Mass Spectrum Pattern Research Articles

Characterization of Aldehyde Oxidase Enzyme Activity in Cryopreserved Human Hepatocytes

Substrates of aldehyde oxidase (AO), for which human clinical pharmacokinetics are reported, were selected and evaluated in pooled mixed-gender cryopreserved human hepatocytes in an effort to quantitatively characterize AO activity. Estimated hepatic clearance (Cl(h)) for BIBX1382, carbazeran, O⁶-benzylguanine, zaleplon, and XK-469 using cryopreserved hepatocytes was 18, 17, 12, <4.3, and <4.3 ml · min⁻¹ · kg⁻¹, respectively. The observed metabolic clearance in cryopreserved hepatocytes was confirmed to be a result of AO-mediated metabolism via two approaches. Metabolite identification after incubations in the presence of H₂¹⁸O confirmed that the predominant oxidative metabolite was generated by AO, as expected isotope patterns in mass spectra were observed after analysis by high-resolution mass spectrometry. Second, clearance values were efficiently attenuated upon coincubation with hydralazine, an inhibitor of AO. The low exposure after oral doses of BIBX1382 and carbazeran (∼5% F) would have been fairly well predicted using simple hepatic extraction (f(h)) values derived from cryopreserved hepatocytes. In addition, the estimated hepatic clearance value for O⁶-benzylguanine was within ∼80% of the observed total clearance in humans after intravenous administration (15 ml · min⁻¹ · kg⁻¹), indicating a reasonable level of quantitative activity from this in vitro system. However, a 3.5-fold underprediction of total clearance was observed for zaleplon, despite the 5-oxo metabolite being clearly observed. These data taken together suggest that the use of cryopreserved hepatocytes may be a practical approach for assessing AO-mediated metabolism in discovery and potentially useful for predicting hepatic clearance of AO substrates.

TLC-MS VERSUS TLC-LC-MS FINGERPRINTS OF HERBAL EXTRACTS. PART I. ESSENTIAL OILS

In our earlier studies, we proposed the low-temperature thin-layer chromatography with densitometric and mass spectrometric detection for fingerprinting of essential oils derived from several different species from the Salvia genus. Development of the proposed LT-TLC-MS approach was only possible with use of the TLC-MS interface able to couple the chromatographic plate with mass spectrometer. The goal of this study was to develop for the same purpose the two-dimensional liquid chromatographic system, which was only possible with use of the TLC-MS interface. It included the low-temperature thin-layer chromatography coupled with high-performance liquid chromatography, to build an overall LT TLC-LC-MS system. We compared the fingerprinting results for the essential oil of Salvia lavandulifolia obtained with use of the one-dimensional system (1D LT TLC-MS) with those obtained with use of the two-dimensional system (2D LT TLC-LC-MS). It was shown that the 2D approach provides more fingerprints for further investigations than the 1D approach. Moreover, it is also clear that the 2D approach is better suited for identification of individual chemical species contained in a given mixture, due to the simpler patterns of mass spectra obtained from the 2D analytical mode than from the 1D one. However, with the constituents of the essential oil derived from Salvia lavandulifolia, a straightforward identification was not possible, basically due to numerous groups of isomers among the terpenes and terpenoids contained in the examined sample that have the same molecular weights and hence, can give identical m/z signals.

Simple mass relations for bulk fermions

Relations between bulk mass parameters for fermions propagating in higher dimensions are studied in analogy with the empirical mass relation for charged leptons. Masses of three generation of four-dimensional charged leptons are achieved from the bulk mass parameters of the same-order values. We find that the observed pattern of charged-lepton mass spectrum is accommodated approximately in a set of simple relations for bulk and physical masses.

Investigation of Biochemical and Genetic Variations in Rapid and Slow Growing Mycobacterium avium subspecies paratuberculosis strains

BackgroundCrohn's disease is a chronic inflammatory disease of the intestinal wall in humans, with unknown etiology. Mycobacterium avium subspecies paratuberculosis (MAP) is an organism that causes paratuberculosis (or Johnes disease) in cattle and other ruminants and one purported to have a causal link with Crohn's disease in humans. Previous works have shown that the growth rates for MAP are slow, with generation times of more than 24 hours.AimThe purpose of this study was to examine for associations between the biochemical and genetic variability of MAP strains and their growth rate and presence of symptom in the source cattle. Additionally, to obtain insights into the pathogenic mechanisms involving MAP in Crohn's disease, we compared the phenotypic and genotypic characteristics of MAP strains isolated from Crohn's disease patients with those from cattle with Johnes disease.MethodsMass spectrometry and pulse field gel electrophoresis (PFGE) of 118 culture‐positive MAP isolates and three human strains of MAP (ATCC 43015, 43544, 49164) were performed. MAP isolates were classified as slow growers if they grew in &gt; 2 weeks and rapid growers if they grew in ≤ 2 weeks. Epi Info version 3.5.1 was used to analyze for associations between the biochemical and genetic variability of MAP strains and their growth rate or presence of symptoms in source cattle using Chi‐square and logistic regression.ResultsDifferent mass spectra patterns were detected and categorized in two groups: [M1 (short carbon chain lengths) and M2 (long carbon chain lengths)]. We observed PFGE patterns that were unique for each group [rapid growers (P1 and P2) and slow growers (P3–P7)], and also identified some PFGE profiles (P7 and P8) that were shared by both groups. A significant difference (P&lt; 0.05) was observed between growth rate and symptom manifestation with 82.7 % of rapid growers having symptoms in source cattle compared to only 30.3 % of slow growers. Also, univariate logistic regression showed a significant association between growth rate and presence of symptoms in source cattle (OR=11.0, 95% CI= 4.5, 26.8; p &lt;0.0001), as well as between growth rate and presence of long chain length mycolic acid (M2) (OR= 4.4, 95% CI= 2.0, 9.8; p = 0.0002). Comparison of PFGE profiles of bovine MAP isolates with those of humans revealed similarities in their profiles. The human (ATCC 43015 and 43544) isolates possessed the PG8 cattle profile, while the other human isolate (ATCC 43015) possessed PG6 cattle profile.ConclusionData from this study provided an insight into the genetic and biochemical diversity among rapid and slow growing MAP strains and associations with manifestation of symptoms in source cattle. The similarities in PFGE profiles between bovine and human MAP isolates could possibly explain the theory of strain sharing, intra‐species and interspecies transmission, which may further support an association between johnne's disease and Crohn's disease. The association between growth rate of MAP strains and presence of symptoms in source cattle, or between growth rate and lipid profiles provided a better understanding of the differences in disease progression and pathogenicity of MAP isolates. This study provides useful data in future management of animal farmingoperations and possibly in future design of diagnostics and therapeutics for both johnne's disease and Crohn's disease.

Highly time-resolved chemical characterization of atmospheric submicron particles during 2008 Beijing Olympic Games using an Aerodyne High-Resolution Aerosol Mass Spectrometer

Abstract. As part of Campaigns of Air Quality Research in Beijing and Surrounding Region-2008 (CAREBeijing-2008), an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed in urban Beijing to characterize submicron aerosol particles during the time of 2008 Beijing Olympic Games and Paralympic Games (24 July to 20 September 2008). The campaign mean PM1 mass concentration was 63.1 ± 39.8 μg m−3; the mean composition consisted of organics (37.9%), sulfate (26.7%), ammonium (15.9%), nitrate (15.8%), black carbon (3.1%), and chloride (0.87%). The average size distributions of the species (except BC) were all dominated by an accumulation mode peaking at about 600 nm in vacuum aerodynamic diameter, and organics was characterized by an additional smaller mode extending below 100 nm. Positive Matrix Factorization (PMF) analysis of the high resolution organic mass spectral dataset differentiated the organic aerosol into four components, i.e., hydrocarbon-like (HOA), cooking-related (COA), and two oxygenated organic aerosols (OOA-1 and OOA-2), which on average accounted for 18.1, 24.4, 33.7 and 23.7% of the total organic mass, respectively. The HOA was identified to be closely associated with primary combustion sources, while the COA mass spectrum and diurnal pattern showed similar characteristics to that measured for cooking emissions. The OOA components correspond to aged secondary organic aerosol. Although the two OOA components have similar elemental (O/C, H/C) compositions, they display differences in mass spectra and time series which appear to correlate with the different source regions sampled during the campaign. Back trajectory clustering analysis indicated that the southerly air flows were associated with the highest PM1 pollution during the campaign. Aerosol particles in southern airmasses were especially rich in inorganic and oxidized organic species. Aerosol particles in northern airmasses contained a large fraction of primary HOA and COA species, probably due to stronger influences from local emissions. The lowest concentration levels for all major species were obtained during the Olympic game days (8 to 24 August 2008), possibly due to the effects of both strict emission controls and favorable meteorological conditions.

Mass spectrometric identification of double bond positional isomers of hexadecenyl acetate without chemical derivatization

A method for the identification of the double bond positional isomers of hexadecenyl acetate has been established by analysing similarity of the mass spectra patterns on a fuzzy classification, in which the intensity ratios of six diagnostic pairs of the predominant ions were selected as standard parameters for the characterization of the double bond position. The procedure was tested with λ2 to λ15-isomers of chemically unmodified hexadecenyl acetate, and the original double bond position in the acetates was located unambiguously.

Proteomic analysis of the G-layer in poplar tension wood

Angiosperm trees bend their stems by forming tension wood at the upper side of leaning stems. Most tension wood has a cellulose-rich G-layer in the innermost surface of the fiber cell wall. Strong tensile stress is considered to occur in the G-layer. This study undertook to identify the proteins involved in G-layer formation and function through a proteomic analysis of G-layer-localized protein. G-layers of poplar were loosened by sonication and isolated as doughnut-shaped pieces of thinly sliced transverse sections. The proteins, once extracted with urea/detergent solution, were separated by two-dimensional polyacrylamide gel electrophoresis, and 110 spots were subjected to liquid chromatography tandem mass spectrometry (LC/MS/MS). A database search for these spots’ mass spectrum patterns identified 72 proteins. In addition, all peptide digestion mixtures of G-layer proteins were separated by strong cation exchange chromatography and 39 proteins were identified using LC/MS/MS analysis. Proteins involved in wall formation, such as lignin biosynthesis-related protein, xyloglucan endotransglucosylase, and fasciclin-like arabinogalactan protein, were notably detected in the G-layer.

Statistical analysis of fragmentation patterns of electron ionization mass spectra of enolized-trimethylsilylated anabolic androgenic steroids

Anabolic androgenic steroids (AAS) are included in the List of prohibited substances of the World Anti-Doping Agency (WADA) as substances abused to enhance athletic performance. Gas chromatography coupled to mass spectrometry (GC–MS) plays an important role in doping control analyses identifying AAS as their enolized-trimethylsilyl (TMS)-derivatives using the electron ionization (EI) mode. This paper explores the suitability of complementary GC–MS mass spectra and statistical analysis (principal component analysis, PCA and partial least squares-discriminant analysis, PLS-DA) to differentiate AAS as a function of their structural and conformational features expressed by their fragment ions. The results obtained showed that the application of PCA yielded a classification among the AAS molecules which became more apparent after applying PLS-DA to the dataset. The application of PLS-DA yielded a clear separation among the AAS molecules which were, thus, classified as: 1-ene-3-keto, 3-hydroxyl with saturated A-ring, 1-ene-3-hydroxyl, 4-ene-3-keto, 1,4-diene-3-keto and 3-keto with saturated A-ring anabolic steroids. The study of this paper also presents structurally diagnostic fragment ions and dissociation routes providing evidence for the presence of unknown AAS or chemically modified molecules known as designer steroids.

Water plasmas for the revalorisation of heavy oils and cokes from petroleum refining

This work investigates the possibility of using plasmas to treat high boiling point and viscous liquids (HBPVL) and cokes resulting as secondary streams from the refining of oil. For their revalorisation, the use of microwave (MW) induced plasmas of water is proposed, as an alternative to more conventional processes (i.e., catalysis, pyrolysis, combustion, etc.). As a main result, this type of energetic cold plasma facilitates the conversion at room temperature of the heavy aromatic oils and cokes into linear hydrocarbons and synthesis gas, commonly defined as syngas (CO + H2 gas mixture). The exposure of the coke to this plasma also facilitates the removal of the sulfur present in the samples and leads to the formation on their surface of a sort of carbon fibers and rods network and new porous structures. Besides, optical emission measurements have provided direct evidence of the intermediates resulting from the fragmentation of the heavy oils and cokes during their exposure to the water plasma. Furthermore, the analysis of the mass spectra patterns suggests a major easiness to break the aromatic bonds mainly contained in the heavy oils. Therefore, an innovative method for the conversion of low value residues from oil-refining processes is addressed.

A laser desorption–electron impact ionization ion trap mass spectrometer for real-time analysis of single atmospheric particles

A novel aerosol ion trap mass spectrometer combining pulsed IR laser desorption with electron impact (EI) ionization for single particle studies is described. The strengths of this instrument include a two-step desorption and ionization process to minimize matrix effects; electron impact ionization, a universal and well-characterized ionization technique; vaporization and ionization inside the ion trap to improve sensitivity; and an ion trap mass spectrometer for MS n experiments. The instrument has been used for mass spectral identification of laboratory generated pure aerosols in the 600 nm–1.1 μm geometric diameter range of a variety of aromatic and aliphatic compounds, as well as for tandem mass spectrometry studies (up to MS 3) of single caffeine particles. We investigate the effect of various operational parameters on the mass spectrum and fragmentation patterns. The single particle detection limit of the instrument was found to be a 325 nm geometric diameter particle (8.7 × 10 7 molecules or 22 fg) for 2,4-dihydroxybenzoic acid. Lower single particle detection limits are predicted to be attainable by modifying the EI pulse. The use of laser desorption-electron impact (LD-EI) in an ion trap is a promising technique for determining the size and chemical composition of single aerosol particles in real time.

Detection and identification of 20-hydroxyecdysone metabolites in calf urine by liquid chromatography-high resolution or tandem mass spectrometry measurements and establishment of their kinetics of elimination after 20-hydroxyecdysone administration

Ecdysteroids, which are steroid hormones in invertebrates, but are also present in plants, could be potentially used as anabolic agents in food-producing animals because of their growth-promoting properties. In this context, the metabolism of 20-hydroxyecdysone (20E) has been investigated in cattle in order to efficiently control its potential misuse. The analytical procedure involves purification on two solid-phase extraction cartridges (SPE octadecylsilyl and SPE silica) prior to detection based on liquid chromatography coupled to high resolution mass spectrometry in negative electrospray ionization mode (LC-(ESI−)-HRMS). Each new signal appearing on full-scan HRMS (30,000) during the analysis was investigated by tandem mass spectrometry (MS/MS). Comparison of the mass spectra pattern between 20E and potential metabolites has given informations on the chemical structures of the metabolites. This targeted approach, combining HRMS and MS n measurements on a linear trap in tandem with an orbital trap, allowed us to elucidate the structure of several 20E metabolites in calf urine: 14-deoxy-20-hydroxyecdysone, 20,26-dihydroxyecdysone and 14-deoxy-20,26-dihydroxyecdysone, the last of which had never previously been reported in bovine. The kinetics of elimination of these metabolites were investigated, and two of them were monitored by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) measurements over 6 days after 20E administration to calves, thus increasing the time-window for detection after 20E administration and thereby allowing for more efficient control of its misuse.

TeV-SCALE TYPE-II SEESAW MODELS AND POSSIBLE COLLIDER SIGNATURES

A natural extension of the standard model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a 6×6 neutrino mass matrix. We show that three light Majorana neutrinos (i.e., the mass eigenstates of νe, νμ and ντ) are exactly massless, if and only if [Formula: see text] exactly holds in this seesaw model. We propose three simple Type-II seesaw scenarios with broken A4 × U(1)x flavor symmetry to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the 3 × 3 neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.

Mass Spectrometry Studies of 60 kDa Proteins Extracted from Calcium Oxalate Stones

We extracted proteins with a molecular weight of 60 kDa from human renal calcium oxalate stones. One-dimensional electrophoresis (SDS-polyacrylamide gel electrophoresis) with Coomassie blue stain was used for molecules separation. After in-gel digestion by trypsin, protein samples were analyzed using Nanospray liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer. Peptide sequence analysis was performed by MASCOT Web searching and National Center for Biotechnology Information database comparison. Our results revealed that the matrix possess only 2.5% of stones in weights. Three most abundant 60 kDa proteins named myeloperoxidase, lactoferrin, and albumin were identified. Because albumin has been previously studied by many researchers including our team, we are highly interested to study the remaining two proteins. Later, their in vitro activities of crystallization were studied by employing methods such as nucleation, crystal growth, and aggregation. The mass spectra pattern of myeloper-oxidase and lactotransferrin precursor (lactoferrin) revealed modifications and deamidations, and their calcium oxalate stones crystallization studies revealed no effects on the nucleation, crystal growth, and aggregation. The mass spectra pattern of albumin indicated no amino acid modifications. In conclusion, we found three commonly seen 60 kDa proteins (albumin, myeloperoxidase and lactoferrin) in calcium oxalate stones in this study. Albumin has been tested before and has effect on stone formation. However, purchased myeloperoxidase and lactoferrin have no effect in the crystallization process; their role play in the process of stone formation should be further elucidated.

Analysis of carbonyl compounds via headspace solid-phase microextraction with on-fiber derivatization and gas chromatographic–ion trap tandem mass spectrometric determination of their O-(2,3,4,5,6-pentafluorobenzyl)oxime derivatives

An improved method for the analysis of carbonyls is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Thermal desorption of the oxime derivatives formed on the fiber is followed by gas chromatographic separation coupled to an ion trap tandem mass spectrometer (GC–ITMS). Selecting specific fragment ions within the electron ionization (EI +) mass spectra of these oxime derivatives as precursor ions for MS–MS fragmentation provides a suitable method for the target analysis of individual carbonyl classes, such as alkanals, ( E)-2-alkenals, ( E, E)-2,4-alkadienals, and others. Retention indices on polar as well as on apolar stationary phases along with EI + mass spectra patterns are presented for a large set of oxime derivatives, giving valuable information needed for unambiguous assignment of substances in complex sample matrices. The fast sample preparation and derivatization step via HS-SPME can be automated and is applicable to a variety of biological samples and foodstuffs, allowing rapid and sensitive screening analyses of important aldehydic biomarkers and aroma active compounds.

Highly Efficient Classification and Identification of Human Pathogenic Bacteria by MALDI-TOF MS

Accurate and rapid identification of pathogenic microorganisms is of critical importance in disease treatment and public health. Conventional work flows are time-consuming, and procedures are multifaceted. MS can be an alternative but is limited by low efficiency for amino acid sequencing as well as low reproducibility for spectrum fingerprinting. We systematically analyzed the feasibility of applying MS for rapid and accurate bacterial identification. Directly applying bacterial colonies without further protein extraction to MALDI-TOF MS analysis revealed rich peak contents and high reproducibility. The MS spectra derived from 57 isolates comprising six human pathogenic bacterial species were analyzed using both unsupervised hierarchical clustering and supervised model construction via the Genetic Algorithm. Hierarchical clustering analysis categorized the spectra into six groups precisely corresponding to the six bacterial species. Precise classification was also maintained in an independently prepared set of bacteria even when the numbers of m/z values were reduced to six. In parallel, classification models were constructed via Genetic Algorithm analysis. A model containing 18 m/z values accurately classified independently prepared bacteria and identified those species originally not used for model construction. Moreover bacteria fewer than 10(4) cells and different species in bacterial mixtures were identified using the classification model approach. In conclusion, the application of MALDI-TOF MS in combination with a suitable model construction provides a highly accurate method for bacterial classification and identification. The approach can identify bacteria with low abundance even in mixed flora, suggesting that a rapid and accurate bacterial identification using MS techniques even before culture can be attained in the near future.

Compromise between neutrino masses and collider signatures in the type-II seesaw model

A natural extension of the standard $\mathrm{SU}(2{)}_{\mathrm{L}}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{\mathrm{Y}}$ gauge model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a $6\ifmmode\times\else\texttimes\fi{}6$ neutrino mass matrix which contains three $3\ifmmode\times\else\texttimes\fi{}3$ submatrices, ${M}_{\mathrm{L}}$, ${M}_{\mathrm{D}}$ and ${M}_{\mathrm{R}}$. We show that three light Majorana neutrinos (i.e., the mass eigenstates of ${\ensuremath{\nu}}_{e}$, ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, and ${\ensuremath{\nu}}_{\ensuremath{\tau}}$) are exactly massless in this model, if and only if ${M}_{\mathrm{L}}={M}_{\mathrm{D}}{M}_{\mathrm{R}}^{\ensuremath{-}1}{M}_{\mathrm{D}}^{T}$ exactly holds. This no-go theorem implies that small but nonvanishing neutrino masses may result from a significant but incomplete cancellation between ${M}_{\mathrm{L}}$ and ${M}_{\mathrm{D}}{M}_{\mathrm{R}}^{\ensuremath{-}1}{M}_{\mathrm{D}}^{T}$ terms in the Type-II seesaw formula, provided three right-handed Majorana neutrinos are of $\mathcal{O}(1)\text{ }\text{ }\mathrm{TeV}$ and experimentally detectable at the LHC. We propose three simple Type-II seesaw scenarios with the ${A}_{4}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{\mathrm{X}}$ flavor symmetry and its explicit breaking to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the $3\ifmmode\times\else\texttimes\fi{}3$ neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.

Sex attractant pheromone of the limabean pod borer, Etiella zinckenella (Treitschke) (Lepidoptera: Pyralidae), in Japan

Four compounds, tetradecyl acetate (14:OAc), (Z)-9-tetradecenyl acetate (Z9-14:OAc), (E)-11-tetradecenyl acetate (E11-14:OAc), and (Z)-11-tetradecenyl acetate (Z11-14:OAc), have been identified in extracts of female pheromone glands of the limabean pod borer, Etiella zinckenella. A mixture of these four components successfully attracted a number of conspecific males in both Hungary and Egypt. Unfortunately, the mixture attracted only a few males, and the attractiveness was not equivalent to that of virgin females in soybean fields in Japan. We therefore analyzed the pheromone gland extract from Japanese E. zinckenella females by using gas chromatography-mass spectrometry. In addition to the four compounds previously identified, we found a dodecenyl acetate. The mass spectrum pattern and retention indices of the acetate coincided well with those of authentic (E)-9-dodecenyl acetate (E9-12:OAc). The attractiveness of the five-component mixture containing E9-12:OAc to male moths was significantly increased and equivalent to that of virgin females in field trapping tests. The numbers of males attracted did not significantly decrease when 14:OAc and E11-14:OAc were removed from the mixture, whereas almost no males were attracted when Z9-14:OAc, Z11-14:OAc, or E9-12:OAc was deleted. The results suggest that Z9-14:OAc, Z11-14:OAc, and E9-12:OAc are essential components of the sex attractant pheromone of E. zinckenella in Japan.

Detection of components in nanoparticles by resonant ionisation and laser breakdown time-of-flight mass spectrometry

Environmental context. The monitoring of aerosol nanoparticles in the atmosphere is a ‘hot’ topic in environmental management. Such particles in the atmosphere are produced by the combustion of fossil fuels such as in engines. Although they make up only a small percentage of particle total mass, nanosized particles account for more than 90% of the particle number in diesel engine exhaust, and their harmful influences on human health are a serious issue. The system developed in this study has great potential to clarify the origin and behaviour of these aerosol particles more precisely using its online characteristics. Abstract. Resonance ionisation and laser breakdown time-of-flight mass spectrometry (TOFMS) with particle size selectivity using a differential mobility analyser (DMA) was developed and applied to detect components in nanoparticles. The resonance ionisation and laser breakdown TOFMS method was demonstrated to have a sensitivity of ng m–3, and was shown to be applicable to nanoparticles using a newly developed standard nanoparticle generator. The developed system was successfully applied to 4-stroke diesel engine exhaust gas to show the mass spectrum patterns measured in 30 and 80-nm particles. The measured spectrum intensities were evaluated to calculate the concentration of organic compounds in nanoparticles, and these values were compared with low-pressure impactor measurement results. The two measurements showed concentrations with the same order of magnitude and the validity of the newly developed TOFMS method was examined using the nanoparticles in the actual diesel gas exhaust.

Energy-Dependent Kinetic Method: Application to the Multicompetitive Fragmentation Pathways of Protonated Peptides

A variation of the kinetic method for the analysis of fragmentation patterns in mass spectra is proposed. The procedure presents three notable features: no evaluation of the effective temperature of the parent ion is required; the ratio of the activation energies for all competitive channels at play are provided; and the measurement is not biased by the mass discrimination of the instrument. The method is based on the analysis of mass spectra recorded as a function of both the excitation energy and the excitation time. Collision-activated dissociation of protonated Leu-enkephalin achieved in a quadrupolar ion trap and analyzed with this method is presented.

Lipid Profiling by Multiple Precursor and Neutral Loss Scanning Driven by the Data-Dependent Acquisition

Data-dependent acquisition of MS/MS spectra from lipid precursors enables to emulate the simultaneous acquisition of an unlimited number of precursor and neutral loss scans in a single analysis. This approach takes full advantage of rich fragment patterns in tandem mass spectra of lipids and enables their profiling by complex (Boolean) scans, in which masses of several fragment ions are considered within a single logical framework. No separation of lipids is required, and the accuracy of identification and quantification is not compromised, compared to conventional precursor and neutral loss scanning.