PHOSPHOLIPID AND PROTEIN MONOLAYERS

We report on X-ray reflectivity and diffraction studies using monolaye rs of phospholipids and of the protein streptavidin specifically bound to monolayers. For phospholipids with the phosphocholine head group a ttached to the glycerol backbone via (flexible) ethylene oxide spacers , we demonstrate that the lateral interactions can be reduced by incre asing of the spacer length. This is reflected in a reduction of the ti lt angle of aliphatic tails. Diffraction of the protein layer can be o bserved in situ. The data reveal that positional order is merely short -ranged and that the structure can be changed reversibly via film comp ression and expansion.