How to Control the Molecular Architecture of a Monolayer of Proteins Supported by a Lipid Bilayer

Abstract

In this work, we report the spontaneous formation of a new structure composed of two lipid layers surrounding a dense monolayer of soluble proteins (lysozyme). We extend a process, initially discovered with nonionic surfactants to phospholipids (DMPC and DOPC). The motor of the protein insertion process is the difference between the protein chemical potential in the solution and in the freshly formed Newton black film (NBF). This process is completely controlled by adjusting the protein chemical potential in the solution. By means of x-ray reflectivity, we follow the evolution of the freestanding sandwich structure until a stable equilibrium state is reached. Depending on the lipid concentration with respect to the protein concentration, we observe two different behaviors of the film leading to the formation of such unique structure: at the highest lipid concentration, the usual protein diffusion into the NBF, and, at the lowest lipid concentration, the spontaneous formation of a sandwich structure immediately obtained after the drainage. Finally, we show that the insertion process is reversible, because, if the lipid concentration varies in the bulk solution, a "deswelling" of the film can be observed.

Direct Investigation of the Vectorization Properties of Amphiphilic Cyclodextrins in Phospholipid Films

“…A general insertion process was found to form a single protein layer embedded in the freestanding surfactant bilayers by adjusting the protein chemical potential in bulk. The use of DMPC instead of C 12 E 6 and lysozyme instead of BSA led to the same result, but with a larger variety of behaviors (10). In this case, the complexity of the film structure is magnified by the use of biological molecules for both the film and the host.…”

Contact angles of protein black foam films under dynamic and equilibrium conditions

“…The goal of these investigations was to penetrate more profoundly into the film with the help of X-ray radiation and to reveal the more detailed structure of the phospholipid films. Some interesting results were obtained [18,20,21], unfortunately, this method requires working with very large films of the order of 2 cm 2 .…”

“…The film thickness, disjoining pressure isotherms, double layer potential, phase transitions, short-range surface forces [3,6,[14][15][16][17], interaction free energy, and influence of additional components [7][8][9] have been investigated by the microinterferometric method [2]. Another technique, the X-Ray reflectivity method, has been used for studying the structure and thickness of black foam films [18,[20][21][22][23]. In all cited papers, equilibrium DMPC black foam films are considered.…”

Effect of surface modification on protein retention and cell proliferation under strain

“…For proteins, SXR is used to elucidate thickness, coverage, and conformation on surfaces. Proteins have been adsorbed on ordered monolayers, such as Langmuir-Blodgett films or self-assembled monolayers, to drive specific interactions [13,14]. SXR is useful in obtaining surface concentrations using protein volume if a tertiary conformation can be assumed with confidence [15].…”