PULSED-FIELD ELECTROPHORESIS IN MICROLITHOGRAPHIC ARRAYS

Transverse pulsed-field electrophoresis of DNA has been conducted in a silicon array engineered by optical lithography and the motion of ind ividual molecules observed by fluorescence microscopy. In strong field s, the molecules can be maintained in highly stretched, linear conform ations. When the field is switched through an obtuse angle, they head off in the new direction led by what was formerly their tail end. This backtracking gives rise to fractionation that is linear with molecula r weight. A simple prescription exists for choosing the field paramete rs to obtain a particular range of separation. Since the molecular mot ions are much more uniform than those that occur in a gel, it is antic ipated that the arrays will permit more efficient fractionation than t raditional pulsed-field gel electrophoresis. Arrays suitably scaled do wn in size may be useful for pulsed-field sequencing.