Abstracts: 

 SBIR— Phase II 



The Separation of Large DNA Fragments with Oscillating 

 Electric and Magnetic Fields* 



Gunter A. Hofniann 



BTX/Biotechnologies and Experimental Research, Inc., San Diego, CA 92109 

 (619)270-0861 



The accurate and fast separation of large DNA fragments is a crucial technology 

 needed for mapping the human genome. Existing methods such as pulsed-field gel 

 electrophoresis appear to have severe limitations. This project uses a novel approach: 

 Lorentz-force-mediated separation in the form of oscillating electric and magnetic 

 fields. DNA exhibits a large induced dipole moment at low frequencies, with a 

 relaxation time dependent on the length of the fragment. The planned separation method 

 makes use of the polarizability of DNA fragments by subjecting them to an oscillating 

 electric field with a superimposed perpendicular oscillating magnetic field in a liquid 

 without matrix. The resulting unidirectional Lorentz force moves the DNA fragments 

 perpendicular to both the electric and the magnetic field with a drift velocity dependent 

 on the DNA polarizability. which depends in turn on the DNA size and configuration. 

 Phase I studies demonstrated that DNA fragments can be polarized by an oscillating 

 electric field and that a superimposed magnetic field results in a unidirectional Lorentz 

 force and a unidirectional drift velocity. The drift velocity increases with the size of the 

 DNA fragment, in contrast to conventional electrophoresis. For large DNA fragments, 

 the drift velocity is two to three orders of magnitude higher than the drift velocity 

 observed in experiments in pulsed-field gel electrophoresis. A theoretical model with a 

 porous sphere simulation of the DNA molecule showed promise in yielding some 

 qualitative agreements with the observed experimental dependencies of the drift 

 velocity. Phase II studies will develop several prototype apparatuses of increasing 

 complexity that will allow the rapid, accurate separation of large DNA fragments. A 

 wider parameter range will be investigated, especially separation at higher frequencies, 

 and optimum operating conditions will be determined. The limits of the crossed-field 

 separation method will be investigated in experiments and theory. 



•1989 award for two years. 



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