Amyloid fibrils are β-sheet-rich protein aggregates commonly found in the organs and tissues of patients with various amyloid-associated diseases. Understanding the structural organization of amyloid fibrils can be beneficial for the search of drugs to successfully treat diseases associated with protein misfolding. The structure of insulin fibrils was characterized by deep ultraviolet resonance Raman (DUVRR) and Nuclear Magnetic Resonance (NMR) spectroscopy combined with hydrogen-deuterium exchange. The compositions of the fibril core and unordered parts were determined at single amino acid residue resolution. All three disulfide bonds of native insulin remained intact during the aggregation process, withstanding scrambling. Three out of four tyrosine residues were packed into the fibril core, and another aromatic amino acid, phenylalanine, was located in the unordered parts of insulin fibrils. In addition, using all-atom MD simulations, the disulfide bonds were confirmed to remain intact in the insulin dimer, which mimics the fibrillar form of insulin.

Amphiphilic homopolymers that self-assemble into reverse micelles in nonpolar solvents have been used by us in the context of a two-phase liquid-liquid extraction protocol to selectively extract peptides from aqueous solution for MALDI-MS detection. In this manuscript, we investigate the scope of these materials in terms of its extraction capabilities, using compounds with varying isoelectric points (pI) and pK(a) values over a range of aqueous solution pHs. We find that the aqueous solution pH and analyte pK(a) values are the major factors controlling extraction selectivity. We also find that the experimental extraction efficiencies correspond very well with the fractional compositions of species calculated using analyte pK(a) values, indicating that these extraction materials can be used to simultaneously generate titration-type curves for each individual peptide in a mixture. We predict that such titration curves, along with accurate mass measurements, could represent a new way of improving protein identification procedures.

Spartin contributes to the formation of dendritic aggresome-like induced structures (DALIS) through a unique ubiquitin-binding region (UBR). Using NMR and in vitro binding, the authors characterize spartin's UBR and show that DALIS formation depends on key residues within its UBR.

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