is the radial distance from the centre of rotation
to bottom of tube, r t is the radial distance from the centre of rotation to liquid meniscus,
ρ is the density of the particle, m is the density of the medium and is the angular velocity
of the rotor.

TLS Online TPP Program

#Id: 2984

#Unit 13. Methods in Biology

The unit of s is seconds Most values of s are between 10-13 and 10-11 second. To
eliminate the exponents, the value of s is usually reported in svedbergs (S). 1 svedberg 10-13 second.