Observation of liquid–liquid phase separation of ataxin-3 and quantitative evaluation of its concentration in a single droplet using Raman microscopy

Liquid–liquid phase separation (LLPS) plays an important role in a variety of biological processes and is also associated with protein aggregation in neurodegenerative diseases. Quantification of LLPS is necessary to elucidate the mechanism of LLPS and the subsequent aggregation process. In this study, we showed that ataxin-3, which is associated with Machado–Joseph disease, exhibits LLPS in an intracellular crowding environment mimicked by biopolymers, and proposed that a single droplet formed in LLPS can be quantified using Raman microscopy in a label-free manner. We succeeded in evaluating the protein concentration and identifying the components present inside and outside a droplet using the O–H stretching band of water as an internal intensity standard. Only water and protein were detected to be present inside droplets with crowding agents remaining outside. The protein concentration in a droplet was dependent on the crowding environment, indicating that the protein concentration and intracellular environment should be considered when investigating LLPS. Raman microscopy has the potential to become a powerful technique for clarifying the chemical nature of LLPS and its relationship with protein aggregation.

Liquid–liquid phase separation (LLPS) plays an important role in a variety of biological processes. We have established a method to quantify a single droplet formed by LLPS using the Raman band of water as an internal standard.     

Analysis of magnetic and structural phase transition behaviors of La1−xSrxCrO3 for preparation of phase diagram

The phase transition behavior of perovskite-type compounds, La_1−xSr_xCrO₃, was investigated by differential scanning calorimetry (DSC), dilatometry, dc magnetic susceptibility measurement and X-ray diffraction analysis. Both second-order magnetic phase transition from antiferromagnetic to paramagnetic and first-order structural phase transition from orthorhombic to rhombohedral were observed in the DSC or dilatometric curve of every specimen. The temperatures of both these magnetic and structural phase transitions decreased linearly with an increase in Sr content. The structural phase transition temperature of La_1−xSr_xCrO₃ with x less than 0.11 is higher than the magnetic phase transition temperature; however, a larger decrease in structural phase transition temperature than in magnetic phase transition temperature was observed with an increase in Sr content, resulting in a structural phase transition temperature lower than the magnetic phase transition temperature for La_1−xSr_xCrO₃ with x of more than 0.12. It was also observed that the heat of absorption of the structural phase transition decreased with an increase in x. In the dependence of dc magnetic susceptibility on temperature, variations by not only magnetic but also structural phase transitions were observed. It was also revealed that thermal expansion coefficient is affected not only by structural phase transition but also magnetic phase transition. Magnetic and structural phase diagram of La_1−xSr_xCrO₃, suggesting the existence of two Sr contents and temperatures at which triple phases coexist, was proposed.     

Stereo-PEEM for three-dimensional atomic and electronic structures of microscopic materials

The principle and design of a new photoemission electron microscope (PEEM), which is called Stereo-PEEM, is described here. Stereo-PEEM can display not only the image of microscopic materials but also the angular distribution of high-energy photoelectrons up to about ±60°, which is about 100-fold the acceptance angle of usual PEEM. This wide angle acceptance for high-energy photoelectrons enables the three-dimensional (3D) display of atomic structure as well as the 3D electronic structure of individual micromaterials. The 3D atomic structure of a sample can be observed directly by taking stereophotographs using photons with angular momentum.     

Analysis of swertiamarin in Swertia herb and preparations containing this crude drug by capillary electrophoresis.

Swertia herb (florescent whole plantof Swertia japonica, Gentianaceae) has long been utilized as a folk medicine in Japan. It is often blended in general gastroenteric drugs as a bitter stomachic. Swertiamarin, a bitter secoiridoid glycoside, is the representative constituent of this crude drug and Swertia herb is normally evaluated by the swertiamarin content. To date, papers have described the discrimination of Swertia herbs from other bitter crude drugs, estimation of swertiamarin and seasonal variation in swertiamarin content using thin-layer chromatography, while other papers have reported quantitative determination of swertiamarin using high-performance liquid chromatography (HPLC). In our previous papers, we reported analyses of the constituents of some crude drugs using capillary electrophoresis (CE). To aid in the evaluation of crude drugs, we succeeded in our attempt to separate and determine the quantity of swertiamarin in Swertia herb. Subsequently, we applied the same analytical condition to estimate the swertiamarin contents in Japanese pharmacopoeia stomachic preparations, in OTC gastroenteric drugs and in OTC hair tonics containing Swertia herb.     

Evaluation of angelicae radix (Touki) by the inhibitory effect on platelet aggregation.

Quality evaluation of Angelicae Radix (Touki) was discussed referring to its inhibitory effect on platelet aggregation. No better correlation was observed in quality determined morphologically from the above-ground part of Touki and that determined by anti-platelet aggregation (APA) effects. Phthalides and adenosine, known to be the major components of Touki, were found not sufficient to evaluate the Touki quality as regards APA active components have been studied and it was concluded that the APA effect of Touki results from the combined action of plural components. The importance of determining quality based on the action of total extract to meet the purpose for which the substance is to be used was suggested.     

Efficient construction of the kedarcidin chromophore ansamacrolide

[Structure: see text] The streamlined assembly of the ansamacrolide framework of the kedarcidin chromophore via an efficient atropselective Sonogashira coupling step is described. To this end, two newly improved practical syntheses of the cyclopentene and diyne fragments have been developed, which feature 0.2 mol % catalytic loadings for an RCM step and i-PrMgCl/CH2I2 as a new entry to gem-disubstituted epoxides from ketones, both being applicable to 49-g scales.