The mol. self-organization and structural properties of peptide assemblies at different interfaces, using either amphipathic or hydrophobic polypeptide helixes, is described. The two peptides under investigation form stable monolayers on the water surface under the conservation of their mol. conformation, as studied by CD and polarization-modulation Fourier transform IR (FTIR) spectroscopy. Using surface plasmon resonance and reflection-absorption FTIR, we show that such mol. layers can be transferred unaltered to solid substrates. Most importantly, the mol. orientation of the hydrophobic helixes on solid supports such as gold can be controlled by choosing a particular procedure for the layer formation. The helixes were oriented parallel to the interface in Langmuir-Blodgett monolayers, and perpendicular to the interface in self-assembled monolayers. Our reflection-absorption FTIR measurements have delivered for the first time direct exptl. evidence for the mol. conformation and orientation of pure peptide monolayers. Suitable ref. spectra of polypeptides with defined conformation and orientation are necessary to use this technique for the detn. of the mol. orientation of peptides in monomol. films. We have solved the problem for a-helical polypeptides by using bacteriorhodopsin as a ref. in combination with synthetic a-helixes of defined interfacial orientation. The present study shows the possibility of constructing immobilized peptide monolayers with predefined macroscopic properties and mol. structure by choosing the proper polypeptide amino acid sequence, the technique used for layer formation, and the supporting surface properties. [on SciFinder (R)]