Functionally Active Membrane Proteins Incorporated in Mesostructured Silica Films

Abstract

A versatile synthetic protocol is reported that allows high concentrations of functionally active membrane proteins to be incorporated in mesostructured silica materials. Judicious selections of solvent, surfactant, silica precursor species, and synthesis conditions enable membrane proteins to be stabilized in solution and during subsequent co-assembly into silica-surfactant composites with nano- and mesoscale order. This was demonstrated by using a combination of non-ionic (n-dodecyl-β-D-maltoside or Pluronic P123), lipid-like (1,2-diheptanoyl-s,n-gycero-3-phosphocholine), and perfluoro-octanoate surfactants under mild acidic conditions to co-assemble the light-responsive transmembrane protein proteorhodopsin at concentrations up to 15 wt% into the hydrophobic regions of worm-like mesostructured silica materials in films. Small-angle X-ray scattering, electron paramagnetic resonance spectroscopy, and transient UV-visible spectroscopy analyses established that proteorhodopsin molecules in mesostructured silica films exhibited native-like function, as well as enhanced thermal stability compared to surfactant or lipid environments. The light absorbance properties and light-activated conformational changes of proteorhodopsin guests in mesostructured silica films are consistent with those associated with the native H+-pumping mechanism of these biomolecules. The synthetic protocol is expected to be general, as demonstrated also for the incorporation of functionally-active cytochrome c, a peripheral membrane protein enzyme involved in electron transport, into mesostructured silica-cationic surfactant films.

Tuning molecular adsorption in SBA-15-type periodic mesoporous organosilicas by systematic variation of their surface polarity

“…This effect is manifested qualitatively in various types of line broadening and the appearance of distinct spectral features. 49 , 50 First, the line width ( H 0 ) of the central peak increases gradually, 22 , 51 from 0.47 to 0.67 mT (grey-shaded region) as the surface polarity decreases from T100 to BP100. The eventual appearance of an outer extremum at 335.5 mT (black arrow) is also a well-established indicator of diminished rotational motion.…”

“…The eventual appearance of an outer extremum at 335.5 mT (black arrow) is also a well-established indicator of diminished rotational motion. 22 , 50 In addition, the gradually changing intensities of two partially resolved peaks at 328.8 mT (blue arrow) and 329.7 mT (green arrow) represent varying populations of slow and fast components, respectively. Further line broadening is caused by the increasing fraction of the slow component.…”

“… 13 We also used EPR lineshape analysis to assess changes in the mobility of TEMPO (2,2,6,6-tetramethylpiperidinyloxy) spin labels covalently attached to and interacting with PMO surfaces. 22 , 23 Finally, we explored how the affinity of these materials for representative organic molecules relevant to the upgrading of lignocellulosic biomass is controlled by surface and solvent polarity.…”

Protein Conformational Dynamics upon Association with the Surfaces of Lipid Membranes and Engineered Nanoparticles: Insights from Electron Paramagnetic Resonance Spectroscopy

“…Therefore, EPR methods have been extensively used to infer the information on physiologically relevant conformational changes of proteins caused, e.g., by transitioning from their soluble state to the membrane surface-bound state [ 7 , 8 , 9 , 10 , 33 , 45 , 46 , 81 , 82 , 83 , 84 ] but also aggregation and misfolding induced by the membrane surface [ 82 , 85 , 86 ]. EPR studies have also proved very useful in biotechnology developments for assessing protein stability when immobilized through absorption or covalent attachment to nanosurfaces and synthetic membranes [ 87 , 88 , 89 , 90 , 91 , 92 , 93 ]. This range of applications of EPR methods is highlighted with the examples provided below.…”

Cell adherence and drug delivery from particle based mesoporous silica films

“…pore sizes and particle morphology, in combination with large surface areas up to 1000 m 2 g À1 and tunable surface functionalities, are a few reasons for why this class of materials attracts extensive interest for use in drug delivery and tissue engineering applications. [3][4][5][6][7][8][9][10][11] The high inner surface area of the particles allows the loading with a large amount of active substance molecules. The synthesis of a variety of silica-based lms has been reported in literature, mainly by using evaporation-induced self-assembly in spin-or dipcoating, 12,13 or e.g.…”