Surface Pressure Induced Structural Effects in Photosynthetic Reaction Center Langmuir-Blodgett Films

Abstract

The structural modifications of photosynthetic reaction centers from Rhodobacter sphaeroides arranged in Langmuir films and after deposition onto solid substrate have been investigated as well as the variations in protein orientation as a function of surface pressure. While at low surface pressure (15−25 mN/m) protein integrity appears to be affected by the action of the surface tension, as results from the film behavior at the air−water interface and from optical spectroscopy data. When the surface pressure (30−45 mN/m) is increased, protein structure is much better preserved. Moreover, at those deposition pressures, the film is characterized not only by a higher surface density but also by an increased anisotropy, as revealed by polarized absorption spectroscopy and confirmed by optical ellipsometry. Measurements of water content desorption in deposited films by means of a gravimetric transducer have consistently confirmed the preservation of protein structure at higher surface pressures.

RETRACTED: Monolayers of pigment-protein complexes on a bare gold electrode: Orientation controlled deposition and comparison of electron transfer rate for two configurations

“…The most striking feature of LB technique is the control of the thickness and orientation of the deposited layers. This method has been extensively used to deposit mono (multi) layers of the various kinds of molecules, including protein complexes onto a variety of substrates with precise control Dutton, 1991a, 1991b;Facci et al,1998;Fang et al,1995;Fukuda et al,1992;Talham et al, 2008;Tredgold, 1985;Ueno et al,1998;Uphaus et al,1997;Yan et al, 2012;Yasuda et al,1997Yasuda et al, ,1994Zhao et al, 1992).…”

Experimental aspects of solid state circular dichroism

“…85 More recently a-helix-bundle proteins have been studied as LB films (and in solution). 86 Surface pressure effects in LB protein films were studied by CD and other techniques by Nicolini et al 87 A tendency to increase b-sheet structure in proteins' films dried on a thin quartz window compared to solution phase samples was observed by Hu et al, 88 whose results were however criticized by Harada and Kuroda 89 using the dedicated J-800KCM instrument. 10 Nakagawa et al studied amino acid films prepared with vacuum sublimation technique.…”

Spectroscopic characterizations of non-amphiphilic 2-(4-biphenylyl)-6-phenyl benzoxazole molecules at the air–water interface and in Langmuir–Blodgett films

“…Perhaps, the most interesting feature associated with LB films which makes them attractive for these photonic devices is the ability to control the spatial distribution and orientation of molecules assembled in these films, to bring about desired changes [15,16] in their optical and electronic properties. Interestingly, LB supramolecular assemblies closely resemble natural biomembranes and provide a unique platform for mimicking energy and electron transfer reactions in real energy-harvesting photosynthetic reaction centers [17][18][19][20]. Advantages of both charged and neutral lipid mixed LB films of micro-heterogeneous media for control of photophysical processes, chemical reactions and tailoring of charged transfer complexes or p electron arrays [21][22][23], are their well-defined composition, flexibility, anisotropic nature and possibility of polarity modulation.…”