AN ELECTRIC-FIELD JUMP APPARATUS WITH NS TIME RESOLUTION FOR ELECTROOPTICAL MEASUREMENTS AT PHYSIOLOGICAL SALT CONCENTRATIONS

An apparatus is described, which can be used for electro-optical measurements at high ionic strengths, including physiological salt concentrations. The electric pulse is generated by the cable discharge technique; complete matching of the load impedance is achieved by a compensation cell, which is supplied with a steady flow of electrolyte solution. At a cable length of 20 m the pulse length is limited to 200 ns; the electric field strength applied to the solution is up to 80 kV/cm. The apparatus can be used for automatic sampling with minimal exposure of the samples to irradiation and with control of temperature and absorbance of the sample. The limit time resolution is a few ns. The electric dichroism of DNA restriction fragments, for example, can be characterized at physiological salt at a high signal-to-noise ratio.