Electrospray Ion Trap Mass Spectrometry Research Articles

Cu and Zn Interactions with Peptides Revealed by High-Resolution Mass Spectrometry.

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by abnormal extracellular amyloid-beta (Aβ) peptide depositions in the brain. Among amorphous aggregates, altered metal homeostasis is considered a common risk factor for neurodegeneration known to accelerate plaque formation. Recently, peptide-based drugs capable of inhibiting amyloid aggregation have achieved unprecedented scientific and pharmaceutical interest. In response to metal ions binding to Aβ peptide, metal chelation was also proposed as a therapy in AD. The present study analyzes the interactions formed between NAP octapeptide, derived from activity-dependent neuroprotective protein (ADNP), amyloid Aβ(9–16) fragment and divalent metal ions such as Cu and Zn. The binding affinity studies for Cu and Zn ions of synthetic NAP peptide and Aβ(9–16) fragment were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), electrospray ion trap mass spectrometry (ESI-MS) and atomic force microscopy (AFM). Both mass spectrometric methods confirmed the formation of metal–peptide complexes while the AFM technique provided morphological and topographic information regarding the influence of metal ions upon peptide crystallization. Our findings showed that due to a rich histidine center, the Aβ(9–16) fragment is capable of binding metal ions, thus becoming stiff and promoting aggregation of the entire amyloid peptide. Apart from this, the protective effect of the NAP peptide was found to rely on the ability of this octapeptide to generate both chelating properties with metals and interactions with Aβ peptide, thus stopping its folding process.

Thymosin β4 and β10 are highly expressed at the deep infiltrative margins of colorectal cancer - A mass spectrometry analysis.

Colorectal cancer (CRC) is a complicated tumor, involving several oncogenic signaling pathways, and with a molecular mechanism not fully understood yet. The implication of thymosin β4 (Tβ4) with tumor insurgence and in migration of CRC cells was evidenced in the past with different methodologies, while Tβ10 connection with CRC has been sporadically investigated. This study focused on the implication of both types of thymosin in CRC progression and invasion by analyzing the changes in their levels according to different zones of the tumor, and to Dukes stage and budding index. Tβ4 and Tβ10 were analyzed in deep and superficial tumor samples, and normal mucosa from 18 patients. Concentrations of Tβ4 and Tβ10 have been measured by high-pressure liquid chromatography (HPLC) coupled to electrospray-ion trap mass spectrometry (ESI-IT-MS). MS data were compared by t-test and ANOVA statistical analysis. Identification of thymosin and their proteoforms has been performed by HPLC-high resolution-ESI-IT-MSMS. Both Tβ4 and Tβ10, exhibited intra-tumoral quantitative differences, being upregulated in the deep part of the CRC. They exhibited, moreover, strong association with the Dukes stage and the budding grade, being more concentrated in patients at Dukes stage B and with budding index "2". The results obtained in the present investigation encouraged the hypothesis that the two thymosin are involved in colorectal cancer progression, and in promoting cancer invasion. Thus, they are good candidates to be diagnostic/prognostic biomarkers and therapy targets.

Carpobrotus edulis (L.) N.E.Br. extract as a skin preserving agent: From traditional medicine to scientific validation

ObjectiveCarpobrotus edulis (L.) N.E.Br. is a succulent perennial plant native to South Africa and grows invasively in the Mediterranean basin. It is commonly used for the treatment of various diseases, including skin wound healing and regeneration, for which experimental validation is lacking. We therefore evaluated the skin healing properties by testing a C. edulis aqueous leaf extract (CAE) on cell cultures and in enzymatic assays. MethodsMicro-morphological analysis of leaves was carried out using scanning electron microscopy and light microscopy. Phytochemical features and antioxidant activity of CAE were evaluated by reversed-phase liquid chromatography coupled with diode array detection and electrospray ion trap mass spectrometry (RP-LC-DAD-ESI-MS), and in vitro cell-free assays. Biological activities were evaluated using keratinocytes and fibroblasts, as well as elastase, collagenase, and hyaluronidase. ResultsCAE showed high carbohydrates (28.59% ± 0.68%), total phenols ([101.9 ± 6.0] g gallic acid equivalents/kg dry extract [DE]), and flavonoids ([545.9 ± 26.0] g rutin equivalents/kg DE). RP-LC-DAD-ESI-MS revealed the predominant presence of hydroxycinnamic acids (51.96%), followed by tannins (14.82%) and flavonols (11.32%). The extract was not cytotoxic, had a strong and dose-dependent antioxidant activity, and inhibited collagenase (> 90% at 500 µg/mL) and hyaluronidase (100% at 1000 µg/mL). In cell culture experiments, CAE increased wound closure and collagen production, which was consistent with its high polyphenol content. ConclusionOur data support the use of the C. edulis for skin care and the treatment of skin problems. Moreover, use of C. edulis for skin care purposes could be an eco-friendly solution to reduce its invasiveness in the environment.

Phytochemical Profile, Safety Assessment and Wound Healing Activity of Artemisia absinthium L.

The aim of study was to validate, by in vitro and in vivo studies, the traditional use for wound-healing activity of Artemisia absinthium L. Reversed-phase liquid chromatography coupled with diode array detection and electrospray ion trap mass spectrometry (RP-LC-DAD-ESI-MS) analysis allowed to identify eleven polyphenols with chlorogenic acid as the most abundant compound (3.75 g/100 g of dry extract). After that, antibacterial activity as well as acute dermal and oral toxicity were assessed in animal models. In order to investigate the wound-healing activity of A. absinthium methanol extract, two ointments were formulated (MEO 5% and 10%). The ointment with the highest concentration of plant extract (10%) showed a statistically significant effect on the rats wound contraction, similar to that exerted by the reference drug Cicatryl-Bio. Moreover, A. absinthium methanol extract showed the best antibacterial activity against the Gram-negative Escherichia coli ATCC 10536 (MIC 1.25–2.5 mg/mL) and the Gram-positive Staphylococcus aureus ATCC 6538 (0.31–0.625 mg/mL). The absence of oral and topical toxicity of the treated animals allowed to establish the safety of the ointments. Overall, data collected in the present study support and validate the use of A. absinthium as a wound healing agent in the Algerian traditional medicine.

Silver Nanoparticle Trypsin Corona Formation and the Impacts on Enzymatic Potency

Herein, the protein corona formation on the spherical metal nanoparticles was studied to investigate the possible effects of silver nanoparticles (AgNPs) on the protein activity and conformation. The digestion capability of trypsin was monitored on the human serum albumin (HSA) at standard enzymatic hydrolysis conditions in the absence and presence of different concentrations of AgNPs. So the ratio of enzyme:HSA, the duration and the temperature of nanoparticle treatment were evaluated. The activity of treated trypsin molecules, in the form of hard (HC) and soft corona (SC) were studied using sodium dodecyl sulfate poly acrylamide gel electrophoresis (SDS-PAGE), and nano liquid chromatography electrospray (ion trap) mass spectrometry (nano LC-ESI/MS, LC-ESI/MS). In addition the characteristics of silver nanoparticles and the formation of HSA corona on the nanoparticle surface were monitored using ultra-violet/visible spectroscopy (UV-Vis), Dynamic light scattering (DLS) and fluorescence spectrophotometry. The results demonstrated that not only the corona formation but also the AgNPs/Trypsin interaction, decreases the hydrolysis potency of trypsin. Furthermore, the encountering of the AgNPs/HSA could influence both nanoparticles and HSA molecule features. Accompanied with fluorescence study, that the HSA secondary structure. Also LC-ESI/MS data revealed the most affected HSA triptics have α-helix structure.

Green Extraction of Alkaloids and Polyphenols from Peumus boldus Leaves with Natural Deep Eutectic Solvents and Profiling by HPLC-PDA-IT-MS/MS and HPLC-QTOF-MS/MS.

Peumus boldus Mol., is a Chilean medicinal tree used for gastrointestinal and liver diseases. Such medicinal properties are associated with the presence of bioactive flavonoids and aporphine alkaloids. In this study, a new green and efficient extraction method used seven natural deep eutectic solvents (NADES) as extraction media. The extraction efficiency of these NADES was assessed, determining the contents of boldine and total phenolic compounds (TPC). Chemical profiling of P. boldus was done by high-performance liquid chromatography coupled to photo diode array detector and electrospray ion-trap mass spectrometry (HPLC-PDA-ESI-IT/MS) and electrospray ionization quadrupole time-of-flight high-resolution mass spectrometry (HPLC-ESI-QTOF-MS). Among the NADES tested, NADES4 (choline chloride-lactic acid) and NADES6 (proline-oxalic acid) enable better extraction of boldine with 0.427 ± 0.018 and 2.362 ± 0.055 mg of boldine g−1 of plant, respectively. Extraction of boldine with NADES4 and NADES6 was more efficient than extractions performed with methanol and water. On the other hand, the highest TPC were obtained using NADES6, 179.442 ± 3.79 mg of gallic acid equivalents (GAE g−1). Moreover, TPC in extracts obtained with methanol does not show significant differences with NADES6. The HPLC-PAD-MS/MS analysis enable the tentative identification of 9 alkaloids and 22 phenolic compounds. The results of this study demonstrate that NADES are a promising green extraction media to extract P. boldus bioactive compounds and could be a valuable alternative to classic organic solvents.

Photocatalytic Activity of BiTaO4 Nanoparticles for the Degradation of Methyl Orange Under Visible Light

BiTaO4 nanoparticles were successfully synthesized by the gel-combustion method using polyvinyl alcohol and freshly prepared precursor Ta2O5.nH2O. Materials were characterized by x-ray diffraction and transmission electron microscopy (TEM). With an average grain size of 30 nm, the prepared particle was used to investigate the photocatalytic capacity under the visible light irradiation. The photodegradation process of methyl orange occurred following the pseudo-first order reaction mechanism on the surface of the materials. BiTaO4 nanoparticles which calcined at 750°C presented the best catalytic capacity with the highest rate constant to degrade methyl orange about 5.43 × 10−2 mg l−1 min−1. Besides, the intermediates coming from the photocatalytic degradation of methyl orange were evaluated by liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry (LC/MS). The results showed that the intermediates of degradation reactions of methyl orange were not more toxic than the initial methyl orange. BiTaO4 nanoparticles can mineralize the methyl orange after 60 min of illumination.

Establishing the Phenolic Composition of Olea europaea L. Leaves from Cultivars Grown in Morocco as a Crucial Step Towards Their Subsequent Exploitation.

In Morocco, the recovery of olive agro-industrial by-products as potential sources of high-added value substances has been underestimated so far. A comprehensive quantitative characterization of olive leaves’ bioactive compounds is crucial for any attempt to change this situation and to implement the valorization concept in emerging countries. Thus, the phenolic fraction of olive leaves of 11 varieties (‘Arbequina’, ‘Hojiblanca’, ‘Frantoio’, ‘Koroneiki’, ‘Lechín’, ‘Lucque’, ‘Manzanilla’, ‘Picholine de Languedoc’, ‘Picholine Marocaine’, ‘Picual’ and ‘Verdal’), cultivated in the Moroccan Meknès region, was investigated. Thirty eight phenolic or related compounds (including 16 secoiridoids, nine flavonoids in their aglycone form, seven flavonoids in glycosylated form, four simple phenols, one phenolic acid and one lignan) were determined in a total of 55 samples by using ultrasonic-assisted extraction and liquid chromatography coupled to electrospray ionization-ion trap mass spectrometry (LC-ESI-IT MS). Very remarkable quantitative differences were observed among the profiles of the studied cultivars. ‘Picholine Marocaine’ variety exhibited the highest total phenolic content (around 44 g/kg dry weight (DW)), and logically showed the highest concentration in terms of various individual compounds. In addition, chemometrics (principal components analysis (PCA) and stepwise-linear discriminant analysis (s-LDA)) were applied to the quantitative phenolic compound data, allowing good discrimination of the selected samples according to their varietal origin.

Modulatory Effect of Polyphenolic Compounds from the Mangrove Tree Rhizophora mangle L. on Non-Alcoholic Fatty Liver Disease and Insulin Resistance in High-Fat Diet Obese Mice.

No scientific report proves the action of the phytochemicals from the mangrove tree Rhizophora mangle in the treatment of diabetes. The aim of this work is to evaluate the effects of the acetonic extract of R. mangle barks (AERM) on type 2 diabetes. The main chemical constituents of the extract were analyzed by high-performance liquid chromatography (HPLC) and flow injection analysis electrospray-iontrap mass spectrometry (FIA-ESI-IT-MS/MS). High-fat diet (HFD)-fed mice were used as model of type 2 diabetes associated with obesity. After 4 weeks of AERM 5 or 50 mg/kg/day orally, glucose homeostasis was evaluated by insulin tolerance test (kiTT). Hepatic steatosis, triglycerides and gene expression were also evaluated. AERM consists of catechin, quercetin and chlorogenic acids derivatives. These metabolites have nutritional importance, obese mice treated with AERM (50 mg/kg) presented improvements in insulin resistance resulting in hepatic steatosis reductions associated with a strong inhibition of hepatic mRNA levels of CD36. The beneficial effects of AERM in an obesity model could be associated with its inhibitory α-amylase activity detected in vitro. Rhizophora mangle partially reverses insulin resistance and hepatic steatosis associated with obesity, supporting previous claims in traditional knowledge.

Metabolite characterization of powdered fruits and leaves from Adansonia digitata L. (baobab): A multi-methodological approach

The metabolite profiling of extracts from Adansonia digitata L. (baobab) fruit pulp and leaf, and the quantification of their major components, was conducted by means of reverse-phase, high-performance liquid chromatography with photodiode array detection, coupled to electrospray ion-trap mass spectrometry (RP-HPLC-PDA-ESI-MS/MS) and high field nuclear magnetic resonance (NMR) spectroscopy. Water-soluble metabolites from chemical classes including sugars, amino acids, organic acids, and phenolic compounds, were identified, in addition to metabolites soluble in organic solvents such as triacylglycerides, sterols, and fatty acids, and most of these were quantified. The profiling of the primary and secondary metabolites of baobab fruit and leaves addresses the limited knowledge of the chemical composition of baobab, and helps support and explain the growing evidence on its nutritional and biological properties, and provide suggestions about the possible uses of baobab fruit and leaves by food, pharmaceutical and cosmetic industries.

Identification of multiple constituents in shuganjieyu capsule and rat plasma after oral administration by ultra-performance liquid chromatography coupled with electrospray ionization and ion trap mass spectrometry

Shuganjieyu (SGJY) capsule is a classical formula widely used in Chinese clinical application. In this paper, an ultra-performance liquid chromatography coupled with electrospray ionization and ion trap mass spectrometry has been established to separate and identify the chemical constituents of SGJY and the multiple constituents of SGJY in rats. The chromatographic separation was performed on a C18 RRHD column (150 × 2.1 mm, 1.8 μm), while 0.1% formic acid–water and 0.1% formic acid–acetonitrile was used as mobile phase. Mass spectral data were acquired in both positive and negative modes. On the basis of the characteristic retention time (Rt) and mass spectral data with those of reference standards and relevant references, 73 constituents from the SGJY and 15 ingredients including 10 original constituents and 5 metabolites from the rat plasma after oral administration of SGJY were identified or tentatively characterized. This study provided helpful chemical information for further pharmacology and active mechanism research on SGJY.

Preliminary investigation of deoxyoligonucleotide binding to ribonuclease A using mass spectrometry: An attempt to develop a lab experience for undergraduates.

Deoxyoligonucleotide binding to bovine pancreatic ribonuclease A (RNase A) was investigated using electrospray ionization ion-trap mass spectrometry (ESI-IT-MS). Deoxyoligonucleotides included CCCCC (dC 5) and CCACC (dC 2AC 2). This work was an attempt to develop a biochemistry lab experience that would introduce undergraduates to the use of mass spectrometry for the analysis of protein-ligand interactions. Titration experiments were performed using a fixed RNase A concentration and variable deoxyoligonucleotide concentrations. Samples at equilibrium were infused directly into the mass spectrometer under native conditions. For each deoxyoligonucleotide, mass spectra showed one-to-one binding stoichiometry, with marked increases in the total ion abundance of ligand-bound RNase A complexes as a function of concentration, but the accurate determination of dC 5 and dC 2AC 2 dissociation constants was problematic.

Preliminary investigation of deoxyoligonucleotide binding to ribonuclease A using mass spectrometry: An attempt to develop a lab experience for undergraduates

Deoxyoligonucleotide binding to bovine pancreatic ribonuclease A (RNase A) was investigated using electrospray ionization ion-trap mass spectrometry (ESI-IT-MS). Deoxyoligonucleotides included CCCCC (dC 5) and CCACC (dC 2AC 2). This work was an attempt to develop a biochemistry lab experience that would introduce undergraduates to the use of mass spectrometry for the analysis of protein-ligand interactions. Titration experiments were performed using a fixed RNase A concentration and variable deoxyoligonucleotide concentrations. Samples at equilibrium were infused directly into the mass spectrometer under native conditions. For each deoxyoligonucleotide, mass spectra showed one-to-one binding stoichiometry, with marked increases in the total ion abundance of ligand-bound RNase A complexes as a function of concentration, but the accurate determination of dC 5 and dC 2AC 2 dissociation constants was problematic.

Preliminary investigation of deoxyoligonucleotide binding to ribonuclease A using mass spectrometry: An attempt to develop a lab experience for undergraduates.

Deoxyoligonucleotide binding to bovine pancreatic ribonuclease A (RNase A) was investigated using electrospray ionization ion-trap mass spectrometry (ESI-IT-MS). Deoxyoligonucleotides included CCCCC (dC 5) and CCACC (dC 2AC 2). This work was an attempt to develop a biochemistry lab experience that would introduce undergraduates to the use of mass spectrometry for the analysis of protein-ligand interactions. Titration experiments were performed using a fixed RNase A concentration and variable deoxyoligonucleotide concentrations. Samples at equilibrium were infused directly into the mass spectrometer under native conditions. For each deoxyoligonucleotide, mass spectra showed one-to-one binding stoichiometry, with marked increases in the total ion abundance of ligand-bound RNase A complexes as a function of concentration, but the accurate determination of dC 5 and dC 2AC 2 dissociation constants was problematic.

Characterization of high-molar-mass fractions in a Scots pine (Pinus sylvestris L.) knotwood ethanol extract

AbstractThe identification of compounds in Scots pine (Pinus sylvestrisL.) knotwood (KnW), obtained by extracting with hydrophilic organic solvents, has been performed previously almost exclusively by gas chromatography-mass spectrometry (GS-MS) equipped with long GC columns (≥25 m). That means that the molar mass (MM) of the majority of the identified compounds was below 500–600 Da, and the analytical data accounted for only about half of the dry extract weight. In the present work, high-molar-mass (HMM) fractions in a Scots pine KnW-EtOH extract were isolated and chemically characterized by means of several advanced analytical techniques, such as high performance size-exclusion chromatography-evaporative light scattering detector (HPSEC-ELSD), high performance liquid chromatography (HPLC)-electrospray ionization-ion trap-mass spectrometry [(HPLC)ESI-IT-MS], ESI-quadrupole time of flight-mass spectrometry (QTOF-MS), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS), nuclear magnetic resonance (NMR) and GC-MS. The results indicate that the MM maxima of the HMM fractions ranged from approximately 500 to 2200 Da, and that the compounds consist mainly of oligomers of hydroxylated resin acids (RAs), especially dehydroabietic acid, but also of fatty acids (FAs), stilbenes and sterols. A large number of RA dimers were tentatively identified in the HMM fractions. However, it remains unknown how the monomer units are linked together, as it was not possible to isolate a RA dimer fraction pure enough for NMR characterization. RA dimers in native KnW have not been identified previously.

Photoinduced degradation of sulfonamides, kinetic, and structural characterization of transformation products and assessment of environmental toxicity

ABSTRACTThis study focuses on the degradation of the sulfonamide antibiotics, sulfadiazine, sulfamethazine, sulfamethoxazole, and sulfathiazole, using ultraviolet irradiation in various conditions. Different pHs were investigated in combination with the addition of hydrogen peroxide and further oxygen removal. High-performance liquid chromatography electrospray ionization ion-trap mass spectrometry was used to identify and elucidate degradation products and to establish concentration–time curves. Previously unknown degradation products could be characterized. Reaction rate constants of all compounds and transformation products were determined. The parent sulfonamides decayed according to first-order kinetics, while the concentrations of the transformation products varied with time according to a subsequent reaction of an intermediate product. Quantum efficiencies were analyzed for mechanistic purposes. As example, sulfamethoxazole was added to effluents from a wastewater treatment plant and irradiated. Phototoxicity and environmental hazard were assessed through quantitative structure-activity relationship computations. In addition, the minimal inhibition concentrations were determined for Pseudomonas fluorescens and Bacillus subtilis. Conclusions for UV-C irradiation as a fourth purification wastewater treatment stage were derived.

Positive electrospray ionization ion trap mass spectrometry and ab initio computational studies of the multi-pathway fragmentation of oxoaporphine alkaloids

We report herein the first collision induced dissociation (CID) study with oxoaporphine alkaloids by electrospray ionization ion-trap mass spectrometry (ESI-IT-MS) associated with ab initio computational studies and isotope labeling experiments. Product ion spectra for a set of 11 oxoaporphine alkaloids were carefully analyzed to assign fragmentation patterns for this natural products class. All common possibilities for different arrangements of the peripheral groups, methylene dioxide bridge, methoxyl, and hydroxyl substituents, were discussed based on MS data and ab initio calculations. We observed that the most suitable protonation site generally occurs on the heterocyclic nitrogen instead of the carbonyl oxygen atom at C-7. In some special cases, a gas-phase proton transfer occurs for compounds bearing a hydroxyl group at C-3, as confirmed by isotope labeling experiments. Results point that the substitution pattern drives the dissociation behaviors of oxoaporphine alkaloids.

Structure and function of adipokinetic hormones of the large white butterfly Pieris brassicae

AbstractThe large white butterfly Pieris brassicae L. (also called cabbage white) is very common in Europe, Asia and the northern region of Africa, and has also been found in South Africa during approximately the last 20 years. The species is considered a pest insect, with larvae attacking brassicaceous crops. The adult is a strong migratory flyer and new territory can be infested this way. As a first step to investigate methods for combating this pest species, the present study aims to determine the complement of adipokinetic peptides, here generically referred to as adipokinetic hormones (AKHs), which are required to regulate the mobilization of fuels for insect flight. Biological assays, as well as mass spectrometry, reveal information about the presence, structure and function of AKHs in P. brassicae: a methanolic extract of the corpora cardiaca has hypertrehalosaemic activity in cockroaches, does not cause hyperlipaemia in locusts, and has adipokinetic activity in P. brassicae itself. Liquid‐chromatography electrospray ion trap mass spectrometry reveals three peptides that can be associated with the AKH family: the non‐amidated undecapeptide Vanca‐AKH (pELTFTSSWGGK‐OH), the nonapeptide Manse‐AKH (pELTFTSSWG amide) and the novel octapeptide Piebr‐AKH (pELTFSSGW amide). Sequence confirmation of all three assigned structures is obtained from matching mass spectrometry spectra from synthetic and native peptides. Moreover, the synthetic peptides Manse‐AKH and Piebr‐AKH have significant hyperlipaemic (=adipokinetic) activity when injected into newly‐emerged adult cabbage white butterflies. The non‐amidated Vanca‐AKH is, apparently, incompletely processed Manse‐AKH without hormonal activity. Simulated dispersal flight is able to release AKHs, as indicated by the higher concentration of lipids in the haemolymph of adult P. brassicae after activity and rest periods.

Applying mini-bore HPAEC-MS/MS for the characterization and quantification of Fc N-glycans from heterogeneously glycosylated IgGs.

High-performance anion-exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD) is a highly sensitive method for the analysis of oligosaccharides without the need for prior derivatization. However, the method suffers from the lack of chemical information with peak assignments based on the retention times of authentic standards or known peaks of reference materials. Here we applied HPAEC coupled on-line with electrospray ion trap mass spectrometry (HPAEC-MS) using a prototype mini-bore (1mm I.D.) CarboPac PA200 column and challenged the analytical separation based method for the structural assignment of heterogeneous mixtures of N-glycans derived from immunoglobulin G from human plasma, glyco-engineered CHO cells, and Sp2/0 mouse myeloma cells. Compared to an analytical scale 3mm I.D. column, the mini-bore column demonstrated a superior performance with up to 8-fold improved limit of detection for specific N-glycans determined by PAD. Quantitative evaluation by extracted ion current chromatograms revealed detection limits in the 50-100 femtomole range using ion trap MS operated in positive ionization mode. In our hands HPAEC-MS/MS allowed the detection and quantification of even low abundant glycan species including biantennary complex-type, high mannose, hybrid and hybrid bisected structures. In comparison to the detection of N-glycans as lithiated or sodiated adducts, we obtained a 65-fold improved signal-to-noise ratio with protonated ions only. Relative quantitative evaluation by single ion current chromatograms was successfully applied and demonstrated an excellent performance with respect to selectivity in the relative quantification of heterogeneous samples of N-glycans compared to HPAEC-PAD and HILIC-UPLC of 2-AB labelled N-glycans.

Studying mass spectrometric behaviors of {Au6 Ag2 (C)[PPh2 (4-CH3 -Py)]6 }(BF4 )4 and {Au8 [(PPh3 )2 O]3 (PPh3 )2 }(NO3 )2 by electrospray time-of-flight mass spectrometry and electrospray ion trap mass spectrometry.

Mass spectrometry (MS) has been recognized as a powerful technique to detect accurate chemical information about metal clusters. Maintaining metal clusters intact, which is a great challenge in MS analysis, was achieved in this work by choosing a suitable mass analyzer and carefully optimizing analysis parameters. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap mass spectrometry (ESI-IT-MS) were applied to characterize the synthesized ligand-protected metal clusters [Au6 Ag2 (C)(L(1) )6 ](BF4 )4 (L(1) =2-diphenylphosphanyl-4-methylpyridine) (1) and [Au8 (L(2) )3 (L(3) )2 ](NO3 )2 (L(2) =bis(2-diphenylphosphinophenyl)ether, L(3) =triphenyl-phosphane) (2). Three kinds of buffer gas (helium, mass: 2; nitrogen, mass: 28; argon, mass: 40) and various radiofrequency (RF) amplitudes (from 70 to 330) were chosen to study the fragmentation rate during the "collision cooling" process in the ion trap analyzer. In the ESI-TOF-MS analysis, metal clusters 1 and 2 were mainly observed as intact clusters, which were Au6 Ag2 (C)(L(1) )6 (BF4 )2 (2+) , Au6 Ag2 (C)(L(1) )6 (BF4 )(3+) , Au6 Ag2 (C)(L(1) )6 (4+) for 1 and Au8 (L(2) )3 (L(3) )2 (2+) for 2. While, in the ESI-IT-MS analysis, only fragments could be found, such as Au6 Ag(C)(L(1) )6 (BF4 )(2+) , Au6 (C)(L(1) )6 (2+) , Au5 Ag(C)(L(1) )4 (2+) , Au6 Ag(C)(L(1) )6 (3+) , Au(L(1) )(+) for 1 and Au8 (L(2) )3 (L(3) )(2+) , Au8 (L(2) )3 (2+) , Au6 (L(2) )3 (2+) for 2. It is obvious that the two kinds of mass analyzers caused different MS behaviors of metal clusters. In the ion trap (IT) mass analyzer, particularly, "collision cooling" was contributing to further dissociation of fragile compounds, in which a higher RF amplitude and a larger mass buffer gas led to more fragmentation. In this work, intact metal clusters were obtained in ESI-TOF-MS, instead of ESI-IT-MS, in which the "collision cooling" process caused more cluster dissociation. It was concluded that the analyzer in ESI-TOF-MS is "softer" than that in ESI-IT-MS for metal clusters. Copyright © 2016 John Wiley & Sons, Ltd.