Ion trap mass spectrometry in the structural analysis of haemoglobin peptides modified by epichlorohydrin and diepoxybutane

Ion trap mass spectrometry has been shown to be particularly suitable for the structural analysis of high molecular weight peptides directly fragmented in the mass analyser without needing further sub-digestion reactions. Here we report the advantages of using multi-stage ion trap mass spectrometry in the structural characterisation of haemoglobin alkylated with epichlorohydrin and diepoxybutane. Alkylated globins were digested with trypsin and the peptide mixtures were analysed by MS(3). This technique allows the sequential fragmentation of peptides under analysis, giving rise to MS(3) product ion spectra with additional information with respect to MS(2) mass spectra. The results obtained complete the previously reported structural characterisation of alkylated haemoglobin, demonstrating the potential of ion trap mass spectrometry.     

The meso-β-linkage as structural motif in porphyrin-based donor-acceptor compounds

Synthetic strategies for using the meso-β-linkage as a structural motif in electron transfer mimics have been tested. Exploratory syntheses of directly meso-β-linked bis- and trisporphyrins and the first representative X-ray structure of a meso-β-linked bisporphyrins are reported. The structure reveals a unique form of intramolecular π-π stabilization between one porphyrin and a meso-aryl substituent in a second porphyrin unit that accounts for the stability of different atropisomers in trimers. Using β-formyl porphyrins, dipyrromethanes, and suitable quinone precursor aldehydes, mixed condensations gave convenient access to porphyrin-porphyrin-quinone (P-P-Q) donor-acceptor systems consisting of a meso-β-linked bisporphyrin, a spacer, and a quinone acceptor.     

Relaxed functional iteration techniques for the numerical solution of M/G/1 type Markov chains

We introduce a new iterative method for the computation of the minimal nonnegative solutionG of the matrix equation , arising in the numerical solution of M/G/1 type Markov chains. The idea consists in applying a relaxation technique to customarily used functional iteration formulas. The proposed method is easy to implement and outperforms, in terms of number of iterations and execution time, the standard functional iteration techniques.     

Die Darstellung von o-Nitrososalicyls?ure und ihre Verwendung zur Bestimmung des Nickels

Zusammenfassung o-Nitrososalicylsäure kann leicht und ohne große Kosten hergestellt werden. Das Reagens gibt mit Nickel-Ionen ein rotes, in Wasser lösliches innerkomplexes Salz. Auf Grund dieser Reaktion kann Nickel-Ion einfach und empfindlich bestimmt werden. Da die meisten anderen Metalle mit dem Reagens gefärbte Salze wechselnder Löslichkeit geben, ist es wünschenswert, die vorstehende experimentelle Arbeit fortzusetzen.Gewidmet aus Anlaß des 100jährigen Bestehens des Laboratoriums Fresenius.Diese Arbeit übersandte Dr. Oskar Baudisch, Research Director of the New York State Research Institute of the Saratoga Springs Commission, Saratoga Springs, New York.     

Validation of an Analytical Method for the Simultaneous Determination of Hyaluronic Acid Concentration and Molecular Weight by Size-Exclusion Chromatography

The hyaluronic acid (HA) global market growth can be attributed to its use in medical, cosmetic, and pharmaceutical applications; thus, it is important to have validated, analytical methods to ensure confidence and security of its use (and to save time and resources). In this work, a size-exclusion chromatography method (HPLC-SEC) was validated to determine the concentration and molecular distribution of HA simultaneously. Analytical curves were developed for concentration and molecular weight in the ranges of 100–1000 mg/L and 0.011–2.200 MDa, respectively. The HPLC-SEC method showed repeatability and reproducibility greater than 98% and limits of detection and quantification of 12 and 42 mg/L, respectively, and was successfully applied to the analysis of HA from a bacterial culture, as well as cosmetic, and pharmaceutical products.     

Regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles by 1,3-dipolar cycloaddition: Role of Er(OTf)3, ionic liquid and water

A simple procedure to obtain 1,5-disubstituted 1,2,3-triazoles, using the Er(OTf)₃/[mpy]OTf/H₂O catalytic system is described. The reaction proceeds through an eliminative azide–olefin cycloaddition (EAOC) offering a highly regioselective approach and good yields (81–94%). The advantages of this method include simple operations of work-up and the ability of the catalytic system to be re-used five times without an evident loss in yield. The role of IL and water were speculated, invoking also a probable ionic self-assembly (ISA) effect.     

Efficient computation of the extreme solutions of

We propose a new quadratically convergent algorithm, having a low computational cost per step and good numerical stability properties, which allows the simultaneous approximation of the extreme solutions of the matrix equations and . The algorithm is based on the cyclic reduction method.

     

Fungal colonization on stoneworks. Interaction fungi-powdered stone samples

The microbial activity plays an important role in the biodegradative processes implied in stonework decay. In natural environments it is not possible to separate the damage produced by microorganisms from damage caused by physical and chemical agents. In vitro assays carried out with microbes isolated from weathered stones are required in order to understand the biological mechanisms involved in stone deterioration. We have described, as commented in the text, how fungal colonization observed on scaglia may be the result of the fine grain size of rock, whereas inhibition of growth on marble may depend on the surface characteristics of calcite grains after grinding. The extent of microbial growth clearly depends on the quantity of cations released in solution. However, fungal growth may, in turn, induce a decrease in pH, thus promoting mineral chemical attack. These observation points to selective action of fungal species in promoting weathering well evidenced by the presence of different extents of cations released in suspension from the same sample. Detailed studies are in progress in order to go into this question.