RESUMO
Invited for this month's cover picture is the group of Professors Michael Köhler at the Technische Universität Ilmenau. The cover picture shows an overlay of an image of a metal nanoparticle network (blue) and sets of non-spherical metal nanoparticles of different shapes (yellow). The particles can be used in plasmonic labelling, nanoparticle-based SERS-sensing and heterogeneous catalysis. Read the full text of their Full Paper at https://doi.org/10.1002/open.201900231.
RESUMO
Non-spherical Au/Ag nanoparticles can be generated by chemical reduction of silver ions in the presence of preformed gold nanoparticles. The process of particle formation can be controlled by concentrations of ligands and reducing agent. The formation of ellipsoidal, nanorod- and peanut-shaped nanoparticles as well as of more complex fractal nanoassemblies can be explained by changes in particle surface state, electrochemical potential formation and particle-internal self-polarization effects. It is possible to create highly fractal nanoassemblies with sizes between the mid-nanometer and the lower micrometer range. The assemblies are marked by high optical absorption and complex nano-networks of very high surface-to-volume ratios and a granular base structure.
RESUMO
For commercial applications refolding process must be fast, inexpensive and highly efficient. In the past many strategies for protein refolding were introduced. Still, simple refolding methods with high product concentrations are still rare. Refolding experiments were performed with fructosyltransferase (FTF, EC 2.4.1.162) from Bacillus subtilis NCIMB 11871 produced as inclusion bodies. Solubilizates were refolded with batch dialysis or by continuous exchange of dialysis buffers with variable ionic strength. By employing dialysis with gentle removal of denaturant the dependence of protein concentration and decreasing refolding yields could be overcome compared to batch dialysis and yields were enhanced by 52% at protein concentrations of approx. 10 mg/mL. The average specific activity of refolded FTF was 123 U/mg, 83% relative to standard FTF. Rising ionic strength of refolding buffers to 600 mM leads to complete renaturation of solubilized protein at equal protein concentration. Buffer composition plays a less significant role on renaturation output. The effect might be correlated with ion charge density of co-solvents.
