A robust affinity chromatography system based on ceramic monoliths coated with poly(amino acid)‐based polymeric constructs

Traditional chromatographic separation systems are disadvantaged by low flow rates, a high pressure drop across the column, low capacity and poor reusability. Searching for more efficient separation systems we introduced the use of a ceramic monolith as robust support in bioseparations. A coating consisting of l ‐asparagine as ligand, poly(l ‐lysine) as spacer arm and a commercial poly(ethylene acrylic acid) film forming copolymer network (Michem 4983‐40R) was developed as a coating for these ceramic monoliths. Poly(l ‐lysine) was synthesized by ring‐opening polymerization of ε‐trifluoroacetyl‐l ‐lysine N‐carboxyanhydride and coupled to a commercial film‐forming poly(ethylene acrylic acid) network. This construct was then ‘decorated’ with l ‐asparagine via the terminal amino functional groups of poly(L‐lysine) and coated onto the ceramic monolith to selectively bind l ‐asparaginase. Adsorption/elution experiments showed reversible binding between l ‐asparagine and l ‐asparaginase, and the subsequent release of l ‐asparaginase, and between 83% and 94% of the active enzyme was recovered by elution with d ‐asparagine and NaCl solutions. The functional activity of the eluted l ‐asparaginase was verified by a Nessler's assay. While traditional separation processes (adsorption and elution) using gel bead packings take many hours, the ceramic monolith system achieves the same of level of separation in about 1 h. This new system served as a proof of concept for its application in protein separation and purification. This work paves the way to a better understanding of the use of ceramic monoliths as stationary phase coated with a stable polymer construct for more robust and efficient supports in affinity chromatography. © 2020 Society of Industrial Chemistry     

Essay for the Rosarium Philosophicum on Electrochemistry Electrochemical Analysis – What it was,is, and Possibly will be

In this essay a survey of the development of electrochemical analysis is given for the last two hundred years. It is shown that the great breakthroughs in this discipline were not predictable, as in all other sciences. The two centuries have led to an enormous diversification of electroanalytical techniques and analytical targets for which electroanalytical techniques can be applied most beneficially. Maintaining the experimental and theoretical expertise as part of the chemistry curricula at Universities is identified as a main task, now and in future.     

Development and performance analysis of real‐world applications for distributed and parallel architectures

Several large real‐world applications have been developed for distributed and parallel architectures. We examine two different program development approaches. First, the usage of a high‐level programming paradigm which reduces the time to create a parallel program dramatically but sometimes at the cost of a reduced performance; a source‐to‐source compiler, has been employed to automatically compile programs—written in a high‐level programming paradigm—into message passing codes. Second, a manual program development by using a low‐level programming paradigm—such as message passing—enables the programmer to fully exploit a given architecture at the cost of a time‐consuming and error‐prone effort. Performance tools play a central role in supporting the performance‐oriented development of applications for distributed and parallel architectures. SCALA—a portable instrumentation, measurement, and post‐execution performance analysis system for distributed and parallel programs—has been used to analyze and to guide the application development, by selectively instrumenting and measuring the code versions, by comparing performance information of several program executions, by computing a variety of important performance metrics, by detecting performance bottlenecks, and by relating performance information back to the input program. We show several experiments of SCALA when applied to real‐world applications. These experiments are conducted for a NEC Cenju‐4 distributed‐memory machine and a cluster of heterogeneous workstations and networks. Copyright © 2001 John Wiley & Sons, Ltd.     

On Homogeneous Gold/Palladium Catalytic Systems

Two substrates containing an aryl iodide and an allenoate ester were prepared and the gold‐induced cycloisomerisation to vinylgold(I) species and their proto‐deauration as well as the intramolecular palladium‐catalysed cross‐coupling reactions were investigated. Switching to catalytic amounts of gold and palladium and stoichiometric amounts of silver did indeed furnish the product of a cycloisomerisation/intramolecular cross‐coupling. Control experiments revealed that silver cannot substitute for gold or palladium in these reactions, but a different palladium catalyst in a different oxidation state also afforded the cycloisomerisation/intramolecular cross‐coupling products in only slightly reduced yields. By ICP analysis the palladium was shown to contain gold only at the sub‐ppm level. This shows how carefully results obtained with such systems have to be interpreted. Then a series of allylic and benzylic o‐alkynylbenzoates were investigated in gold‐ and palladium‐catalysed reactions. For esters of benzyl alcohol and cinnamyl alcohol no palladium co‐catalyst was needed for the conversion. All reagents were thoroughly checked for palladium traces by ICP analysis in order to thoroughly exclude a gold/palladium co‐catalysis. Optimisation of the gold complex, counter ion and solvent showed that gold(I) isonitrile pre‐catalysts and silver triflate as activator in dioxane are suitable to convert a number of substrates with aryl, alkyl and even cyclopropyl substituents. Crossover experiments proved an intermolecular allyl transfer.