An on-line affinity selection method using a polymeric monolithic support is proposed for the retention of histidine-containing peptides and their subsequent separation by capillary zone electrophoresis (CZE). Monolithic capillary columns were prepared in fused-silica capillaries of 150 mum inner diameter (ID) by ionizing radiation-initiated in situ polymerization and cross-linking of diethylene glycol dimethacrylate and glycidyl methacrylate, and chemically modified with iminodiacetic acid (IDA) and copper ion. Monolithic microextractors were coupled on-line near the inlet of the separation capillary (fused-silica capillary, 75 mum ID x 28 cm from the microextractor to the detector). Model peptide mixtures of histidine-containing and histidine-noncontaining peptides were assessed. Peptides were released from the sorbent by a 5 mM imidazole solution and then separated by CZE with ultraviolet detection. Relative standard deviation values for migration times and corrected peak areas were found to be lower than 5.8 and 10.5%, respectively. IDA-Cu(II) ion modified monolithic microextractors showed a chromatographic behavior and could be reused at least 25 times. The use of monolithic supports proved to be an advantageous alternative to packed particles for the preparation of microextractors.
graphic steps within established downstream processes would result in a significant decrease of overall production cost [4,5]. The concept of process intensification refers to any process adaptation or optimization that results in a less resource-intensive biomanufacturing scheme, including, but not limited to, lower water consumption, energy demand and environmental burden. This review will primarily focus on multifaceted approaches addressing process integration and intensification based on the utilization of non-traditional chromatographic or extractive methods, which include advances in bioprocess material development, hardware design and advantageous modes of operation. While adsorptive methods, such as chromatography, are widely used in industry as a key purification technology, liquid-liquid extraction technologies, such as aqueous twophase separation (ATPS) systems, are elegant emerging examples of process integration. In this technique, direct extraction of bioproducts from crude feedstocks can be accomplished by the use of two incompatible polymers or of a polymer and a salt in an aqueous environment. It is
Radiation-induced graft copolymerization is a powerful technique to prepare a grafted chain with the desired properties pending onto the trunk material. In this work, a polyethylene hollow-fiber membrane was modified by this technique. The monomers glycidyl methacrylate (GMA) and N,N-dimethylacrylamide (DMAA) were cografted onto macroporous polyethylene hollow fiber with a grafting degree in the order of 200%. DMAA/GMA cografted membranes were compared to GMA grafted ones for the introduction of an amino acid as a specific ligand. Grafted membranes with a copolymer composition between 0 and 2 DMAA/GMA were prepared by soaking them in solutions of different mixtures of monomers. Copolymers were characterized by FTIR and their composition was estimated by the analysis of the ratio of carbonyl signals. Copolymers with a higher proportion of DMAA showed improved hydrophilic properties and higher conversion rates of epoxy groups on phenyalanine ligands than those of the GMA grafted ones. However, copolymers with a DMAA/GMA ratio higher than 1 showed a detrimental effect on the pure water flux.
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