Characteristic Mass Spectra Research Articles

Comparative Assessment of Cooking Emission Contributions to Urban Organic Aerosol Using Online Molecular Tracers and Aerosol Mass Spectrometry Measurements

Cooking organic aerosol (COA) is an important source of particulate pollutants in urbanized regions. Yet, the diversity and complexity of COA components make direct identification and quantification of COA difficult. In this study, we conducted collocated OA measurements with an aerosol mass spectrometer (AMS) and a thermal desorption aerosol gas chromatography-mass spectrometer (TAG) in Shanghai. Cooking molecular tracers (e.g., C18 fatty acids, azelaic acid) measured by TAG provide unambiguous source information for evaluating the tracer ion (C6H10O+, m/z 98) used for identification and apportionment of COA in AMS analysis. Based on the collocated AMS and TAG measurements, two COA factors, namely, a primary COA (PCOA) and an oxygenated COA (OCOA) produced from rapid oxygenation of freshly emitted PCOA, were identified. Criteria for identifying COA factors from AMS analysis with different oxygenation levels are proposed, i.e., characteristic mass spectra, temporal variations, etc. Furthermore, two positive matrix factorization approaches, namely, AMS-PMF and the molecular marker (MM)-PMF, were compared for COA quantification, where high consistency was found with the contribution of COA to total PM2.5 mass estimated to be 9 ± 7% by AMS-PMF and 6 ± 5% by the MM-PMF. Our study highlights the important impacts of cooking activities on air quality in urban areas. We also demonstrate the advantage of conducting collocated measurements using multiple high time resolution mass spectrometric techniques in advancing our understanding of atmospheric OA chemistry and improving the accuracy of source apportionment.

Rapid Characterization of Polymer Materials Using Arc Plasma-Based Dissociation-Mass Spectrometry

Fingerprinting spectra of polymer materials containing information of monomers' molecular weight and detailed structure, constituents, and sequences were obtained by a direct analytical process using arc plasma-based dissociation (APD)-mass spectrometry. The thermal arc plasma generated using a simple arc discharge device induces the dissociation of the polymeric backbone, producing mass spectra with strong regularity within seconds. The molecular weight of the repeating unit was revealed by equal intervals between peak series and protonated monomer ions in the mass spectra. Meanwhile, lots of secondary fragment ions were produced to provide abundant structural information. For polyethers, it is even possible to decipher (read) the "sequence" directly from their spectra. Polymers composed of isomers or only differing in their initiator moieties were easily distinguished with their characteristic APD mass spectra. The spectra were highly reproducible according to the results of similarity calculation. Unlike pyrolysis mass spectrometry, in the APD device, polymers in liquid, solid, powder, and crude samples can be analyzed directly without any pretreatment, and the regular spectra are easier to interpret. Compared with other direct analytical methods, more structural informative spectra can be acquired owing to the high energy, high temperature, and unique chemical reactivity of arc plasma. Thus, this technique is promising to be a valuable tool in rapid elucidation of polymer materials.

Simple and robust differentiation of Ganoderma species by high performance thin-layer chromatography coupled with single quadrupole mass spectrometry QDa.

In this study, a high performance thin-layer chromatography/single quadrupole mass spectrometry QDa (HPTLC-QDa) method for robust authentication of Ganoderma lucidum, a popular and valuable herbal medicine, has been developed. This method is simple and practical, which allows direct generation of characteristic mass spectra from the HPTLC plates automatically with the application of in situ solvent desorption interface. The HPTLC silica gel plates were developed with toluene-ethyl formate-formic acid (5 : 5 : 0.2, V/V) and all bands were transferred to QDa system directly in situ using 80% methanol with 0.1% formic acid as desorption solvent. The acquired HPTLC-QDa spectra showed that luminous yellow band b3, containing ganoderic acid B/G/H and ganodeneric acid B, the major active components of Ganoderma, could be found only in G. lucidum and G. lucidum (Antler-shaped), but not in G. sinense and G. applanatum. Moreover, bands b13 and b14 with m/z 475/477 and m/z 475/491/495, respectively, could be detected in G. lucidum (Antler-shaped), but not in G. lucidum, thus allowing simple and robust authentication of G. lucidum with confused species. This method is proved to be simple, practical and reproducible, which can be extended to analyze other herbal medicines.

Investigation of the influence of double modification of starch as of natural polymer, on rheological characteristics of compositions and their film-producting properties

Starch is a natural polymer that has unique properties, which consist of the annual renewal of raw materials and the ability to create biodegradable materials based on starch. Modification of starch leads to changes in its chemical structure, which is associated with both the method of modification and the introduction of active chemicals into its structure. Double modification occurs due to the simultaneous use of physical or mechanical method with the addition of the necessary chemicals. Physical methods of starch modification include microwave and ultrasonic irradiation. The aim of the work was to study the physicochemical properties of corn starch after double modification and its use in the creation of film-forming samples. The urgency of this work is due to the need that in order to protect the environment the basis of technological compositions used in industry should be natural polymers, this will minimize the negative impact on the environment and develop environmentally friendly compositions and functional systems for various purposes. The structure of two types of corn starch was studied by pyrolytic mass spectrometry and their characteristic mass spectra were determined. The influence of physical modification by ultrasonic and microwave irradiation of corn starch using plasticizing additives based on modified soybean and rapeseed oils on the rheological properties of the compositions, solubility and swelling was studied. It was found that the modification of starch using ultrasonic irradiation leads to a significant decrease in dynamic viscosity, while after microwave irradiation the viscosity increases. Double-modified corn starch was investigated for the formation of film-forming materials with the addition of NaКMC and polyvinyl alcohol. The strength characteristics of the films of the compositions are determined.

Screening of lipid metabolism biomarkers in patients with coronary heart disease via ultra-performance liquid chromatography–high resolution mass spectrometry

Coronary heart disease (CHD) has a high mortality worldwide. This study aimed to screen lipid metabolism biomarkers in patients with coronary heart disease via ultra-performance liquid chromatography–high resolution mass spectrometry. Extraction and reconstitution solvents, liquid chromatographic and mass spectrometry conditions were optimized to detect more plasma lipid metabolites. In this study, the chromatographic and mass spectra characteristics of lipid metabolites were summarized. A total of 316 lipid metabolites were annotated via diagnostic fragment ion filtration, nitrogen rule filtration, and neutral loss filtration. Glycerophospholipid metabolism and sphingolipid metabolism were revealed as the main lipid disorders of CHD. This study provides a novel insight for high-throughput detection of lipid metabolites in plasma and provides a further understanding of the occurrence of CHD, which can provide valuable suggestions for the prevention of CHD.

Biosaur: An open-source Python software for liquid chromatography-mass spectrometry peptide feature detection with ion mobility support.

One of the important steps in initial data processing of peptide mass spectra is the detection of peptide features in full-range mass spectra. Ion mobility offers advantages over previous methods performing this detection by providing an additional structure-specific separation dimension. However, there is a lack of open-source software that utilizes these advantages and detects peptide features in mass spectra acquired along with ion mobility data using new instruments such as timsTOF and/or FAIMS-Orbitrap. Recently, a utility called Dinosaur was presented, which provides an efficient way for feature detection in peptide ion mass spectra. In this work we extended its functionality by developing Biosaur software to fully employ the additional information provided by ion mobility data. Biosaur was developed using the Python 3.8 programming language. Biosaur supports the processing of data acquired using mass spectrometers with ion mobility capabilities, specifically timsTOF and FAIMS. In addition, it processes mass spectra obtained in negative ion mode and reports cosine correlation table for peptide features which is useful for differentiation between in-source fragments and semi-tryptic peptides. Biosaur is a utility for detecting peptide features in liquid chromatography-mass spectra with ion mobility and negative ion supports. The software is distributed with an open-source APACHE 2.0 license and is freely available on Github: https://github.com/abdrakhimov1/Biosaur.

Analyzing aristolochic acids in Chinese herbal preparations using LC/MS/MS

This paper introduces a newly developed method of applying liquid chromatography- tandem mass spectrometry (LC/MS/MS) to the analysis of aristolochic acids (AAs) in Chinese herbal (medicinal) preparations. Sensitive and highly accurate readings were obtained for this study using both a photodiode array (PDA) detector and tandem mass spectrometer. The following optimized conditions for LC/MS/MS were set for this study: Separation was accomplished using a reverse phase C18 column (2.1 × 150 mm, 5 μm). The mobile phase comprised 35% acetonitrile and a 65% aqueous solution containing 0.1% formic acid and 0.1% ammonium acetate at a flow rate of 0.3 mL/min with a split ratio of 1:1 into the PDA detector and the tandem mass spectrometer. MS/MS qualitative analysis was performed at 3.0 kV capillary voltage, with a collision energy level for aristolochic acid I (AA-1) of 10 eV and for aristolochic acid II (AA-II) of 12eV. The electrospray ionization source was operated in the positive mode. AA-I [M + NH4]+ ions at m/z 359 and AA-II [M + NH4]+ ions at m/z 329 were selected as precursor ions for daughter ion scanning. The characteristic daughter ion mass spectra for AA-I and AA-II were generated and studied carefully. Quantification of results was done using the multiple reaction monitoring (MRM) method. The [M + NH4]+ and [(M + NH4)- NH3-CO2]+ ions of both AA-I and AA-II were selected as precursor and daughter ions for the MRM analysis. MS/MS detection limits were defined as 2.0 ng/mL of AA-I, and 2.8 ng/mL of AA-II. The linear regression correlation coefficients of the calibration cure were 0.9992 of AA-I within the range of 0.02-16.00 μg/mL and 0.9988 of AA-II within the range of 0.028-22.40 μg/mL. Relative standard deviations of 0.73% and 10.44% for AA-I, and 1.38% and 6.10% for AA-II were determined for the intraday and interday tests. Recoveries for five differing concentrations of AA-I ranged from 99.0% to 106.9% and, for five differing concentrations of AA-II, ranged from 92.0% to 104.5%. Levels of AA-I and AA-II detected in the 12 commercial Chinese medicinal preparation samples ranged from 11.1 to 3376.0 μg/g and from 5.4 to 725.4 μg/g, respectively.

A "Brick" Mass Spectrometer with Photoionization for Direct Analysis of Trace Volatile Compounds.

With high portability and favorable performance, miniature mass spectrometers have become one of the most attractive tools for on-site analysis of trace volatile compounds. Based on the "Brick" mass spectrometer (BMS) developed previously, a hand-held BMS integrated with a photoionization source (PI-BMS) was developed in this study for volatile compound analysis. With compact dimensions of 30 cm × 18.5 cm × 27.6 cm (length × width × height), the PI-BMS was equipped with a 10.6 eV UV lamp and capable of generating molecular ions. The capabilities of qualitative and quantitative analyses for different volatile samples were demonstrated and characterized. Under optimized conditions, high detection sensitivity in open air was obtained for the PI-BMS with a limit of detection (LOD) of ∼10 ppbv. As demonstrations of mixture analysis, four different fresh fruits were directly analyzed using PI-BMS, observing characteristic mass spectra for each type of fruit.

Thermal desorption and pyrolysis direct analysis in real time mass spectrometry for qualitative characterization of polymers and polymer additives.

Direct analysis in real time mass spectrometry (DART-MS) provides qualitative information about additives and polymer composition. However, the observed mass spectra are dependent on sampling conditions, in particular the DART gas temperature. This report describes the combination of a heated sample stage with DART-MS for polymer characterization. Industrial polymers with different compositions were examined by thermal desorption and pyrolysis (TDPy) DART. Samples were heated on disposable copper stages from ambient temperature to 600°C, and the evolved gases were introduced directly into a DART ion source through a glass tee. Time- and temperature-dependent mass spectra were acquired using a high-resolution time-of-flight mass spectrometer. Kendrick mass analysis was applied to the interpretation of complex mass spectra observed for fluorinated polymers. Positive-ion DART mass spectra of common polymers exhibited peak series differing by monomer masses, often accompanied by a peak corresponding to the protonated monomer. Even polymers that did not exhibit a clear series of peaks produced characteristic mass spectra. Positive-ion and negative-ion mass spectra were recorded for fluorinated polymers, with polytetrafluoroethylene (PTFE) producing only negative ions. Thermal desorption provided characteristic temperature profiles for volatile species such as polymer additives and polymer pyrolysis products. In comparison with direct analysis by positioning sample directly in the heated DART gas stream, TDPy DART provides a more versatile sampling method and provides thermal separation and profiling of polymer additives, intact short polymer chains, and pyrolysis fragments.

Forensic Fiber Analysis by Thermal Desorption/Pyrolysis-Direct Analysis in Real Time-Mass Spectrometry.

The thermal desorption/pyrolysis-direct analysis in real time-mass spectrometry (TD/Py-DART-MS) method was developed for the analysis of fibers in this study. The fiber samples were pyrolyzed with a temperature gradient and the pyrolysis products were determined by DART-MS. The pyrogram from the TD/Py-DART-MS fiber analysis was found to be associated with the physical properties such as the melting points. At the same time, the TD/Py-DART-MS allows the analyst to obtain the chemical information such as polymeric backbone structures and dyes on the fiber. The pyrolysis profiles of common polymeric fibers in textile materials such as cotton, cellulose triacetate (CT), poly(caprolactam) (nylon-6), poly(hexamethylene adipamide) (nylon-6/6), poly(acrylonitrile) (PAN), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(propylene) (PP), and polytrimethylene terephthalate (PTT) and their respective characteristic mass spectra were reported in this study. The fibers from 40 commercial textile samples were analyzed by the TD/Py-DART-MS method, and the statistical methods including principal component analysis (PCA) and Pearson product moment correlation (PPMC) were applied to classify and associate the fibers based on their mass spectral data. The strong correlation between the reference fiber mass spectral profiles and tested fiber mass spectral profiles was observed by using the PPMC method, and the identification accuracy was 97.5%. When combined, the mass spectral and pyrogram data, the types of fibers including the blended fibers were identified effectively. The TD/Py-DART-MS method also demonstrated the promising capability for the identification of dyes on fibers. Overall, the TD/Py-DART-MS method requires small sample size and minimal sample preparation but offers reproducible and multidimensional information for the fiber evidence rapidly (i.e., ∼6.7 min). Since the proposed method is simple to perform and the data are easy to interpret, this approach may significantly contribute to the fiber identification and comparison procedures in forensic settings with high sample throughput potential.

Polyvinylpyrrolidone composite nanofibers as efficient substrates for surface-assisted laser desorption/ionization mass spectrometry

A matrix-free laser desorption/ionization mass spectrometry (LDI-MS) approach was developed using electrospun composite nanofibers with controllable size, morphology and composition. Composite polyvinylpyrrolidone (PVP) nanofibers with added nanoparticles to enhance the absorption of laser energy absorber were studied. Fractal dimensional analysis was conducted to evaluate the electrospinning process for the first time, which provided useful information on the repeatability of nanofiber production. The performance of the nanofiber-assisted laser desorption/ionization method was investigated through characterization of small drug molecules and synthetic oligomers. Homogeneous sample distribution was achieved by eliminating the “sweet spot”, resulting in good reproducibility. Mass spectra features clean background, that is especially beneficial for interpretation of small molecules. High sensitivity for small drug molecules and synthetic oligomers was obtained with limits of detection limits down to the low attomolar range. The combination of composite nanofibers with LDI-MS is a versatile and sensitive approach for detection and characterization of analytes with broad range of molecular weight.

Extracts from Cell Suspension Cultures of Strawberry (Fragaria x ananassa Duch): Cytotoxic Effects on Human Cancer Cells.

Natural compounds are emerging as agents for the treatment of malignant diseases. We previously showed that extracts from in vitro cell suspension cultures of strawberry reduced murine melanoma cell proliferation, as shown for fruit extracts. In this work, chromatographic, mass spectrometric, and spectrophotometric analyses were carried out to identify the bioactive compound exerting the detected cytotoxic activity. Moreover, aiming to confirm the anti-proliferative activity of the extracts against both paediatric and adult human tumors, cytotoxic experiments were performed on neuroblastoma, colon, and cervix carcinoma cell lines. Extracts from in vitro cell suspension cultures of strawberry induced a statistically significant reduction of cell growth in all the tumor cell lines tested. Interestingly, human fibroblasts from healthy donors were not subjected to this cytotoxic effect, highlighting the importance of further preclinical investigations. The accurate mass measurement, fragmentation patterns, and characteristic mass spectra and mass losses, together with the differences in chromatographic retention times and absorbance spectra, led us to hypothesize that the compound acting as an anti-proliferative agent could be a novel acetal dihydrofurofuran derivative (C8H10O3, molecular mass 154.0630 amu)

Suitable in-situ derivatization of alcohols by reaction with basic amines in Direct Analysis in Real Time mass spectrometry

This work highlights the discovered in-situ analytical reaction between primary/secondary alcohols and nitrogenous bases (pyridine, quinoline) that involves the substitution of hydroxyl groups for nitrogen-containing charged species and proceeds in an ionization region of Direct Analysis in Real Time mass spectrometry (DART-MS) instrument at gas stream temperature of 150–450 °C. Resulted cations provide strong signals in mass spectra and this ensures high sensitivity of the analysis. Collision induced dissociation of such precursor ions gives rise to characteristic and simple fragmentation mass spectra revealing mainly protonated nitrogenous bases and carbonium cations resulting from the elimination of neutral nitrogen-containing bases. The dependence of signal response on gas stream temperature was elucidated. It was also found that, independently of gas stream temperature, high volatility low-molecular weight alcohols did not demonstrate characteristic DART spectra owing to a high rate of desorption/evaporation which does not provide sufficient probability of the reaction. To the best of our knowledge, this type of specific reactions in a plasma-based source of DART mass spectrometer is reported for the first time. It represents a new and interesting derivatization approach providing a rapid and sensitive complement method for the detection and identification of individual monools of various origin, profiling plant sterols and other steroid alcohols in different matrices.

Multivariate Analysis of MALDI Imaging Mass Spectrometry Data of Mixtures of Single Pollen Grains.

Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from > 10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted. Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry. Graphical Abstract ᅟ.

Novel Neuroprotective Lead Compound Ligustrazine Derivative Mass Spectrometry Fragmentation Rule and Metabolites in Rats by LC/LTQ-Orbitrap MS.

The neuroprotective evaluation of ligustrazine derivatives has become a research focus all over the world. A novel ligustrazine derivative, (3,5,6-Trimethylpyrazin-2-yl)methyl(E)-3-(4-((3,5,6-trimethylpyrazin-2-l)methoxy)phenyl)acrylate (T-CA), has shown protective effects against CoCl2-induced neurotoxicity in a differentiated PC12 cell model and middle cerebral artery occlusion (MCAO) model in our previous studies. However, nearly none of the parent drugs existed after rapid metabolism due to uncertain reasons. Thus, the fragmentation regularities of mass spectra, and metabolites, of T-CA in rats were examined using liquid chromatography-electrospray ionizationion trap mass spectrometry (LC/LTQ-Orbitrap MS) in this research. The main fragment ion, mass spectrum characteristics, and the structural information were elucidated. When compared with a blank sample, we identified five kinds of T-CA metabolites, including three phase I metabolites and two phase II metabolites. The results showed that the metabolic pathways of T-CA in rats via oral administration were hydrolysis (ether bond rupture, ester bond rupture), oxidation, reduction, glucose aldehyde acidification, etc. In addition, three main metabolites were synthesized and their structures were identified by superconducting high-resolution NMR and high-resolution mass spectroscopy (HR-MS). The neuroprotective activity of these metabolites was validated in a PC12 cell model. One of the metabolites (M2) showed significant activity (EC50 = 9.67 μM), which was comparable to the prototype drug T-CA (EC50 = 7.97 μM). The current study provides important information for ligustrazine derivatives, pertaining to the biological conversion process in vivo.

Rapid and robust analytical protocol for E. coli STEC bacteria subspecies differentiation using whole cell MALDI mass spectrometry

Whole cell MALDI is regularly used for the identification of bacteria to species level in clinical Microbiology laboratories. However, there remains a need to rapidly characterize and differentiate isolates below the species level to support outbreak management. We describe the implementation of a modified preparative approach for MALDI-MS combined with a custom analytical computational pipeline as a rapid procedure for subtyping Shigatoxigenic E. coli (STEC) and accurately identifying strain-specifying biomarkers. The technique was able to differentiate E. coli O157:H7 from other STEC. Within O157 serotype O157:H7 isolates were readily distinguishable from Sorbitol Fermenting O157 isolates. Overall, nine homogeneous groups of isolates were distinguished, each exhibiting distinct profiles of defining mass spectra features. This offers a robust analytical tool useable in reference/diagnostic public health scenarios.

Application and limitation of molecular data and essential oil content in identification of Leutea elbursensis Mozaff in northern Iran

Abstract In this paper, the internal transcribed spacer (ITS) sequences, genetic structure and the chemical composition of essential oils of four populations belonging to Leutea elbursensis and Leutea petiolaris, two species endemic to northern Iran, are analyzed. Phylogenetic analysis based on the ITS data showed that all accessions of L. elbursensis formed a monophyletic clade, and L. elbursensis was a sister to the rest of Leutea species. Results of amplified fragment length polymorphism (AFLP) analysis performed on the total genome showed that all individuals presented in the study belonged to two different genetic clusters. The individuals belong to L. petiolaris had a different genetic structure and yielded no traceable amount of essential oils. The essential oil obtained from the ripe fruits of L. elbursensis yielded 0.5–0.6% of volatile essential oils. In total, 15-29 volatile natural components were identified on the basis of their mass spectra characteristics and retention indices, in which α-pinene (33.18-43.22%), β-pinene (32.4-40.9%) were the major constituents. Our results indicate that L. elbursensis is a distinct species, segregated from the other species based on morphology, ITS data and AFLP profile. In addition, despite the relatively uniform genetic structure of L. elbursensis, the chemical composition of essential oil could be highly affected by different factors.

Rapid differentiation of Ganoderma species by direct ionization mass spectrometry

In this study, direct ionization mass spectrometry (DI-MS) has been developed for rapid differentiation of Ganoderma (known as Lingzhi in Chinese), a very popular and valuable herbal medicine. Characteristic mass spectra can be generated by DI-MS directly from the raw herbal medicines with the application of a high voltage and solvents. Rapid differentiation of the Ganoderma species that are officially stated in the Chinese pharmacopoeia from easily confused Ganoderma species could be achieved based on this method, as the acquired DI-MS spectra showed that ganoderic acids, the major active components of Ganoderma, could be found only in the official Ganoderma species but not in the confused Ganoderma species. In addition, classification of wild and cultivated Ganoderma and potential differentiation of Ganoderma from different geographical locations could be accomplished based on principal component analysis (PCA) or hierarchical clustering analysis (HCA). The method is rapid, simple and reproducible, and can be further extended to analysis of other herbal medicines.

Semiochemicals released from five bacteria identified from animal wounds infested by primary screwworms and their effects on fly behavioral activity.

BackgroundThe Primary screwworm, Cochliomyia hominivorax (Coquerel), is a serious pest feeding on living flesh of any warm-blooded animal, including humans. It was eradicated from the United States in the early 1980s using the sterile male technique. However, it was recently detected in populations of wild deer and pets in the Florida Keys of the US. For monitoring purposes, screwworm flies are normally trapped using attractant bait with liver. However, there has been little effort to develop an efficient monitoring system for detection of screwworm flies using a specific synthetic attractant blend. Several studies have shown that odors from animal wound fluids attract screwworm adults, particularly gravid females. Bacteria associated with animal wounds have been identified that act as a major source for this attraction. To understand what volatiles attract screwworms we inoculated bovine blood with previously identified bacteria. We identified volatile chemicals released from the inoculated blood and other selected media over time and assessed the effect of those chemicals on behavioral activity of adult screwworm flies.Methodology/Principal findingsA total of 7 volatile compounds were collected from bacteria incubated in either broth or blood using solid-phase microextraction, and their chemical structures were identified by their characteristic mass spectrum fragments and confirmed by retention times in comparison to those of synthetic standards via gas chromatograph combined mass spectrometry analyses. Five major volatiles including dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol and indole were detected from a mixture of 5 bacteria incubated in blood. The ratios of volatiles released differed among different incubation media, time and individual bacteria. A synthetic mixture containing the five compounds was demonstrated to be attractive to adult screwworm flies both in laboratory assays and field trapping trials.Conclusions/SignificanceThe results obtained from this study may assist in developing an efficient trapping system using the identified attractant blend to detect the infestation of primary screwworms. This is also the first study to explore the complex systems in volatile release profiles from 5 bacteria isolated from screwworm-infested animal wounds that are incubated with different media and incubation time, as well as individual and multi-species bacterial communities.

New cardioprotective agent flokalin and its supramolecular complexes with target amino acids: An integrated mass-spectrometry and quantum-chemical study

This study is devoted to examining the molecular structure and molecular mechanisms of action of the recently developed cardioprotective agent flokalin (Fl), a fluorine containing analogue of pinacidil, which is known as an activator of ATP sensitive potassium membrane channels. A combined experimental and computational investigation of flokalin and its biologically relevant supramolecular complexes with selected amino acids involved in KATP-channels proteins is performed by electrospray ionization mass spectrometry (ESI MS) and by B3LYP/aug-cc-pVDZ quantum-mechanical calculations. First Fl solution is probed by ESI MS and a characteristic mass spectrum of the agent is obtained. Next the intermolecular interactions of Fl with the potentially targeted aminoacids (AA), Lys and Thr, are experimentally investigated. The spectra of the model Fl:AA systems (in 1:1 M ratio) contain information on the ions characteristic to the individual components of the mixtures; though the most interesting spectral results from the biophysical view point are related to the ions of stable molecular clusters formed by flokalin with AA. The peaks of such ions are quite prominent in the spectrum for the Fl:Lys system and less prominent for Fl:Thr. The equilibrium geometries and the corresponding interaction energies of the noncovalent supramolecular complexes registered in the mass spectra are determined in the quantum chemical calculations. The formation of the stable noncovalent complexes of Fl with Lyz and Thr revealed by the ESI MS probing and by the theoretical modelling testify to a possibility of interaction of flokalin with the KATP-channel domains enriched with the two amino acids in biological systems.