Mechanisms of retardation of rigid spherical particles with 3 to 1,085 nm radius in capillary electrophoresis, using buffered polyacrylamide (molecular weight 5 x 10(6)) solutions.
Subjecting particles in the size range of 3 to 1085 nm radius (R) to capillary electrophoresis in buffered solution of entangled uncrosslinked polyacrylamide (M(r) 5 x 10(6)), it was found that particle size-dependent retardation ("molecular sieving") becomes electric field- and particle size range-dependent once the particle size exceeds 15-20 nm in radius. The field strength dependence of the retardation coefficient [KR = d(log mobility)/ d(polymer concentration] and the positive or negative sign of dKR/dR suggest the existence of two different mechanisms of molecular sieving depending on the particle size range: particles with diameters less than the screening length (or blob size) of the polymer network are thought to penetrate into the available spaces within a discontinuous polymer network; particles with diameters larger than the screening length (or blob size) of the polymer network are thought to undergo size-dependent retardation by exerting shear stress against polymer chains, and displacing them, so as to cause local deformations in a continuous polymer network. A limit in the separating capacity of molecular sieving, due to a sharp increase in the rate of band widening with polymer concentration, was found when the value of the retardation coefficient exceeded 60 (mL/g).
Radko
S P
SP
Section on Macromolecular Analysis, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA.
Chrambach
A
A
D000180:Acrylic Resins; D002021:Buffers; D019075:Electrophoresis, Capillary / Q000379:methods*; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods*; D005782:Gels; D008432:Mathematical Computing; D008958:Models, Molecular; D010316:Particle Size; D012996:Solutions
D000180:Acrylic Resins; D002021:Buffers; D005782:Gels; D012996:Solutions; C016680:polyacrylamide gels