Protein diffusion in a bicontinuous microemulsion: inducing sub-diffusion by tuning the water domain sizeElectronic supplementary information (ESI) available. See DOI: 10.1039/c6sm02107g

We study the diffusion of an enhanced green fluorescent protein (GFP+) in bicontinuous sugar-surfactant based microemulsions. The size of the water domains in such systems is controlled by changes of the oil-to-water ratio. Hence, microemulsions allow to produce confinement effects in a controlled way. At high water content the protein is found to exhibit Fickian diffusion. Decreasing the water domain size leads to a slowing down of the protein diffusion and sub-diffusive behavior is obtained on the scale observed by fluorescence correlation spectroscopy. Further decrease of the water domain size finally nearly fixes the GFP+ in these domains and forces it to increasingly follow the breathing mode of the microemulsion matrix. We study the diffusion of an enhanced green fluorescent protein (GFP+) in bicontinuous sugar-surfactant based microemulsions. The water domains are controlled by the microemulsion composition.