Airborne particles in the Miyagi Museum of Art in Sendai, Japan, studied by electron probe X-ray microanalysis and energy dispersive X-ray fluorescence analysis.

The presented work provides baseline data on the existing airborne conditions in the Miyagi Museum of Art in Sendai, Japan, during the summer of 2000. The chemical composition, size and indoor and outdoor origin of the suspended particulate matter were identified using a number of advanced X-ray techniques, such as Electron Probe X-Ray Microanalysis (EPXMA) and Energy Dispersive X-Ray Fluorescence Analysis (EDXRF). Our results, to the best of our knowledge, represent the first detailed study of the chemical nature of the indoor particulate matter in a Japanese museum and, as such, may contribute to future improvements of the air quality inside museums and to the lasting conservation of works of art.     

Negative ion MALDI‐TOF MS,ISD and PSD of neutral underivatized oligosaccharides without anionic dopant strategies,using 2,5‐DHAP as a matrix

Oligosaccharides represent complex class of analytes for mass spectrometric analysis due to the high variety of structural isomers concerning glycosidic linkages and possible branching. A systematic study of the negative ion mode matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry of various neutral oligosaccharides under selection of an appropriate matrix, like 2,5‐dihydroxyacetophenone (2,5‐DHAP) is reported here, without commonly used anion dopant strategies. Nevertheless, we were able to generate relevant in‐source decay (ISD) cross‐ring fragment ions, typically obtained in the negative ion mode. Data observed indicate that the intrinsic property of the terminal non‐reduced aldose is crucial for this behavior. A systematic study of the post source decay (PSD) of molecular, pseudomolecular and ISD cross‐ring cleavage precursor ions is reported here. A direct comparison of the positive and negative ion mode MALDI MS1 and PSD behavior of neutral oligosaccharides could also be performed under the use of the same matrix preparation, because 2,5‐DHAP is fully compatible with positive ion mode acquisition. We found that PSD spectra of deprotonated neutral oligosaccharides obtained in the negative ion mode are richer, because they contained both glycosidic and cross‐ring fragment ions. However, we also found that cross‐ring fragment ions are readily produced in the positive ion mode when potassiated precursor ions were selected. In addition, we show evidence that non‐anionic dopants and specific instrumental parameters can also significantly influence the ISD fragmentation. Taken together, our results should increase our understanding of oligosaccharide behavior in the negative ion mode as well as increase our knowledge regarding many aspects of in‐source MALDI chemistry. Copyright © 2016 John Wiley & Sons, Ltd.     

A sialylation study of mouse brain gangliosides by MALDI a-TOF and o-TOF mass spectrometry

Matrix-assisted laser desorption/ionization (MALDI) process of sialoglycoconjugates is generally accompanied by different levels of cleavage of sialic acid residues and/or by dehydration, and decarboxylation reactions. Quantitative densitometry of the mouse brain ganglioside (MBG) components separated by high-performance thin layer chromatography (HPTLC) and evidenced by orcinol staining was a basis to verify the ganglioside composition pattern with respect to the relative abundances of individual components in the mixture. A systematic mass spectrometry (MS) sialylation analysis has been carried out to evaluate the feasibility of an axial time-of-flight (a-TOF) MS, equipped with a vacuum MALDI source and an orthogonal-TOF (o-TOF) instrument with an ion source operated at about 1 mbar of N(2). Besides, the esterification by one methyl group of the carboxyl group in sialic acid to increase the stability of the ganglioside species for MALDI MS analysis has been tested and the yield of intact ganglioside species and of the neutral loss of water and carbon dioxide estimated. For the sialylation analysis of native ganglioside mixtures the MALDI o-TOF analysis with 6-azo-2-thiothymine/diammonium citrate (ATT/DAC) as a matrix appears as an optimal approach for ganglioside profiling.     

Agglutination of like-charged red blood cells induced by binding of beta2-glycoprotein I to outer cell surface

Plasma protein-mediated attractive interaction between membranes of red blood cells (RBCs) and phospholipid vesicles was studied. It is shown that beta(2)-glycoprotein I (beta(2)-GPI) may induce RBC discocyte-echinocyte-spherocyte shape transformation and subsequent agglutination of RBCs. Based on the observed beta(2)-GPI-induced RBC cell shape transformation it is proposed that the hydrophobic portion of beta(2)-GPI molecule protrudes into the outer lipid layer of the RBC membrane and increases the area of this layer. It is also suggested that the observed agglutination of RBCs is at least partially driven by an attractive force which is of electrostatic origin and depends on the specific molecular shape and internal charge distribution of membrane-bound beta(2)-GPI molecules. The suggested beta(2)-GPI-induced attractive electrostatic interaction between like-charged RBC membrane surfaces is qualitatively explained by using a simple mathematical model within the functional density theory of the electric double layer, where the electrostatic attraction between the positively charged part of the first domains of bound beta(2)-GPI molecules and negatively charged glycocalyx of the adjacent RBC membrane is taken into account.     

Determination of dithiothreitol in complex protein mixtures by HPLC-MS

Dithiothreitol (DTT) and other reducing agents are typically used in refolding processes of recombinant human proteins during their purification from inclusion bodies. Due to its toxicity, it is essential to monitor the clearance of DTT throughout the analytical flow from the refolding phase to the final formulated product. Here we report a direct, simple, and fast liquid chromatography method using UV and tandem mass spectrometry (MS/MS) detection for DTT evaluation in complex protein mixtures. In aqueous solution DTT exists as an equilibrium mixture of the oxidized and the reduced form (H(2)DTT --> DTT(ox)) and the quantitation tools should therefore be applicable to both forms in a single step or in multiple steps. Oxidation of DTT with aqueous copper(II) nitrate trihydrate solution was introduced to determine a single oxidized compound, i. e. DTT(ox). Proteins and other components of high molecular masses were separated from DTT(ox) by ultrafiltration. Consequently, efficient separation of the DTT(ox )from other flow-through mixture components (sugars, polymers, salts, protein stabilizers) was achieved on an Atlantis dC(18) column. After chromatographic separation, DTT(ox) was selectively identified by UV absorbance at 285 nm or by selected reaction monitoring, measuring signal transition between m/z 151 --> 105. The method was validated in terms of specificity, accuracy, precision, linearity, and limit of quantification and detection. A reversed-phase HPLC separation method with atmospheric pressure chemical ionization and MS/MS detection in negative ion mode is highlighted as a viable alternative to currently existing quantitation methods involving DTT derivatization and HPLC fluorescence detection. The described approach offers simple, straightforward, selective, and high-throughput DTT quantitation in protein mixtures.     

Parenchyma cell wall structure in twining stem of <Emphasis Type="Italic">Dioscorea balcanica</Emphasis>

Anatomical adaptation of liana plants includes structural changes in cell walls of different tissues: fibers, vessel elements and tracheids. However, the contribution of parenchyma cells to stem twining in liana plants is mostly unknown. The aim of this investigation is to determine changes in stem parenchyma cell walls that are correlated with the twinning process in liana plants. Parenchyma cell wall structure was studied on the stem cross sections of straight and twisted internodes of monocotyledonous liana Dioscorea balcanica, by different microscopy techniques: light microscopy, scanning electron microscopy, fluorescence detected linear dichroism microscopy and Fourier transform infrared microspectrometry. In addition, chemical analysis of the entire stem internodes was performed using photometric and chromatographic methods. Parenchyma cell walls of twisted D. balcanica internodes are characterized by: lower amounts of cellulose (obtained by FTIR microspectrometry) with different cellulose microfibril orientation (shown by Scanning electron microscopy), but no changes in “cellulose fibril order” (obtained by Differential polarization laser scanning microscopy); lower amounts of xyloglucan, higher amounts of xylan, higher amounts of lignin with modified organization—less condensed lignin (obtained by FTIR microspectrometry). At the same time, chemical analysis of the entire internodes did not show significant differences in lignin content and cell wall bound phenols related to stem twining, except for the presence of diferulate cross-links exclusively in twisted internodes. Our results indicate that adaptations to mechanical strain in D. balcanica stems involve modifications in parenchyma cell wall structure and chemistry, which provide decreased stiffness, higher strength and increased elasticity of twisted internodes.     

Influence of surface modified TiO2 nanoparticles by gallates on the properties of PMMA/TiO2 nanocomposites

Nanocomposites based on poly(methyl methacrylate) (PMMA) and TiO₂ nanoparticles were synthesized by in situ radical polymerization of MMA in solution. The surface of TiO₂ nanoparticles was modified with four gallic acid esters (octyl, decyl, lauryl and cetyl gallate). The content of gallates present on the surface of TiO₂ was calculated from the TGA results. The influence of length of hydrophobic tail of amphiphilic alkyl gallates on dispersability of surface modified TiO₂ nanoparticles in PMMA matrix, the molecular weight and glass transition temperature of PMMA, as well as the thermal stability of the prepared PMMA/TiO₂ nanocomposites in nitrogen and air was investigated. The influence of content of TiO₂ nanoparticles on the properties of these nanocomposites was also examined. The formation of a charge transfer complex between the surface Ti atoms and the gallates was confirmed by FTIR and UV spectroscopy. TEM micrographs of the PMMA/TiO₂ nanocomposites revealed that degree of TiO₂ aggregation can be significantly lowered by increasing the length of aliphatic part of the used gallates. The molecular weight of PMMA slightly decreases with the increase of TiO₂ content, indicating that used TiO₂ nanoparticles act as radical scavengers during the polymerization of MMA. The presence of surface modified TiO₂ nanoparticles do not have an influence on the mobility of PMMA chain segments leading to the same values of glass transition temperature for all investigated samples. Thermal and thermo-oxidative stability of the PMMA matrix are improved by introducing TiO₂ nanoparticles modified with gallates.     

On the properties of McShane’s functional and their applications

In this paper we derive some remarkable properties of McShane’s functional, defined by means of positive isotonic linear functionals. These properties are then applied to weighted generalized means. A series of consequences among additive and multiplicative type mean inequalities is given, as well as a special consideration of Hölder’s inequality, in view of the new results.     

N‐(o‐Chloro­phenyl)‐2,5‐di­methyl­pyrrole‐3‐carb­aldehyde

Crystal structure analysis of the title compound, C₁₃H₁₂ClNO, reveals three crystallographically independent mol­ecules in the asymmetric unit. The main conformational difference between these mol­ecules is the orientation of the phenyl rings with respect to the pyrrole rings. The coplanar arrangement of the aldehyde groups attached to the pyrrole rings influences the pyrrole‐ring geometry. The C2—C3 and N1—C5 bonds are noticeably longer than the C4—C5 and N1—C2 bonds. Two independent mol­ecules of the title compound form dimers via intermolecular C—H⃛O hydrogen bonds [D⃛A = 3.400 (3) Å and D—H⃛A = 157°]. The perpendicular orientation of the phenyl and pyrrole rings of one independent mol­ecule and its symmetry‐related mol­ecule allows C—H⃛π interactions, with an H⃛centroid distance of 2.85 Å and a C—H⃛π angle of 155°. The distances between the H atom and the pyrrole‐ring atoms indicate that the C—H bond points towards one of the bonds in the pyrrole ring.