The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)

We have carried out the first very long baseline interferometry (VLBI) imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds x 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than approximately 650 km corresponding to 100 Mlambda in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ~ 5 mas x 2 mas, which corresponds to the linear size of ~ 15 AU x 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ~ 3.5 x 10^{8} to 1.0 x 10^{10} K, which are higher than estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ~ 50 mas. The 44 GHz class I methanol maser in IRAS 18151-1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser.Comment: 19 pages, 3 figure

Dynamic Properties of Human alpha-Synuclein Related to Propensity to Amyloid Fibril Formation

Alpha-synuclein (aSyn) is an intrinsically disordered protein (IDP) that can form amyloid fibrils. Fibrils of aSyn are implicated with the pathogenesis of Parkinson\u27s disease and other synucleinopathies. Elucidating the mechanism of fibril formation of aSyn is therefore important for understanding the mechanism of the pathogenesis of these diseases. Fibril formation of aSyn is sensitive to solution conditions, suggesting that fibril formation of aSyn arises from the changes in its inherent physico-chemical properties, particularly its dynamic properties because IDPs such as aSyn utilize their inherent flexibility to function. Characterizing these properties under various conditions should provide insights into the mechanism of fibril formation. Here, using the quasielastic neutron scattering (QENS) and small-angle X-ray scattering (SAXS) techniques, we investigated the dynamic and structural properties of aSyn under the conditions, where mature fibrils are formed (pH 7.4 with a high salt concentration), where clumping of short fibrils occurs (pH 4.0), and where fibril formation is not completed (pH 7.4). The SAXS measurements showed that the extended structures at pH 7.4 with a high salt concentration become compact at pH 4.0 and 7.4. The QENS measurements showed that both intra-molecular segmental motions and local motions such as side-chain motions are enhanced at pH 7.4 with a high salt concentration, compared to those at pH 7.4 without salt, whereas only the local motions are enhanced at pH 4.0. These results imply that fibril formation of aSyn requires not only the enhanced local motions but also the segmental motions such that proper inter-molecular interactions are possible