A new approach to 3-hydroxyquinoline-2-carboxylic acid

Quinoline-2-carboxylic acid derivatives cap the N-terminal of several natural cyclic peptides with antitumoral activity. A new and convenient route for the preparation of 3-hydroxyquinoline-2-carboxylic acid is discussed. The preparation of the title compound is accomplished by a four-step procedure from 3-hydroxyquinoline via MOM protection of the hydroxyl group, followed by a 1,2-addition of methyllithium to the quinoline ring with concomitant oxidation, and, finally, a two-step oxidation procedure for the transformation of the methyl group to the carboxylic acid along with removal of the MOM group. Furthermore, different attempts to its preparation led to other interesting quinolines, such as 2-chloro-3-hydroxyquinoline-4-carboxylic acid and a protected 3,3′-dihydroxy-2,2′-biquinoline.     

The effect of interstitial hydrogen on the electronic structure of Fe-Pd alloys

The electronic structure and bonding in Fe-Pd alloys were computed using a tight binding method. Two phases have been identified for these alloys, a high temperature fcc and a low temperature fct structure. The hydrogen absorption turns out to be a favorable process in both structures. The hydrogen at tetrahedral interstitial site for the fct structure is 2.2 eV more stable than that impurity atom located at an octahedral interstitial site in the fcc structure.The density of states curves show a peak below the d metal band which is made up mostly of hydrogen based states (>50% H_1s) while the metal contribution includes mainly s and p orbitals.In the fcc structure, both Fe-H and Pd-H bonds are developed while the Fe-Pd interface shows antibonding filled states near the Fermi level. When the fct phase is considered, the Fe-H overlap population (OP) decreases, while the Pd-H remains similar to the previous case. The Fe-Fe OP decreases and the Pd-Pd bonds are almost unaltered. The interfacial Fe-Pd bonds are almost unaffected by hydrogen. The band structure of the hydrogenated alloys in the fcc and fct phases were also computed.     

Quantitative analysis of N-glycans from human alfa-acid-glycoprotein using stable isotope labeling and zwitterionic hydrophilic interaction capillary liquid chromatography electrospray mass spectrometry as tool for pancreatic disease diagnosis

In this work we demonstrate the potential of glycan reductive isotope labeling (GRIL) using [¹²C]- and [¹³C]-coded aniline and zwitterionic hydrophilic interaction capillary liquid chromatography electrospray mass spectrometry (μZIC-HILIC-ESI-MS) for relative quantitation of glycosylation variants in selected glycoproteins present in samples from cancer patients. Human α₁-acid-glycoprotein (hAGP) is an acute phase serum glycoprotein whose glycosylation has been described to be altered in cancer and chronic inflammation. However, it is not clear yet whether some particular glycans in hAGP can be used as biomarker for differentiating between these two pathologies. In this work, hAGP was isolated by immunoaffinity chromatography (IAC) from serum samples of healthy individuals and from those suffering chronic pancreatitis and different stages of pancreatic cancer, respectively. After de-N-glycosylation, relative quantitation of the hAGP glycans was carried out using stable isotope labeling and μZIC-HILIC-ESI-MS analysis. First, protein denaturing conditions prior to PNGase F digestion were optimized to achieve quantitative digestion yields, and the reproducibility of the established methodology was evaluated with standard hAGP. Then, the proposed method was applied to the analysis of the clinical samples (control vs. pathological). Pancreatic cancer samples clearly showed an increase in the abundance of fucosylated glycans as the stage of the disease increases and this was unlike to samples from chronic pancreatitis. The results gained here indicate the mentioned glycan in hAGP as a candidate structure worth to be corroborated by an extended study including more clinical cases; especially those with chronic pancreatitis and initial stages of pancreatic cancer. Importantly, the results demonstrate that the presented methodology combining an enrichment of a target protein by IAC with isotope coded relative quantitation of N-glycans can be successfully used for targeted glycomics studies. The methodology is assumed being suitable as well for other such studies aimed at finding novel cancer associated glycoprotein biomarkers.     

Multicomponent Analysis Of Environmental Matrices

Abstract

The paper reviews several modalities of multicomponent analysis, namely: multilinear regression by using single or multiple standards, non-linear optimization systems by using the Gauss-Newton or the Simplex methods and factor analysis, which have been used by the authors in recent papers.

These multicomponent methods have been applied to environmental samples by different analysis techniques, such as UV- visible spectrophotometry, fluorimetry, polarography-voltametry, simultaneous kinetic processes. monitoring of liquid-liquid extraction processes and HPLC (resolution of overlapped peaks). In this way, the advantages and limitations of the methodology of multicomponent analysis are shown.     

Weighted shapley values for games in generalized characteristic function form

We study the family of weighted Shapley values for games in generalized characteristic function form. These values are defined and characterized.     

Application of flowing stream techniques to water analysis Part III. Metal ions: alkaline and alkaline-earth metals, elemental and harmful transition metals, and multielemental analysis

In the earlier parts of this series of reviews [1] and [2], the most relevant flowing stream techniques (namely, segmented flow analysis, continuous flow analysis, flow injection (FI) analysis, sequential injection (SI) analysis, multicommuted flow injection analysis and multisyringe flow injection analysis) applied to the determination of several core inorganic parameters for water quality assessment, such as nutrients and anionic species including nitrogen, sulfur and halogen compounds, were described.In the present paper, flow techniques are presented as powerful analytical tools for the environmental monitoring of metal ions (alkaline and alkaline-earth metals, and elemental and harmful transition metals) as well as to perform both multielemental and speciation analysis in water samples. The potentials of flow techniques for automated sample treatment involving on-line analyte separation and/or pre-concentration are also discussed in the body of the text, and demonstrated for each individual ion with a variety of strategies successfully applied to trace analysis. In this context, the coupling of flow methodologies with atomic spectrometric techniques such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICPMS) or hydride-generation (HG)/cold-vapor (CV) approaches, launching the so-called hyphenated techniques, is specially worth mentioning.     

A multisyringe flow injection method for the automated determination of sulfide in waters using a miniaturised optical fiber spectrophotometer

In this paper, a fully software-controlled multisyringe flow injection (MSFIA) spectrophotometric system is proposed for the determination of sulfide in environmental and waste waters. The implementation of ancillary solenoid valves into the flow network allows a multitude of injection modalities to be explored, the selected modality being directly dependent on the aim of the assays. The multicommuted sandwich-type approach is introduced in this work as an efficient means to warrant high sensitivity for the particular assay with excellent repeatabilities and a considerable reagent saving. Moreover, a high injection frequency may be easily attained by carrying out a multiple injection modality during a single forward displacement of the piston driver bar. The interfacing of the robust and versatile multisyringe piston pump with an optical fiber plug-in spectrophotometer furnished with a light emitting diode enables the miniaturization of the flow analyzer, which is thus readily adaptable to in-situ and real-time monitoring schemes. The flow method is based on the coupling Fischer’s reaction of sulfide with N,N-dimethyl-p-phenylenediamine in the presence of Fe(III) as oxidizing reagent in a 0.7 M HCl medium. Careful selection of the physical and chemical variables enabled coefficients of variations better than 1.5% (n = 10) at the 1 mg l⁻¹ level for both injection modalities. Dynamic working ranges of 0.2–2.0 and 0.5–5 mg l⁻¹ sulfide for sandwich and multiple injection techniques, and detection limits of 0.09 and 0.15 mg l⁻¹, respectively, were obtained. Furthermore, the sandwich modality featured an average slope of 0.43 ± 0.02 l mg⁻¹ calculated from 10 day-to-day calibration plots. This result reveals better sensitivity than other flowing stream methods described in the literature. The multiple injection technique allowed an improvement of the injection throughput up to 80 h⁻¹, although a decrease of sensitivity was concomitantly observed (average slope of 0.17 ± 0.01 l mg⁻¹).

The multisyringe flow method was successfully applied to the determination of sulfide in different spiked water matrices (namely, mineral, tap, freshwater, seawater and wastewater) with recoveries ranging from 96 to 104%. Good agreement was also found in water samples between the MSFIA results and those of the batch APHA-standard method.     

Application of flowing-stream techniques to water analysis Part II. General quality parameters and anionic compounds: halogenated, sulphur and metalloid species

In the first part of this review [Talanta 60 (2000) 867], flowing-stream methods (namely, segmented flow analysis (SFA), continuous-flow analysis (CFA), flow-injection analysis (FIA), sequential-injection analysis (SIA), multicommuted flow-injection analysis (MCFIA) and multisyringe flow-injection analysis (MSFIA)) were presented as powerful analytical tools for nutrient determination in water samples when coupled to photometric/fluorimetric detection, flow-through ion-selective electrodes or amperometric sensors.In the present paper, relevant flow methods applied to the monitoring of anionic species as well as to the determination of general parameters for water quality evaluation (such as pH, alkalinity, chemical and biochemical oxygen demand, conductivity and total ionic content) are reviewed, and their background, detection technique and noteworthy analytical features are detailed. Furthermore, other techniques, such as flow systems connected to hydride-generation atomic absorption spectrometry, should be highlighted as practical approaches for metalloid determination since a series of speciation schemes are demonstrated to be readily adaptable.