Surface structure, membrane proteins INDEX

The excitement generated by these hydropathy index plots, which predict that most of the thylakoid proteins indeed span the membrane, may have led to a view that it is unnecessary to experimentally demonstrate that the proteins have segments exposed at the outer and inner surfaces. Nevertheless, biochemical evidence such as antibody labelling, protease studies and chemical modification is needed to prove all predicted structures. Already it has become evident that caution is needed in the interpretation of the Hydropathy index plots. This need is demonstrated by the hydropathy index plots of the D1 (herbicide-binding) and D2... 

Surface plasmon resonance (SPR) allows monitoring label-free interactions between biomolecules in real time. In SPR measurements, one of the biomolecules is immobilized on a sensor surface and the other one is transported in solution across the surface. Binding of the second biomolecule will cause an increase in mass and a proportional increase in refractive index that can be monitored. Gold surfaces are the most commonly used ones and they can be modified or functionalized for the specific binding of particular molecules. For example, biotinylated surfaces enable the immobilization of streptavidin-labeled proteins, and surfaces modified with lipophilic groups allow the immobilization of vesicles creating membrane-like structures to study protein association and dissociation with membranes. 

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