To avoid spectroscopic peak interferences such as H resonance frequency or O-H vibrational frequency in nuclear magnetic resonance (NMR), infrared (IR) spectroscopy etc., deuterium oxide (D2O) is used as a solvent for a deuteration of sample molecules. Such deuteration conveniently is used to avoid spectroscopic interferences, but it is controversial whether deuteration effects protein structures. Due to lower vibrational frequency of O-D (~1200 cm-1) than that of O-H (~1600 cm-1), D2O is more stable than H2O, with stronger hydrophobic effect. For this reason, there is a research that a globular protein is more stable in D2O. But there is few researches about the protein structural changes or protein fibrillation mechanisms in D2O. Proteins form secondary structures with hydrogen bonding and secondary structures form tertiary structures by hydrophobic interactions. On the other hand, intrinsically disordered proteins (IDPs), which do not have a distinct or a stable structure, perform many functions with various conformations. When IDPs are misfolded, intermolecular hydrophobic interactions drives proteins to form fibrils, which are closely related to neurodegenerative disease, such as Alzheimer’s disease, Parkinson’s disease. Such amyloidogenic proteins are α-synculein (αSyn), amyloid-β, tau-proteins etc. In this research, we used human insulin, which is frequently used as a model protein for amyloidogenic protein, and αSyn to study the effect of reinforced hydrophobic effect on the structured protein and IDPs structures and protein stability-fibrillation. In addition, the experiment was further carried out under conditions of structural denaturation by adding sodium dodecyl sulfate (SDS), a protein denaturant, to insulin. Small angle X-ray scattering (SAXS) and ion mobility mass spectrometry (IM-MS) were utilized for the study of solution phase and gas phase initial protein structures, and thioflavin-T (ThT) assay, circular dichroism (CD) and transmission electron microscopy (TEM) were utilized to compare the fibrillation kinetics in H2O and D2O.

Analysis of the effect of enhanced hydrophobic interaction in heavy water on the structure and stability of structured and intrinsically disdordered proteins

ACS Spring Meeting 2021

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