Formation of platinum-coated templates of insulin nanowires used in reducing 4-nitrophenol.

Modern technology demands ever smaller and more efficient nanoparticles, wires and networks. The natural tendency for amyloid proteins to form fibrillar structures is leveraged in creating high aspect ratio, nano-sized protein fibers as scaffolds for metallized nanowires. The morphology of fibrils is influenced by induced strain during denaturing and early aggregation and subsequent fibril deposition with platinum leads to controlled catalyst surfaces based on the initial protein precipitate. Here we have created insulin fibrils with varying morphologies produced in the presence of heat and strain and investigated their metallization with platinum by TEM. The catalytic activity of the metal-coated protein fibrils was resolved by tracking the reaction kinetics of the conversion of 4-nitrophenol to 4-aminophenol in the presence of the produced nanowires using UV-Vis spectroscopy. The effects of fibril morphology and temperature on the pseudo-first-order kinetics of conversion are investigated. Conversion to 4-aminophenol occurs on the order of minutes and is independent of temperature in the range tested (7 to 20°C). Two regimes of conversion are identified, an early higher rate, followed by a slower later rate.

Agitation of amyloid proteins to speed aggregation measured by ThT fluorescence: a call for standardization.

This retrospective study of protein aggregation measured by Thioflavin T (ThT) fluorescence assay in published literature has assessed protein sensitivity to denaturing conditions that include elevated temperatures, fluctuations in pH, and concentration and, in particular, agitation to induce amyloid structure formation. The dynamic tracking of fluorescence shows a sigmoidal evolution as aggregates form; the resulting kinetics of association have been analyzed to explore the range of aggregation behavior which occurs based on environmental parameters. Comparisons between the experimental results of different groups have been historically difficult due to subtleties of experimental procedures including denaturing temperature, protein type and concentration, formulation differences, and how agitation is achieved. While it is clear that agitation has a strong influence on the driving force for aggregation, the use of magnetic stirring bar or shaker table rotational speed is insufficient to characterize the degree of turbulence produced during shear. The pathway forward in resolving dependence of aggregate formation on shear may require alternative methodologies or better standardization of the experimental protocols.