Mass Spectrometric Study Research Articles

Reactions of Aluminum Oxide Cluster Cations with Ethane: A Mass-Spectrometric and Vibrational Spectroscopy Study.

The pathways for the reactions of aluminum oxide cluster ions with ethane have been measured. For selected ions (Al2O+, Al3O2 +, Al3O4 +, Al4O7 +) the structure of the collisionally-stabilized reaction intermediates were explored by measuring the photodissociation vibrational spectra from 2600 cm-1-3100 cm-1. Density functional theory was used to calculate features of the potential energy surfaces for the reactions and the vibrational spectra of intermediates. Generally, more than one isomer contributes to the observed spectrum. The oxygen-deficient clusters Al2O+ and Al3O2 + have large C-H activation barriers, so only the entrance channel complexes in which intact C2H6 binds to aluminum are observed. This interaction leads to a substantial (~200 cm-1) red shift of the C-H symmetric stretch in ethane, indicating significant weakening of the proximal C-H bonds. In Al3O4 +, the complex formed by interactions with three C2H6 is investigated and, in addition to entrance channel complexes, the C-H activation intermediate Al3O4H+(C2H5)(C2H6)2 is observed. For oxygen-rich Al4O7 +, the C2H6 is favored to bind at an aluminum site far from the reactive superoxide group, reducing the reactivity. As expected, oxygen-rich species and open-shell cluster ions have smaller barriers for C-H bond activation, except for Al3O4 + which is predicted and observed to be reactive.

Geometric structures and adsorption energies of mixed methanol and C60 cationic clusters produced within helium nanodroplets

Mass spectrometry is a useful technique for studying molecular cluster sizes, their distributions, compositions, and stability. Methanol and fullerenes are among the species identified in the interstellar medium and, due to their high abundance, their interactions are an interesting investigation topic. A mass spectrometric study of mixed clusters of methanol and C60 inside helium nanodroplets is presented. Anomalies in the distribution intensities or magic numbers were observed for [CH3OH]4[C60]m+,1≤m≤7. Water molecules within clusters were also detected, arising as one of the products of intermolecular methanol dehydration. Optimized and supposedly stable geometrical structures of these molecules are presented along with corresponding HOMO–LUMO gaps and adsorption energies. A linear decrease in adsorption energy and saturation at a critical cluster size was noticed.

Targeted MRM-analysis of plasma proteins in frozen whole blood samples from patients with COVID-19: a retrospective study.

The COVID-19 pandemic has exposed a number of key challenges that need to be urgently addressed. Mass spectrometric studies of blood plasma proteomics provide a deep understanding of the relationship between the severe course of infection and activation of specific pathophysiological pathways. Analysis of plasma proteins in whole blood may also be relevant for the pandemic as it requires minimal sample preparation. The frozen whole blood samples were used to analyze 203 plasma proteins using multiple reaction monitoring (MRM) mass spectrometry and stable isotope-labeled peptide standards (SIS). A total of 131 samples (FRCC, Russia) from patients with mild (n=41), moderate (n=39) and severe (n=19) COVID-19 infection and healthy controls (n=32) were analyzed. Levels of 94 proteins were quantified and compared. Significant differences between all of the groups were revealed for 44 proteins. Changes in the levels of 61 reproducible COVID-19 markers (SERPINA3, SERPING1, ORM1, HRG, LBP, APOA1, AHSG, AFM, ITIH2, etc.) were consistent with studies performed with serum/plasma samples. The best-performing classifier built with 10 proteins achieved the best combination of ROC-AUC (0.97-0.98) and accuracy (0.90-0.93) metrics and distinguished patients from controls, as well as patients by severity. Here, for the first time, frozen whole blood samples were used for proteomic analysis and assessment of the status of patients with COVID-19. The results obtained with frozen whole blood samples are consistent with those from plasma and serum.

Vaporisation thermodynamic studies over and biphasic regions of U-Sn system using high temperature mass spectrometry

High-temperature vaporisation thermodynamic studies over <U3Sn7(cr) + USn2(cr)> and <USn2(cr) + USn(cr)> two-phase regions were carried out by employing Knudsen Effusion Mass Spectrometry (KEMS) in the temperature range 1148–1465 and 1222–1471 K, respectively. Sn(g) was the only species observed in the mass spectra of the equilibrium vapour phase over both the biphasic regions. The partial pressure-temperature relations of Sn(g) were deduced aslog(pSn/Pa) = (−15,737 ± 73)/(T/K)) + (9.52 ± 0.06) (1148–1465 K) <U3Sn7(cr) + USn2(cr)> andlog(pSn/Pa) = (−16,151 ± 67)/(T/K)) + (9.70 ± 0.05) (1222–1471 K) <USn2(cr) + USn(cr)>Using p-T relations, the enthalpies of the following heterogeneous reaction equilibria were evaluated by the second law method: U3Sn7(cr) = 3USn2(cr) + Sn(g) and USn2(cr) = USn(cr) + Sn(g). Subsequently, the Gibbs energies of the formation of U3Sn7(cr) and USn2(cr) were derived. Knudsen effusion mass spectrometric studies over these two biphasic regions are being reported for the first time.

Influence of soil degradation on radiation-chemical transformations of oil

Protecting soil from pollution by oil and petroleum products is an important environmental task. Sources of oil contamination of soil are not only oil fields, but also industrial facilities that directly or indirectly use petroleum products. Of interest are studies aimed at studying the processes of changes in oil during its degradation in the soil. When oil degrades, polycondensation processes occur on the soil surface, which leads to structural changes in the oil. We compared the composition and properties of oil after production and long-term presence on the soil surface. An analysis of oil-contaminated soils was carried out at a distance of 0–5 and 0–10 m from the source of pollution and from a depth of 0–15 cm. Oils degraded in the soil are also susceptible to the effects of natural radionuclide background. In this regard, the work investigated the impact of gamma radiation on oil degraded in the soil of the Surakhani oil field of Azerbaijan. Oil samples were taken from a well and from oil-contaminated soil and separated into three components: oils, resins, and asphaltenes. The results of mass spectrometric and IR spectrometric studies of the indicated fractions of crude and degraded oil samples are presented, and the patterns of formation of gaseous products during their radiolysis are established.

Mass Spectrometric Study of the Interaction of Y2O3 with Carbon at High Temperatures

Mass Spectrometric Study of the Interaction of Y2O3 with Carbon at High Temperatures

Mass Spectrometric Study of Evaporation of Hydroxyapatite at Temperatures up to 2200 K

Mass Spectrometric Study of Evaporation of Hydroxyapatite at Temperatures up to 2200 K

Long-term degradation study of Polytetrafluoroethylene in a low temperature oxygen plasma

Atomic oxygen (AO) is the most common gas species in the Low-Earth-Orbit (LEO) and responsible for material degradation of the outer shell of spacecrafts within this space region. Due to their similar properties, low temperature oxygen plasmas are suited for material degradation studies taking place on earth instead of quite expensive space studies. Here we focus on the long-term degradation of Polytetrafluoroethylene (PTFE), which is often employed on the outside of spacecrafts. Up to date, there is no complete understanding of the degradation process on molecular level, which is necessary for materials improvement and new materials development.For the degradation studies, a self-constructed capacitively driven 13.56 MHz RF reactor was used to generate an oxygen plasma for the simulation of LEO conditions. PTFE was characterised in the pristine state and after AO treatment at different times by ToF-SIMS, XPS and SEM. During plasma treatment, the samples show a linear mass loss behaviour. ToF-SIMS surface analysis reveal mass fragments which show a clear chemical reaction of oxygen species with PTFE. The presence of these molecular indicators was verified by XPS, where additional carbon species were found after plasma treatment. SEM micrographs showed an inhomogeneous degradation on the surface in the first hours similar to actual LEO exposure. For a complete understanding of the degradation progress, operando mass spectrometric studies of the plasma composition were carried out to detect volatile degradation products.In summary, a steady degradation has been observed that leads to constant mass loss, defluorination, chain shortening and insertion of oxygen into the polymer.

Unraveling the mechanism of small molecule induced activation of Staphylococcus aureus signal peptidase IB

Staphylococcus aureus signal peptidase IB (SpsB) is an essential enzyme for protein secretion. While inhibition of its activity by small molecules is a well-precedented mechanism to kill bacteria, the mode of activation is however less understood. We here investigate the activation mechanism of a recently introduced activator, the antibiotic compound PK150, and demonstrate by combined experimental and Molecular Dynamics (MD) simulation studies a unique principle of enzyme stimulation. Mass spectrometric studies with an affinity-based probe of PK150 unravel the binding site of PK150 in SpsB which is used as a starting point for MD simulations. Our model shows the localization of the molecule in an allosteric pocket next to the active site which shields the catalytic dyad from excess water that destabilizes the catalytic geometry. This mechanism is validated by the placement of mutations aligning the binding pocket of PK150. While the mutants retain turnover of the SpsB substrate, no stimulation of activity is observed upon PK150 addition. Overall, our study elucidates a previously little investigated mechanism of enzyme activation and serves as a starting point for the development of future enzyme activators.

Trimethyltin(IV) (p-fluoro-/p‑hydroxy-/p-nitro-)benzoates and their benzimidazole complexes: X-ray structures of [Me3Sn(p-NO2C6H4CO2)]n, and [Me3Sn(p-NO2C6H4CO2). bz], DFT calculations, DNA binding, and DNA cleavage studies

A series of trimethyltin(IV) carboxylates with Sn‒O bonds: [Me3Sn(p-FC6H4CO2)] (1), [Me3Sn(p-HOC6H4CO2)] (2), [Me3Sn(p-NO2C6H4CO2)]n (3), and their benzimidazole complexes with Sn‒N bond: [Me3Sn(p-FC6H4CO2).bz] (4), [Me3Sn(p-HOC6H4CO2).bz] (5), and [Me3Sn(p-NO2C6H4CO2).bz] (6) (bz = benzimidazole) have been synthesized and characterized by elemental analysis, FT-IR, 1H, 13C, 119Sn NMR, and electrospray ionization mass spectrometric (ESI-MS) studies. The crystal structures for (3) and (6) have been authenticated by X-ray diffraction. In the crystal structure, polymeric coordination compound (3) and the monocrystal system (6) have trigonal bipyramidal geometry around the Sn centre, where most electronegative atoms occupied the axial positions, and three methyl groups occupied the equatorial positions. The gas-phase tetrahedral geometries of (1) and (2), asymmetric unit (Sc-XRD) of (3), and trigonal bipyramidal geometries of (4–6) have been optimized using the B3LYP function and LanL2Z basis, and obtained ∠C-Sn-C bond angles agree with those obtained from NMR/X-ray studies. The interaction of (1–6) with calf thymus DNA (ctDNA) has been investigated by spectroscopic titrations such as UV–visible, fluorescence, and circular dichroism (CD) titrations, and calculated binding constant values found in the 104–105 M−1 range which suggest a groove binding or electrostatic interaction between complexes and ctDNA. The gel electrophoresis studies suggest that (1–6) effectively cleaved the plasmid pBR322 DNA into three bands: the supercoiled, nicked/circular, and linear structures. The intriguing biophysical findings from the study indicate that these complexes have properties that make them strong contenders for additional research as potential anti-cancer agents.

Mass Spectrometric Study of the Most Common Potential Migrants Extractible from the Inner Coatings of Metallic Beverage Cans.

Population exposure to endocrine disrupting chemical- bisphenols, which are used commonly in food containers and drinking water pipes in Europe, is above acceptable health and safety levels, according to updated research data. In order to evaluate the most abundant potential migrants in canned sweetened beverages marketed in Poland, we performed the HPLC-MS screening test of the migrants present in the can coating material. The analyzed samples represented the three top-ranked companies of the global soft drink market; it is reasonable to assume that the obtained data are of global validity. The tested can coatings and beverages contained bisphenols conjugates such as five butoxyethanol (BuOEtOH) adducts with bisphenol A diglycidyl ether (BADGE), one butoxyethanol adduct with bisphenol A monoglycidyl ether (BAMGE), and cyclo-di-BADGE. The performed HPLC-MS/MS analysis in the MRM mode enabled evaluation of the concentrations of the detected conjugates in canned beverages which were found to be very low, namely at the level of 1 µg/L. On the other hand, the high consumption of canned beverages may yield a risk associated with the presence of these compounds in the diet. The subsequent HPLC-QTOF-MS/MS experiments allowed, for the first time, a detailed determination of the fragmentation pathways of the detected migrants as well as detection of the isomers of the two migrants, namely BADGE + BuOEtOH and BADGE + BuOEtOH + HCl.

Propargyl amines by aldehyde-amine-acetylene coupling mediated by Ag(I) and Cu(I) complexes of super bulky N-heterocyclic carbenes: Unveiling the role of the super bulky ligands in the coupling reaction

The copper (1–2)a and the silver (1–2)b complexes of the super bulky N-heterocyclic carbene (NHC) variants namely, [1,3-{2,4,6-(Ph2CH)3C6H2}2-imidazol-2-ylidene]MX [where, M = Cu; X = Cl (1a), Br (2a): M = Ag; X = Cl (1b), Br (2b)] effectively facilitated the A3 coupling reaction of diverse amine, aldehyde, and acetylene substrates yielding a wide array of propargylamines in moderate to good (ca. 24−89 %) yields. A metal bound acetylide species, [1,3-{2,4,6-(Ph2CH)3C6H2}2-imidazol-2-ylidene]M(CCPh) [where, M = Cu (A), Ag (B)] has been identified as a key catalytic species by mass spectrometric studies. The Density functional theory (DFT) studies further revealed the rate-limiting step as the formation of the C-C coupling transition state (TS2) from the silver-acetylide species (Int2). The super bulky ligand framework plays a pivotal role in this step by anchoring the protonated Schiff's base imine in the vicinity of the alkyne through several non-covalent-interactions, including a strong C–H•••O interaction, thereby reducing the corresponding kinetic barrier leading to an efficient catalytic transformation as reflected in the high propargylamine yields. Furthermore, the catalytic utility of the coupling reaction was further extended by synthesising pargyline, which is a monoamine oxidase B (MAO-B) inhibitor drug molecule, in a one-pot manner and that to in a gram-scale synthesis.

Nerve Epidermal Growth Factor-Like 1 Protein (NELL-1) Expression in Mercury-Related Membranous Nephropathy: Is It a True Association or a Chance Occurrence?

Neural epidermal-like growth factor-like 1 (NELL-1) is a protein kinase C binding protein expressed in osteoblasts and renal tubules. It is expressed in 5%-25% glomerular cells at the mRNA level. Membranous Nephropathy (MN) is characterized by the presence of antibodies against certain types of antigens on the glomerular basement membrane. The most common one implicated in primary MN is an antibody against PLA2R. Many newer antigens have been discovered in the recent past, which are proven to cause secondary MN, one of which is NELL-1. NELL-1 has been associated with malignancy-associated MN and also recently associated with traditional indigenous medications containing mercury. In this study, we study the expression of NELL-1 in mercury-associated MN. Records of ten cases of Mercury -associated MN were retrieved from the Institute medical archives and NELL-1 Immunohistochemistry was performed in all ten cases. NELL-1 was found to be positive in 50% of the cases of Mercury associated MN. In addition, mass spectrometric studies was performed, which revealed the common Mercuric compound associated to be 'Swaskalpa', 'Sudarshana Melugu' and 'Rasagandhi Mezhugu'. This study highlights why it is important to diagnose mercury-associated MN by a pathologist by picking up the finer histopathological clues and by using NELL-1 immunohistochemistry, especially in PLA2R-negative patients. The former is true as most of the time a history of mercuric compound intake is missed out.

Concentration of HSPA1A and transthyretin proteins in the blood serum of patients with bipolar disorder

IntroductionInsufficient knowledge about the pathophysiological processes in bipolar disorder (BD) leads to difficulties in differentiating this disorder from other affective disorders. Quantitative analysis of serum protein profiles in BD expands our understanding of the pathophysiology of the disease and may aid in subsequent diagnosis. As a result of a previously conducted comparative mass spectrometric study of serum proteins in patients with depression, bipolar disorder and healthy donors, increased expression of Heat Shock 70kDa Protein1A (HSPA1A) and transthyretin was identified.ObjectivesDetermination of HSPA1A and transthyretin concentrations in the blood serum of patients with mental disorders.MethodsBlood serum of 28 patients with bipolar disorder aged 49 years [33;52], 30 patients with recurrent depressive disorder aged 40 years [31; 51] and 130 patients with schizophrenia aged 38 years [31;49], as well as 20 mentally and somatically healthy individuals aged 35 years [31;40] was studied. The amount of Heat shock protein 1A (HSPA1A) and Transthyretin (thyroxine and retinol transport protein) was determined using a Enzyme-linked Immunosorbent Assay Kit from Homo sapiens (Cloud-Clone Corp). Statistical data processing was carried out in the Statistica 12.0 program.ResultsA statistically significant (p = 0.016) increase in the level of HSPA1A was found in patients with BD (0.84 [0.59; 1.09] ng/ml), compared with healthy individuals (0.61 [0.51; 0.77] ng/ml). HSPA1A plays a pivotal role in the protein quality control system, ensuring the correct folding of proteins. It is known that this protein is involved in the embryonic development of the central nervous system, as well as in neuroprotection by preventing the death of neurons due to its anti-apoptotic properties. A statistically significant (p = 0.047) increase in the level of transthyretin was found in patients with BD 21.8 рg/ml, compared with healthy individuals 19.4 pg/ml. Transthyretin plays an important role in ensuring the normal state of the central nervous system and is involved in cognitive processes.ConclusionsThus, the HSPA1A and transthyretin are probably involved in the pathogenesis of BD and can be proposed as be proposed as an additional paraclinical criterion for differential diagnosis.Support by RSF №23-75-00023.Disclosure of InterestNone Declared

Abstract 1114: Evaluating strategies to harness metabolic vulnerabilities in cervical

Abstract Tumor cells frequently alter their metabolism to generate biomolecular intermediates for tumor maintenance and proliferation. Previous reports from Dr. Julie Schwarz’s laboratory have shown that cervical cancer cells with altered AKT/mTOR pathways show increased reliance on glucose and exogenous glutamine. The laboratory has introduced PIK3CA E545K mutation and PTEN null mutation in cervical cancer cell line SiHa. Further, to evaluate the role of glutamine metabolism in these genotypes, these cells were cultured in sequentially lower levels of glutamine until these cells were able to proliferate without exogenous glutamine supplementation. These isogenic long-term glutamine-deprived (QD) cells allow us to tease out the role of these specific mutations in cellular metabolism. In our study, long-term glutamine deprivation inhibits the proliferation of rapidly proliferating PI3K-AKT-altered cell lines. Even though glutamine is required for GSH synthesis, which quenches reactive oxygen species, QD cells were refractory to cisplatin and irradiation. Since PI3K-AKT altered were dependent on exogenous glutamine, it was expected that QD cells would have lower GLS levels to inhibit glutaminolysis. However, GLS levels in WT and QD were similar. Altogether, these data indicate that in PI3K-AKT altered cervical tumor glutamine antagonists can reduce tumor proliferation. Further glutamine reduction does not alter GLS levels and hence GLS can be targeted as well to further improve treatment outcomes. To evaluate the alternate metabolic dependencies in cervical cancer tumors, both cellular as well as secreted metabolites were evaluated. To identify alternative pathways that are activated in these glutamine-deprived cell lines, we cultured these cells in uniformly labeled 13C glucose. Mass spectrometric studies also evaluated the protein levels of various metabolic intermediates in glutamine-deprived cell lines compared to control cells. To confirm our observations, we used kit-based assays to evaluate metabolites in the cells. To further confirm the change in the metabolite pathway we evaluated changes in transcriptional changes of regulating proteins/enzymes. This pre-clinical study reinforced efforts that are anticipated to reveal new metabolic vulnerabilities of cancer cells that can be targeted by therapeutic interventions. This study also helped us evaluate druggable metabolic targets that can be targeted for effective tumor eradication along with conventional treatment. This understanding will help advance the pre-clinical trials persistent to the cure of cervical cancer. Citation Format: Dr Julie K. Schwarz, Dr Nishanth Gabriel, Aunannya Banik. Evaluating strategies to harness metabolic vulnerabilities in cervical [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1114.

Abstract 5896: Platform approach to develop antibodies specifically recognizing cancer-associated glycoforms

Abstract Introduction: Recent advances in antibody engineering have created a portfolio of highly potent therapeutic approaches like antibody-drug conjugates (ADCs), radioimmunoconjugates (RITs), chimeric antigen receptors (CARs) or bi-specifics. Due to the increased potency, these drugs are more than ever dependent on very clean targets to prevent side effects. We aim to address this major problem through our approach to develop antibodies with improved tumor specificity and reduced on-target/off-tumor binding utilizing the aberrant O-glycosylation on tumor cells. Altered glycosylation of proteins and lipids is one of the most drastic changes in cancer, giving rise to truncated or highly fucosylated and highly sialylated glycans which are almost absent on normal cells. Thus, developing antibodies against protein/carbohydrate combined epitopes (GlycoTargets) comprising these tumor-specific glycans enables highly potent therapies with reduced off-tumor toxicity. Experimental procedures: A workflow and corresponding database was established to evaluate the O-glycosylation of proteins. The first and most basic criterion is the presence of suitable O-glycosylated peptide stretches in the extracellular domain of a protein based on predictions. For proteins fulfilling this criterion cancer-relevant expression is analyzed in a second step. This is done either using publicly available data or experimentally (immunohistochemistry or protein expression data). During the final major step, the theoretical existence of suitable O-glycosylation is confirmed by our own experimental data. This includes analysis of cellularly expressed proteins by anti-glycan antibodies and mass spectrometric studies. Results summary: Case studies will be presented that highlight our workflow to identify suitable GlycoTargets based on publicly available data analysis and experimental confirmation. Additionally, the subsequent development of antibodies against the identified GlycoTargets will be shown. Conclusion: A standardized process was developed for the data collection and prioritization of potential GlycoTargets. The obtained information is subsequently used for targeted discovery of antibodies that bind to protein/carbohydrate combined glycoepitopes (GlycoTargets) offering increased tumor-specificity compared to simple protein targets. Citation Format: Patrik Kehler, Johanna Gellert, Lisa Kalfhues, Sophie Marinoff, Manon Weis, Andreas Franz, Naomi Kast, Stephanie Gurka, Marianne Morche, Evelyn Hartung, Timo Lischke, Sarah Mayer-Hain, Antje Danielczyk. Platform approach to develop antibodies specifically recognizing cancer-associated glycoforms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5896.

Gas-phase solvent-free complexation of phenolic acids in cyclodextrins: A mass spectrometric study

Phenolic acids are phytochemicals commonly existing in plants that are also beneficial to the human body after consumption. As additives in the food industry, phenolic acids typically need stabilization by encapsulation. We have been studying cyclodextrins as potential encapsulating agents, elucidating the structure and energetics of the complexes they form with phenolic acids. To highlight the role of the solvent in these interactions and to investigate the possible component ratios available to these complexes, we first carried out gas-phase studies monitored through mass spectrometry that allowed us to work in solvent-free conditions. In addition to detecting the products of these complexation equilibria qualitatively, we were also able to find conditions to quantitative determine the relative binding affinities associated with these processes. As well as on the unusual complex stoichiometry observed in the gas phase for a series of phenolic acids with α-CD, β-CD, and γ-CD. We propose an explanation of these uncommon stoichiometries through solvation effects involving the cyclodextrin host as the solvating species. We also report on the observed trends in the measured relative affinities of these interactions.

Probing the Structure of the 1:1 Hydrogen-Bonded Complexes of Metallocenes with HCl.

Matrix isolation infrared spectroscopy combined with density functional calculations has been used to form, isolate, and characterize the 1:1 hydrogen-bonded complexes of HCl with ferrocene and ruthenocene. Two unique structures were calculated for each complex, analogous to the two binding sites proposed for the attachment of proton to these metallocenes. The spectra, combined with calculated shifts of the H-Cl stretching mode, support the formation of a complex with the HCl hydrogen bonding to one of the cyclopentadienyl rings, exo to the plane of the ring. Evidence also was obtained for a second structure with the hydrogen of the HCl subunit directed toward the Fe or Ru center between the two cyclopentadienyl rings. This structure is similar to the proposed metal-bound proton structure based on earlier mass spectrometric and computational studies. Importantly, these results were supported by parallel experiments with DCl and the two metallocenes.

Mass spectrometric study of low energy Cs+ ion-induced sputtered fragmentation of PADC polymer.

In this study, low-energy cesium (Cs+ ) ion-induced sputtered fragmentation of poly allyl diglycol carbonate (PADC) was investigated using mass spectrometry. The collision-induced dissociation mechanism revealed emission of various fragments, including monoatomic (H- , C1 - , O1 - ), diatomic (C2 - ), and multiatomic (C3 - , CO2 - , C2 O2 - , C3 O2 - ) species within the Cs+ ion energy range of 1-5keV. The anion current of these fragments exhibited a linear increase with rising incident Cs+ ion energy, indicating a corresponding rise in fragment abundance. Analysis of normalized yield indicated that at 1keV incident energy, the dominant fragment was monoatomic hydrogen (H- ), followed by diatomic carbon (C2 - ), monoatomic carbon (C1 - ), and monoatomic oxygen (O1 - ). Although C2 - remained dominant up to 5keV, other fragments exhibited varying normalized yields at different ion energy steps. The sputter yield estimation revealed that monoatomic hydrogen (H- ) and diatomic carbon (C2 - ) exhibited the highest yields, increasing exponentially beyond 3keV, while multiatomic fragments like C3 - , CO2 - , C2 O2 - , and C3 O2 - displayed the lowest yields. The sputter dissociation mechanism pointed to dehydrogenation, chain scission, and bond breakage as the primary processes during low-energy Cs+ ion impact. Postsputtering Scanning Electron Mircoscope (SEM) micrographs show craters, pits, and micropores on the PADC surface, indicating significant surface degradation. X-ray Diffraction (XRD) spectra exhibited reduced diffraction intensity, while Fourier Transform Infrared Spectroscopy (FTIR) analysis indicated the absence of molecular bands in the IR spectrum, confirming extensive surface damage due to Cs+ ion-induced sputtering.

Visualization of the Active Sites of Zinc-Chromium Oxides and the CO/H2 Activation Mechanism in Direct Syngas Conversion.

Despite wide studies demonstrating the versatility of the metal oxide-zeolite (OXZEO) catalyst concept to tackle the selectivity challenge in syngas chemistry, the active sites of metal oxides and the mechanism of CO/H2 activation remain to be elucidated. Herein, we demonstrate experimentally the role of Cr in zinc-chromium oxides and unveil visually, for the first time, the active sites for CO activation employing scanning transmission electron microscopy-electron energy loss spectroscopy using the volumetric density of surface carbon species as a descriptor. The ZnCr2O4 spinel surface with atomic ZnOx overlayer is the most active site for C-O bond dissociation, particularly at the narrow ZnCr2O4(110) facets constrained between the (311) and (111) facets, followed by the Cr-doped wurtzite ZnO surface. In comparison, the surfaces of ZnCr2O4 with aggregated ZnOx overlayers, pure ZnO, and the stoichiometric ZnCr2O4 exhibit a significantly lower activity. In situ synchrotron-based vacuum ultraviolet photoionization mass spectrometric study on different temperature programmed surface reactions with isotopes of C18O, 13CO, and D2 validates direct CO dissociation over ZnCrn oxides in CO, forming CH2 and further to hydrocarbons if H2 is present and CH2CO intermediates in syngas. The activity of CO dissociation and hydrogenation over ZnCrn oxides correlates well with the syngas-to-light-olefins activity of ZnCrn-SAPO-18 composite catalysts as a function of the Cr/Zn ratio.