X-ray diffraction of a protein crystal anchored at the air/water interface

Abstract

We report the first successful in situ x-ray diffraction experiment with a 2D protein array at the lipid/water interface and demonstrate that the order can be controlled via lateral pressure or density. A protein (streptavidin) was bound to a monolayer of biotinylated lipid at the air/water interface, and diffraction of the protein layer could be measured to many orders. Compression of the monolayer changed the diffraction pattern drastically, indicating that the protein structure can be strongly influenced by external parameters like lateral pressure or density. From the width of the peaks, we find that aggregates consisting of as few as 100 monomers contribute to the diffraction. This indicates that the structure of even low order aggregates can be studied in situ. Grazing incidence diffraction can become a strong new method to study the crystallization and the interactions between proteins free from artifacts by staining or sample preparation.

Organization of Two-Dimensional Phospholipid Monolayers on a Gel-Forming Substrate

“…The surface properties of such gelling structures are largely unexplored. As a model system, we report here on measurements at the surface of aqueous clay gels [1,2] which, beside their fundamental interest, have also practical applications in many industrial processes [3,4].Recently, the air/water interface proved to be ideal to the study of associations of lipid monolayers with adsorption layers such as proteins [5] or polyelectrolytes [6]. Furthermore, organic complexes with clay minerals [7,8] and ternary systems made up of clay minerals, organic compounds, and water [9] are of great interest in many aspects of adsorption processes in physics, chemistry, and biology.…”

Fluorescence and Phosphorescence Methods to Probe Protein Structure and Stability in Ice: The Case of Azurin

“…We are left to consider protein-ice interactions, which may take the form of an adsorption process, in the fashion of antifreeze proteins [30] or even of physical distortion of the protein globule by anisotropic compression in the intergranular space of ice crystals [31]. In the first case the protein will distribute between the liquid and the interface to the solid phase and the extent of adsorption will be determined by the volume fraction of liquid water V L and the surface area of ice.…”

The influence of hydrophilic spacers on the phase behavior of ether lipids

“…They play an important role in coupling mechanisms at surfaces and interfaces. In the system Streptavidin/Biotin the lateral protein density is mainly dependent on the length of the spacer between the biotin and the hydrophobic anchor of the functionalized lipid [11][12][13].…”