EFFECT OF SPIKE PULSES ON THE ORIENTATION OF THE AGAROSE-GEL MATRIX

The orientation of the agarose gel matrix in two-part, ''stair-step'' electric fields has been studied by transient electric birefringence. Stair-step electric fields are those in which a pulse of a given ampli tude is immediately followed by a short, higher voltage ''spike'' puls e of the same polarity. A single stair-step pulse orients the agarose gel matrix as though the two portions of the pulse were individually a pplied to the gel. However, a series of consecutive stair-step pulses causes an anomalous increase in the amplitude of the birefringence, su ggesting that increased numbers of agarose fiber bundles are orienting in the electric field. Spike pulses greater than or equal to 10 V/cm appear to cause junction zone breakdown, freeing large numbers of agar ose fiber bundles and microgel domains from the constraints of the gel matrix. The implications of these results for pulsed field gel electr ophoresis are discussed.