Self-assembly of proteins and inorganic nanoparticles driven by weak interactions opens the door for engineering organic-inorganic analogs of cellular organelles comprised of diverse components and with integrated functionalities. Such systems are fundamentally and technologically attractive due to their uniformity, versatility and simplicity of preparation. To demonstrate such assemblies, we combine ~3.4 nm FeS2 nanoparticles with ~5 nm protease protein and observe spontaneous formation of spherical supraparticles with a narrow size distribution containing both components. Assembly was originated from the competition between electrostatic repulsion and non-covalent attractive interactions. Non-covalent interactions between protease and like-charged NPs lead to drastically different self-assembly behavior previously unseen for each component individually, and which mimics the cooperative assemblies of proteins. We also demonstrate remarkable that the catalytic curve profile has changed, but the catalytic activity is retained in a determinate temperature and pH. Examination by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of 1:3 FeS2 NPs-protease assembly reveals the formation of uniformly sized, spherical SPs with a TEM diameter of 112 ± 13nm which matches the diameter determined from Dynamic light scattering (DLS). Image of individual NP inside a SP can be distinguished by its crystal lattice with periodicity of 0.23nm. Besides the SPs were investigated by tomography 3D and the overall attractive potential between the similarly charged FeS2 NPs and Protease is investigated by theoretical calculations. Further were examined the effect of ionic strength and temperature of assembly on the diameter of the SPs. Various spectroscopy data were performed which shows the positions of all peaks in the UV-Visible / Circular Dichroism spectra remain unchanged, indicating that the electronic state and conformation of the protease molecules in the SPs are preserved. Catalytic activity of FeS2-protease SPs using casein as substrate at pH 11 and at 4°C and 20°C showed a huge catalytic curve profile change, demonstrating that Superstructures display complex internal organization and can incorporate biological component which retains its functionality.

Stability of proteins in supraparticles

251st National Meeting (2016)

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