Stability of Purple Membranes from <i>Halobacterium salinarum</i> toward Surfactants: Inkjet Printing of a Retinal Protein

Inkjet printing is a versatile technique widely applied in biological microarray technology. Because of its photochemical and photophysical properties, bacteriorhodopsin (BR) from <i>Halobacterium salinarum</i> holds promise for applications in nanotechnology, and inkjet printing would simplify the transfer of BR to suitable substrates. Surfactants are essential parts of inkjet formulations tuning viscosity, rheology, and spreading behavior of the solution. However, many surfactants destabilize the structure of proteins and often cause denaturation accompanied by a complete loss of function. Inkjet printing of membrane proteins is particularly challenging and special care must be taken in the choice of the surfactant. For BR, the situation is complicated by the fact that the structural integrity of BR depends on its native membrane environment, the so-called purple membrane (PM). PM contains 10 lipid molecules per BR monomer and is very sensitive toward surfactants. In this work, we identified surfactants suitable for inkjet formulations containing PM. Initially, we screened a variety of technically relevant surfactants for compatibility with PM using the UV–vis absorption of the retinal chromophore as a natural probe. Promising candidates were selected, and their impact on the structure of PM and BR was analyzed using UV–vis spectroscopy, CD spectroscopy, and small-angle X-ray scattering (SAXS). We identified two surfactants compatible with PM and suitable for inkjet formulations. An inkjet formulation containing PM as dye component was developed. We demonstrate that the photochromic properties of BR are maintained upon inkjet printing

Additional file 2: Table S2. of Communicating BRCA research results to patients enrolled in international clinical trials: lessons learnt from the AGO-OVAR 16 study

Shows the countries and respective populations that were involved in AGO-OVAR 16. (DOC 28 kb

Additional file 1: Table S1. of Communicating BRCA research results to patients enrolled in international clinical trials: lessons learnt from the AGO-OVAR 16 study

Lists names and affiliations of local Institutional Review Boards and Independent Ethics Committees that approved the study. (PDF 211 kb