ELECTROPHORESIS最新文献

We present the coupling of capillary electrophoresis to a custom-built high-resolution ion mobility spectrometer (IMS). This system integrates a shifted inlet potential IMS configuration with a customised nanoflow ESI sheath interface. It enables the rapid analysis of quaternary ammonium compounds (QACs) and their impurities in real-world samples. It allowed the detection of six non-chromophoric compounds in about 3 min. The assignment of the IMS signals to compounds was supported by matching experimentally determined collision cross-section (CCS) values with predicted values. The system achieved a detection limit in the single-digit picogram range with IMS resolutions of over 80.

A capillary electrophoresis system capable of measuring streaming potentials was used for the determination of critical micelle concentration (CMC) of anionic, cationic, zwitterionic and non-ionic surfactants. The CMC values of anionic surfactant sodium dodecyl sulphate (SDS), cationic surfactant cetyltrimethylammonium bromide (CTAB), zwitterionic surfactant 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate (CHAPS) and non-ionic surfactant polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (Triton X-100) in water or salt solutions were determined by determining the abrupt change in the trend of streaming potential change with the surfactant concentration. The CMC values were 8.23, 0.93, 5.80 and 0.16 mM, respectively. This method was also used to demonstrate how the CMCs of SDS and CTAB change differently with temperature. The CMC of SDS decreased from 10°C to 25°C and then increased from 25°C to 40°C, whereas CTAB only increased linearly within 10°C–40°C. The capillary wall zeta potentials in surfactant solutions can be calculated from the measured streaming potential, conductivity and solution viscosity. Surface charge densities were calculated using the zeta potentials obtained. The surface charge densities of SDS were calculated to be 5.6–0.8 C/m² when SDS solutions with concentrations of 2–20 mM zeta potentials were used. The calculated zeta potentials and surface charge densities reached a plateau at about 8 mM, which coincided with the CMC of SDS determined in the present study and the literature values. The CMC values obtained from streaming potential measurement are comparable to values obtained with other CMC determination techniques such as surface tension and conductometric measurements.

Immunoblot, also known as western blot, is a well-established procedure in life science. It is commonly used to determine the relative size and abundance of specific proteins, as well as posttranslational modifications of proteins. While this method is widely employed due to its simplicity, it can take hours or even days to complete. Despite considerable efforts to reduce the overall procedure time, particularly for antibody incubation, the steps involving membrane rinsing have remained unchanged since the development of the immunoblot technique. In this context, we introduce an innovative device called the “Smart Wash,” designed to significantly reduce the washing intervals by utilizing a motorized salad spinner. The principle of Smart Wash is akin to that of a household washing machine: the container holds the membranes during the rinsing cycle, and the basket moves the membranes along with the washing solution in the container. We have optimized the rinsing conditions, including the volume of the washing solution, rotation speed, number of washing cycles, and direction. This straightforward device empowers researchers to significantly enhance the efficiency and productivity of immunoblotting analysis.

In diabetes management, oral formulation of insulin (INS) has the potential to improve safety, convenience, and patient-centered care compared to subcutaneous injections. However, its bioavailability remains limited, necessitating improved delivery strategies. Recent clinical trials indicate that taurocholic acid (TCA) can enhance the bioavailability of oral INS as an absorption enhancer. In this work, electrospray ionization mass spectrometry (ESI-MS) analysis revealed the formation of 1:1–1:4 INS–TCA complexes. MS/MS was used to explore the fragmentation pathway of complex ions and confirm binding stability in the gas phase. Circular dichroism spectra showed no clear conformational change in INS upon TCA binding, even though TCA enhanced INS's structural stability. Using Taylor dispersion analysis (TDA), we determined the diffusion coefficient and hydrodynamic radius of INS and its complexes. TCA binding was observed to increase INS size in both the 1:1 and 1:2 INS–TCA complexes. The binding constant of INS and TCA (1.3 × 10³ L/mol) with approximately five binding sites was obtained via pressure-assisted capillary electrophoresis frontal analysis. Molecular docking simulations indicated that TCA binds to external binding sites on the INS B chain (near Ser-B9, Glu-B13, and Phe-B24 residues), consistent with ESI-MS and TDA results. These findings suggest that TCA binding may enhance INS absorption and increase the bioavailability of oral INS therapy.

Amino acids (AAs) in their cationic form at pH 2.2 and usual ionic strength show a non-intuitive migration order in CZE. This is explained by setting up four postulates. The central points in these postulates are the influence of the AA side chain on the $��p�K_a�$ value and the adoption of a defined, preferred conformation to build up the different $��p�K_a�$ values. This conformation then also influences the hydrodynamic radius. The rotational orientation of an AA in the electric field aligns it, which also affects the hydrodynamic radius. Overall a special electrophoretical hydrodynamic radius is postulated and distinguished from the hydrodynamic radius, which is determined by the translational diffusion constant. With the help of the four postulates, the migration order could be explained. Glutamic acid has a special feature in this study: due to its observed higher mobility than the smaller and even higher charged aspartic acid, the hypothesis is that it would deprotonate first at the C5 and not at the C1 carboxylic group as all other AAs. This has the consequence of a more streamlined conformation and by that a faster migration in capillary electrophoresis.