Structural studies of DNA cationic lipid complexes confined in lithographically patterned microchannel arrays

We have used lithographically patterned microchannel arrays with channel wi dths ranging from 1 to 20 mu m, fabricated using electron beam lithography and reactive ion etching, in structural studies of DNA-cationic lipid compl exes in confinement. Various techniques have been developed for loading the se DNA-membrane complexes into the microchannels or to form the complexes i n situ by sequentially depositing DNA and lipid solutions into the microcha nnels. Optical microscopy studies indicate that such complex formation is s trongly influenced by the periodic channel structure even at channel widths much larger than the persistent length of the DNA molecules. Preliminary x -ray diffraction experiments conducted at Stanford Synchrotron Radiation La boratory (SSRL) yielded only a weak signal from the lipid bilayers in the c omplexes. The use of a microfocused x-ray beam produced by the newly develo ped Bragg-Fresnel optics at a third-generation synchrotron facility may dra matically increase the signal-to-noise ratio and allow observation of orien tational as well as positional ordering of DNA molecules induced by the mic rochannels. Structural control of the DNA-membrane complexes has a broad ra nge of potential applications in gene probe technology and as mesoscopic bi omolecular composites.