Chirality of products in acid-catalysed rearrangement of α-pinene

Protonation of (1R)-(+)-a-pinene using gaseous H₃ ⁺ ions led to a racemic mixture of camphene and limonene, to partial and no racemization, in acidic solutions and in solid acids, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Radiation-Induced Polymerization of Vinylidene Chloride in Bulk and Included in Thiourea Crystals

Vinylidene chloride (VDC) or 1,1-dichloroethylene was polymerized with γ radiation in bulk or as inclusion complex in thiourea crystals (inclusion polymerization). The resulting poly(vinylidenechloride) (PVDC) samples obtained from the two different polymerization techniques were characterized by FT-IR and electronic absorption spectroscopies, by ozonolysis and by thermal analysis (TGA, DTG and DTA). It was found that two selective secondary reactions occur in the two PVDC samples, respectively obtained from bulk polymerization or from inclusion polymerization. In the former case, the main reaction is only a crosslinking reaction, while in the latter case, with the PVDC included into the thiourea channels, the crosslinking reaction is fully inhibited and instead a dehydrohalogenation reaction takes place producing the polyene structures. The presence of polyene structures in the PVDC synthesized by the inclusion polymerization was demonstrated by electronic absorption spectroscopy and by ozonolysis experiments. The presence of polyene segments in the PVDC causes a reduction in the thermal stability of the polymer, lowers its melting point and reduces its crystallinity.     

Pinus sylvestris L. and Syzygium aromaticum (L.) Merr. & L. M. Perry Essential Oils Inhibit Endotoxin-Induced Airway Hyperreactivity despite Aggravated Inflammatory Mechanisms in Mice

Scots pine (SO) and clove (CO) essential oils (EOs) are commonly used by inhalation, and their main components are shown to reduce inflammatory mediator production. The aim of our research was to investigate the chemical composition of commercially available SO and CO by gas chromatography–mass spectrometry and study their effects on airway functions and inflammation in an acute pneumonitis mouse model. Inflammation was evoked by intratracheal endotoxin and EOs were inhaled three times during the 24 h experimental period. Respiratory function was analyzed by unrestrained whole-body plethysmography, lung inflammation by semiquantitative histopathological scoring, myeloperoxidase (MPO) activity and cytokine measurements. α-Pinene (39.4%) was the main component in SO, and eugenol (88.6%) in CO. Both SO and CO significantly reduced airway hyperresponsiveness, and prevented peak expiratory flow, tidal volume increases and perivascular edema formation. Meanwhile, inflammatory cell infiltration was not remarkably affected. In contrast, MPO activity and several inflammatory cytokines (IL-1β, KC, MCP-1, MIP-2, TNF-α) were aggravated by both EOs. This is the first evidence that SO and CO inhalation improve airway function, but enhance certain inflammatory parameters. These results suggest that these EOs should be used with caution in cases of inflammation-associated respiratory diseases.     

Electrospray ionization for determination of non‐polar polyaromatic hydrocarbons and polyaromatic heterocycles in heavy crude oil asphaltenes

Electrospray ionization (ESI) is the most common ionization method in atmospheric pressure ionization mass spectrometry because of its easy use and handling and because a diverse range of components can be effectively ionized from high to medium polarity. Usually, ESI is not employed for the analysis of non‐polar hydrocarbons, but under some circumstances, they are effectively ionized. Polyaromatic hydrocarbons and aromatic heterocycles can form radical ions and protonated molecules after ESI, which were detected by Fourier transform ion cyclotron resonance mass spectrometry. The highly condensed aromatic structures are obtained from a heavy crude oil, and the results show class distribution from pure hydrocarbons up to more non‐basic nitrogen‐containing species. By using different solvent compositions [toluene/methanol (50/50 v/v), dichloromethane/methanol (50/50 v/v), dichloromethane/acetonitrile (50/50 v/v) and chloroform], the results show that the lack of proton donor agent helps to preserve the radical formation that was created at the metal/solution interface inside the electrospray capillary. The results demonstrate that with an appropriate selection of solvent and capillary voltage, the ratio between the detected radical ion and protonated molecule form can be manipulated. Therefore, ESI can be expanded for the investigation of asphaltene and other polyaromatic systems beyond the polar constituents as non‐polar hydrocarbons can be efficiently analyzed. Copyright © 2015 John Wiley & Sons, Ltd.     

On the action of ozone at high concentration on various grades of polyethylene and certain straight chain paraffins

The surface functionalisation of UHMWPE (ultra high molecular weight polyethylene) was successfully achieved by the action of ozone (10% by weight in oxygen) under mild conditions. The kinetics of the gas-solid reaction between O₃ and UHMWPE in powder form were measured in an IR gas cell and the pseudo-first-order rate constant was k′_UHMWPE = 1.9 × 10⁻⁴ s⁻¹. The resulting surface-oxidized UHMWPE was studied by FT-IR spectroscopy and the nature of the surface functionalities was determined. Furthermore, the surface-oxidized UHMWPE was studied by DSC (differential scanning calorimetry). It was evident that ozone attacks and oxidizes the amorphous phase of UHMWPE preserving the crystalline phase because after the ozone treatment there was an increase in the % of crystallinity. Two other polyethylene grades having respectively M_w = 15,000 Da (defined as LMWPE = low molecular weight polyethylene) and M_w = 4000 Da (defined as VLMWPE = very low molecular weight polyethylene) were studied as model compounds in comparison to UHMWPE in their reaction with ozone. Commercial liquid paraffin and n-dodecane were used as model compounds to study the reaction between high ozone concentration and alkanes.     

Evaluation of Total Phenolic and Flavonoid Contents,Antibacterial and Antibiofilm Activities of Hungarian Propolis Ethanolic Extract against Staphylococcus aureus

Propolis is a natural bee product that is widely used in folk medicine. This study aimed to evaluate the antimicrobial and antibiofilm activities of ethanolic extract of propolis (EEP) on methicillin-resistant and sensitive Staphylococcus aureus (MRSA and MSSA). Propolis samples were collected from six regions in Hungary. The minimum inhibitory concentrations (MIC) values and the interaction of EEP-antibiotics were evaluated by the broth microdilution and the chequerboard broth microdilution methods, respectively. The effect of EEP on biofilm formation and eradication was estimated by crystal violet assay. Resazurin/propidium iodide dyes were applied for simultaneous quantification of cellular metabolic activities and dead cells in mature biofilms. The EEP1 sample showed the highest phenolic and flavonoid contents. The EEP1 successfully prevented the growth of planktonic cells of S. aureus (MIC value = 50 µg/mL). Synergistic interactions were shown after the co-exposition to EEP1 and vancomycin at 10⁸ CFU/mL. The EEP1 effectively inhibited the biofilm formation and caused significant degradation of mature biofilms (50–200 µg/mL), as a consequence of the considerable decrement of metabolic activity. The EEP acts effectively as an antimicrobial and antibiofilm agent on S. aureus. Moreover, the simultaneous application of EEP and vancomycin could enhance their effect against MRSA infection.     

Identification of bifucosylated glycoforms using low‐energy CID spectra

We have used tandem mass spectrometry (MS/MS)‐based analysis of glycopeptides in order to identify the composition and structure of rare glycoforms. The results illustrate utility of low‐energy MS/MS for structure identification. We have shown the presence of bifucosylated and trifucosylated glycoforms in human α‐1‐acid glycoprotein (AGP), a major plasma glycoprotein. Fucosylation in the case of AGP always occurs on the antennae; core fucosylation was not observed.     

Radiation-induced gas-phase dealkylation and isomerization of p-tert-butyltoluene

D₃ ⁺ ions, produced by deuterium -radiolysis, were allowed to react with gaseous p-tert-butyltoluene. The excited arenium ions formed, if not collisionally stabilized, underwent predominantly dealkylation to form toluene and, to a minor extent, isomerization. The dependence of reaction product yields on the substrate pressure is discussed.     

Characterization of complex,heterogeneous lipid A samples using HPLC–MS/MS technique I. Overall analysis with respect to acylation,phosphorylation and isobaric distribution

We established a new reversed phase‐high performance liquid chromatography method combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry for the simultaneous determination and structural characterization of different lipid A types in bacteria (Escherichia coli O111, Salmonella adelaide O35 and Proteus morganii O34) showing serological cross‐reactivity. The complex lipid A mixtures (obtained by simple extraction and acid hydrolysis of the outer membrane lipopolysaccharides) were separated and detected without phosphate derivatization. Several previously unidentified ions were detected, which differed in the number and type of acyl chains and number of phosphate groups. In several cases, we observed the different retention of isobaric lipid A species, which had different secondary fatty acyl distribution at the C2′ or the C3′ sites. The fragmentation of the various, C4′ monophosphorylated lipid A species in deprotonated forms provided structural assignment for each component. Fragmentation pathways of the tri‐acylated, tetra‐acylated, penta‐acylated, hexa‐acylated and hepta‐acylated lipid A components and of the lipid A partial structures are suggested. As standards, the hexa‐acylated ion at m/z 1716 with the E. coli‐type acyl distribution and the hepta‐acylated ion at m/z 1954 with the Salmonella‐type acyl distribution were used. The results confirmed the presence of multiple forms of lipid A in all strains analyzed. In addition, the negative‐ion mode MS permitted efficient detection for non‐phosphorylated lipid A components, too. Copyright © 2016 John Wiley & Sons, Ltd.     

Near-optimal MIP solutions for preference based self-scheduling

Making a high quality staff schedule is both difficult and time consuming for any company that has employees working on irregular schedules. We formulate a mixed integer program (MIP) to find a feasible schedule that satisfies all hard constraints while minimizing the soft constraint violations as well as satisfying as many of the employees’ requests as possible. We present the MIP model and show the result from four real world companies and institutions. We also compare the results with those of a local search based algorithm that is designed to emulate the solution strategies when the schedules are created manually. The results show that using near-optimal solutions from the MIP model, with a relative MIP gap of around 0.01–0.1, instead of finding the optimal solution, allows us to find very good solutions in a reasonable amount of time that compare favorably with both the manual solutions and the solutions found by the local search based algorithm.