Determination of R‐Deprenyl using a Maltodextrin‐Based Enantioselective,Potentiometric Membrane Electrode

Abstract

The enantioselective, potentiometric membrane electrode (EPME) based on maltodextrin with dextrose equivalence (DE) 16.5–19.5 is proposed for the assay of R‐deprenyl. The linear concentration range for the proposed electrode is 10^?10?10^?3 mol L^?1. The slope of the electrode is 53.1 mV per decade of concentration. The detection limit is 3.6×10^?11 mol L^?1. The proposed electrode could be reliably employed for the assay of R‐deprenyl raw material and its pharmaceutical formulation, Lentogesic tablets.     

Organizing the nozzle magazine of a gantry-type PCB assembly machine

The present work studies the operation control of so-called collect-and-place component placement machines. These kinds of machines are suited for the flexible manufacturing of various printed circuit board products. These machines operate in cycles where a set of components is first collected from the component feeders to the vacuum nozzles of the component placement head. The head then moves on the circuit board and places the components to their appropriate locations. Different component types require the use of different nozzle types, but the placement head has only a limited capacity for nozzles. Hence, the ability to change nozzles every now and then allows the manipulation of a great variety of component types with the same machine. This is accomplished by storing a larger selection of nozzles in a separate nozzle magazine from where the nozzle collection of the placement head can be updated. The cost of changing the nozzle setup is, however, relatively large compared to the time costs of other operations in the placement cycle. What complicates things more is that the nozzle change cost is affected by the organization of nozzles in the magazine, too. The aim of this work is to determine the contents of the nozzle magazine in such a way that the change operation times are as small as possible. We develop two heuristics (a genetic algorithm and a swarm optimization algorithm) for this purpose and evaluate their performance on sample problems. Both heuristic approaches are capable of processing realistic production problems, in particular the genetic algorithm finds near-optimal results for small problem instances and outperforms clearly our other approaches for larger problems.     

Learn more by training less: systematicity in sentence processing by recurrent networks

Connectionist models of sentence processing must learn to behave systematically by generalizing from a small training set. To what extent recurrent neural networks manage this generalization task is investigated. In contrast to Van der Velde et al. (Connection Sci., 16, pp. 21–46, 2004), it is found that simple recurrent networks do show so-called weak combinatorial systematicity, although their performance remains limited. It is argued that these limitations arise from overfitting in large networks. Generalization can be improved by increasing the size of the recurrent layer without training its connections, thereby combining a large short-term memory with a small long-term memory capacity. Performance can be improved further by increasing the number of word types in the training set.     

Ubiquitin binds to a short peptide segment of hydrolase UCH-L3: a study by FCS, RIfS, ITC and NMR

Screening for small peptidic affinity tags for the detection of ubiquitin and ubiquitinated proteins yielded the dodecapeptide amide DPDELRFNAIAL-NH(2) as a specific ubiquitin-interacting ligand. A peptide collection--based on crystal structures with ubiquitin-interacting proteins--was designed and confirmed by sequence comparison of ubiquitin-interacting motifs. Four independent physical detection methods demonstrated that the peptide binds to monomeric ubiquitin with an affinity of about 10 muM and with fast on and off rates. Fluorescence correlation spectroscopy with fluorescent peptides showed specific interaction with ubiquitin. Reflectometric interference spectroscopy with surface-immobilized peptides and isothermal calorimetry measurements confirmed the specific binding of ubiquitin and fast rate constants. (1)H,(15)N heteronuclear NMR localised the interaction site across the beta sheet of ubiquitin. The peptide aligns well with the ubiquitin-interacting motif and represents a lead structure for the rational design of high-affinity tags for targeting ubiquitinated protein in vitro and in vivo.     

Functional cell-surface display of a lipase-specific chaperone

Lipases are important enzymes in biotechnology. Extracellular bacterial lipases from Pseudomonads and related species require the assistance of specific chaperones, designated "Lif" proteins (lipase specific foldases). Lifs, a unique family of steric chaperones, are anchored to the periplasmic side of the inner membrane where they convert lipases into their active conformation. We have previously shown that the autotransporter protein EstA from P. aeruginosa can be used to direct a variety of proteins to the cell surface of Escherichia coli. Here we demonstrate for the first time the functional cell-surface display of the Lif chaperone and FACS (fluorescence-activated cell sorting)-based analysis of bacterial cells that carried foldase-lipase complexes. The model Lif protein, LipH from P. aeruginosa, was displayed at the surface of E. coli cells. Surface exposed LipH was functional and efficiently refolded chemically denatured lipase. The foldase autodisplay system reported here can be used for a variety of applications including the ultrahigh-throughput screening of large libraries of foldase variants generated by directed evolution.     

Analysis of IgG heavy chain to light chain ratio with mutant Encephalomyocarditis virus internal ribosome entry site

Immunoglobulin G (IgG) is a heterotetrameric protein assembled from two identical heavy chain (HC) and two identical light chain (LC) polypeptides. The HC and LC folding and assembly are a crucial step for IgG production. It is affected by the ratio of HC to LC expression (HC:LC). To date, the HC:LC ratio was analysed mainly by cotransfection of different amounts of two monocistronic HC and LC expression plasmids, an approach biased by different transfection efficiencies. To circumvent this problem, a series of Encephalomyocarditis virus internal ribosome entry site (EMCV IRES) variants with different translation efficiencies were created and used to mediate HC translation in bicistronic constructs. HC and LC were translated from the same mRNA, which provides a more accurate method for the evaluation of the optimal ratio of HC:LC. The results show that the IgG optimal expression levels were obtained when the IRES mediated translation efficiency of the HC was about 50% compared to the cap-dependent translation of the LC. A surprisingly sharp transition to low production was shown when the ratios were below 40%. This study provides a new method to investigate the production of heterodimeric proteins in mammalian cells and adds understanding to the mechanisms of IgG folding and assembly.     

Evaluation and characterization of ammoniumpolyphosphate–pentaerythritol‐based systems for intumescent coatings

Intumescent coatings are increasingly used as a method of passive fire protection on steel constructions. By forming a carbon network and releasing a blowing agent, the thin intumescent film swells 100‐fold at elevated temperatures. The highly insulating foam effectively prevents the load bearing steel from reaching its critical temperature at which it looses its mechanical properties and collapses. The role of the carbon donor in intumescent coatings has been studied. Comparison in temperature development, foaming ratios, and rheological behavior has been performed between formulations containing pentaerythritol (penta), di–penta, and tri–penta. A simulated fire test, in which the temperature development during intumescence was studied, showed that the formulations containing penta were considerably more efficient in keeping a low temperature throughout the process. A more rapid temperature development was displayed when using di–penta and tri–penta as the carbon donor. Rheometer tests indicate that penta formulations enter the intumescent process at a lower temperature and stays in it for a longer time than di–penta and tri–penta formulations. Furthermore, the crossover temperature and maximum phase angle are shifted towards higher temperatures by replacing penta with di–penta and with tri–penta in the formulations, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 748–753, 2007     

A novel approach to the interpretation and prediction of solvent effects in the synthesis of macroporous polymers

A trivariate interpolation technique, the modified Shepard's method, was applied for the first time to explain and predict various properties of macroporous polymers from the Hansen solubility parameters of the porogens employed for polymerization. Highly crosslinked polymers and copolymers were prepared from ethylene glycol dimethacrylate and methacrylic acid by free‐radical polymerization with 30 different porogenic solvents. Instead of the spherical model used by Hansen, detailed three‐dimensional maps were computed to represent the measured properties in a δ_d–δ_p–δ_h diagram (where δ_d, δ_p, and δ_h are the Hansen solubility parameters according to the three types of bonding forces: dispersion, polar, and hydrogen‐bonding, respectively). This method was able to detect unapparent correlations between the different polymer properties, thus providing a better understanding of the pore‐formation process. An important finding was the crucial role of the initiator solubility and its partitioning between the solution and the polymer surface, which proved to be key factors for the explanation of many contradictory solvent effects. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

„Medizinische Notwendigkeit“: Herausforderungen eines unscharfen Begriffs

Definition of the problem

“Medical necessity” (MedN) is the central regulatory concept for decisions about which services are covered by German statutory health insurance. Despite its seeming objectivity and dependence on physicians’ expert judgment, the concept is by no means clearly defined.

Arguments

In this first of five planned papers on the conceptual analysis of MedN from the perspectives of philosophy and ethics of medicine, law, and (social) medicine, the focus lies on systemizing ongoing controversies.

Conclusion

Our goal is to come up with a so far missing foundation for detailed debates. We aim to clarify MedN’s conceptual structure, function, contextuality, and ambiguities as well as the fundamental limits of conceptual investigations for the normative questions at issue of regulating medical services.