AFM and ellipsometric studies on LB films of natural asymmetric and symmetric bolaamphiphilic archaebacterial tetraether lipids on silicon wafers.

The monomolecular organisation of the natural asymmetric and symmetric bolaamphiphilic (archaebacterial tetraether lipids) was studied using a combination of Langmuir film balance, ellipsometry, and atomic force microscopy (AFM). Monolayer films were transferred onto silicon wafer substrates. After transfer of the lipids onto several kinds of silicon wafer substrates (hydrophobic, hydrophilic, and amino-silanised), the monolayer films were further investigated by ellipsometry and AFM in order to determined whether bolaamphiphiles are oriented differently at the water-air interface, including "horseshoe" and "upright" configurations. The thickness of the monolayer film, which was determined by ellipsometry, represents a combined mean value of the domains. The surface morphology, which was evaluated by AFM showed that in all films, the domains were arranged in small domains or the most homogeneous organisation, depending on the properties of the wafer silicon substrates. From all films, the hydrophobically transferred lipids showed the most homogeneous organisation on the substrates. After transfer onto hydrophilic and amino-silanised surfaces, the lipids were arranged in small islands on the substrates.