PALLADIUM ION ASSISTED FORMATION AND METALLIZATION OF LIPID TUBULES

Tubules have been formed at pH 5.6 from the negatively charged diacetylenic phospholipid 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphohydroxyethanol in the presence of tetraammine palladium (II) chloride. Transmission electron microscopy revealed the formation of predominantly 0.07 mum-0.16 mum diameter tubules. Unbound palladium salt was removed by dialyzing tubule dispersion against water. The palladium bound to the lipid headgroups acted as a catalyst for the electroless metal plating of the tubules with nickel and cobalt metals. Sustained dialysis prior to metallization resulted in an increase in the diameter of the tubules. Palladium salt did not bind to the neutral phosphocholine headgroup of the analogous diacetylenic lipid and therefore no metallization was observed. Thin slices of metal coated tubules embedded in epoxy resin were characterized by atomic force and scanning tunneling microcopy.