A capillary electrophoresis and off-line capillary electrophoresis/electrospray ionization-quadrupole time of flight-tandem mass spectrometry approach for ganglioside analysis

A systematic study for the optimization and implementation of high-performance capillary electrophoresis (HPCE) in conjunction with negative ion electrospray ionization-quadrupole time of flight-tandem mass spectrometry (ESI-QTOF-MS/MS) for the analysis of complex glycolipids is described. The performance of the capillary electrophoresis (CE) and off-line CE/ESI-QTOF-MS approach has been explored for screening a complex ganglioside mixture from bovine brain. All instrumental and solution parameters demonstrated to require special adjustment and to have the most substantial effect on the CE separation, abundance of product ions produced in a low-energy collision-induced dissociation (CID) process and their detection by MS/MS, when attempting to identify and sequence single ganglioside molecular species from CE eluted fractions. Upon optimization of the experimental parameters, an efficient methodology emerged providing the general basic requirements for combined CE/ESI-MS analysis of this type of complex glycoconjugate.     

Thin chip microsprayer system coupled to quadrupole time-of-flight mass spectrometer for glycoconjugate analysis

A thin chip polymer-based microsprayer has been coupled to a hybrid quadrupole time-of-flight mass spectrometer (QTOF MS) and introduced in carbohydrate research. The feasibility of the approach is demonstrated for mapping, sequencing and structural elucidation of glycoconjugates originating from human body fluids and tissues such as a glycopeptide mixture from normal human urine and an isolated and purified GT1 ganglioside fraction from normal adult human brain. The optimization procedure required by each glycoconjugate category is described and the advantages of the system in terms of flexibility and adaptability to QTOF MS, stability of the ESI MS signal, carbohydrate ionization and sequencing, sensitivity, speed of analysis and sample consumption are discussed.     

Gold-ligand interaction studies of water-soluble aminoalcohol capped gold nanoparticles by NMR

Novel reproducible preparations of gold nanoparticles capped by aminoalcohols have been set up by reduction of HAuCl4 with NaBH4 in aqueous solution. The characterization of Au@aminoalcohol nanoparticles performed by 1H NMR, ATR-FTIR, UV-vis spectroscopies, and TEM microscopy highlighted the binding site and the nature of the Au-NH bond.     

Analysis of human hippocampus gangliosides by fully-automated chip-based nanoelectrospray tandem mass spectrometry

Modern microfluidic devices are currently introduced in electrospray (ESI) mass spectrometry (MS), tending to substitute the classical capillary-based ESI infusion. Automated systems using the combination of robotized sample handling and chip-based ESI are significantly increasing the analysis reproducibility, precision, throughput, and efficiency. In the last couple of years our group developed the chip-based ESI-MS approach for glycomics in biomedical research and applied it for oligosaccharide, glycopeptide and ganglioside investigation. Here we report upon the optimization and application of this modern technique for the analysis of differential ganglioside expression patterns in human fetal and adult hippocampus. By this methodology, ganglioside species exhibiting high degree of heterogeneity in the ceramide motifs and biologically-relevant modifications could be identified in human hippocampus. The ultra-high reproducibility of the experiments uniquely provided by the chip-ESI approach allowed for a reliable MS-based ganglioside comparative assay. Moreover, the particular feature of chip ESI-tandem MS to provide structural information at high sensitivity was useful for detailed characterization of hippocampus-associated species. The experimental data presented in this study indicate the benefits of microfluidic/MS for determination of the topospecific brain ganglioside composition and development-related changes in their expression, which might be of high value in clinical investigation and for studies related to ganglioside-based therapy of central nervous system diseases.     

A thin chip microsprayer system coupled to Fourier transform ion cyclotron resonance mass spectrometry for glycopeptide screening

A thin polymer microchip was coupled with a Fourier transform ion cyclotron resonance (FTICR) 9.4 T mass spectrometer and the method was optimized in negative ion mode for glycopeptide screening. The interface between the polymer microchip and FTICR mass spectrometer consists of an in-laboratory conceived and designed mounting system that exhibits robust and controllable alignment of the chip toward the inlet of the mass spectrometer. The particular attribute of the polymer chip coupled to the FTICR mass spectrometer, to achieve an increase in ionization efficiency and sensitivity under the premise of high mass accuracy of detection, is highlighted by the large number of major and minor glycopeptide structures detected and identified in highly heterogeneous mixtures obtained from urine matrices. Glycoforms expressing various saccharide chain lengths ranging from tri- to dodecasaccharide, bearing up to three sialic acid moieties, could be detected and assigned based on the accuracy of the mass measurement (average mass deviation below 6 ppm) of their molecular ions. -Thin chipESI-FTICRMS is a potent novel system for glycomic screening of complex mixtures, as demonstrated for identification of singly sialylated O-glycosylated amino acids and peptides from urine matrices, and could be considered for general applicability in the glycoanalytical field.     

Solvolysis of 1,1-dimethyl-4-alkenyl chlorides: evidence for pi-participation

Tertiary 1,1-dimethyl-4-alkenyl chloride (1) solvolyzes with significantly reduced secondary beta-deuterium kinetic isotope effect (substrate with two trideuteromethyl groups) and has a lower entropy and enthalpy of activation than the referent saturated analogue 4 (k(H)/k(D) = 1.30 +/- 0.03 vs k(H)/k(D) = 1.79 +/- 0.01; Delta Delta H(++) = -9 kJ mol(-1), Delta Delta S(++) = -36 J mol(-1) K(-1), in 80% v/v aqueous ethanol), indicating participation of the double bond in the rate-determining step. Transition structure 1-TS computed at the MP2(fc)/6-31G(d) level of theory revealed that the reaction proceeds through a late transition state with considerably pronounced double bond participation and a substantially cleaved C-Cl bond. The doubly unsaturated compound 3 (1,1-dimethyl-4,8-alkadienyl chloride) solvolyzes with further reduction of the isotope effect, and a drastically lower entropy of activation (k(H)/k(D) = 1.14 +/- 0.01; DeltaS(++) = -152 +/- 12 J mol(-1) K(-1), in 80% v/v aqueous ethanol), suggesting that the solvolysis of 3 proceeds by way of extended pi-participation, i.e., the assistance of both double bonds in the rate-determining step.     

New sorafenib derivatives: synthesis, antiproliferative activity against tumour cell lines and antimetabolic evaluation

Sorafenib is a relatively new cytostatic drug approved for the treatment of renal cell and hepatocellular carcinoma. In this report we describe the synthesis of sorafenib derivatives 4a-e which differ from sorafenib in their amide part. A 4-step synthetic pathway includes preparation of 4-chloropyridine-2-carbonyl chloride hydrochloride (1), 4-chloro-pyridine-2-carboxamides 2a-e, 4-(4-aminophenoxy)-pyridine-2-carboxamides 3a-e and the target compounds 4-[4-[[4-chloro-3-(trifluoromethyl)phenyl]carbamoylamino]-phenoxy]-pyridine-2-carboxamides 4a-e. All compounds were fully chemically characterized and evaluated for their cytostatic activity against a panel of carcinoma, lymphoma and leukemia tumour cell lines. In addition, their antimetabolic potential was investigated as well. The most prominent antiproliferative activity was obtained for compounds 4a-e (IC(50) = 1-4.3 μmol·L-1). Their potency was comparable to the potency of sorafenib, or even better. The compounds inhibited DNA, RNA and protein synthesis to a similar extent and did not discriminate between tumour cell lines and primary fibroblasts in terms of their anti-proliferative activity.     

High‐pressure sorption of carbon dioxide and methane in all‐aromatic poly(etherimide)‐based membranes

The sorption of compressed carbon dioxide and methane in a series of all‐aromatic poly(etherimide) (PEI) thin films is presented. The polymer films are derived from the reactions between an arylether diamine (P1) and four different dianhydrides [3,3′,4,4′‐oxydiphthalic dianhydride (ODPA), 3,3′,4,4′ biphenyltetra‐carboxylic dianhydride (BPDA), 3,3′,4,4′‐benzo‐phenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA)] that have been selected to systematically change the flexibility of the polymer backbone, the segmental mobility, and the nonequilibrium excess free volume (EFV) of the polymer. The EFV, gas sorption capacities, and sorption‐ and temperature‐induced dynamic changes in film thickness and refractive index have been investigated by spectroscopic ellipsometry. The sorption capacity depends to a great extent on the PEI backbone composition. PMDA‐P1 shows the highest carbon dioxide sorption, combined with the lowest sorption selectivity because of the predominant sorption of methane in the EFV. For ODPA‐P1, the highest sorption selectivity is obtained, while it shows little long‐term relaxations at carbon dioxide pressures up to 25 bar. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 986–993     

Heavy metal and trace element accumulation in muscle,liver and gills of the Pontic shad (Alosa immaculata Bennet 1835) from the Danube River (Serbia)

Pontic shad (Alosa immaculata Bennet 1835) is an anadromous species that lives in the heavily polluted north-western part of the Black Sea and migrates into the Danube River to spawn. To assess their heavy metal contamination levels, samples of Pontic shad were collected at 863 river kilometre of the Danube River. Muscle, liver and gill samples were prepared using microwave digestion, and the analysis of Al, As, Cd, Cu, B, Ba, Fe, Mg, Sr, Zn, Li, Co, Cr, Mn, Mo, Ni and Pb was performed with inductively-coupled plasma-optic emission spectroscopy (ICP-OES). Significant differences in concentrations of analyzed elements were observed among different tissues, as well as between the genders. Al, Sr, Ba, Mg, and Li had the highest concentrations in gills, while Cd, Cu, Zn, Fe and B were highest in the liver. While the muscle had the lowest concentrations of most of the analyzed elements, it had the highest concentration of As. This study has revealed that the concentrations of Cd and As in Pontic shad muscle tissue were above the maximum acceptable concentrations for human consumption, thus precautions need to be taken in order to prevent future heavy metal contamination.     

Chip-nanoelectrospray quadrupole time-of-flight tandem mass spectrometry of meningioma gangliosides: a preliminary study

A strategy combining high-performance thin layer chromatography (HPTLC), laser densitometry, and fully automated chip-based nanoelectrospray (nanoESIchip) performed on a NanoMate robot coupled to QTOF-MS was developed, optimized, and for the first time applied for mapping and structural identification of gangliosides (GGs) extracted and purified from a human angioblastic meningioma specimen. While HPTLC pattern indicated only seven fractions migrating as GM3, GM2, GM1, GD3, GD1a (nLD1, LD1), GD1b, GT1b, and possibly GD2, due to the high sensitivity, mass accuracy, and ability to ionize minor species in complex mixtures, nanoESIchip-QTOF MS was able to discover significantly more GG species than ever reported in meningioma. Thirty-four distinct glycosphingolipid components of which five asialo, one GM4, nine GM3, two GM2, two GD3, nine GM1, and six GD1 differing in their ceramide compositions were identified. All structures presented long-chain bases with 18 carbon atoms, while the length of the fatty acid was found to vary from C11 to C25. MS screening results indicated also that the diversity of the expressed GM1 structures is higher than expected in view of the low proportions evidenced by densitometric quantification. Simultaneous fragmentation of meningioma-associated GM1 (d18:1/24:1) and GM1 (d18:1/24:0) by MS/MS using CID confirmed the postulated structures of the ceramide moieties and provided data on the glycan core, which document that for each of the GM1 (d18:1/24:1) and GM1 (d18:1/24:0) forms both GM1a and GM1b isomers are expressed in the investigated meningioma tissue.