Sammendrag
The use of symmetric reversing electric field pulses in electrooptic studies of rigid macromolecules in order to determine the ratio between the permanent and the induced dipole moments is well established. Application of this method to studies of small macromolecules requires a field reversal time of only a few nanoseconds. No high current pulse generator capa ble of producing symmetric kV pulses with such a short reversal time is available for studies of small macromolecules in physiological salt solutions, but it has long been known howto make such reversing pulses that are asymmetric. In order to take advantage of the opportunity offered by the latter fact we here present a theoretical analysis in the thermaldomain of the electrooptic properties of solutions containing rigid macromolecules with axial symmetry, when exposed to asymmetric reversing elect ric field pulses. The analytical expressions needed for quantitative determination of the ratio between the permanent andthe induced electric dipole moments of rigid macromoleculesusing electrooptic data obtained employing reversing electric pulses with given asymmetry, are presented. The feasibility of this new approach is demonstrated by including experimental electric birefringence datafor a 12 kDa protein (segment 14 of alpha-spectrin from Drosophila brains) in near physiological salt solutions obtained using a coaxialcable pulser producing 2 mics long pulses with a reversal time of about 15 ns.
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