Bibliografie tematiche / Molecular beam mass spectrometry

Letteratura scientifica selezionata sul tema "Molecular beam mass spectrometry"

Autore: Grafiati

Pubblicato: 8 giugno 2024

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Articoli di riviste sul tema "Molecular beam mass spectrometry":

Grieser, Manfred, Viviane C. Schmidt, Klaus Blaum, Florian Grussie, Robert von Hahn, Ábel Kálosi, Holger Kreckel et al. "Isochronous mass spectrometry in an electrostatic storage ring". Review of Scientific Instruments 93, n. 6 (1 giugno 2022): 063302. http://dx.doi.org/10.1063/5.0090131.

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For sensitive studies of molecular ions in electrostatic storage rings, the exact knowledge of the isobaric composition of stored beams from a variety of ion sources is essential. Conventional mass-filtering techniques are often inefficient to resolve the beam components. Here, we report the first isochronous mass spectrometry in an electrostatic storage ring, which offers a high mass resolution of Δ m/ m < 1 × 10−5 even for heavy molecular species with m > 100 u and uncooled ion beams. Mass contaminations can be resolved and identified at relative fractions down to 0.02%.

KASPER, T., P. OSWALD, M. KAMPHUS e K. KOHSEHOINGHAUS. "Ethanol flame structure investigated by molecular beam mass spectrometry". Combustion and Flame 150, n. 3 (agosto 2007): 220–31. http://dx.doi.org/10.1016/j.combustflame.2006.12.022.

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Fárník, Michal, e Jozef Lengyel. "Mass spectrometry of aerosol particle analogues in molecular beam experiments". Mass Spectrometry Reviews 37, n. 5 (27 novembre 2017): 630–51. http://dx.doi.org/10.1002/mas.21554.

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Korobeinichev, Oleg P., Leonid V. Kuibida, Alexander A. Paletsky e Andrey G. Shmakov. "Molecular-Beam Mass-Spectrometry to Ammonium Dinitramide Combustion Chemistry Studies". Journal of Propulsion and Power 14, n. 6 (novembre 1998): 991–1000. http://dx.doi.org/10.2514/2.5364.

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Aranda Gonzalvo, Y., T. D. Whitmore, J. A. Rees, D. L. Seymour e E. Stoffels. "Atmospheric pressure plasma analysis by modulated molecular beam mass spectrometry". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 24, n. 3 (maggio 2006): 550–53. http://dx.doi.org/10.1116/1.2194938.

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Dantus, M., M. H. M. Janssen e A. H. Zewail. "Femtosecond probing of molecular dynamics by mass-spectrometry in a molecular beam". Chemical Physics Letters 181, n. 4 (giugno 1991): 281–87. http://dx.doi.org/10.1016/0009-2614(91)80071-5.

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Zavilopulo, A. N., e A. I. Dolgin. "Mass-spectrometry of cluster molecular beams". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 126, n. 1-4 (aprile 1997): 305–9. http://dx.doi.org/10.1016/s0168-583x(97)01104-x.

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Hsu, Wen L., Mark C. McMaster, Michael E. Coltrin e David S. Dandy. "Molecular Beam Mass Spectrometry Studies of Chemical Vapor Deposition of Diamond". Japanese Journal of Applied Physics 33, Part 1, No. 4B (30 aprile 1994): 2231–39. http://dx.doi.org/10.1143/jjap.33.2231.

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Balooch, M., D. R. Olander, W. J. Siekhaus e D. E. Miller. "Reaction of chlorine and molybdenum by modulated molecular beam mass spectrometry". Surface Science Letters 249, n. 1-3 (giugno 1991): A270. http://dx.doi.org/10.1016/0167-2584(91)90149-l.

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Balooch, M., D. R. Olander, W. J. Siekhaus e D. E. Miller. "Reaction of chlorine and molybdenum by modulated molecular beam mass spectrometry". Surface Science 249, n. 1-3 (giugno 1991): 322–34. http://dx.doi.org/10.1016/0039-6028(91)90856-n.

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Tesi sul tema "Molecular beam mass spectrometry":

Secco, Andrea. "Use of the molecular beam mass spectrometry to study the low-temperature combustion chemistry". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14506/.

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With the aim to reduce the global pollution caused by the increasing levels of NOx, CO and CO2 emitted by internal combustion engines, the study of low-temperature chemistry (LTC) of the combustion process has been greatly enhanced. The goal of this thesis work is to evaluate the performances of the time-of-flight Molecular Beam Mass Spectrometry (TOF-MBMS) in the analysis of the oxidation of propane at low temperature with strong interest in the detection of fleeting species to verify the low-temperature oxidation mechanism. To do that we performed two different experiments: propane oxidation in jet stirred reactor and ozone activated cool diffusion flame in a counterflow setup. The first was carried out flowing a mixture of C3H8/O2/Ar with molar fraction 2/13/85%, respectively, corresponding to a equals to 0.77, in the temperature range 750-1100 K and residence time τ=1 s. To support the results obtained from MBMS, we analyzed the propane oxidation in the same conditions with the gas chromatograph (GC) technique. The results have been compared with the MBMS ones showing good agreement for most of the analysed species. Numerical simulations of the molar fraction of all species were performed and compared with experimental data. The results indicate that the model well predicts the trends of the molar fraction of the species, except for C2H2 and the allyl radical. The onset of the reaction is predicted at a lower temperature than in the experiment. In cool flame experiments the fuel/N2 and O2/O3 streams are facing each other and both propane and n-butane were used as fuel. In propane experiments a 50/50% C3H8/N2 mixture has been used with O2 flow rate of 5 dm3/min, which corresponds to an ozone concentration of 5.94%. For n-butane tests the mixture used was 45/55% for C4H10/N2, O2 flow rate 7 dm3/min and ozone concentration of 5.02%. Numerical analysis was performed showing a good prediction of flame position and species profiles through the reaction zone.

Osaka, J., Senthil M. Kumar, H. Toyoda, T. Ishijima, H. Sugai e T. Mizutani. "Role of atomic nitrogen during GaN growth by plasma-assisted molecular beam epitaxy revealed by appearance mass spectrometry". American Institute of Physics, 2007. http://hdl.handle.net/2237/8775.

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Tsang, Roland S. "Characterisation of the gas-phase environment in a hot filament diamond chemical vapour deposition chamber using molecular beam mass spectrometry". Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389238.

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Leeds, Stuart M. "Characterisation of the gas-phase environment in a microwave plasma enhanced diamond chemical vapour deposition reactor using molecular beam mass spectrometry". Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297978.

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Fox, Oliver James Louis. "Deposition of nanocrystalline diamond films by MW plasma CVD & gas-phase diagnostics using in-situ molecular-beam mass spectrometry and emission spectroscopy". Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544422.

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Crichton, Edward. "Construction of a molecular beam mass spectrometer for in-situ probing of a diamond chemical vapour deposition environment". Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443689.

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Ellerweg, Dirk [Verfasser], Achim von [Gutachter] Keudell e Peter [Gutachter] Awakowicz. "Reaction chemistry in oxygen or hexamethyldisiloxane containing noble gas microplasma jets : a quantitative molecular beam mass spectrometry study / Dirk Ellerweg ; Gutachter: Achim von Keudell, Peter Awakowicz ; Fakultät für Physik und Astronomie". Bochum : Ruhr-Universität Bochum, 2012. http://d-nb.info/1209358409/34.

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Fischer, Andreas [Verfasser], Wolfram [Akademischer Betreuer] Sander e Martina [Akademischer Betreuer] Havenith. "Development of a molecular beam mass spectrometer and a supersonic jet expansion pyrolyzer for the characterization of reactive organic intermediates / Andreas Fischer. Gutachter: Wolfram Sander ; Martina Havenith". Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1089006306/34.

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Moreira, Ana Sofia Pereira. "Study of modifications induced by thermal and oxidative treatment in oligo and polysaccharides of coffee by mass spectrometry". Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17074.

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Abstract (sommario):

Doutoramento em Bioquímica
Os polissacarídeos são os componentes maioritários dos grãos de café verde e torrado e da bebida de café. Os mais abundantes são as galactomananas, seguindo-se as arabinogalactanas. Durante o processo de torra, as galactomananas e arabinogalactanas sofrem modificações estruturais, as quais estão longe de estar completamente elucidadas devido à sua diversidade e à complexidade estrutural dos compostos formados. Durante o processo de torra, as galactomananas e arabinogalactanas reagem com proteínas, ácidos clorogénicos e sacarose, originando compostos castanhos de alto peso molecular contendo nitrogénio, designados de melanoidinas. As melanoidinas do café apresentam diversas atividades biológicas e efeitos benéficos para a saúde. No entanto, a sua estrutura exata e os mecanismos envolvidos na sua formação permanecem desconhecidos, bem como a relação estrutura-atividade biológica. A utilização de sistemas modelo e a análise por espectrometria de massa permitem obter uma visão global e, simultaneamente, detalhada das modificações estruturais nos polissacarídeos do café promovidas pela torra, contribuindo para a elucidação das estruturas e mecanismos de formação das melanoidinas. Com base nesta tese, oligossacarídeos estruturalmente relacionados com a cadeia principal das galactomananas, (β1→4)-Dmanotriose (Man3), e as cadeias laterais das arabinogalactanas, (α1→5)-Larabinotriose (Ara3), isoladamente ou em misturas com ácido 5-Ocafeoilquínico (5-CQA), o ácido clorogénico mais abundante nos grãos de café verde, e péptidos compostos por tirosina e leucina, usados como modelos das proteínas, foram sujeitos a tratamento térmico a seco, mimetizando o processo de torra. A oxidação induzida por radicais hidroxilo (HO•) foi também estudada, uma vez que estes radicais parecem estar envolvidos na modificação dos polissacarídeos durante a torra. A identificação das modificações estruturais induzidas por tratamento térmico e oxidativo dos compostos modelo foi feita por estratégias analíticas baseadas principalmente em espectrometria de massa, mas também em cromatografia líquida. A cromatografia de gás foi usada na análise de açúcares neutros e ligações glicosídicas. Para validar as conclusões obtidas com os compostos modelo, foram também analisadas amostras de polissacarídeos do café obtidas a partir de resíduo de café e café instantâneo. Os resultados obtidos a partir dos oligossacarídeos modelo quando submetidos a tratamento térmico (seco), assim como à oxidação induzida por HO• (em solução), indicam a ocorrência de despolimerização, o que está de acordo com estudos anteriores que reportam a despolimerização das galactomananas e arabinogalactanas do café durante a torra. Foram ainda identificados outros compostos resultantes da quebra do anel de açúcares formados durante o tratamento térmico e oxidativo da Ara3. Por outro lado, o tratamento térmico a seco dos oligossacarídeos modelo (individualmente ou quando misturados) promoveu a formação de oligossacarídeos com um maior grau de polimerização, e também polissacarídeos com novos tipos de ligações glicosídicas, evidenciando a ocorrência de polimerização através reações de transglicosilação não enzimática induzidas por tratamento térmico a seco. As reações de transglicosilação induzidas por tratamento térmico a seco podem ocorrer entre resíduos de açúcares provenientes da mesma origem, mas também de origens diferentes com formação de estruturas híbridas, contendo arabinose e manose como observado nos casos dos compostos modelo usados. Os resultados obtidos a partir de amostras do resíduo de café e de café instantâneo sugerem a presença de polissacarídeos híbridos nestas amostras de café processado, corroborando a ocorrência de transglicosilação durante o processo de torra. Além disso, o estudo de misturas contendo diferentes proporções de cada oligossacarídeo modelo, mimetizando regiões do grão de café com composição distinta em polissacarídeos, sujeitos a diferentes períodos de tratamento térmico, permitiu inferir que diferentes estruturas híbridas e não híbridas podem ser formadas a partir das arabinogalactanas e galactomananas, dependendo da sua distribuição nas paredes celulares do grão e das condições de torra. Estes resultados podem explicar a heterogeneidade de estruturas de melanoidinas formadas durante a torra do café. Os resultados obtidos a partir de misturas modelo contendo um oligossacarídeo (Ara3 ou Man3) e 5-CQA sujeitas a tratamento térmico a seco, assim como de amostras provenientes do resíduo de café, mostraram a formação de compostos híbridos compostos por moléculas de CQA ligadas covalentemente a um número variável de resíduos de açúcar. Além disso, os resultados obtidos a partir da mistura contendo Man3 e 5-CQA mostraram que o CQA atua como catalisador das reações de transglicosilação. Por outro lado, nas misturas modelo contendo um péptido, mesmo contendo também 5-CQA e sujeitas ao mesmo tratamento, observou-se uma diminuição na extensão das reações transglicosilação. Este resultado pode explicar a baixa extensão das reações de transglicosilação não enzimáticas durante a torra nas regiões do grão de café mais ricas em proteínas, apesar dos polissacarídeos serem os componentes maioritários dos grãos de café. A diminuição das reações de transglicosilação na presença de péptidos/proteínas pode dever-se ao facto de os resíduos de açúcares redutores reagirem preferencialmente com os grupos amina de péptidos/proteínas por reação de Maillard, diminuindo o número de resíduos de açúcares redutores disponíveis para as reações de transglicosilação. Além dos compostos já descritos, uma diversidade de outros compostos foram formados a partir dos sistemas modelo, nomeadamente derivados de desidratação formados durante o tratamento térmico a seco. Em conclusão, a tipificação das modificações estruturais promovidas pela torra nos polissacarídeos do café abre o caminho para a compreensão dos mecanismos de formação das melanoidinas e da relação estrutura-atividade destes compostos.
Polysaccharides are the major components of green and roasted coffee beans, and coffee brew. The most abundant ones are galactomannans, followed by arabinogalactans. During the roasting process, galactomannans and arabinogalactans undergo structural modifications that are far to be completely elucidated due to their diversity and complexity of the compounds formed. During the roasting process, galactomannans and arabinogalactans react with proteins, chlorogenic acids, and sucrose, originating high molecular weight brown compounds containing nitrogen, known as melanoidins. Several biological activities and beneficial health effects have been attributed to coffee melanoidins. However, their exact structures and the mechanisms involved in their formation remain unknown, as well as the structure-biological activity relationship. The use of model systems and mass spectrometry analysis allow to obtain an overall view and, simultaneously, detailed, of the structural modifications in coffee polysaccharides promoted by roasting, contributing to the elucidation of the structures and formation mechanisms of melanoidins. Based on this thesis, oligosaccharides structurally related to the backbone of galactomannans, (β1→4)-D-mannotriose, and the side chains of arabinogalactans, (α1→5)-Larabinotriose, alone or in mixtures with 5-O-caffeoylquinic acid, the most abundant chlorogenic acid in green coffee beans, and dipeptides composed by tyrosine and leucine, used as models of proteins, were submitted to dry thermal treatments, mimicking the coffee roasting process. The oxidation induced by hydroxyl radicals (HO•) was also studied, since these radicals seem to be involved in the modification of the polysaccharides during roasting. The identification of the structural modifications induced by thermal and oxidative treatment of the model compounds was performed mostly by mass spectrometry-based analytical strategies, but also using liquid chromatography. Gas chromatography was used in the analysis of neutral sugars and glycosidic linkages. To validate the conclusions achieved with the model compounds, coffee polysaccharide samples obtained from spent coffee grounds and instant coffee were also analysed. The results obtained from the model oligosaccharides when submitted to thermal treatment (dry) or oxidation induced by HO• (in solution) indicate the occurrence of depolymerization, which is in line with previous studies reporting the depolymerization of coffee galactomannans and arabinogalactans during roasting. Compounds resulting from sugar ring cleavage were also formed during thermal treatment and oxidative treatment of Ara3. On the other hand, the dry thermal treatment of the model oligosaccharides (alone or when mixed) promoted the formation of oligosaccharides with a higher degree of polymerization, and also polysaccharides with new type of glycosidic linkages, evidencing the occurrence of polymerization via non-enzymatic transglycosylation reactions induced by dry thermal treatment. The transglycosylation reactions induced by dry thermal treatment can occur between sugar residues from the same origin, but also of different origins, with formation of hybrid structures, containing arabinose and mannose in the case of the model compounds used. The results obtained from spent coffee grounds and instant coffee samples suggest the presence of hybrid polysaccharides in these processed coffee samples, corroborating the occurrence of transglycosylation during the roasting process. Furthermore, the study of mixtures containing different proportions of each model oligosaccharide, mimicking coffee bean regions with distinct polysaccharide composition, subjected to different periods of thermal treatment, allowed to infer that different hybrid and non-hybrid structures may be formed from arabinogalactans and galactomannans, depending on their distribution in the bean cell walls and on roasting conditions. These results may explain the heterogeneity of melanoidins structures formed during coffee roasting. The results obtained from model mixtures containing an oligosaccharide (Ara3 or Man3) and 5-CQA and subjected to dry thermal treatment, as well as samples derived from spent coffee grounds, showed the formation of hybrid compounds composed by CQA molecules covalently linked to a variable number of sugar residues. Moreover, the results obtained from the mixture containing Man3 and 5-CQA showed that CQA acts as catalyst of transglycosylation reactions. On the other hand, in the model mixtures containing a peptide, even if containing 5-CQA and subjected to the same treatment, it was observed a decrease in the extent of transglycosylation reactions. This outcome can explain the low extent of non-enzymatic transglycosylation reactions during roasting in coffee bean regions enriched in proteins, although polysaccharides are the major components of the coffee beans. The decrease of transglycosylation reactions in the presence of peptides/proteins can be related with the preferential reactivity of reducing residues with the amino groups of peptides/proteins by Maillard reaction, decreasing the number of reducing residues available to be directly involved in the transglycosylation reactions. In addition to the compounds already described, a diversity of other compounds were formed from model systems, namely dehydrated derivatives formed during dry thermal treatment. In conclusion, the identification of the structural modifications in coffee polysaccharides promoted by roasting pave the way to the understanding of the mechanisms of formation of melanoidins and structure-activity relationship of these compounds.

Stenby, Ejsing Christer. "Molecular characterization of the lipidome by mass spectrometry". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1172770038324-91461.

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Cells, whether bacterial, fungal or mammalian, are all equipped with metabolic pathways capable of producing an assortment of structurally and functionally distinct lipid species. Despite the structural diversity of lipids being recognized and correlated to specific cellular phenomena and disease states, the molecular mechanisms that underpin this structural diversity remain poorly understood. In part, this is due to the lack of adequate analytical techniques capable of measuring the structural details of lipid species in a direct, comprehensive and quantitative manner. The aim of my thesis study was to establish methodology for automated and quantitative analysis of molecular lipid species based on mass spectrometry. From this work a novel high-throughput methodology for lipidome analysis emerged. The main assets of the methodology were the structure-specific mass analysis by powerful hybrid mass spectrometers with high mass resolution, automated and sensitive infusion of total lipid extracts by a nanoelectrospray robot, and automated spectral deconvolution by dedicated Lipid Profiler software. The comprehensive characterization and quantification of molecular lipid species was achieved by spiking total lipid extracts with unique lipid standards, utilizing selective ionization conditions for sample infusion, and performing structure-specific mass analysis by hybrid quadrupole time-of-flight and ion trap mass spectrometry. The analytical routine allowed the comprehensive characterization and quantification of molecular glycerophospholipid species, molecular diacylglycerol species, molecular sphingolipid species including ceramides, glycosphingolipids and inositol-containing sphingolipids, and sterol lipids including cholesterol. The performance of the methodology was validated by comparing its dynamic quantification range to that of established methodology based on triple quandrupole mass spectrometry. Furthermore, its efficacy for lipidomics projects was demonstrated by the successful quantitative deciphering of the lipid composition of T cell receptor signaling domains, mammalian tissues including heart, brain and red blood cells, and the yeast Saccharomyces cerevisiae.

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Libri sul tema "Molecular beam mass spectrometry":

Simone, Koenig, a cura di. Biomacromolecular mass spectrometry research. New York: Nova Science Publishers, 2008.

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Whitelegge, Julian P. Protein mass spectrometry. Amsterdam: Elsevier, 2009.

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Lin, He. Mass spectrometry imaging of small molecules. New York: Humana Press, 2014.

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NATO, Advanced Research Workshop on Methods and Mechanisms for Producing Ions from Large Molecules (1990 Minaki Ont ). Methods and mechanisms for producing ions from large molecules. New York: Plenum Press, 1991.

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Matthiesen, Rune. Mass spectrometry data analysis in proteomics. New York: Humana Press, 2013.

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Rune, Matthiesen, a cura di. Mass spectrometry data analysis in proteomics. Totowa, N.J: Humana Press, 2007.

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Clarke, Charlotte H., e Diane L. Bankert McCarthy. SELDI-TOF mass spectrometry: Methods and protocols. New York, N.Y: Humana, 2012.

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C, Tuniz, a cura di. Accelerator mass spectrometry: Ultrasensitive analysis for global science. Boca Raton, Fla: CRC Press, 1998.

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United States. Environmental Protection Agency., a cura di. Improved method for estimating molecular weights of volatile organic compounds from low resolution mass spectra. [Washington, D.C: U.S. Environmental Protection Agency, 1992.

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Gibson, W. C. Fast ion mass spectrometry and charged particle spectrography investigations of transverse ion acceleration and beam-plasma interactions. [Washington, DC: National Aeronautics and Space Administration, 1987.

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Capitoli di libri sul tema "Molecular beam mass spectrometry":

Mahoney, Christine M., e Andreas Wucher. "Molecular Depth Profiling with Cluster Ion Beams". In Cluster Secondary Ion Mass Spectrometry, 117–205. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118589335.ch5.

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Mafuné, F., N. Horimoto e T. Kondow. "Electronic Structure and Dynamics of Solute Molecules on Solution Surfaces by Use of Liquid Beam Multiphoton Ionization Mass Spectrometry". In Atomic and Molecular Beams, 793–803. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-56800-8_54.

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Milne, Thomas A., Robert J. Evans e Jonathan Filley. "Molecular Beam Mass Spectrometric Studies of HZSM-5 Activity During Wood Pyrolysis Product Conversion". In Research in Thermochemical Biomass Conversion, 910–26. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-2737-7_69.

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Evans, Robert J., e Thomas Milne. "Molecular-Beam, Mass-Spectrometric Studies of Wood Vapor and Model Compounds over an HZSM—5 Catalyst". In ACS Symposium Series, 311–27. Washington, DC: American Chemical Society, 1988. http://dx.doi.org/10.1021/bk-1988-0376.ch026.

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Yergey, Alfred L., Charles G. Edmonds, Ivor A. S. Lewis e Marvin L. Vestal. "Particle Beam Interfaces". In Liquid Chromatography/Mass Spectrometry, 87–88. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4899-3605-9_5.

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Reichenbächer, Manfred, e Jürgen Popp. "Mass Spectrometry". In Challenges in Molecular Structure Determination, 1–61. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-24390-5_1.

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Kaltashov, Igor A., e Cedric E. Bobst. "Mass Spectrometry". In Molecular Biophysics for the Life Sciences, 215–56. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8548-3_7.

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Cooper, Scott, e Anton Sanderfoot. "Mass Spectrometry Approaches". In Molecular Life Sciences, 1–5. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-6436-5_4-3.

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Cooper, Scott, e Anton Sanderfoot. "Mass Spectrometry Approaches". In Molecular Life Sciences, 655–58. New York, NY: Springer New York, 2018. http://dx.doi.org/10.1007/978-1-4614-1531-2_4.

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Rubakhin, Stanislav S., e Jonathan V. Sweedler. "A Mass Spectrometry Primer for Mass Spectrometry Imaging". In Methods in Molecular Biology, 21–49. Totowa, NJ: Humana Press, 2010. http://dx.doi.org/10.1007/978-1-60761-746-4_2.

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Atti di convegni sul tema "Molecular beam mass spectrometry":

Lubman, David M., Chung Hang Sin e Ho Ming Pang. "Analytical Applications Of Supercritical Fluid/Supersonic Beam Laser Ionization Mass Spectrometry". In Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/laca.1987.tua4.

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Supercritical fluids of CO2 and N2O are used as a means of solubilizing nonvolatile polynuclear aromatic hydrocarbons and small thermally labile biologicals for expansion into supersonic beams for mass spectrometry. The resulting expansion into vacuum results in internally ultracold molecules with sharp spectral features for unique identification in UV-VIS absorption spectroscopy. In this work laser resonant two-photon ionization is used as a means of selectively producing ions for detection in mass spectrometry where the first photon excites the molecule to a real resonant state and the second photon ionizes the molecule. Although ions are produced for mass spectrometry, the ionization cross section reflects the SO → S1 transition so that ionization spectroscopy can be used as a means of identifying molecules in a mass spectrometer. We have applied this method to detection of several PNAH's where supercritical fluid expansion was used to solubilize these molecules essentially at room temperature, i.e. without heating. In addition, small biological and pharmaceutical analogs have been examined and the effect of the supercritical fluid solvent is studied. Most recently supercritical ammonia has been investigated as a highly polar solvent for dissolving indoleamines, catecholamines and other polar biological species. The key to this experiment is a novel compact molecular beam apparatus for supercritical fluid injection which takes advantage of (a) efficient liquid N2 cryopumping of CO2 and (b) a special high-pressure pulsed valve. This valve is capable of operation up to 400 atm backpressure at 250°C. The combination of pulsed valve injection with cryopumping allows the use of a 150-200 μ orifice for high on-axis density and thus sensitivity. The resulting chamber pressure at 400 atm reservoir pressure is <2×10−5 torr so that the ions produced by R2PI can be detected and mass analyzed in a time-of-flight mass spectrometer. The future potential of this method is discussed and compared to the use of the laser desorption method for volatilizing labile compounds into jet expansions.

Lubman, David M., Roger Tembreull, Chung Hang Sin e Homing Pang. "Laser-induced ionization spectroscopy of small biological precursors in supersonic beam-mass spectrometry". In International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.tue3.

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In our work resonant two-photon ionization (R2PI) in supersonic jets is used as a means of optically selecting ions for mass spectrometry. The use of supersonic beam injection provides internally ultracold molecules with sharp spectral features for chemical analysis for molecules whose spectra would otherwise exhibit broad, unresolvable spectral contours at room temperature. The use of high-powered tunable monochromatic laser sources can be used to probe this sharp structure by using laser R2PI spectroscopy. This method has been used for analysis of small biological species based on the combination of wavelength selectivity and the high efficiency for producing molecular ions by the R2PI technique. One method investigated for use in solubilizing nonvolatile and thermally labile molecules involves expansions of supercritical fluids of CO2 and N2O at up to 400-atm backpressure in to a mass spectrometer at 10-5 Torr. The expansion of this ultradense jet is shown to provide cold spectra for molecules which would normally require significant heating for volatilization into the gas phase. A second method used in our work for volitilization of nonvolatiles uses laser desorption to rapidly heat molecules off a surface before they can decompose. The resulting desorbed cloud is then swept into a supersonic jet and into a TOFMS for analysis by R2PI. The parameters required to volatilize various compounds and the spectroscopic and mass spectrometric results for several small biological systems including amino acids, drugs, catecholamines, and vitamins are discussed.

Appelhans, Anthony D., Gary S. Groenewold, Jani C. Ingram, D. A. Dahl e J. E. Delmore. "Molecular beam static secondary ion mass spectrometry for surface analysis". In Photonics West '95, a cura di Bryan L. Fearey. SPIE, 1995. http://dx.doi.org/10.1117/12.206432.

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Korobinichev, Oleg, Leonid Kuibida, Andrey Shmakov e Alexander Paletsky. "GAP decomposition and combustion chemistry studied by molecular beam mass-spectrometry". In 37th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1999. http://dx.doi.org/10.2514/6.1999-596.

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Houle, F. A. "Mechanism of Chemical Etching of doped GaAs by Cl2". In The Microphysics of Surfaces: Beam-Induced Processes. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/msbip.1991.tua2.

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Consideration of product volatility and thermodynamic stability have been central to models developed for the thermal etching and deposition of GaAs by Cl21,2 Mass spectrometric studies of the etching chemistry have tended to support some of the basic assumptions of these models: that the thermodynamically most stable product is formed and that product volatility controls the etch rate. Surface analyses, for example, have revealed the presence of a Ga-rich scale after etching, to be expected if the As chlorides arc more volatile and desorb more readily.3-5 Consequently, models of beam modification of GaAs in the presence of Cl2 have focussed on how energetic particles or light might perturb the thermal reaction. In this work the validity of the basis for these models has been examined by investigation of the etching chemistry of doped GaAs by molecular beam mass spectrometry and in situ Auger spectroscopy.

Willey, K. F., V. Vorsa e N. Winograd. "Molecular Photoionization and Chemical Imaging". In Laser Applications to Chemical and Environmental Analysis. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/lacea.1998.ltub.4.

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It is now possible to desorb a variety of organic molecules from surfaces using a tightly focused energetic ion beam. The molecules are detected as secondary ions using time-of-flight mass spectrometry, and may be spatially resolved by rastoring the ion beam over a larger area. A chemically resolved image is then acquired by examining the intensity of a particular mass as a function of x,y position. Presently, liquid metal ion sources using 25 KeV Ga+ ion projectiles can be focused to a spot of less than 20 nm in diameter. The limiting factor for molecule-specific imaging is sensitivity. The ion dose must be kept less than 1% of the total number of surface molecules to prevent chemical damage. Moreover, the ionization probability of desorbed molecules is generally less than 1 in 104. Since the molecules desorb from the first layer and since there are at most 4 × 106 molecules per square micron (depending on size of course), the signal rapidly approaches zero as the spatial resolution or beam probe size is reduced below 1 micron.1 Here we investigate the use of high intensity 100 fs laser pulses to photoionize the desorbed neutral molecules in an attempt to increase the measurement efficiency of this type of experiment. Our model system is dopamine, an important neurotransmitter that has aromatic character, but is subject to significant fragmentation using ns laser pulses. The results suggest that this approach can indeed expand the performance of mass-spectrometry based imaging experiments and can open new applications in bioimaging.

Korobeinichev, O., L. Kuibida, A. Paletsky e A. Shmakov. "Development and application of molecular beam mass-spectrometry to the study of ADN combustion chemistry". In 36th AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-445.

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Qin, Qi-Zong, Yu-Lin Li, Ping-He Lu, Zhuang-Jian Zhang, Zhong-Kao Jin e Qi-Ke Zheng. "Laser-Induced Reactions of Semiconductor Surfaces with Chlorine". In The Microphysics of Surfaces: Beam-Induced Processes. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/msbip.1991.tua1.

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Laser-induced chemical reaction of semiconductor with halogen and halogen compounds has attracted much attention in recent years due to its potential application in fabrication of microelectronic devices. We have reported UV and visible laser-induced reactions of Si and GaAs surfaces with chlorine using a CW molecular beam technique coupled with time-resolved mass spectrometry(1,2,). This paper will present recent studies in our laboratory on laser-induced reactions of Ge(111), Si(111), GaAs(100) and lnP(100) surfaces with chlorine molecules under 355-, 560-, and 1064-nm laser irradiations. We are particularly interested in the use of near infrared (1064-nm) laser photons as well as the promotion of reaction by raising the incident chlorine molecules’ translational energy. The objective is to achieve a better understanding of the mechanism of laser-induced reaction and its potential application in the chemical etching of semiconductor.

Lemmens, Alexander, e Musahid Dias, Ahmed. "NON-COVALENT DYNAMICS WITH A FEMTOSECOND LASER MOLECULAR BEAM MASS SPECTROMETER". In 2023 International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2023. http://dx.doi.org/10.15278/isms.2023.6885.

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Steadman, J., E. W. Fournier e J. A. Syage. "Detection and Differentiation of Neutral and Ionic Reaction Mechanisms in Molecular Clusters". In Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/laca.1990.pd4.

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A longstanding goal in the chemical analysis of reaction mechanisms is understanding the role of the solvent. We have been involved in work that addresses this issue on a single molecule basis by studying reactions in molecular clusters.1–3 In this report we describe a means for detecting and measuring rapid intermolecular cluster chemistry using mass-selective picosecond resonance-enhanced multiphoton ionization (REMPI). Molecular beam mass spectrometry offers a powerful means for identifying a variety of product species and distinguishing precursor cluster size. However, such investigations demand an independent means for differentiating neutral cluster reactions from ionic reactions. Our approach is to obtain direct measurements of the ion dissociation mechanisms by electron-impact (El) ionization and by mass-selective ion photodissociation.

Rapporti di organizzazioni sul tema "Molecular beam mass spectrometry":

Author, Not Given. Molecular Beam Mass Spectrometry (MBMS) (Revised) (Fact Sheet). Office of Scientific and Technical Information (OSTI), luglio 2011. http://dx.doi.org/10.2172/1015883.

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Carpenter, D., M. Ratcliff e D. Dayton. Catalytic Steam Reforming of Gasifier Tars: On-Line Monitoring of Tars with a Transportable Molecular-Beam Mass Spectrometer; Milestone Completion Report. Office of Scientific and Technical Information (OSTI), maggio 2002. http://dx.doi.org/10.2172/15000383.

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Pollard, James E., e Ronald B. Cohen. Electron-Impact Ionization Time-of-Flight Mass Spectrometer for Molecular Beams,. Fort Belvoir, VA: Defense Technical Information Center, aprile 1989. http://dx.doi.org/10.21236/ada207585.

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Stacey, Gary, Akos Vertes, Ljiljana Paša-Tolić, Christopher Anderton e David Koppenaal. Development and refinement of an in situ ‘molecular microscope’ utilizing ultrahigh resolution mass spectrometry. Office of Scientific and Technical Information (OSTI), giugno 2019. http://dx.doi.org/10.2172/1532356.

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Tucker, Mark L., Shimon Meir, Amnon Lers, Sonia Philosoph-Hadas e Cai-Zhong Jiang. Elucidation of signaling pathways that regulate ethylene-induced leaf and flower abscission of agriculturally important plants. United States Department of Agriculture, gennaio 2012. http://dx.doi.org/10.32747/2012.7597929.bard.

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The Problem: Abscission is a highly regulated process, occurring as a natural terminal stage of development, in which various organs are separated from the parent plant. In most plant species, the process is initiated by a decrease in active auxin in the abscission zone (AZ) and an increase in ethylene, and may be accelerated by postharvest or environmental stresses. Another potential key regulator in abscission is IDA (Inflorescence Deficient in Abscission), which was identified as an essential peptide signal for floral organ abscission in Arabidopsis. However, information is still lacking regarding the molecular mechanisms integrating all these regulators. In our previous BARD funded research we made substantial progress towards understanding these molecular events in tomato, and the study is still in progress. We established a powerful platform for analysis of genes for regulatory proteins expressed in AZ. We identified changes in gene expression for several transcription factors (TFs) directly linked to ethylene and auxin signaling and several additional regulatory proteins not so obviously linked to these hormones. Moreover, we demonstrated using a virus-induced gene silencing (VIGS) assay that several play a functional role in the onset of abscission. Based on these results we have selected 14 genes for further analysis in stably transformed tomato plants. All 14 genes were suppressed by RNA interference (RNAi) using a constitutive promoter, and 5 of them were also suppressed using an abscission-specific promoter. Transformations are currently at different stages of progress including some lines that already display an abscission phenotype. Objectives: We propose here to (1) complete the functional analysis of the stably transformed tomato plants with T2 lines and perform transcriptome analysis using custom abscission-specific microarrays; (2) conduct an indepth analysis of the role of IDA signaling in tomato leaf and flower abscission; (3) perform transcriptome and proteome analyses to extend the earlier gene expression studies to identify transcripts and proteins that are highly specific to the separation layer (i.e., target cells for cell separation) prior to the onset of abscission; (4) extend and compliment the work in tomato using a winnowed set of genes in soybean. Methodology: Next Generation Sequencing (NGS) of mRNA will be used to further increase the list of abscission-associated genes, and for preparation of a custom tomato abscission microarray to test altered gene expression in transgenic plants. Tandem mass spectrometry (LC-MS/MS) of protein extracts from leaf petiole, flower pedicel and their AZ tissues will be used to identify the proteome of the AZ before and during abscission. AZ-specific gene promoters will be used in stably transformed tomato plants to reduce non-target phenotypes. The bean pod mottle virus (BPMV) plasmid vectors will be used for VIGS analysis in soybean. Expected Contribution: Our study will provide new insights into the regulation of ethylene-induced abscission by further revealing the role of key regulators in the process. This will permit development of novel techniques for manipulating leaf and flower abscission, thereby improving the postharvest performance of agriculturally important crops.

Niu, Hongsen. Fundamental studies of the plasma extraction and ion beam formation processes in inductively coupled plasma mass spectrometry. Office of Scientific and Technical Information (OSTI), febbraio 1995. http://dx.doi.org/10.2172/103532.

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Russell, David H. Developing Ion Mobility-Mass Spectrometry for Structural Characterization of Complex Molecular Systems, Final Report/Product Number: DOE_ER-15520-3. Office of Scientific and Technical Information (OSTI), giugno 2017. http://dx.doi.org/10.2172/1430105.

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Chess, E. K., e R. D. Smith. Development and evaluation of supercritical fluid chromatography/mass spectrometry for polar and high-molecular-weight coal components. Technical progress report. Office of Scientific and Technical Information (OSTI), gennaio 1986. http://dx.doi.org/10.2172/6275627.

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Amirav, Aviv, e Steven Lehotay. Fast Analysis of Pesticide Residues in Agricultural Products. United States Department of Agriculture, novembre 2002. http://dx.doi.org/10.32747/2002.7695851.bard.

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The overall theme of this project was to increase the speed of analysis for monitoring pesticide residues in food. Traditionally, analytical methods for multiple pesticides are time-consuming, expensive, laborious, wasteful, and ineffective to meet critical needs related to food safety. Faster and better methods were needed to provide more cost-effective detection of chemical contaminants, and thus provide a variety of benefits to agriculture. This overarching goal to speed and improve pesticide analysis was successfully accomplished even beyond what was originally proposed by the investigators in 1998. At that time, the main objectives of this project were: 1) to further develop a direct sample introduction (DSI) device that enables fast sampling and introduction of blended-only agricultural products for analysis by gas chromatography (GC); 2) to evaluate, establish, and further develop the method of simultaneous pulsed flame photometric detector (PFPD) and mass spectrometry (MS) detection for enhanced pesticide identification capabilities; and 3) to develop a new and novel MS pesticide analysis method, based on the use of supersonic molecular beams (SMB) for sampling and ionization. The first and third objectives were successfully accomplished as proposed, and the feasibility of the second objective was already demonstrated. The capabilities of the GC/SMB-MS approach alone were so useful for pesticide analysis that the simultaneous use of a PFPD was considered superfluous. Instead, the PFPD was investigated in combination with an electron-capture detector for low-cost, simultaneous analysis of organophosphorus and organochlorine pesticides in fatty foods. Three important, novel research projects not originally described in the proposal were also accomplished: 1) development of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for pesticides in foods; 2) development and optimization of a method using low-pressure (LP) GC/MS to speed pesticide residue analysis; and 3) innovative application of analyte protectants to improve the GC analysis of important problematic pesticides. All of the accomplishments from this project are expected to have strong impact to the analytical community and implications to agriculture and food safety. For one, an automated DSI approach has become commercially available in combination with GC/MS for the analysis of pesticide residues. Meanwhile, the PFPD has become the selective detector of choice for the analysis of organophosphorus pesticides. Great strides were made in SMB-MS through the manufacture of a prototype "Supersonic GC/MS" instrument, which displayed many advantages over commercial GC/MS instruments. Most notably, the QuEChERS method is already being disseminated to routine monitoring labs and has shown great promise to improve pesticide analytical capabilities and increase lab productivity. The implications of these developments to agriculture will be to increase the percentage of food monitored and the scope of residues detected in the food, which will serve to improve food safety. Developed and developing countries alike will be able to use these methods to lower costs and improve results, thus imported/exported food products will have better quality without affecting price or availability. This will help increase trade between nations and mitigate certain disputes over residue levels in imported foods. The improved enforcement of permissible residue levels provided by these methods will have the effect to promote good agricultural practices among previously obstinate farmers who felt no repercussions from illegal or harmful practices. Furthermore, the methods developed can be used in the field to analyze samples quickly and effectively, or to screen for high levels of dangerous chemicals that may intentionally or accidentally appear in the food supply.

Chess, E. K., H. T. Kalinoski e R. D. Smith. Development and evaluation of supercritical fluid chromatography/mass spectrometry for polar and high-molecular-weight coal components: Technical progress report, October 1, 1986-September 30, 1987. Office of Scientific and Technical Information (OSTI), febbraio 1988. http://dx.doi.org/10.2172/5539304.

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