jp3057459_si_001.pdf (643.9 kB)
Stability of Purple Membranes from Halobacterium salinarum toward Surfactants: Inkjet Printing of a Retinal Protein
journal contribution
posted on 2012-08-16, 00:00 authored by Martin Imhof, Jens Pudewills, Daniel Rhinow, Ivan Chizhik, Norbert HamppInkjet printing is a versatile technique widely applied
in biological microarray technology. Because of its photochemical
and photophysical properties, bacteriorhodopsin (BR) from Halobacterium salinarum 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.