Mass spectral similarity mapping applied to fentanyl analogs.

This manuscript outlines a straight-forward procedure for generating a map of similarity between spectra of a set. When applied to a reference set of spectra for Type I fentanyl analogs (molecules differing from fentanyl by a single modification), the map illuminates clustering that is applicable to automated structure assignment of unidentified molecules. An open-source software implementation that generates mass spectral similarity mappings of unknowns against a library of Type I fentanyl analog spectra is available at http://github.com/asm3-nist/FentanylClassifier.

Intermetallic Compounds of the Type MNi5 as Methanation Catalysts.

Catalytic reactions of carbon monoxide with hydrogen have been studied in which intermetallic compounds of the formula MNi(5) (where M is thorium, uranium, or zirconium) have been used as the catalysts. The materials perform effectively as methanation catalysts; ThNi(5) has a specific activity exceeding that of a typical commercial oxide-supported methanation catalyst by a factor of about 5. This material also shows superior resistance to hydrogen sulfide poisoning. Nickel, formed as a decomposition product of the MNi(5) intermetallic compound, is probably the active species, but its properties are influenced by the nature of M in the precursor MNi(5) system.

Quantitative measurement of the polydispersity in the extent of functionalization of glass-forming calix[4]resorcinarenes.

The polydispersity in the degree of functionalization for two calix[4]resorcinarenes was determined by measuring quantitatively their molecular mass distribution with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. A mathematical method for polydisperse materials is described that creates a calibration curve to correct the ion signal intensities in the mass spectrum to give a more reliable molecular mass distribution. Correction is required due to various sample preparation and instrumental effects that may produce a systematic mass bias in the number of oligomers measured. This method employs gravimetric mixtures of analytes with different degrees of functionalization. One calix[4]resorcinarene was found to give accurate molecular mass distributions with little correction, while another, having a very similar molecular structure, was found to exhibit strong over-counting of the oligomers having a high degree of functionalization.

Laser desorption ionization and MALDI time-of-flight mass spectrometry for low molecular mass polyethylene analysis.

Polyethylene's inert nature and difficulty to dissolve in conventional solvents at room temperature present special problems for sample preparation and ionization in mass spectrometric analysis. We present a study of ionization behavior of several polyethylene samples with molecular masses up to 4000 Da in laser desorption ionization (LDI) time-of-flight mass spectrometers equipped with a 337 nm laser beam. We demonstrate unequivocally that silver or copper ion attachment to saturated polyethylene can occur in the gas phase during the UV LDI process. In LDI spectra of polyethylene with molecular masses above approximately 1000 Da, low mass ions corresponding to metal-alkene structures are observed in addition to the principal distribution. By interrogating a well-characterized polyethylene sample and a long chain alkane, C94H190, these low mass ions are determined to be the fragmentation products of the intact metal-polyethylene adduct ions. It is further illustrated that fragmentation can be reduced by adding matrix molecules to the sample preparation.

Exogenous lipoid pneumonia due to nasal application of petroleum jelly.

We describe a patient who presented with a history of unexplained exertional dyspnea and pulmonary infiltrates. She was evaluated for interstitial lung disease, presumed to be idiopathic and underwent an open lung biopsy. The pathologic findings were compatible with exogenous lipoid pneumonia and her history revealed longstanding use of intranasal petroleum jelly (Vaseline) at bedtime.

Phospholipid surfactant adsorption by respirable quartz and in vitro expression of cytotoxicity and DNA damage.

Respirable-sized quartz was treated with a saline dispersion of dipalmitoyl phosphatidylcholine (DPPC), a primary component of pulmonary surfactant, to model the adsorption of phospholipid surfactant onto quartz dust following particle deposition in the bronchoalveolar region of the lung. Control and surfactant-treated dusts were used to challenge lavaged rat pulmonary macrophages in vitro over a 1-week period, to determine the effects of adsorbed surfactant on the expression of quartz cytotoxicity and genotoxicity. DNA damage was determined by the single cell gel electrophoresis 'comet' assay. Untreated quartz induced DNA damage, increasing with dose and with time of incubation of dust with macrophages over a 5 day period. DPPC treatment of quartz suppressed DNA damage through 1 day of macrophage challenge. DNA damage then increased over a 5 day period, to approximately half the positive control (untreated quartz) values. Cytotoxicity was measured by trypan blue dye exclusion and by the Live-Dead fluorescence assay for cell viability. Cytotoxicity of surfactant-treated quartz measured one day after challenge of lavaged macrophages was suppressed to values near those of the negative controls, and then increased over a 1 week incubation period to levels near those expressed by native quartz positive controls. Quartz similarly treated with dioleoyl phosphatidylcholine mixed with DPPC substituted in one acyl group with a boron-containing fluorescent chromophore was used with confocal microscopy to measure particle-associated fluorescent surfactant in cells. Approximately half of the fluorescence intensity was lost over a 1 week period following challenge of lavaged macrophage. Results are discussed in terms of a model of restoration of quartz particle surface toxicity as prophylactic surfactant is removed from particle surface by cellular enzymatic digestion processes.

In vitro genotoxicity studies of chrysotile asbestos fibers dispersed in simulated pulmonary surfactant.

Micronucleus (MN) formation and sister-chromatid exchange (SCE) assays were performed for asbestos in cultured Chinese hamster lung (V79) cells to determine the effect of surfactant treatment on the genotoxicity of two chrysotile asbestos samples of different fiber lengths. The cells were challenged in vitro with NIEHS intermediate- and short-length chrysotile fibers in both their native state and with surfactant pretreatment. For the surfactant pretreatment, the fibers were incubated in a simulated pulmonary surfactant which was prepared by ultrasonically dispersing dipalmitoyl lecithin (DPL), a primary component of pulmonary surfactant, in minimal essential medium (MEM). Chrysotile asbestos was ultrasonically mixed into the prepared surfactant dispersion or into MEM. V79 cells were exposed to DPL-treated intermediate-length chrysotile (TICA), intermediate-length chrysotile (ICA), DPL-treated short-length chrysotile (TSCA) or short-length chrysotile (SCA) fibers for 48 h. For each treatment, 2000 mononucleated cells were scored for MN formation, and 30 M2 metaphase cells were scored for SCE induction. The results showed that all samples, TICA, ICA, TSCA and SCA, caused significant elevation in the frequency of cells with micronuclei and of cells with two or more nuclei. The increase in micronucleus frequency was greatest in cells challenged with untreated intermediate-length fibers, and was greater for untreated than for DPL-treated short-length fibers. For the short-length fiber samples, DPL surfactant treatment decreased activity for multiple nucleus formation, while DPL treatment did not result in consistent changes in that activity for intermediate-length fibers. Results of SCE assays were either negative or inconclusive. Cells were more viable following TICA and TSCA than following ICA and SCA challenge as measured by cell counts after 48 h of incubation.

Micronucleus formation in V79 cells treated with respirable silica dispersed in medium and in simulated pulmonary surfactant.

Chinese hamster lung fibroblasts (V79 cells) were challenged with respirable silica particles using an in vitro genotoxicity assay. Two particle sizes of crystalline quartz and a non-crystalline silica were assayed for induction of micronuclei (MN) in V79 cells. Some of the silica dusts used were pretreated with simulated pulmonary surfactant to model in vivo exposure conditions. The results showed that both crystalline and non-crystalline silica dispersed in medium (MEM) induced MN formation in a dose-dependent manner. Crystalline silica was more active in this assay than non-crystalline silica on a mass basis. The results also show that the frequency of micronucleated cells in cultures treated with surfactant-coated silica was not significantly different from that of the non-treated control cultures. These results seem to indicate that silica can cause chromosomal aberrations and/or aneuploidies in V79 cells; however, pretreatment of silica particles with simulated pulmonary surfactant reduces or delays genotoxicity in this assay.

Genotoxicity of diesel-exhaust particles dispersed in simulated pulmonary surfactant.

Diesel-exhaust particles from two sources were dispersed in aqueous mixtures of dipalmitoyl phosphatidyl choline, a major component of pulmonary surfactant, and were tested for genotoxicity. Diesel samples from the same sources were extracted with dichloromethane and transferred into dimethyl sulfoxide and subjected to the same assays. Both types of extractions yielded similar results in both the Salmonella mutagenicity assay and the sister-chromatid exchange assay using V79 cells. After separation of the samples into supernatant and sediment fractions, the activity of both diesel samples was shown to reside exclusively in the supernatant fraction for the solvent-extracted samples, and exclusively in the sedimented fraction for surfactant dispersed samples. These findings indicate that genotoxic activity associated with diesel particles inhaled into the lung may be made bioavailable by virtue of the solubilization/dispersion properties of pulmonary surfactant components.

Induction of micronuclei in BALB/c-3T3 cells by selected chemicals and complex mixtures.

The genotoxicity of benzo[a]pyrene, cyclophosphamide, 2-aminoanthracene, 2-nitrofluorene, nitrosated coal-dust extracts, and cigarette-smoke condensate were tested with the micronucleus assay using an established mammalian cell line. The results showed that all chemicals and complex mixtures studied induced micronuclei in BALB/c-3T3 cells. These results indicate that BALB/c-3T3 cells are capable of activating certain promutagens and procarcinogens. It seems, therefore, that in addition to cell transformation, the micronucleus assay in BALB/c-3T3 cells without an exogenous activation system may be useful for in vitro studies to detect genotoxic chemicals and complex mixtures.

Genotoxicity of vanadium pentoxide in Chinese hamster V79 cells.

Workers in many mining and manufacturing industries are potentially exposed to vanadium. Inhalation of dust containing vanadium pentoxide (V2O5), a pentavalent compound of vanadium, has been reported to cause lung diseases. Information related to the genotoxicity and potential carcinogenicity of V2O5, however, is still limited. In this study, the effect of V2O5 on mitosis, sister-chromatid exchange (SCE), micronucleus formation (MN), and gene mutation in Chinese hamster V79 cells was determined. Cells were treated with varying concentrations of V2O5 for 24 h. The results showed that no significant increases in the frequencies of SCE or gene mutation occurred in V2O5-treated cultures. However, dose-related increases were noted for micronucleated cells in cultures exposed to this compound, and the number of binucleated cells in the presence of cytochalasin B was found to decrease with increasing V2O5 concentrations. Since the micronucleated cells induced by V2O5 contained kinetochore-positive micronuclei, their induction appears to be due to damage to the spindle apparatus. These results indicate that V2O5 is cytotoxic and aneuploidogenic to V79 cells.

Micronucleus induction and phagocytosis in mammalian cells treated with diesel emission particles.

Micronucleus induction and phagocytosis in V79 and CHO cells treated with diesel emission particles (DEP) were studied. After separation of the sample into supernatant and sediment fractions, the genotoxic activity of DEP was shown to reside in the supernatant fraction for the DMSO-extracted sample, and in the sedimented fraction for the dipalmitoyl lecithin (DPL), a primary component of pulmonary surfactant, dispersed sample. More particles from DMSO sediment samples were phagocytized than DPL sediment by both types of cells. This had no effect, however, on micronucleus induction. CHO cells phagocytized fewer particles, but gave a higher number of micronuclei than V79 cells. CHO cells seem to be more sensitive to DEP. Evidently, micronucleus induction is not the result of phagocytosis per se, but is due to the different response of the indicator cells to the DEP sample tested. These results further indicate that most, if not all, genotoxic compounds associated with DEP can be extracted by DMSO and that genotoxic activity associated with DEP inhaled into the lung may also be expressed by dispersion of particles in pulmonary surfactant.

Effects of simulated pulmonary surfactant on the cytotoxicity and DNA-damaging activity of respirable quartz and kaolin.

Respirable-sized quartz and kaolin dusts were pretreated with simulated pulmonary surfactant dispersions of dipalmitoyl phosphatidylcholine (DPPC) in saline to model the conditioning of particles depositing in alveolar regions of the lung. DPPC-treated and untreated dusts were used to challenge lavaged rat pulmonary alveolar macrophages in vitro. Cytotoxicity was determined over a 5-d period using both total and viable cell counts from a fluorescence-based viability assay. DNA damage, as an indication of genotoxicity, was determined over a 7-d period by the single-cell gel electrophoresis assay. Untreated quartz and kaolin both expressed a significant and potent cytotoxicity, which increased with concentration and time. DPPC-surfactant pretreatment delayed significant expression of this cytotoxicity until 3 to 5 d after challenge. Untreated quartz also caused DNA damage, which increased with concentration and time. DPPC-surfactant treatment of quartz delayed most DNA damage expression to 5 and 7 d. Untreated kaolin expressed weaker activity for DNA damage, significant at the highest concentration through 5 d, and at the higher concentrations on d 7. Surfactant treatment delayed most kaolin activity for DNA damage to 7 d after challenge.

A study of the effect of chrysotile fiber surface composition on genotoxicity in vitro.

Chrysotile fibers (NIEHS intermediate length) were treated with ultrapure HCl to alter the fiber surface chemistry without substantially changing fiber morphology or dimensions. The objective of the study was to determine whether fiber surface chemistry is an important variable in fiber genotoxicity in vitro. The modified fibers, along with native chrysotile fibers, were used to challenge Chinese hamster lung fibroblasts (V79) in vitro using the micronucleus induction genotoxicity assay. Fiber dimensions were assessed using scanning electron microscopy by measuring the distribution of fiber lengths in 3 length ranges: less than 3 microm, 3-10 microm, and greater than 10 microm. For both treated and native fiber samples, 500 fibers were examined. Results indicate that acid-treated fibers were about 20% shorter than untreated chrysotile. Surface chemistry alterations were verified by zeta-potential reversal, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM-EDS) elemental analysis. Scanning Auger spectrometry indicated the presence of Mg, O, and Si in both treated and native chrysotile samples, which confirmed the surface purity of both fiber samples. Both XPS and SEM-EDS analysis demonstrated substantial depletion of Mg from fiber surfaces. Results of the micronucleus assay showed a positive concentration-related response for both samples, with toxicity evident only at the highest concentration. No significant difference was found for the treated and untreated chrysotile samples. These results indicate that the surface chemistry is not an important variable in the in vitro genotoxicity of chrysotile asbestos in V79 cells as detected by the micronucleus assay under the conditions used in this study, and support a model of chemically nonspecific chromosomal and spindle damage effects.

Monte Carlo analysis of the detection of clay occlusion of respirable quartz particles using multiple voltage scanning electron microscopy.

The electron incident-energy dependence of the relative intensities of Al and Si x-rays produced in a respirable-sized quartz particle by scanning electron microscopy is sensitive to the inhomogeneity of the distribution of Al and Si in the particle. Realistic Monte Carlo calculations of this energy dependence validate the proposal to use this effect for the detection of particles in which an aluminosilicate coating occludes the surface of a silica core.

Pairwise alignment of chromatograms using an extended Fisher-Rao metric.

A conceptually new approach for aligning chromatograms is introduced and applied to examples of metabolite identification in human blood plasma by liquid chromatography-mass spectrometry (LC-MS). A square-root representation of the chromatogram's derivative coupled with an extended Fisher-Rao metric enables the computation of relative differences between chromatograms. Minimization of these differences using a common dynamic programming algorithm brings the chromatograms into alignment. Application to a complex sample, National Institute of Standards and Technology (NIST) Standard Reference Material 1950, Metabolites in Human Plasma, analyzed by two different LC-MS methods having significantly different ranges of elution time is described.

A general method for quantitative measurement of molecular mass distribution by mass spectrometry.

A method is presented to test whether the conversion of the mass spectrum of a polydisperse analyte to its molecular mass distribution is quantitative. Mixtures of samples with different average molecular masses, coupled with a Taylor's expansion mathematical formalism, were used to ascertain the reliability of molecular mass distributions derived from mass spectra. Additionally, the method describes how the molecular mass distributions may be corrected if the degree of mass bias is within certain defined limits. This method was demonstrated on polydisperse samples of C(60) fullerenes functionalized with ethylpyrrolidine groups measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; however, it is applicable to any polydisperse analyte and mass spectrometric method as long as spectrum resolution allows individual oligomers to be identified. Mass spectra of the derivatized fullerenes taken in positive ion mode were shown to give an accurate measurement of the molecular mass distribution while those taken in negative ion mode were not. Differences in the mechanisms for ion formation are used to explain the discrepancy. Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States of America.

Numerical optimization of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: application to synthetic polymer molecular mass distribution measurement.

A novel approach is described for the selection of optimal instrument parameters that yield a mass spectrum which best replicates the molecular mass distribution of a synthetic polymer. The application of implicit filtering algorithms is shown to be a viable method to find the best instrument settings while simultaneously minimizing the total number of experiments that need to be performed. This includes considerations of when to halt the iterative optimization process at a point when statistically-significant gains can no longer be expected. An algorithm to determine the confidence intervals for each parameter is also given. Details on sample preparation and data analysis that ensure stability of the measurement over the time scale of the optimization experiments are provided. This work represents part of an effort to develop an absolute molecular mass distribution polymer Standard Reference Material.