An Integrated Mass Spectrometry-Based Glycomics-Driven Glycoproteomics Analytical Platform to Functionally Characterize Glycosylation Inhibitors

Cancer progression is linked to aberrant protein glycosylation due to the overexpression of several glycosylation enzymes. These enzymes are underexploited as potential anticancer drug targets and the development of rapid-screening methods and identification of glycosylation inhibitors are highly sought. An integrated bioinformatics and mass spectrometry-based glycomics-driven glycoproteomics analysis pipeline was performed to identify an N-glycan inhibitor against lung cancer cells. Combined network pharmacology and in silico screening approaches were used to identify a potential inhibitor, pictilisib, against several glycosylation-related proteins, such as Alpha1-6FucT, GlcNAcT-V, and Alpha2,6-ST-I. A glycomics assay of lung cancer cells treated with pictilisib showed a significant reduction in the fucosylation and sialylation of N-glycans, with an increase in high mannose-type glycans. Proteomics analysis and in vitro assays also showed significant upregulation of the proteins involved in apoptosis and cell adhesion, and the downregulation of proteins involved in cell cycle regulation, mRNA processing, and protein translation. Site-specific glycoproteomics analysis further showed that glycoproteins with reduced fucosylation and sialylation were involved in apoptosis, cell adhesion, DNA damage repair, and chemical response processes. To determine how the alterations in N-glycosylation impact glycoprotein dynamics, modeling of changes in glycan interactions of the ITGA5–ITGB1 (Integrin alpha 5-Integrin beta-1) complex revealed specific glycosites at the interface of these proteins that, when highly fucosylated and sialylated, such as in untreated A549 cells, form greater hydrogen bonding interactions compared to the high mannose-types in pictilisib-treated A549 cells. This study highlights the use of mass spectrometry to identify a potential glycosylation inhibitor and assessment of its impact on cell surface glycoprotein abundance and protein–protein interaction.     

Anodic reactions of sulphate in molten salts

Electrochemical behaviour of sulphate under anodic polarization in molten sodium chloride, cryolite and sodium fluoride was investigated by cyclic voltammetry and chronopotentiometry at the temperatures of 820°C, 1010°C, and 1000°C, respectively. Using a platinum working electrode, two waves were observed on the chronopotentiograms in the systems: NaCl-Na₂SO₄ and Na₃AlF₆-Na₂SO₄. The first wave was attributed to the formation of oxygen. The second wave probably originated from the reaction of oxygen with platinum, or from oxidation of SO₃ decomposition products. Three waves were observed for the anodic process of sulphate ions dissolved in molten sodium fluoride. The first wave was attributed to the formation of oxygen. The second and the third wave were attributed to the formation of PtO and PtO₂. This conclusion was supported by cyclic voltammetry experiments of the in-situ formed sulphide in molten NaCl at 820°C and by chronopotentiometry on a gold working electrode in the system NaCl-Na₂SO₄, where no anodic wave was observed.     

Optimization of parameters of sampling and determination of reduced sulfur compounds using cryogenic capture and gas chromatography in tropical urban atmosphere

Reduced sulfur compounds, RSCs (H₂S, COS, CH₃SH, CH₃SCH₃, CS₂ and CH₃S₂CH₃) play a role in global cycle and acid rain formation. At trace levels RSCs in air are difficult to collect, store and analyze because of their highly adsorptive and reactive properties. This work optimizes parameters of sampling and instrumental determination of RSCs for urban measurements. The method used is based on cryogenic sampling and gas chromatography provided with a cryofocusing trap and flame photometric detection.Greater sampling efficiency was obtained with liquid argon as freezing fluid and air flow rate of 150 mL min^? 1 for two hours. Best results have been obtained with preconcentration for 3 min and injection volume of 3 ml. For H₂S, CH₃SH and CH₃S₂CH₃ the method showed a precision of 89%, limit of detection of 0.10 µg m^? 3 and limit of quantification 0.3 µg m^? 3. For CH₃SCH₃ and CS₂ the corresponding values were 89%, 0.15 µg m^? 3 and 0.5 µg m^? 3 and for COS were 75%, 0.18 µg m^? 3 and 0.8 µg m^? 3 respectively. Sampling efficiency varied between 70–80% for all the RSCs. Accuracy of H₂S from field measurements obtained with parallel measurements using a continuous monitor varied between 88 and 98%. The optimized methodology proved to be suitable for field measurements in urban tropical atmospheres with different characteristics.     

Adsorption of SO2 on alumina

The adsorption of SO₂ on alumina used in the aluminium industry, the so-called smelter-grade alumina, was studied in the temperature range 15–120°C. It was found that at temperatures lower than 40°C, sulphur dioxide was bonded to alumina reversibly by physical forces, and the adsorption could be described satisfactorily by the Langmuir adsorption isotherm. The heat of adsorption was estimated to be −33 kJ mol⁻¹. At temperatures ranging from 80°C to 120°C, which prevail in dry scrubbers in the aluminium industry, the heat of adsorption was determined to be −56 kJ mol⁻¹. When SO₂ was adsorbed at temperatures higher than 80°C, about 30 % of the SO₂ could not be desorbed even if the samples were heated up to 250°C. In the presence of SO₂ and oxygen, the formation of sulphate was observed at temperatures above 90°C.     

Computer modelling of mixed metal fluorides for optical applications

This paper describes a new computational method for predicting the optical behaviour of doped inorganic materials. There is considerable interest in using inorganic materials in photonic devices, and in many cases, the optical properties of these materials depend on doping by ions such as those from the rare earth series. Among the inorganic materials of interest are the mixed metal fluorides (e.g. BaLiF(3), BaY(2)F(8), YLiF(4), LiCaAlF(6), LiSrAlF(6)), doped with trivalent rare earth ions. The paper describes the use of Mott-Littleton calculations to determine the optimum location for dopant ions, followed by crystal field calculations which make direct use of the output of the Mott-Littleton calculations to calculate the optical properties of the dopant ion taking into account its symmetry and the positions of the surrounding ions, including any vacancies or interstitial ions present by virtue of charge compensation. It is then possible to predict whether a given dopant ion at a particular site in a material will have favourable optical properties.     

Reactions of sulphides in molten cryolite

The freezing point depression of cryolite (Na₃AlF₆) by the addition of Al₂S₃ and FeS was investigated. It was found that for contents of up to 10 wt.% Al₂S₃, it brings into the melt three new species. X-ray analysis of solidified melts of the system Na₃AlF₆–Al₂S₃ showed that it contained chiolite, Na₅Al₃F₁₄ and Na₂S. Chiolite originates from a reaction between Na₃AlF₆ and AlF₃. This suggests that the system Na₃AlF₆–Al₂S₃ is a part of the reciprocal system NaF, AlF₃//Na₂S, Al₂S₃. The solubility of FeS in cryolite melt is so low that it cannot be determined by the thermal analysis. When FeO is added to the Na₃AlF₆–Al₂S₃ melt, Fe²⁺ cations and S²⁻ anions react under the formation of solid FeS. A similar reaction was observed for Ni²⁺ and S²⁻ ions.     

Transport numbers in the molten system NaF–KF–AlF3–Al2O3

Transport numbers in the molten system NaF–KF–AlF₃ (Al₂O₃, CaF₂) were investigated by the Hittorf method. It was confirmed that in molten cryolite, Na₃AlF₆, 1,010 °C, the current is transported almost exclusively by the Na⁺ cations (t(Na⁺)?=?0.99). When AlF₃ was added to a Na₃AlF₆ melt, the transport number of sodium cations decreased to 0.74 at the composition corresponding to NaAlF₄. In molten K₃AlF₆, the transport number of K⁺ cations equals 0.836 at 1,005 °C. In melts containing both Na⁺ and K⁺, the cations contribute to the charge transport approximately in the ratio of the squares of their ionic radii. When 5 mass % of CaF₂ was added to the molten NaF–KF–AlF₃ system, it remarkably influenced the transport numbers of potassium and fluoride anions.     

Determination of sulphur species in solidified cryolite melts

Solidified cryolite melts containing a known amount of Na₂SO₄ (0?C713 mg kg^?1 SO ₄ ^2? ), Na₂S, FeS, and CdS (0?C400 mg kg^?1 S^2?) together with industrial electrolyte samples were tested for the content of sulphate and sulphide ions by ion chromatography. Added and analytically determined contents of sulphate and sulphide were compared and processed by means of linear regression analysis. It was found that the method of ion chromatography yields satisfying results (uncertainty below 1.1 %) and that it is especially suitable for the determination of low content of soluble sulphate or sulphide in solidified cryolite electrolytes. The method can be used for the estimation of insoluble sulphide content in cryolite melts as well. Results of industrial samples analysis showed that the content of sulphate and sulphide in the samples is influenced by their treatment before the analysis.