Water‐in‐Oil Micro‐Emulsion Enhances the Secondary Structure of a Protein by Confinement |
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Authors: | Dr. Stepan Shipovskov Prof. Cristiano L. P. Oliveira Søren Vrønning Hoffmann Dr. Leif Schauser Prof. Duncan S. Sutherland Prof. Flemming Besenbacher Prof. Jan Skov Pedersen |
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Affiliation: | 1. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Ny Munkegade 8000 Aarhus (Denmark);2. Danisco A/S, Genencor Division, Edwin Rahrs Vej 38, 8220 Brabrand (Denmark);3. Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 130, 8000 Aarhus (Denmark);4. Complex Fluids Group, Department of Experimental Physics, Institute of Physics, University of S?o Paulo, 05314‐970 S?o Paulo (Brazil);5. Institute for Storage Ring Facilities (ISA), Aarhus University, Ny Munkegade, DK‐8000 Aarhus (Denmark);6. Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Ny Munkegade 8000 Aarhus (Denmark) |
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Abstract: | A scheme is presented in which an organic solvent environment in combination with surfactants is used to confine a natively unfolded protein inside an inverse microemulsion droplet. This type of confinement allows a study that provides unique insight into the dynamic structure of an unfolded, flexible protein which is still solvated and thus under near‐physiological conditions. In a model system, the protein osteopontin (OPN) is used. It is a highly phosphorylated glycoprotein that is expressed in a wide range of cells and tissues for which limited structural analysis exists due to the high degree of flexibility and large number of post‐translational modifications. OPN is implicated in tissue functions, such as inflammation and mineralisation. It also has a key function in tumour metastasis and progression. Circular dichroism measurements show that confinement enhances the secondary structural features of the protein. Small‐angle X‐ray scattering and dynamic light scattering show that OPN changes from being a flexible protein in aqueous solution to adopting a less flexible and more compact structure inside the microemulsion droplets. This novel approach for confining proteins while they are still hydrated may aid in studying the structure of a wide range of natively unfolded proteins. |
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Keywords: | circular dichroism light scattering microemulsions protein structures X‐ray diffraction |
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