Disulfide Bridges Remain Intact while Native Insulin Converts into Amyloid Fibrils

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

Carbohydrate secondary and tertiary structure using raman spectroscopy

Raman spectroscopy is a long-established analytical technique that has now proliferated into a variety of research tools that are able to identify and characterize almost any type of molecule under most conditions. As such, Raman spectroscopies are well suited to the study of carbohydrates, from simple monosaccharides to the largest glycosaminoglycans and from industrial bioreactors to in situ measurements on living cells. This review covers a range of examples of how Raman techniques are addressing the questions of glycobiologists working on diverse aspects of this fascinating but poorly understood class of biomolecules. Focus is placed on the application of Raman, surface-enhanced Raman, Raman optical activity, and related spectroscopies to characterizing carbohydrates of all types, with only a general introduction to the theory of the techniques themselves. Particular attention is also paid to the computational tools now regularly used by spectroscopists to analyze complex data. Although this review is aimed at the glycobiology community, the examples discussed also demonstrate to the expert spectroscopist how their techniques can impact on the exciting opportunities presented by working with carbohydrates