A Photochemical Study of Diclofenac and Its Major Transformation Products

The photolytic transformation of 2-(2-(2,6-dichlorophenylamino)phenyl)acetic acid (diclofenac) and its transformation products (TPs) (8-chloro-9H-carbazol-1-yl) acetic acid (Cz1), 2-(2-chloro-phenylamino)-benzaldehyde (Ald) and (1,4-dioxo-4,9-dihydro-1H-carbazol-8-yl) acetic acid (Cz4) in aqueous solutions have been studied. The previously unreported TP (Cz4) was isolated by LC and completely characterized by NMR and MS. UV-absorption spectra of diclofenac and three of its TPs were determined and used to calculate disappearance quantum yields. The dominating transformation pathway of diclofenac occurs via initial formation of Cz1 and proceeds to form mainly (Cz4) over 200 min of UV-irradiation. A second minor transformation pathway, which yields Ald as the sole product, was observed only under deaerated conditions.     

A self-polishing platinum ring voltammetric sensor and its application to complex media

A self-polishing voltammetric sensor was recently developed and has been applied to samples of urea, milk and sewage water. The polishing device continuously grinds a platinum ring electrode, offering a reproducible and clean electrode surface. Principal component analysis (PCA) and partial least squares (PLS) techniques were applied to interpret the data and to build prediction models. In an evaluation of samples with different urea concentrations, the grinding step allows for repeatable measurements, similar to those after electrochemical cleaning. Furthermore, for the determination of sewage water concentrations in drinking water and for the evaluation of different fat contents in milk samples, the polishing eliminates sensor drift produced by electrode fouling. The results show that the application of a self-polishing unit offers a promising tool for electrochemical studies of difficult analytes and complex media.     

β-Mannosidase and β-hexosaminidase inhibitors: synthesis of 1,2-bis-epi-valienamine and 1-epi-2-acetamido-2-deoxy-valienamine from d-mannose

A partially protected C-5C-5a unsaturated carbasugar with α-lyxo configuration is synthesised in five steps and 26% overall yield from a known mannose-derived hemiacetal, using ring-closing metathesis as a key step. This carbasugar is converted into valienamine derivatives with β-lyxo (i.e., corresponding to β-manno at C-1–C-4), α-lyxo (i.e., corresponding to α-manno at C-1–C-4) and β-2-acetamido-2-deoxy-xylo (i.e., corresponding to β-GlcNAc at C-1–C-4) configurations. This is the first report of the synthesis of the β-lyxo compound, 1,2-bis-epi-valienamine, which was found to inhibit Cellulomonas fimi β-mannosidase (CfMan2A) with K_i 140 μM. We report the crystal structures of three protected C-5C-5a unsaturated carbasugars with lyxo configuration.     

Conditions for sample preparation and quantitative HPLC/MS-MS analysis of bulky adducts to serum albumin with diolepoxides of polycyclic aromatic hydrocarbons as models

Stable adducts to serum albumin (SA) from electrophilic and genotoxic compounds/metabolites can be used as biomarkers for quantification of the corresponding in vivo dose. In the present study, conditions for specific analysis of stable adducts to SA formed from carcinogenic polycyclic aromatic hydrocarbons (PAH) were evaluated in order to achieve a sensitive and reproducible quantitative method. Bulky adducts from diolepoxides (DE) of PAH, primarily DE of benzo[a]pyrene (BPDE) and also DE of dibenzo[a,l]pyrene (DBPDE) and dibenzo[a,h]anthracene (DBADE), were used as model compounds. The alkylated peptides obtained after enzymatic hydrolysis of human SA modified with the different PAHDE were principally PAHDE-His-Pro, PAHDE-His-Pro-Tyr and PAHDE-Lys. Alkaline hydrolysis under optimised conditions gave the BPDE-His as the single analyte of alkylated His, but also indicated degradation of this adduct. It was not possible to obtain the BPDE-His as one analyte from BPDE-alkylated SA through modifications of the enzymatic hydrolysis. The BPDE-His adduct was shown to be stable during the weak acidic conditions used in the isolation of SA. Enrichment by HPLC or SPE, but not butanol extraction, gave good recovery, using Protein LoBind tubes. A simple internal standard (IS) approach using SA modified with other PAHDE as IS was shown to be applicable. A robust analytical procedure based on digestion with pronase, enrichment by HPLC or SPE, and analysis with HPLC/MS-MS electrospray ionisation was achieved. A good reproducibility (coefficient of variation (CV) 11 %) was obtained, and the achieved limit of detection for the studied PAHDE, using standard instrumentation, was approximately 1 fmol adduct/mg SA analysing extract from 5 mg SA.

Preparation and characterization of prototypes for multi-modal separation media aimed for capture of negatively charged biomolecules at high salt conditions

Several prototypes of multi-modal ligands suitable for the capture of negatively charged proteins from high conductivity (28 mS/cm) mobile phases were coupled to Sepharose 6 Fast Flow. These new prototypes of multi-modal anion-exchangers were found by screening a diverse library of multi-modal ligands and selecting anion-exchangers resulting in elution of test proteins at high ionic strength. Candidates were then tested with respect to breakthrough capacity of BSA in a buffer adjusted to a high conductivity (20 mM Piperazine and 0.25 M NaCl, pH 6.0). The recovery of BSA was also tested with a salt step (from 0.25 to 2.0 M NaCl using 20 mM Piperazine as buffer, pH 6.0) or with a pH-step to pH 4.0. We have found that non-aromatic multi-modal anion-exchange ligands based on primary or secondary amines (or both) are optimal for the capture of proteins at high salt conditions. Furthermore, these new multi-modal anion-exchange ligands have been designed to take advantage not only of electrostatic but also hydrogen bond interactions. This has been accomplished through modification of the ligands by the introduction of hydroxyl groups in the proximity of the ionic group. Experimental evidence on the importance of the relative position of the hydroxyl groups on the ligand in order to improve the breakthrough capacity of BSA has been found. Compared to strong anion-exchangers such as Q Sepharose Fast Flow the new multi-modal weak anion-exchangers have breakthrough capacities of BSA at mobile phases of 28 mS/cm and pH 6.0 that are 20-30 times higher. The new multi-modal anion-exchangers can also be used at normal anion-exchange conditions and with either a salt step or a pH-step to acidic pH can accomplish the elution of proteins. In addition, the functional performance of the new anion-exchangers was found to be intact after treatment in 1.0 M sodium hydroxide solution for 1 week. A number of multi-modal anion-exchange ligands based on aromatic amines exhibiting high breakthrough capacity of BSA have been found. With these ligands recovery was often found to be low due to strong non-electrostatic interactions. However, for phenol derived anion-exchange media the recovery can be improved by desorption at high pH.     

General methods to render macroporous stationary phases nonporous and deformable,exemplified with agarose and silica beads and their use in high-performance ion-exchange and hydrophobic-interaction chromatography of proteins

Summary New general methods for the preparation of nonporous beads from macroporous beads are described. One method is based on filling the inner volume of the beads with a solution of a monomer which binds to the matrix at the same time as it is allowed to polymerize. The method is illustrated with agarose and silica as matrices and glycidol as monomer. In an alternative, but principally similar method, we first attached allyglycidyl ether to agarose via the epoxide groups and then allowed acrylamide to react with the immobilized allyl groups during polymerization. In an analogous way, nonporous silica beads were prepared by coupling -methacryloxypropyltrimethoxy silane to the macroporous beads followed by polymerization of acrylamide or N-methylolacrylamide on the immobilized methacryl groups. The latter monomer has the advantage of giving a polymer rich in OH groups, which can be used for crosslinking or/and attachment of different ligands (the glycidol polymers have the same advantage).The nonporous agarose beads have chromatographic properties similar to those of the previously described nonporous agarose beads prepared by shrinkage and subsequent crosslinking. For instance, the beds are compressible, which favors the resolution: compressed beds of large beads give the same or higher resolution than do beds of small beads. Another similarity is that the resolution is independent of flow rate or is even enhanced upon an increase in flow rate, maybe in part owing to the generation of a flow pattern which transports the solute from one bead to another faster than does diffusion. These similarities are demonstrated by anion-exchange and hydrophobic-interaction chromatography of proteins. Even the nonporous silica beads are somewhat deformable owing to the relatively thick polymer coating and share with the nonporous agarose beads the attractive relation between resolution and flow rate. In addition, in comparison with naked silica beads they exhibit very little protein adsorption and are more pH stable. A compressed bed of nonporous, coated 30–45 m silica beads gave in an HIC experiment a resolution comparable to that obtained with a bed of noncompressed, nonporous 1.5-m silica beads, which give a very high resolution, as shown by Unger and coworkers [5].     

Alternative method for reconstruction of antihydrogen annihilation vertices

The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.     

Study of the effect of the substitution of O by F,S, and Cl on the superconductivity of Y1Ba2Cu3O7−δ

We have studied the superconducting transitions of Y₁Ba₂Cu₃D _x O_7–x– samples where O has been replaced by D=F, S, or Cl andx=0.2-2. No single phase compounds were obtained forx>0.2. No dramatic increase inT _c was registered. Generally the results can be interpreted as a dilution of the highT _c 1 2 3 phase by other phases as the dopant concentration increases, ultimately suppressingT _c completely. Possibly there is an increase ofT _c for an intermediate dopant range,x, in the Cl series.     

AD performance and its extension towards ELENA

The CERN’s Antiproton Decelerator (AD) is devoted to special experiments with low energy antiprotons. A main topic is the antihydrogen production with the present aim to produce these antimatter atoms with such low energy that they can be trapped in a magnetic gradient field. First very convincing results have been published recently by ALPHA. Still, it appears to be cumbersome, time consuming and ineffective when collecting the needed large numbers and high densities of antiproton clouds with the present AD. Both the effectiveness and the availability for additional experiments at this unique facility would drastically increase, if the antiproton beam of presently 5 MeV kinetic energy would be reduced by an additional decelerator to something like 100 keV. Such a facility ”ELENA”, as an abbreviation for Extra Low ENergy Antiproton Ring and first discussed in 1982 for LEAR, was freshly proposed with a substantial new design and revised layout and is presently under consideration. ELENA will increase the number of useful antiprotons by up to two orders of magnitude and will allow to serve up to four experiments in parallel.     

Weak and strong wall boundary procedures and convergence to steady-state of the Navier–Stokes equations

We study the influence of different implementations of no-slip solid wall boundary conditions on the convergence to steady-state of the Navier–Stokes equations. The various approaches are investigated using the energy method and an eigenvalue analysis. It is shown that the weak implementation is superior and enhances the convergence to steady-state for coarse meshes. It is also demonstrated that all the stable approaches produce the same convergence rate as the mesh size goes to zero. The numerical results obtained by using a fully nonlinear finite volume solver support the theoretical findings from the linear analysis.