Development of versatile ruthenium olefin-metathesis catalysts with high activity, stability, and selectivity is a continuous challenge. Here we report highly controllable ruthenium catalysts using readily accessible and versatile N -vinylsulfonamides as carbene precursors. Catalyst initiation rates were controlled in a straightforward manner, from latent to fast initiating, through the facile modulation of the N -vinylsulfonamide ligands. Trifluoromethanesulfonamide-based catalysts initiated ultrarapidly even at temperatures as low as −60 °C and continuously propagated rapidly, enabling the enthalpically and entropically less-favored ring-opening metathesis polymerizations of low-strained functionalized cyclopentene derivatives, some of which are not accessible with previous olefin-metathesis catalysts. To our surprise, the developed catalysts facilitated the polymerization of cyclopentadiene (CPD), a feedstock that is easily and commonly obtainable through the steam cracking of naphtha, which has, to the best of our knowledge, not been previously achieved due to its low ring strain and facile dimerization even at low temperatures (below 0 °C).

Several point mutations can modulate protein structure and dynamics, leading to different natures. Especially in the case of amyloidogenic proteins closely related to neurodegenerative diseases, structural changes originating from point mutations can affect fibrillation kinetics. Herein, we rationally designed mutant candidates to inhibit the fibrillation process of amyloid-β with its point mutants through multistep in silico analyses. Our results showed that the designed mutants induced kinetic self-assembly suppression and reduced the toxicity of the aggregate. A multidisciplinary biophysical approach with small-angle X-ray scattering, ion mobility-mass spectrometry, mass spectrometry, and additional in silico experiments was performed to reveal the structural basis associated with the inhibition of fibril formation. The structure-based design of the mutants with suppressed self-assembly performed in this study could provide a different perspective for modulating amyloid aggregation based on the structural understanding of the intrinsically disordered proteins.

Advanced understanding of Alzheimer's disease (AD) and several tauopathies over the past decades indicates the pathological importance of tau aggregation in these diseases. Herein, we demonstrated that adenosine triphosphate (ATP), a highly charged anionic molecule abundant in the cytosol of cells, catalyses tau fibrillation via supramolecular complexation with basic residues of tau. Our results showed that ATP attracts multiple lysine residues of four-repeat domain of tau (K18), thereby immediately forming dimers which convert to nuclei to accelerate fibril elongation. However, ATP was not directly incorporated in the K18 fibrils suggesting a catalytic role of ATP in K18 fibrillation. We also characterized the correlation between ATP dyshomeostasis and tau aggregation in the cellular environment. Our multiple biophysical approaches, including native mass spectrometry (MS), small-angle X-ray scattering (SAXS), and molecular dynamics (MD) simulation, provided insights into the molecular-level influence of ATP on the structural change and fibrillation of tau. File list (2) download file view on ChemRxiv 200314_TauATP_Preprint.pdf (1.62 MiB) download file view on ChemRxiv 200314_SI_TauATP_Preprint.pdf (1.47 MiB)

Practical applications of innovative host-guest systems are challenging because of unexpected guest competitors and/or subtle environmental differences. Herein, a supramolecular mass spectrometry (MS)-based method using a synthetic host, cucurbit[7]uril (CB[7]), was developed for identifying and quantifying N-glycolylneuraminic acid (Neu5Gc) in therapeutic glycoproteins, which critically reduces drug efficacy. The development of a reliable derivatization-free analytical method for Neu5Gc is highly challenging because of the interference by the abundant N-acetylneuraminic acid (Neu5Ac). CB[7] recognized the subtle structural differences between Neu5Gc and Neu5Ac. Distinct host-guest interactions between CB[7] and the two sialic acids produced a highly linear relationship between the complexation and concentration proportions of the two sialic acids in MS. Furthermore, the developed method had sub-picomolar quantification limits and a wide range of applicability for diverse glycoproteins, demonstrating the potential utility of this method as a reliable assay of Neu5Gc in therapeutic glycoproteins.

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Flexible structures of intrinsically disordered proteins (IDPs) are crucial for versatile functions in living organisms, which involve interaction with diverse partners. Electrospray ionization ion mobility mass spectrometry (ESI‐IM‐MS) has been widely applied for structural characterization of apo‐state and ligand‐associated IDPs via two‐dimensional separation in the gas phase. Gas‐phase IDP structures have been regarded as kinetically trapped states originated from conformational features in solution. However, an implication of the states remains elusive in the structural characterization of IDPs, because it is unclear what structural property of IDPs is preserved. Recent studies have indicated that the conformational features of IDPs in solution are not fully reproduced in the gas phase. Nevertheless, the molecular interactions captured in the gas phase amplify the structural differences between IDP conformers. Therefore, an IDP conformational change that is not observed in solution is observable in the gas‐phase structures obtained by ESI‐IM‐MS. Herein, we have presented up‐to‐date researches on the key implications of kinetically trapped states in the gas phase with a brief summary of the structural dynamics of IDPs in ESI‐IM‐MS.