Dma 5000 density meter

All protein samples were gel filtrated into AUC buffer (25 mm HEPES, 200 mm KCL, 0.5 mm tris(2-carboxyethyl)phosphine, pH 7.4) prior to analysis. Sedimentation velocity ultra-centrifugation (SV-AUC) was carried out using a Beckman Optima XL-I analytical ultracentrifuge at 20 °C using an AnTi50 rotor. Interference optics data sets were collected at rotor speeds of 30,000 rev/min in sector cells with column heights of 12 mm. Scans were recorded at 1-min intervals over 15 h. The observed sedimentation boundaries were fitted to yield a c(s) plot according to the Lamm equation using SEDFIT (version 14.1) (24 (link), 25 ). The best-fit frictional ratio was calculated using SEDFIT by applying a fixed resolution of 200 and floating the frictional ratio, the meniscus and the base line until the overall root mean square deviations and visual appearance of the fits between observed and calculated sedimentation boundaries were satisfactory. Buffer density was measured using an Anton Paar DMA 5000 Density meter and was found to be 1.009946 g/ml.

Sedimentation velocity ultracentrifugation experiments (SV-AUC) were carried out using a Beckman Optima XL-I analytical ultracentrifuge. Samples were loaded into Beckman AUC sample cells with 12-mm optical path two-channel centerpieces, with matched buffer in the reference sector. Cells were spun at 50,000 rpm in an AnTi-50 rotor, and scans were acquired using both interference and absorbance optics (at 280 nm) at 10-min intervals over 16 h. The sedimentation profiles were analyzed using the software SEDFIT (v13b) (45 (link)). Partial specific volumes for mouse PrP^91–231 and PrP^23–231 were calculated from the amino acid sequence using SEDNTERP software (46 ). Buffer densities and viscosities were measured using an Anton Paar DMA5000 density meter and an Anton Paar AMVn automated microviscometer, respectively. Sedimentation velocity data were analyzed using the c(s) method of distribution (45 (link)) to characterize the sedimentation coefficient distribution of all species present in solution. For the β-PrP samples, it was necessary to use a bimodal f/f0 fit, to separately fit the frictional ratios for monomer and larger species. The proportions of each sample occupying the main peaks in the distribution were calculated by integration of the peaks.

An Agilent 7890B gas chromatograph (GC) equipped with a flame ionization detector (250°C) and an HP-5 column (30 m × 0.25 mm, film thickness 0.25 μm) was used for analyzing the products in the liquid phase and determining the methanol concentration by using ethyl acetate as the internal standard. The NADH concentration was measured by the UV-vis spectrophotometer (UV-1280, Shimadzu). Thermogravimetric analyses (TGA) were performed using a thermal gravimetric analyzer (Netzsch, STA449 F5, Germany) and the samples were heated from 30 to 400°C at 20.0°C/min under the nitrogen atmosphere. The freezing point of each DES was determined by a differential scanning calorimeter (DSC) (Netzsch DSC 200F3, Germany), and the samples were heated from −78 to 50°C at 10.0°C/min. The density and viscosity were measured by the Anton Paar DMA 5000 density meter with an uncertainty of ±0.0005 g cm⁻³ and Anton Paar AMVn with ±0.5% precision.

SAP microparticles fully swollen with water (2.0 g) were added to an aqueous solution of βCD-NH₂ or Ad-NH₂·HCl (5.0 mM, 20 mL) and the mixture was stirred at room temperature (ca. 25 °C) for 18 h. After removing the SAP microparticles by filtration, the concentration of solution of βCD-NH₂ or Ad-NH₂·HCl was determined by an Anton-Paar DMA5000 density meter using the calibration curve prepared separately. Using the volume and concentration of solution, the amount of βCD-NH₂ or Ad-NH₂·HCl adsorbed per gram of SAP microparticles swollen was estimated.