Molecular Mass Range Research Articles

Development of an Ultrasonic Nebulization System for an Inverse Low Temperature Plasma Ionization Source.

An effective nebulization and evaporation of a liquid sample, like in liquid chromatography, mass spectrometry (LC-MS) couplings, is an essential requirement for the ionization of analyte molecules in the gas phase by, for example, atmospheric pressure chemical ionization (APCI) or the novel low temperature plasma (LTP)-based ion source. These LTP-based ion sources have recently gained interest in the field of atmospheric pressure ion sources, as they can cover a wide range of polarity and molecular mass. They can be used in combination with separation techniques like liquid chromatography or used as an ambient ion source. However, commercial nebulizer systems are of course not constructed to fit to home-built LTP-based ion sources, and this was one incentive to develop a new nebulization system. Instead of an atmospheric pressure chemical ionization (APCI) nebulizer, two commercial nebulizers were disassembled and remodeled to be used as nebulizing systems in an LC-MS setup using an LTP-based ion source. Based on these results, a novel nebulizer system was subsequently developed. To further improve the degree of ionization, cones to focus the LC eluent spray on the plasma region, heating applications, and auxiliary nitrogen gas for dispersion of the solvent droplets were implemented. The LOD that could be calculated via the rule of three resulted in an average of 2.0 μg/L for the APCI-nebulizer and 41 μg/L for the USN. Both could be reduced to 1.4 and 18 μg/L, respectively, by using a TPI-configuration instead of an iLTP. The linearity was equally good for both types of nebulization devices. The final nebulizer could also be operated with a high water content and flow rates higher than those of the two previous ones, indicating an important improvement step.

Methanol gel electrophoresis: Separation of human fast and slow myosin light chain 1 and other myofibrillar protein isoforms on a single gel format.

This report describes a novel sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) resolving gel format that consistently yields the electrophoretic separation of the fast and slow isoforms of human sarcomeric myosin light chain 1 (MLC1). The inclusion of methanol as a constituent of the resolving gel impacted the electrophoretic mobility of proteins across a broad range of molecular masses. There was greater separation of the fast and slow isoforms of human MLC1, as well as separation and high resolution of fast and slow isoforms of the three myosin heavy chain isoforms that are expressed in human skeletal muscle on the same gel format. Furthermore, the same resolving gel format substantially altered the electrophoretic mobility of at least one isoform of tropomyosin in human striated muscle. It is possible that the inclusion of methanol in SDS-PAGE resolving gels could improve the separation of other proteins that are expressed in muscle and in other tissues and cell types.

Cold molecules in H I 21 cm absorbers across redshifts ∼0.1–4

Absorption lines at high-redshift in front of quasars are quite rare in the millimeter (mm) domain. Only five associated and five intervening systems have been reported in the literature. Nevertheless, these discoveries provide very useful information that is complementary to emission lines, allowing, for instance, to distinguish between inflows and outflows. These lines are also good candidates for studying the variations of the fundamental constants of physics. Here we report the findings of our search for CO and other molecules in emission and absorption in front of a sample of 30 targets, comprising 16 associated and 14 intervening H I 21 cm absorbers. The observations were made with the IRAM-30 m telescope simultaneously at 3 mm and 2 mm, exploring several lines of the CO ladder and HCO+, depending on the redshift. We detected eight targets in emission, of which five are new. The derived molecular gas masses range from 109 to 7 × 1011 M⊙ and the highest redshift detection (z = 3.387) corresponds to a relatively average-metallicity damped Lyman-α absorber for this redshift. We also report four new detections in absorption. Two of the associated CO absorption line detections at high-redshift (z = 1.211 and 1.275) result from high-spatial-resolution follow-up observations with NOEMA. The disparity between the mm molecular and H I 21 cm absorption lines for these and another intervening system detected in HNC at z = 1.275 is attributable to radio and mm sight lines tracing different media. We compare the atomic and molecular column densities of 14 known high-redshift (z > 0.1) molecular absorption line systems. The associated H I absorption lines are broad and exhibit multiple components, and the molecular absorption generally corresponds to the broader and weaker 21 cm absorption component. This indicates two distinct phases: one near galaxy centers with a larger CO-to-H I abundance ratio, and another with lower molecular abundance in the outer regions of the galaxy. In comparison, intervening absorption profiles correspond primarily to H I-dominated gas structure in galaxy outskirts, except for gas at low impact parameters in gravitationally lensed systems. The comparison of interferometric and single-dish observations presented here shows that the detection of absorption requires sufficient spatial resolution to overcome the dilution by emission and will be an important criterion for mm follow-up of 21 cm absorbers from ongoing large-scale surveys.

Characterisation of the forest cobra (Naja melanoleuca) venom using a multifaceted mass spectrometric-based approach

Snake venoms consist of highly biologically active proteins and peptides that are responsible for the lethal physiological effects of snakebite envenomation. In order to guide the development of targeted antivenom strategies, comprehensive understanding of venom compositions and in-depth characterisation of various proteoforms, often not captured by traditional bottom-up proteomic workflows, is necessary. Here, we employ an integrated ‘omics’ and intact mass spectrometry (MS)-based approach to profile the heterogeneity within the venom of the forest cobra (Naja melanoleuca), adopting different analytical strategies to accommodate for the dynamic molecular mass range of venom proteins present. The venom proteome of N. melanoleuca was catalogued using a venom gland transcriptome-guided bottom-up proteomics approach, revealing a venom consisting of six toxin superfamilies. The subtle diversity present in the venom components was further explored using reversed phase-ultra performance liquid chromatography (RP-UPLC) coupled to intact MS. This approach showed a significant increase in the number of venom proteoforms within various toxin families that were not captured in previous studies. Furthermore, we probed at the higher-order structures of the larger venom proteins using a combination of native MS and mass photometry and revealed significant structural heterogeneity along with extensive post-translational modifications in the form of glycosylation in these larger toxins. Here, we show the diverse structural heterogeneity of snake venom proteins in the venom of N. melanoleuca using an integrated workflow that incorporates analytical strategies that profile snake venom at the proteoform level, complementing traditional venom characterisation approaches.

Capillary electrophoresis in the analysis of therapeutic peptides-A review.

Therapeutic peptides are a growing class of innovative drugs with high efficiency and a low risk of adverse effects. These biomolecules fall within the molecular mass range between that of small molecules and proteins. However, their inherent instability and potential for degradation underscore the importance of reliable and effective analytical methods for pharmaceutical quality control, therapeutic drug monitoring, and compliance testing. Liquid chromatography-mass spectrometry (LC-MS) has long time been the "gold standard" conventional method for peptide analysis, but capillary electrophoresis (CE) is increasingly being recognized as a complementary and, in some cases, superior, highly efficient, green, and cost-effective alternative technique. CE can separate peptides composed of different amino acids owing to differences in their net charge and size, determining their migration behavior in an electric field. This review provides a comprehensive overview of therapeutic peptides that have been used in the clinical environment for the last 25 years. It describes the properties, classification, current trends in development, and clinical use of therapeutic peptides. From the analytical point of view, it discusses the challenges associated with the analysis of therapeutic peptides in pharmaceutical and biological matrices, as well as the evaluation of CE as a whole and the comparison with LC methods. The article also highlights the use of microchip electrophoresis, nonaqueous CE, and nonconventional hydrodynamically closed CE systems and their applications. Overall, the article emphasizes the importance of developing new CE-based analytical methods to ensure the high quality, safety, and efficacy of therapeutic peptides in clinical practice.

Relationship between Dehydrins and Adaptation of Cajander Larch to Yakutia Cryolithozone Conditions

Composition and seasonal fluctuations of stress dehydrin proteins of Cajander larch (Larix cajanderi Mayr) growing under extremely cold climatic conditions in Central Yakutia, which are notable for an extraordinary frost resistance, were investigated. Immunoblotting technique made it possible to detect major dehydrins in a molecular mass range of 17–20, 37–42, and 73 kD in the shoots of L. cajanderi for the first time. A high level of polymorphism of dehydrins within a population of L. cajanderi was detected and differences between the examined specimens of trees were mainly revealed in a molecular mass range of 20–37 kD. Within the circannual cycle of larch, the greatest seasonal fluctuations were observed in low-molecular dehydrins, with their content rising at the end of phenological autumn and reaching a steady level in the period of ultralow winter temperatures. The pattern of seasonal fluctuations and wide variety of dehydrins in larch shoots may point to their possible participation in the formation of a unique frost resistance of L. cajanderi upon adaptation of this conifer species to conditions existing in the cryolithozone.

Bioactive properties of peptide fractions from Brazilian soy protein hydrolysates: In silico evaluation and experimental evidence

Soybeans are a known source of dietary proteins and potential bioactive peptides. In this study, a protein hydrolysate from soybean protein concentrate was produced using papain. The peptides were separated by ultrafiltration (< and > 3 kDa, LMMH (low molecular mass) and HMMH (high molecular mass), respectively) and sequenced through LC-MS/MS. To obtain a thorough identification of the peptides in the hydrolysate, different analysis methods and bioinformatics techniques were applied, covering a molecular mass range from more than 480 Da up to small dipeptides. The antioxidant and the inhibitory α -glucosidase and lipase potentials were evaluated by different in vitro tests. Sixty-nine peptides were identified in the HMMH fraction and 32 in LMMH, but only 16 matched the 118 sequences obtained by in silico simulated hydrolysis. Unlike previous reports, the HMMH fraction showed higher antioxidant activity, by all 5 in vitro methods applied, which was not accompanied by the in silico evaluation. Both high and low molecular mass fractions showed similar inhibitory activities against α -glucosidase and pancreatic lipase. LMMH, however, showed better results for α -glucosidase inhibition (IC50 = 0,94), in agreement with the in silico evaluation. This combination of bioactivities makes the fractions of this hydrolysate potential food ingredients with the possible ability to delay the lipid peroxidation of meat products, limiting the digestion of lipids in the product and also with the potential to delay the digestion of carbohydrates ingested in the same meal.

Development of native mass spectrometry with nanoelectrospray ionization coupled to size exclusion chromatography for proteins.

Native mass spectrometry (MS) is an analytical technique used to determine the molecular mass of protein complexes without cross-linking. Size exclusion chromatography (SEC) coupled with native MS using conventional electrospray ionization (ESI) has been reported to allow online buffer exchange. To detect a wide variety of protein complexes without a collapse in the ionization process, it is important to build an online system that enables robust analysis with a low flow rate. We created an online native MS system equipped with nanoESI connected to the SEC component (online SEC/nanoESI system) and optimized several parameters for SEC separation and ionization. The constructed system was used to measure a solution consisting of a protein mixture of various molecular masses (10-300 kDa) to verify characteristics such as the measurable molecular mass range, reproducibility, and online buffer exchange. The optimal flow rates for SEC separation and nanoESI analysis using this system were 200 and 1μL/min, respectively. This system was able to analyze proteins in the ranges of 10-300 and 20-300 kDa for protein samples in ammonium acetate and nonvolatile buffer, respectively. Furthermore, the results of consecutive measurements showed that the relative standard deviations of the retention times and observed masses for each protein were sufficiently small. We created an online SEC/nanoESI system and evaluated its utility for the analysis of various proteins in conventional measurement solvent and nonvolatile buffer. As a result, the structural stability and resolution of the proteins were found to be sufficient when using online buffer exchange. Therefore, this online SEC/nanoESI system would be a useful technique for obtaining mass spectra of various proteins automatically with good resolution, simply by loading samples into an autosampler.

Data-driven modeling of H2 solubility in hydrocarbons using white-box approaches

As a result of technological advancements, reliable calculation of hydrogen (H2) solubility in diverse hydrocarbons is now required for the design and efficient operation of processes in chemical and petroleum processing facilities. The accuracy of equations of state (EOSs) in estimating H2 solubility is restricted, particularly in high-pressure or/and high-temperature conditions, which could result in energy loss and/or potential safety and environmental problem. Two strong machine learning techniques for building advanced correlation were used to evaluate H2 solubility in hydrocarbons in this study which were Group method of data handling (GMDH) and genetic programming (GP). For that purpose, 1332 datasets from experimental results of H2 solubility in 32 distinct hydrocarbons were collected from 68 various systems throughout a wide range of operating temperatures from 98 K to 701 K and pressures from 0.101325 MPa to 78.45 MPa. Hydrocarbons from two distinct classes include alkane, alkene, cycloalkane, aromatic, polycyclic aromatic, and terpene. Hydrocarbons have a molecular mass range of 28.054–647.2 g/mol, which corresponds to a carbon number of 2–46. Solvent molecular weight, critical pressure, and critical temperature, as well as pressure and temperature operational parameters, were used to create the features. With a regression coefficient (R2) which was equal to 0.986 and root mean square error (RMSE) which was 0.0132, the GP modeling approach estimated experimental solubility data more accurately than the GMDH approach. Operating pressure, followed by molecular weight of hydrocarbon solvents and temperature, had the greatest influence on estimation H2 solubility, according to sensitivity analysis. The GP model shown in this paper is a reliable development that may be used in the chemical and petroleum sectors as a reliable and effective estimator for H2 solubility in diverse hydrocarbons.

Development of analytical methods to study the salivary metabolome: impact of the sampling.

Advances in metabolomics have allowed the identification and characterization of saliva metabolites that can be used as biomarkers. However, discrepancies can be noted with the content of the same biomarker being increased or decreased for a given disease. Differences in the way saliva is collected, stored, and/or treated could cause these discrepancies. Indeed, there is no standardized method for saliva sampling and analysis. In this work, two chromatographic modes were used, i.e., RP-LC and HILIC both coupled to MS used in positive and negative ionization modes. The analytical conditions were optimized with a mixture of 90 compounds naturally present in saliva, representative of the wide range of molecular mass and polarity of salivary metabolites and being described as having a differential expression in various pathologies. These four methods were applied to the analysis of saliva samples collected by spitting, aspiration, or Salivette® with or without prior rinsing of the mouth. Rinsing had an effect on some metabolite concentrations. As it can induce an additional parameter of variability to the sampling, it seems therefore preferable to use methods without rinsing while effects of these parameters on the metabolites are investigated. Saliva obtained by spitting and aspiration gave statistically equivalent results for 84% of the metabolites studied. Conversely, Salivette® gave different results since the majority of the metabolites chosen for the study were not quantified in the samples. The Salivette® does not seem therefore to be a suitable sampling method for an untargeted analysis of the salivary metabolome, unlike aspiration and spitting.

Geochemical matrix differently affects the response of internal standards and target analytes for pesticide transformation products measured in groundwater samples

Electrospray ionization (ESI) is the most common technique in liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) allowing for sensitive detection of polar compounds with online water concentration. The technique is popular in groundwater monitoring programs and has permitted great progress in the detection and quantification of polar pesticide transformation products (TP) in recent years. However, ESI is also known to be prone to matrix effects. The common solution to this potential bias is the use of labelled internal standards. Unfortunately, these are not available for all target compounds, which leads to the linkage of target compounds to non-homologue internal standards with unknown consequences for quantification in variable geochemical settings. We investigated these matrix effects for polar TP with a molecular mass range of 225–350 Da and logDpH7 between −0.27 and −1.7 as well as for parent compounds with logDpH3 between 0.84 and 3.22. The acquired internal standards were tested on a gradient of DOC, anions, conductivity and inorganic carbon with a set of ten carefully chosen groundwater samples. Internal standards that were measured in positive ionization mode proved to be insensitive to geochemical variations while those that were measured in negative ionization mode showed reduced response with increasing anion concentration. All pairs of internal standards and target analytes were investigated for deviating matrix effects using standard addition experiments. Positive ionization compounds and target compounds with deuterated homologues showed little deviation while non-homologue pairs in negative mode proved to be strongly biased. Although bias was up to factor five for some compounds it was remarkably stable over the entire gradient studied, suggesting an identical suppression mode at varying matrix levels for different compounds. We advocate the conduct of standard addition experiments if homologue internal standards are not available.

Analyzing Interferometric CO (3-2) Observations of NGC 4039

Starburst merging galaxies are important in the history of galaxy evolution timeline. For this work, we have chosen the Antennae galaxy (NGC4039), which is one of the most famous starburst merging galaxies. We analyzed the CO (3–2) interferometric observations for the southern mosaic of the NGC 4039, together with the CO (2–1) data taken from Atacama Large Millimeter/Sub-millimeter Array (ALMA). Using the galactic CO luminosity to H2 mass conversion factor, we found molecular gas mass range in this galaxy to be (0.8–2.92) × 108 Mʘ. Line emissions at CO (2–1) and CO (3–2) were detected at selected regions in the nucleus of NGC 4039. The CO (3–2) / CO (2–1) ratio for this galaxy was calculated to be approximately 0.62. In addition, we found a significant correlation between the brightness temperature ratio and IR luminosity for this galaxy. We used a new model to interpret the rotation curve and found that the most important factor is related to gas mass distribution. The disturbance in the gas distribution may be caused by the merging process. We have also analyzed the spatially resolved star formation law in this galaxy up to 345 parsec. We found a breakdown of the Kennicutt–Schmidt law at this scale. The results are consistent with the previous findings that there is a possibility of sub-thermally excited widespread gas in the neighborhood of denser regions, which causes the flatter star formation law.

Structure and Intermolecular Interactions in Aqueous Solutions of Polyethylene Glycol.

Aqueous solutions of polyethylene glycol are studied by small-angle neutron scattering over a broad range of polymer molecular masses and concentrations. The scattering data were modeled by a Gaussian chain form factor combined with random phase approximation, which provided good fits over the whole studied concentration range. The results showed that polyethylene glycol in the molecular mass range –20 kDa in water at physiological temperature T = 37 C behaves like a random coil in nearly theta solvent conditions. The obtained results serve as a reference for the description of complex mixtures with PEG used in various applications.

Migration of mineral oil aromatic hydrocarbons (MOAH) from cardboard containers to dry food and prediction tool

This research aimed to study the migration of mineral oil aromatic hydrocarbons (MOAH) from primary carton packages to dry foods, using 16 aromatic hydrocarbons as model substances, covering a wide range of molecular masses and chemical structures. Migration experiments were performed using modified polyphenylene oxide as a food simulant and couscous and polenta as dry foods. The migration tests were carried out to simulate storage at room temperature for long periods and in hot food containers as the worst scenario. Multivariate analysis algorithms were applied to correlate and group the migration of model substances, and a partial least squares regression (PLSR) model was built to predict the worst-case migration. The results showed strong correlations in the migration patterns of the model substances, based on their volatility, food matrix, migration time and temperature. Different behaviour between the migration of the most volatile and the heaviest model substances was observed.

Pediatric Brain Tumors: Signatures from the Intact Proteome.

The present investigation aimed to explore the intact proteome of tissues of pediatric brain tumors of different WHO grades and localizations, including medulloblastoma, pilocytic astrocytoma, and glioblastoma, in comparison with the available data on ependymoma, to contribute to the understanding of the molecular mechanisms underlying the onset and progression of these pathologies. Tissues have been homogenized in acidic water–acetonitrile solutions containing proteases inhibitors and analyzed by LC–high resolution MS for proteomic characterization and label-free relative quantitation. Tandem MS spectra have been analyzed by either manual inspection or software elaboration, followed by experimental/theoretical MS fragmentation data comparison by bioinformatic tools. Statistically significant differences in protein/peptide levels between the different tumor histotypes have been evaluated by ANOVA test and Tukey’s post-hoc test, considering a p-value > 0.05 as significant. Together with intact protein and peptide chains, in the range of molecular mass of 1.3–22.8 kDa, several naturally occurring fragments from major proteins, peptides, and proteoforms have been also identified, some exhibiting proper biological activities. Protein and peptide sequencing allowed for the identification of different post-translational modifications, with acetylations, oxidations, citrullinations, deamidations, and C-terminal truncations being the most frequently characterized. C-terminal truncations, lacking from two to four amino acid residues, particularly characterizing the β-thymosin peptides and ubiquitin, showed a different modulation in the diverse tumors studied. With respect to the other tumors, medulloblastoma, the most frequent malignant brain tumor of the pediatric age, was characterized by higher levels of thymosin β4 and β10 peptides, the latter and its des-IS form particularly marking this histotype. The distribution pattern of the C-terminal truncated forms was also different in glioblastoma, particularly underlying gender differences, according to the definition of male and female glioblastoma as biologically distinct diseases. Glioblastoma was also distinguished for the peculiar identification of the truncated form of the α-hemoglobin chain, lacking the C-terminal arginine, and exhibiting oxygen-binding and vasoconstrictive properties different from the intact form. The proteomic characterization of the undigested proteome, following the top-down approach, was challenging to originally investigate the post-translational events that differently characterize pediatric brain tumors. This study provides a contribution to elucidate the molecular profiles of the solid tumors most frequently affecting the pediatric age, and which are characterized by different grades of aggressiveness and localization.

First analyses of lysine succinylation proteome and overlap between succinylation and acetylation in Solenopsis invicta Buren (Hymenoptera: Formicidae)

BackgroundLysine succinylation (Ksu) exists in both eukaryotes and prokaryotes, and influences a variety of metabolism processes. However, little attention has been paid to Ksu in insects, especially the notorious invasive pest Solenopsis invicta.ResultsIn this study, the first analyses of Ksu proteome and overlap between Ksu and lysine acetylation (Kac) in S. invicta were presented. 3753 succinylated sites in 893 succinylated proteins were tested. The dihydrolipoyl dehydrogenase, V-type proton ATPase subunit G, and tubulin alpha chain all had evolutionary conservatism among diverse ant or bee species. Immunoblotting validation showed that there were many Ksu protein bands with a wide range of molecular mass. In addition, 1230 sites in 439 proteins were highly overlapped between Ksu and Kac. 54.05% of Ksu proteins in cytoplasm were acetylated. The results demonstrated that Ksu may play a vital part in the allergization, redox metabolism, sugar, fat, and protein metabolism, energy production, immune response, and biosynthesis of various secondary metabolites.ConclusionsKsu and Kac were two ubiquitous protein post-translational modifications participated in a variety of biological processes. Our results may supply rich resources and a starting point for the molecular basic research of regulation on metabolic pathways and other biological processes by succinylation and acetylation.

Unmodified and tyrosine-modified polyethylenimines as potential carriers for siRNA: Biophysical characterization and toxicity

Polyethylenimines (PEIs) are being explored as efficient non-viral nanocarriers for nucleic acid delivery in vitro and in vivo. To address limitations regarding PEI efficacy and biocompatibility, modifications of the chemical structure of linear and branched PEIs have been introduced, including grafting with tyrosine. The aim has been to compare linear and branched polyethylenimines of a wider range of different molecular mass with their tyrosine-modified derivatives. To do so, physico-chemical and biological properties of the polymers were investigated.Even in the absence of a negatively charged nucleic acid counterpart, PEIs form particle structures with defined size and surface potential. Tyrosine modification of PEI led to significantly reduced toxicity, while simultaneously increasing interaction with cellular membranes. All the effects were also dependent on the PEI molecular weight and structure (i.e., linear vs. branched). Especially in the case of linear PEIs, the improved membrane interaction also translated into slightly enhanced hemolysis, whereas their genotoxic potential was essentially abolished. Due to the improvement of properties critical for nano-vector efficacy and biocompatibility, our data demonstrate that tyrosine-modified PEIs are very promising and safe nanocarriers for the delivery of small RNAs, like siRNAs and miRNAs.

Enhancing Sensitivity for High-Selectivity Gas Chromatography-Molecular Rotational Resonance Spectroscopy.

A next-generation gas chromatograph-molecular rotational resonance (MRR) spectrometer (GC-MRR) with instrumental improvements and higher sensitivity is described. MRR serves as a structural information-rich detector for GC with extremely narrow linewidths and capabilities surpassing 1H nuclear magnetic resonance/Fourier transform infrared spectroscopy/mass spectrometry (MS) while offering unparalleled specificity in regard to a molecule's three-dimensional structure. With a Fabry-Pérot cavity and a supersonic jet incorporated into a GC-MRR, dramatic improvements in sensitivity for molecules up to 244 Da were achieved in the microwave region compared to the only prior work, which demonstrated the GC-MRR idea for the first time with millimeter waves. The supersonic jet cools the analytes to ∼2 K, resulting in a limited number of molecular rotational and vibrational levels and enabling us to obtain stronger GC-MRR signals. This has allowed the limits of detection of the GC-MRR to be comparable to a GC thermal conductivity detector with an optimized choice of gases. The performance of this GC-MRR system is reported for a range of molecules with permanent dipole moments, including alcohols, nitrogen heterocyclics, halogenated compounds, dioxins, and nitro compounds in the molecular mass range of 46-244 Da. The lowest amount of any substance yet detected by MRR in terms of mass is reported in this work. A theoretically unexpected finding is reported for the first time about the effect of the GC carrier gas (He, Ne, and N2) on the sensitivity of the analysis in the presence of the gas driving the supersonic jet (He, Ne, and N2) in the GC-MRR. Finally, the idea of total molecule monitoring in the GC-MRR analogous to selected ion monitoring in GC-MS is illustrated. Structural isomers and isotopologues of bromobutanes and bromonitrobenzenes are used to demonstrate this concept.

Molecular gas budget and characterization of intermediate-mass star-forming galaxies at z ≈ 2–3

Star-forming galaxies (SFGs) with stellar masses below 1010 M⊙ make up the bulk of the galaxy population at z &gt; 2. The properties of the cold gas in these galaxies can only be probed in very deep observations or by targeting strongly lensed galaxies. Here we report the results of a pilot survey using the Atacama Compact Array of molecular gas in the most strongly magnified galaxies selected as giant arcs in optical data. The selection in rest-frame ultraviolet (UV) wavelengths ensures that sources are regular SFGs, without a priori indications of intense dusty starburst activity. We conducted Band 4 and Band 7 observations to detect mid-J CO, [C I] and thermal continuum as molecular gas tracers from four strongly lensed systems at z ≈ 2 − 3: our targets are SGAS J1226651.3+215220 (A and B), SGAS J003341.5+024217 and the Sunburst Arc. The measured molecular mass was then projected onto the source plane with detailed lens models developed from high resolution Hubble Space Telescope observations. Multiwavelength photometry was then used to obtain the intrinsic stellar mass and star formation rate via spectral energy distribution modeling. In only one of the sources are the three tracers robustly detected, while in the others they are either undetected or detected in continuum only. The implied molecular gass masses range from 4 × 109 M⊙ in the detected source to an upper limit of ≲109 M⊙ in the most magnified source. The inferred gas fraction and gas depletion timescale are found to lie approximately 0.5–1.0 dex below the established scaling relations based on previous studies of unlensed massive galaxies, but in relative agreement with existing literature about UV-bright lensed galaxies at these high redshifts. Our results indicate that the cold gas content of intermediate to low mass galaxies should not be extrapolated from the trends seen in more massive high-z galaxies. The apparent gas deficit is robust against biases in the stellar mass or star formation rate. However, we find that in this mass-metallicity range, the molecular gas mass measurements are severely limited by uncertainties in the current tracer-to-gas calibrations.

Characterization of crude oils derived from carbonate and siliciclastic source rocks using FTICR-MS

The scope of this study was to develop robust lithofacies proxies which are less affected by other geochemical processes such as maturity and biodegradation. Here, crude oils derived from carbonate and siliciclastic source rocks from different petroleum settings were investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), thereby providing information on the role of depositional environment in controlling the chemical composition of hydrocarbons. The carbonate oils belong to the Western Canada Sedimentary Basin (WCSB) and the siliciclastic oils were mainly collected from the Austrian parts of the Molasse Basin and the Vienna Basin, Austria. The variations in chemical composition, aromaticity as well as alkylation degree of the main compound classes in both oil types are discussed in detail using data from FTICR-MS in two different ionization modes: electrospray ionization in negative ion mode (ESI–N) and atmospheric pressure photoionization in positive ion mode (APPI–P). The results obtained from both ionization modes indicate that the chemical compound distributions of acidic constituents such as oxygen-only components (the O1 to O4 classes) and the N1S1 class, as well as sulfur and hydrocarbon species in oils from carbonates are clearly different from those generated by siliciclastic rocks. Most likely, the observed differences are attributed to depositional environments of the respective source rocks as the impacts of other processes such as thermal maturity and biodegradation, were mitigated by selection of non-biodegraded oils that display comparable maturation levels. The calculated vitrinite reflectance (%Rc) in most of the selected oils range between 0.5 and 0.8. The observed differences in chemical composition of oils from carbonates and siliciclastics lead to suggested novel source-sensitive proxies based on the DBE distribution of the S1 and HC species (from APPI–P) and the O1 and N1S1 classes (from ESI–N). The former proxy is the ratio of the S1 class DBE 9 group (radical ions; likely sum of alkylated dibenzothiophenes) relative to the HC class DBE 10 group (radical ions; likely sum of alkylated phenanthrenes). It appears that this proxy is mirroring the “DBT/P ratio” obtained from GC–MS data over a much broader range of molecular masses up to approximately 1000 Da. The other proxy is based on the observed differences between the O1 class DBE 4 group and the N1S1 class DBE 14 group. Whereas oils derived from the siliciclastic source rocks show higher concentrations of the O1 class, oils originated from the carbonate source units are enriched in the N1S1 species. Finally, published FTICR-MS data (APPI–P) from both oil source types with varying levels of maturation and biodegradation are included, in order to verify the robustness of the proposed proxies.