LALI Electrophoretic Methods[1]

LALI Electrophoretic Methods[1] - Electrophoretic Methods...

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Unformatted text preview: Electrophoretic Methods Chemistry 543 Fall 2006 Kantardjieff What is electrophoresis? Forced migration of charged particles (proteins, nucleic acids) in an electric field F el = qE, where q is the charge, E is the applied electric field Molecule accelerates rapidly and is soon retarded by a frictional force F frict = -fv, where f is the friction coefficient, and v is the velocity After reaching equilibrium, qE + fv = 0 or V = qE/f We define electrophoretic mobility as U = v/E = q/f U is an intrinsic property of the macromolecule, depending only on its charge and frictional properties, which is quite useful for characterization About charge Unlike isolated ions, such as Na+ or Cl-, which have definite charge, macromolecules have a variable net charge that depends on pH (zwitterion, polyelectrolyte) pH at which net charge = 0 is pI Macromolecules, having charged regions, are solvated with a cloud of counterions that provide electrical shielding I = c i z i 2 Coulomb forces are long range, thus screening changes for different concentrations of ions L D = ( o k B T/2e 2 ) 1/2 I-1/2 Problem: modest electric field createssubstantial heating in solution. Answer: gel avoids convection SDS PAGE...
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LALI Electrophoretic Methods[1] - Electrophoretic Methods...

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