Urine profiling using capillary electrophoresis-mass spectrometry and multivariate data analysis

This work presents the development of a general and fast method for metabolic profiling of urine, using capillary electrophoresis-electrospray ionisation mass spectrometry (CE-ESIMS) and multivariate data analysis (DA). Human urine samples collected before and after ingestion of paracetamol were analysed at acidic and basic CE conditions, using both positive and negative ESI-MS detection. Analysis of the entire resulting data set, with no prior knowledge of the target compounds, using pair-wise 'fuzzy' correlation and eigenvalue analysis enabled the samples to be discriminated between on the basis of blank urine and urine collected after drug intake. By generating two-dimensional loadings plots, it was also possible to identify the m/z values of the substances responsible for the differentiation between control and dosed samples.     

Globotriose- and oligo(ethylene glycol)-terminated self-assembled monolayers: surface forces, wetting, and surfactant adsorption

A set of oligo(ethylene glycol)-terminated and globotriose-terminated self-assembled monolayers (SAMs) has been prepared on gold substrates. Such model surfaces are well defined and have good stability due to the strong binding of thiols and disulfides to the gold substrate. They are thus very suitable for addressing questions related to effects of surface composition on wetting properties, surface interactions, and surfactant adsorption. These issues are addressed in this report. Accurate wetting tension measurements have been performed as a function of temperature using the Wilhelmy plate technique. The results show that the nonpolar character of oligo(ethylene glycol)-terminated SAMs increases slightly but significantly with temperature in the range 20-55 degrees C. On the other hand, globotriose-terminated SAMs are fully wetted by water at room temperature. Surface forces measurements have been performed and demonstrated that the interactions between oligo(ethylene glycol)-terminated SAMs are purely repulsive and similar to those determined between adsorbed surfactant layers with the same terminal headgroup. On the other hand, the interactions between globotriose-terminated SAMs include a short-range attractive force component that is strongly affected by the packing density in the layer. In some cases it is found that the attractive force component increases with contact time. Both these observations are rationalized by an orientation- and conformation-dependent interaction between globotriose headgroups, and it is suggested that hydrogen-bond formation, directly or via bridging water molecules, is the molecular origin of these effects.     

Monte Carlo simulations of cross-linked polyelectrolyte gels with oppositely charged macroions

The volume and structural changes upon replacement of oppositely charged network counterions for oppositely charged macroions in cross-linked polyelectrolyte gels have been investigated by Monte Carlo simulations using a coarse-grained model. Initially, the gel deswells, but after an approximately equivalent amount of macroions, the gel starts to swell again. The deswelling effect is greatest for small and highly charged macroions. The role of different network properties on the deswelling has also been examined. The initial deswelling is understood in terms of a replacement of confined counterions with macroions, thereby reducing the osmotic pressure originating from the counterions. At these conditions, macroions are located near network nodes with various degrees of network chains wrapping them. At charge equivalence, a profound change in the network structure has appeared. At these conditions, the cohesive electrostatic interaction and the excluded volume effect of the macroions strongly influence the equilibrium volume of the gel. Our model system reproduces many characteristic experimental observations of polyelectrolyte gels containing oppositely charged surfactants.     

Monitoring substrate and products in a bioprocess with FTIR spectroscopy coupled to artificial neural networks enhanced with a genetic-algorithm-based method for wavelength selection

An experiment was developed as a simple alternative to existing analytical methods for the simultaneous quantitation of glucose (substrate) and glucuronic acid (main product) in the bioprocesses Kombucha by using FTIR spectroscopy coupled to multivariate calibration (partial least-squares, PLS-1 and artificial neural networks, ANNs). Wavelength selection through a novel ranked regions genetic algorithm (RRGA) was used to enhance the predictive ability of the chemometric models. Acceptable results were obtained by using the ANNs models considering the complexity of the sample and the speediness and simplicity of the method. The accuracy on the glucuronic acid determination was calculated by analysing spiked real fermentation samples (recoveries ca. 115%).     

Effect of alkali metal hydroxides on the enantioseparation of amines using di-O-isopropylidene-keto-L-gulonic acid as the selector in NACE

The present work demonstrates the importance of the ionic composition in the BGE for enantioseparation. (-)-2,3:4,6-di-O-Isopropylidene-2-keto-L-gulonic acid ((-)-DIKGA) has been used as the chiral selector in methanolic and ethanolic BGEs. The influence of added alkali metal hydroxides on the EOF and the chiral separation of amines (atenolol, isoprenaline, pindolol and propranolol) have been studied. The ion-pair formation constants in ethanol were determined by precision conductometry for the enantiomers of pindolol with (-)-DIKGA, for Li(+), Na(+) and Cs(+) with (-)-DIKGA, and also for the corresponding alkali metal hydroxides. The effective mobilities and the enantiomeric mobility differences were affected by the type of alkali metal hydroxide (LiOH, NaOH, KOH, RbOH or CsOH) added to the BGE. The effective mobility and mobility difference were increased with decrease in solvated radius of the alkali metal cation. These differences could partly be correlated to the ion-pair formation constants of the alkali metal cations with the chiral selector, affecting the equilibrium concentration of the free selector. The electroosmosis was also affected by the alkali metal hydroxide added to the BGE. The cathodic electroosmosis decreased with decreasing solvated radius of the alkali metal cation added to the BGE. Interestingly, the cathodic EOF was even reversed, i.e. became anodic in the ethanolic BGEs containing KOH, RbOH or CsOH and the methanolic ones with RbOH and CsOH.     

Sample pretreatment on a microchip with an integrated electrospray emitter

This study presents a microbead-packed PDMS microchip with an integrated electrospray emitter for sample pretreatment prior to sheathless ESI-MS. We prove the concept of analytical functions integrated onto a cm-sized area of a single bulk material. The microchip consists of two PDMS substrates replicated from SU-8 fabricated silicon wafer masters, bonded together after oxidation by corona discharge treatment. The channel within the microchip contains a grid structure that was used to trap 5 microm hypercross-linked polystyrene beads. The beads acted as a medium for sample desalting and enrichment. Electrical contact for the sheathless ESI process was achieved by coating the integrated emitter with conductive graphite powder after applying a thin layer of PDMS as glue. The coating as well as the bond of the PDMS structures showed excellent durability. A continuous spray was obtained from the microchip for over 800 h in a long-term electrospray stability experiment. Desalting and enrichment of neuropeptides from a physiological salt solution was successful by loading the sample onto the packed beads, followed by a washing and an eluting step. The results were obtained and evaluated using a TOF MS. An LOD of approximately 20 fmol (loaded onto the beads) for angiotensin II was obtained from a sample of neuropeptides dissolved in physiological salt solution.     

Oxidative addition of phenyl bromide to Pd(BINAP) vs Pd(BINAP)(amine). Evidence for addition to Pd(BINAP)

[STRUCTURE: SEE TEXT] The rates of oxidative addition of phenyl bromide to [Pd(BINAP)2] have been measured in the presence and absence of added amine to assess a previous hypothesis that addition to [Pd(BINAP)(amine)] is faster than addition to [Pd(BINAP)]. These data show that addition to the amine complex is not faster than addition to [Pd(BINAP)]. Instead, they are consistent with oxidative addition, even in the presence of amine, to [Pd(BINAP)] as the major pathway. These data underscore the value of studying the stoichiometric reactions of isolated complexes when assessing the mechanism of a catalytic process.     

Determination of the immunomodulator laquinimod in human plasma by liquid chromatography/tandem mass spectrometry; development, validation and application of two methods in clinical pharmacokinetic profiling

Laquinimod (ABR-215062) is a synthetic compound currently undergoing clinical development for oral treatment of multiple sclerosis. The present paper describes the development, validation and clinical application of two rapid and sensitive methods for the determination of ABR-215062 in human plasma. Both methods use liquid chromatography/tandem mass spectrometry (LC/MS/MS) with electrospray ionization in positive mode and a stable isotope (13C6)-labeled ABR-215062 as internal standard for calibration. The selected reaction monitoring was based on the transitions m/z 357.1 --> 236.1 for ABR-215062, and either m/z 363.2 --> 236.1 or 365.2 --> 238.1 for 13C6-ABR-215062. Method 1, aimed and validated for low level determinations (0.4-100 nmol/L) of ABR-215062, utilizes solid-phase extraction followed by isocratic elution. Method 2, aimed and validated for wide range determinations (0.75-15000 nmol/L) of ABR-215062, utilizes protein precipitation followed by fast gradient elution. The methods were validated with respect to selectivity, lower limit of quantification (LLOQ), dynamic range, precision, accuracy, extraction recovery and ruggedness. Furthermore, the stability of low level ABR-215062 in plasma was investigated. The methods were also applied in clinical trials. The LLOQs were 0.4 and 0.75 nmol/L for methods 1 and 2, respectively. The intra- and inter-day precision for the methods were 1.6-3.5% and 2.1-5.7%. The extraction recoveries were 90-97% for both methods. ABR-215062 was stable in plasma for at least 3 months when stored at -20 degrees C. In conclusion, our developed methods were found to be selective, sensitive, robust and suitable for applications in clinical pharmacokinetic profiling.     

Immunoaffinity chromatographic and immunoprecipitation methods combined with mass spectrometry for characterization of circulating transthyretin

Transthyretin (TTR) is a small serum protein that is involved in distinct phenotypes of amyloidosis with different tissue localization, age of onset, and rate of progression. Some types of TTR-amyloidosis (such as familial amyloid polyneuropathy) are associated with various amino acid point mutations, while cardiac amyloid myopathy may also be associated with precipitation of the wild-type molecules, e.g., in senile systemic amyloidosis. Because of the unsettled relationship between circulating and precipitated TTR we here explore on-line immunoaffinity (IA) chromatography-MS and immunoprecipitation (IP)-MS methods for characterizing the circulating TTR population in normal individuals and in patients with known TTR-amyloidosis. It was found necessary to reduce the samples, e.g., with DTT, prior to ESI-TOF-MS. This reversed oxidative modifications to sufficiently resolve the two mass peaks isolated from sera of heterozygous patients. A simple IP technique without the use of centrifugal filtration was found to be convenient for the assessment of the TTR population in serum as demonstrated for both normal and variant (the Met111Leu mutation) TTR. This approach also readily allowed the identification of oxidation, S-sulfation, and S-cysteinylation in unreduced samples, while these modifications were less well resolved in the on-line IA chromatography-MS approach.     

Synthesis of Styrenes by Palladium(II)‐Catalyzed Vinylation of Arylboronic Acids and Aryltrifluoroborates by Using Vinyl Acetate

One Heck of a reaction : Treatment of arylboronic acids or aryltrifluoroborates with vinyl acetate by using a palladium(II) catalyst gives the corresponding styrenes (see scheme). No palladium reoxidant is needed and the vinylation is performed under non‐inert conditions