Scale-up of protein purifications using aqueous two-phase systems: comparing multilayer toroidal coil chromatography with centrifugal partition chromatography

Two different laboratory scale liquid-liquid extraction processes using aqueous two-phase systems (ATPS) are compared: centrifugal partition chromatography (CPC) and multilayer toroidal coil chromatography (MTCC). Both use the same phase system, 12.5% (w/w) PEG-1000:12.5% (w/w) K(2)HPO(4), the same flow rate of 10 mL/min and a similar mean acceleration field of between 220 × g and 240 × g. The main performance difference between the two processes is that there is a continuous loss of stationary phase with CPC, while for MTCC there is not - even when sample loading is increased. Comparable separation efficiency is demonstrated using a mixture of lysozyme and myoglobin. A throughput of 0.14 g/h is possible with CPC despite having to refill the system with stationary phase before each injection. A higher throughput of 0.67 g/h is demonstrated with MTCC mainly due to its ability to tolerate serial sample injections which significantly reduces its cycle time. While CPC has already demonstrated that it can be scaled to pilot scale, MTCC has still to achieve this goal.     

High photocurrent in silicon photoanodes catalyzed by iron oxide thin films for water oxidation

Silicon splits: The application of silicon to water oxidation is limited due to unfavorable interface properties. However, these can be circumvented by using a high-performance silicon photoanode with a catalytically active iron oxide thin film (see picture). This approach results in photocurrents as high as 17?mA?cm(-2) under 1?sun and zero overpotential conditions.     

Reversed-phase systems for the separation of pentapeptides by high-performance liquid chromatography

Summary Reversed-phase systems using octyl modified silica as such and as a support for dynamically coated ion-exchangers, were investigated for their ability to separate pentapeptides. Normal reversed-phase adsorption with C-8 bonded silica in combination with citrate bufferpropanol-1 mixtures were found useful for the separation of a number of pentapeptides. The separation of pentapeptides differing widely in retention can be speeded up by applying an organic modifier and/or sodium citrate gradient. A solvent generated cation-exchange system with sodium dodecylsulfate as surfactant showed a high selectivity for the pentapeptides under investigation and is better for analytical purposes than the normal reversed-phase adsorption systems investigated. With respect to the detection of pentapeptides with fluorescamine, the use of dry pyridine as a basic buffer and as diluent for the fluorescamine was also investigated. Compared to the commonly used diluent acetone, pyridine is better when using acidic eluents of moderate buffer strength. At pH>6 no significant differences in sensitivity between acetone and pyridine could be noticed.