Hiroki Kitayama

Distinguishing crystal-like amyloid fibrils and glass-like amorphous aggregates from their kinetics of formation

Amyloid fibrils and amorphous aggregates are two types of aberrant aggregates associated with protein misfolding diseases. Although they differ in morphology, the two forms are often treated indiscriminately. β2-microglobulin (β2m), a protein responsible for dialysis-related amyloidosis, forms amyloid fibrils or amorphous aggregates depending on the NaCl concentration at pH 2.5. We compared the kinetics of their formation, which was monitored by measuring thioflavin T fluorescence, light scattering, and 8-anilino-1-naphthalenesulfonate fluorescence. Thioflavin T fluorescence specifically monitors amyloid fibrillation, whereas light scattering and 8-anilino-1-naphthalenesulfonate fluorescence monitor both amyloid fibrillation and amorphous aggregation. The amyloid fibrils formed via a nucleation-dependent mechanism in a supersaturated solution, analogous to crystallization. The lag phase of fibrillation was reduced upon agitation with stirring or ultrasonic irradiation, and disappeared by seeding with preformed fibrils. In contrast, the glass-like amorphous aggregates formed rapidly without a lag phase. Neither agitation nor seeding accelerated the amorphous aggregation. Thus, by monitoring the kinetics, we can distinguish between crystal-like amyloid fibrils and glass-like amorphous aggregates. Solubility and supersaturation will be key factors for further understanding the aberrant aggregation of proteins.

Solid-State Slit Camera (SSC) Aboard MAXI

Solid-state Slit Camera (SSC) is an X-ray camera onboard the MAXI mission of the International Space Station. Two sets of SSC sensors view X-ray sky using charge-coupled devices (CCDs) in 0.5--12\,keV band. The total area for the X-ray detection is about 200\,cm

A common mechanism underlying amyloid fibrillation and protein crystallization revealed by the effects of ultrasonication

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The First MAXI/GSC Catalog in the High Galactic-Latitude Sky

which is the largest among the missions of X-ray astronomy. The energy resolution at the CCD temperature of

Revisit of Local X-Ray Luminosity Function of Active Galactic Nuclei with the MAXI Extragalactic Survey

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Spectral Evolution of a New X-Ray Transient MAXI J0556−332 Observed by MAXI, Swift, and RXTE

70 \degc is 145\,eV in full width at the half maximum (FWHM) at 5.9\,keV, and the field of view is 1\deg .5 (FWHM)

A spectral study of the black hole candidate XTE J1752-223 in the high/soft state with MAXI, Suzaku, and Swift

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Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

90\deg for each sensor. The SSC could make a whole-sky image with the energy resolution good enough to resolve line emissions, and monitor the whole-sky at the energy band of

Outburst of LSV+44 17 Observed by MAXI and RXTE, and Discovery of a Dip Structure in the Pulse Profile

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Long-Term Monitoring of the Black Hole Binary GX 339-4 in the High/Soft State during the 2010 Outburst with MAXI/GSC

2\,keV for the first time in these decades.