NOVEL CHELATE-INDUCED MAGNETIC ALIGNMENT OF BIOLOGICAL-MEMBRANES

A phospholipid chelate complexed with ytterbium (DMPE-DTPA:Yb3+) is sh own to be readily incorporated into a model membrane system, which may then be aligned in a magnetic field such that the average bilayer nor mal lies along the field. This so-called positively ordered smectic ph ase, whose lipids consist of less than 1% DMPE-DTPA:Yb3+, is ideally s uited to structural studies of membrane proteins by solid-state NMR, l ow-angle diffraction, and spectroscopic techniques that require orient ed samples. The chelate, 1,2-dimyristoyl-sn-glycero-3-phosphoethanolam ine diethylenetriaminepentaacetic acid, which strongly binds the lanth anide ions and serves to orient the membrane in a magnetic field, prev ents direct lanthanide-protein interactions and significantly reduces paramagnetic shifts and line broadening. Similar low-spin lanthanide c helates may have applications in field-ordered solution NMR studies of water-soluble proteins and in the design of new magnetically aligned liquid crystalline phases.