SODIUM DODECYL-SULFATE CAPILLARY ELECTROPHORESIS OF PROTEINS IN ENTANGLED SOLUTIONS OF POLY(VINYL ALCOHOL)

A novel polymer network is described for efficient sieving of sodium d odecyl sulfate (SDS)-protein complexes: poly(vinyl alcohol) (PVA; aver age M(r) 133000). The entanglement threshold of these solutions was fo und to be at 3% (w/v) PVA. Solutions from 4 to 6% PVA offer excellent resolution in the 14400-94000 protein molecular mass interval. Ferguso n plot analysis showed that the separation is indeed based on mass dis crimination, as it should in SDS electrophoresis, with extrapolated (a t 0% polymer) limit values of mobility for all particles in the range (2.34-2.87) 10(-8) m(2) V(-1)s(-1). The advantages of PVA are full tra nsparency in the UV region down to 200 nm and extremely low viscositie s (e.g., a 5% PVA solution has a viscosity 25 times greater than that of buffer at 30 degrees C). A unique wall effect was found, by which, on decreasing the inner diameter of the capillary from 75 to 25 mu m, the apparent entanglement threshold was shifted to extremely dilute PV A solutions, since in 25-mu m capillaries efficient sieving was obtain ed below 1% PVA, i.e., at concentrations well below the entangled regi me. It is hypothesized that residual, free silanols present (even in a coated capillary) act as nucleation sites for H-bond formation and ag gregation of free PVA molecules.