Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Pneumatically assisted desorption/ionization.
Дисертації з теми "Pneumatically assisted desorption/ionization"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Pneumatically assisted desorption/ionization".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
ZANCANARO, Flavio. "Mass spectrometry pneumatically assisted desorption/ionization in forensic toxicology." Doctoral thesis, Università degli Studi di Verona, 2010. http://hdl.handle.net/11562/342863.
Повний текст джерелаАнотація:
La spettrometria di massa è una delle tecniche più rilevanti in tossicologia clinica e forense. Il suo sviluppo e il miglioramento si basano sull'invenzione e l'uso di nuove sorgenti di ioni, nuovi metodi di ionizzazione, nuovi analizzatori di massa e nuove tecniche di pre-trattamento dei campioni. Una recente innovazione è la capacità di registrare spettri di massa su campioni reali direttamente nel loro ambiente nativo, senza preparazione del campione o pre-separazione. In questo ambito è stato descritto un nuovo metodo di ionizzazione/desorbimento chiamato DESI (desorbimento Electrospray ionizzazione), in seguito è stato sviluppato un metodo chiamato Dessì (Desorbimento Sonic Spray ionizzazione), a prima vista simile a DESI, ma in fondo sostanzialmente diverso. Questa tesi consiste nello sviluppo di una nuova interfaccia di desorbimento / ionizzazione per indagare il vero meccanismo coinvolto nella formazione di ioni, perché abbiamo ritenuto questo passaggio propedeutico per garantire il successivo uso del metodo in campo tossicologico analitico. Abbiamo verificato che il contributo pneumatico è preponderante per ottenere risultati. Quindi, la nostra nuova interfaccia di desorbimento/ionizzazione utilizza solo uno spray di solvente puro, senza alcuna tensione elettrica applicata allo sprayer. Un aspetto fondamentale di questo progetto, applicato a diverse matrici complesse, è il numero di parametri di funzionamento controllabili che possono essere studiati e ottimizzati per ottenere un'efficace analisi di superficie. Le variabili più importanti prese in considerazione sono state la geometria della sorgente (l'angolo di spray e l'angolo di diffusione di ioni, come pure le varie distanze nell'allineamento dello spray, del campione e dello spettrometro di massa) e la caratteristica dello spray (il contenuto del solvente ed il gas di portata). Tutte le misurazioni sono state eseguite in condizioni di ionizzazione positiva e negativa, variando tensione del capillare, pressione del gas di nebulizzazione, il flusso di gas al capillare e la temperatura del capillare. L'acquisizione è stata prodotta in modalità multiple mass spectra (MSn). Abbiamo applicato questa nuova soluzione tecnica per l'identificazione di composti tal quali, di principi attivi in campioni di farmaci mediante analisi diretta di compresse, principi attivi contenuti in specie vegetali. Gli sviluppi futuri saranno connessi ad applicare l’analisi diretta di analiti presenti sulle superfici originali di interesse nel settore tossicologico per il campionamento in vivo su superfici di tessuti, per individuare l’esposizione a farmaci e xenobiotici, oltre alla possibilità di costruire un’immagine chimica della distribuzione spaziale di analiti sulle superfici dei campioni.Mass spectrometry is one of the most relevant techniques in clinical and forensic toxicology. Its development and improvement are based on the invention and utilization of new ion sources, new ionization methods, new mass analyzers and new sample pre-treatment techniques. A recent innovation is the ability to record mass spectra on ordinary samples in their native environment, without sample preparation or pre-separation. In this field, a new desorption ionization method called DESI (Desorption Electrospray Ionization) has been described; subsequently, method called DeSSI (Desorption Sonic Spray Ionization), at first sight similar to DESI, but in deep substantially different, has been developed. This thesis consist in developing a new desorption/ionization interface to investigate the real mechanism involved in ions formation because we considered that propaedeutic for the extensive use of the method in the toxicological analytical field. We verified that the pneumatic contribution is preponderant to the obtained results. Hence, our new desorption/ionization interface uses only a spray of pure solvent with no high voltage on needle. A key aspect of this project, applied to several complex matrix, is the number of controllable operating parameters that can be investigated and optimized to obtain an efficient surface analysis. The most important variables are taken in consideration were the source geometry (the spray angle and the ion uptake angle, as well as the various distances in aligning the spray, sample and mass spectrometer) and the characteristic of sprayer (contents of the solvent spray and gas flow rate). All measurements have been performed in positive and negative ionization conditions, varying capillary voltage, nebulizing gas pressure, drying gas flow and end plate temperature. Acquisition was in multiple mass spectrometry mode (MSn). 2 We have applied this new technical solution to compound identification, active principles and drugs identification in direct tablet analysis, active principles and drugs identification in vegetable species. Future developments will be related to apply the direct analysis of analytes present on the original surfaces of interest in the toxicological field for in vivo sampling of living tissue surfaces, to identify drug and xenobiotic exposure, besides the chemical imaging of spatial distribution of analytes onto sample surfaces.
2
Peng, Ivory Xingyu. "Electrospray-assisted laser desorption ionization mass spectrometry for proteomic studies." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1997571271&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Повний текст джерела
3
Berhane, Beniam T. "Rapid Characterization of Posttranscriptional Modifications in RNA Using Matrix Assisted Laser Desorption Ionization Mass Spectrometry and Matrix Assisted Laser Desorption Ionization Post Source Decay Mass Spectrometry." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1052319621.
Повний текст джерела
4
Dubois, Frédéric Dubois Frédéric. "Ion formation and detection in matrix-assisted laser desorption/ionization mass spectrometry /." [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13255.
Повний текст джерела
5
Dai, Yuqin. "Development of matrix-assisted laser desorption ionization mass spectrometry for biopolymer analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0003/NQ39519.pdf.
Повний текст джерела
6
Tummala, Manorama. "Surfactant-Aided Matrix Assisted Laser Desorption/Ionization Mass Spectrometry (SA-MALDI MS)." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100672049.
Повний текст джерела
7
Dashtiev, Maxim. "Fluorescence spectroscopy of trapped molecular ions produced with matrix-assisted laser desorption/ionization /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16949.
Повний текст джерела
8
Segu, Mohideen Mohamed Zaneer. "TARGET MODIFICATION FOR ENHANCED PERFORMANCE MATRIX ASSISTED LASER DESORPTION IONIZATION (MALDI) MASS SPECTROMETRY." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1674093101&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Southern Illinois University Carbondale, 2008."Department of Chemistry." Keywords: Enhanced MALDI, MALDI-MS, On-probe separation, Protein-surface interactions, Sublayers, Surface binding capacity. Includes bibliographical references (p. 130-148). Also available online.
9
Akinapalli, Srikanth. "MICROFLUIDIC DYNAMIC ISOELECTRIC FOCUSING COUPLED TO MATRIX ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1289.
Повний текст джерелаАнотація:
Proteomics is an increasingly important area of biological research and has gathered much attention over recent years. Major challenges that make a proteomic analysis difficult are sample complexity, diversity and dynamic range. Progress in the area of proteomics relies heavily on new analytical tools for the sensitive, selective, and high-throughput studies of target analytes. It is estimated that there are several hundred thousand proteins in a human cell. In order to be able to analyze such a complex sample, an analytical method must be capable of separating and detecting many different sample peaks. The complexity of such samples indicates that a single separation method will not be able to provide the needed resolution. If two methods that are orthogonal are combined, then the peak capacity of the combined system is the product of the two individual peak capacities. Development of such systems would cater to the current demands of proteomics studies. Matrix assisted laser desorption/ionization (MALDI) mass spectrometry has evolved into a primary analytical tool for proteomics research. MALDI is fast and efficient and has a high tolerance to non-volatile buffers and impurities. The samples for MALDI are typically applied to solid supports after having been subjected to off-line liquid or gel separations. Several methods have been reported involving various chromatographic or electrophoretic separation methods. However, the current methods often require highly sophisticated sample handling systems, which are often expensive and in need of skilled human resources. The current demands of proteomic analyses require fast, efficient and inexpensive methods for separation to fully harness the capability of MALDI mass spectrometry. In this work a microfluidic device has been designed to perform dynamic isoelectric focusing (DIEF) based protein separation with digital sample deposition directly on a MALDI target for offline analysis. DIEF is related to capillary isoelectric focusing which and can facilitate the interface without the loss of the separation resolution. Compared to traditional capillary isoelectric focusing (cIEF) DIEF uses additional high-voltage power supplies to control the pH gradient by manipulating the electric field. The proteins can be focused at a desired sampling position according to their isoelectric point, to be collected for further analysis by MALDI mass spectrometry. DIEF has a peak capacity of over a thousand and offers an ease of interfacing to other techniques making it a preferred separation method for the interface with mass spectrometric techniques such as MALDI. The design of the microfluidic device is based on a digital droplet fractionation. Multiple fractions of the sample solution from DIEF are generated to retain the resolution and to act as an additional separation mode. The microfluidic device is controlled by actuating pneumatic valves built into the device. The DIEF operational parameters were optimized according to the surface functionality and the design of the microfluidic device. A suitable MALDI sample preparation method was found by studying different existing methods. The methods were studied using test proteins prepared in solutions having the additives used in the experiment. A simple mixture of three proteins was used to demonstrate the application of the developed method. The separation between the proteins insulin, hemoglobin and the myoglobin was demonstrated by varying the separation resolution in three experiments.
10
Xiang, Fan. "Improvement and investigation of sample preparation for matrix-assisted laser desorption/ionization of proteins." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25780.pdf.
Повний текст джерела
11
Wang, Jian. "Analyses of food and feed compounds using matrix-assisted laser desorption/ionization mass spectrometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0013/NQ59690.pdf.
Повний текст джерела
12
Köchling, Heinrich J. (Heinrich Josef) 1962. "Advancements in matrix-assisted laser desorption ionization mass spectrometry of peptides, proteins and polymers." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10020.
Повний текст джерела
13
Mowat, Ian A. "Synthetic polymer analysis using matrix assisted laser desorption/ionization time-of-flight mass spectrometry." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/12128.
Повний текст джерелаАнотація:
The aim of the work described in this thesis was to assess 'Matrix Assisted Laser Desorption/Ionization' (MALDI) Time-of-Flight mass spectrometry as a possible technique for the analysis of synthetic polymers. A compact home-built time-of-flight mass spectrometer of cylindrically symmetrical geometry was used to carry out all the mass spectrometry detailed described in this thesis. A survey of the literature describing the development of matrix assisted laser desorption/ionization spectrometry and also the previous analysis of polymers by laser mass spectrometry was carried out. Experiments comparing the performance of the apparatus with published data on peptides and proteins were carried out, followed by experiments to assess the possibility of analyzing synthetic polymers. Initially polar polymers were investigated, since they could be anlayzed using sample preparations very similar to those developed for peptide and protein analysis. Later investigations were carried out on non-polar polymers such as polystyrene. The attachment of a range of transition metals to a low mass polystyrene was investigated using laser desorption/ionization time-of-flight mass spectrometry, without the use of matrices to increase the ion yield. Systematic investigations into the effects of sample spot composition, i.e. the amounts of matrix, polymer and salt present, were carried out, and used to suggest possible models for the processes leading to the generations of large gas phase ions. The effects of sample spot composition on the size and shape of the polymer molecular weight distributions obtained was also investigated. Liquid polymers such as polysiloxanes and perfluorinated polyethers were investigated using laser desorption/ionization and matrix assisted laser desorption/ionization. Carbon cluster generation from such polymers was investigated, and fullerene and polycyclic aromatic hydrocarbon analysis was also briefly studied. Novel new molecules such as aryl ester dendrimers were investigated, since they could not be successfully analyzed by other mass spectrometric techniques. Single molecular ions were obtained, helping to confirm the expected masses of these molecules. Novel new polymers such as hyperbranched aromatic polyesters were also analyzed, and molecular weight distributions were successfully obtained for a number of samples, showing the utility of MALDI for the analysis of new materials.
14
Mazarin, Michaël. "L'ionisation MALDI [Matrix assisted laser desorption/ionization] de polymères synthétiques en spectrométrie de masse." Aix-Marseille 1, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX11034.pdf.
Повний текст джерелаАнотація:
La spectrométrie de masse après ionisation/désorption laser assistée par matrice (MALDI) apparaît comme une technique de choix pour la caractérisation structurale des polymères synthétiques. Néanmoins, parce que les processus fondamentaux qui régissent la technique MALDI sont encore mal connus, l’optimisation des conditions expérimentales reste empirique. L’objectif de ces travaux de thèse est d’utiliser conjointement des techniques de spectrométrie de masse et de résonance magnétique nucléaire (RMN) pour rationaliser les méthodologies d'analyse des polymères synthétiques par MALDI. Une première approche consiste à utiliser la RMN diffusionnelle pour pré-évaluer la masse moyenne des polymères, valeur qui sert ensuite de guide pour la préparation des dépôts MALDI et l’interprétation des données spectrales obtenues. Un deuxième axe de recherche s’intéresse à la fragilité des groupements terminaux des macromolécules synthétisées par polymérisation radicalaire contrôlée. Les mécanismes de rupture de ces groupements pendant l’ionisation MALDI ont été élucidés en combinant des expériences de dissociation induite par collision après ionisation electrospray, des expériences de RMN en phase liquide et des calculs théoriques. Il ressort de cette étude que seule la protonation du groupement fragile permet la production d’ions oligomères intacts. A cet effet, une préparation sans solvant des dépôts MALDI a été développée pour promouvoir la protonation des macromolécules étudiées. Son efficacité reste néanmoins limitée aux polymères de faible taille. Enfin, le potentiel de la RMN du solide pour caractériser la microstructure des dépôts MALDI a été évaluéMatrix assisted laser desorption/ionization (MALDI) mass spectrometry is a key technique for synthetic polymer structural characterization. Nevertheless, because fundamental process of MALDI is still not fully understood, no standard protocol is available and experimental conditions are empirically optimized. The aim of this PhD work is to combine mass spectrometric techniques with nuclear magnetic resonance (NMR) spectroscopies to develop rationalized MALDI methodologies for structural studies of synthetic polymers. A first approach consists of using diffusion NMR for a rapid evaluation of polymer average mass, to be further used as a guideline in MALDI sample preparation and spectral data interpretation. A second axis deals with fragile end-groups of macromolecules synthesized via controlled radical polymerization reactions. Combining collision-induced dissociation of electrosprayed oligomers with liquid state NMR and theoretical calculations allowed the elucidation of mechanisms involved in the bond cleavage which is observed to occur within such end-groups during the MALDI process. This study shows that protonation of the fragile termination is the main way to allow intact oligomer ions to be produced. A solvent-free MALDI sample preparation was thus developed to promote macromolecule protonation but its efficiency was shown to be limited to the case of small polymers. Finally, the potential of solid state NMR to characterize the microstructure of MALDI sample was evaluated
15
Garrett, Timothy J. "Imaging small molecules in tissue by matrix-assisted laser desorption/ionization tandem mass spectrometry." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013807.
Повний текст джерела
16
Priyasantha, Kandalama KD. "DEVELOPMENT OF A NOVEL MATRIX ASSISTED LASER DESORPTION / IONIZATION (MALDI) BASED PEPTIDE QUANTITATION APPROACH." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/989.
Повний текст джерелаАнотація:
Matrix Assisted Laser Desorption / Ionization (MALDI) Mass Spectrometry (MS) has emerged as an important tool in the field of proteomics mainly because it is simple, quick and efficient. The identification and quantitation of biomarkers, protein targets for drugs, and metabolites are some of the important fields in proteomics research. Although MALDI MS is an important tool in proteomics research there are drawbacks of the technique that need further development in order for the approach to be used in clinical laboratories. One major limitation of MALDI MS is the generally poor reproducibility of ion signal intensities, which negatively impacts the quantitation of peptides and protein by MALDI MS. A considerable amount of research has been performed in an effort to improve the ion signal reproducibility in MALDI MS. However, many of the approaches developed have introduced specific drawbacks with respect to the traditional dried-droplet sample preparation technique, negating many of the advantages of the MALDI MS approach. This project has focused on the development of a novel approach to quantify peptides by MALDI MS while preserving traditional known advantages of the technique. The studies performed show that an approach in which the ion signal base widths are manipulated to match that of a reference ion signal, through adjustments in desorption laser intensity, leads to much higher reproducibility in the integrated ion signal intensities. A standard curve acquired using the constant ion signal base width approach showed lower average RSDs (< 10.00% vs.> 39.00%) and improved R2 values (> 0.9600 vs. < 0.809) as compared to the conventional constant desorption laser intensity approach. Subsequent work also revealed that the peptide hydrophobic / hydrophilic properties influenced the applicability of the quantitation approach to mixtures of peptides. Specifically, the data revealed that peptides with differing hydrophobic / hydrophilic properties appear to co-crystallize with the MALDI matrix differently leading to an inability to use a hydrophobic peptide signal to quantitate a hydrophilic peptide, and vice versa. This latter conclusion was further supported in similar studies performed on the mixture of peptides resulting from tryptic digestion of the protein bovine serum albumin.
17
Astorga-Wells, Juan. "Microfluidic electrocapture technology in protein and peptide analysis /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7349-965-x/.
Повний текст джерела
18
Erb, William Joseph Owens Kevin G. "Exploration of the fundamentals of matrix assisted laser desorption/ionization time-of- flight mass spectrometry /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1765.
Повний текст джерела
19
Tang, Ho-wai, and 鄧浩維. "Studies on surface-assisted laser desorption/ionization and its analytical application in imaging mass spectrometry." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47145559.
Повний текст джерелаАнотація:
Surface-Assisted Laser Desorption/Ionization Mass Spectrometry (SALDI-MS) is an analytical technique enabling direct chemical analysis of solid samples. Analytes could be desorbed/ionized upon nitrogen laser irradiation from a SALDI substrate-coated sample, then analyzed by MS. The substrate is involved in the transfer of laser energy to the analytes, and eventually assists the desorption/ionization of analytes. The analytical performance of SALDI-MS, such as detection sensitivity, is dependent on different parameters of the substrate, such as size, morphology and form. In this thesis, the effects of several substrate parameters on the SALDI process were investigated. SALDI-MS based Imaging Mass Spectrometry (IMS) method was also developed using efficient SALDI substrate identified in the fundamental studies. IMS is a chemical-specific mapping technique which allows parallel mapping of multiple analytes in solid samples.
The desorption mechanism of SALDI is investigated using two groups of substrate, the carbon allotropes and the noble metal nanoparticles. Ion desorption efficiency and internal energy transfer were probed and correlated in carbon-based SALDI. It was found that the ion desorption efficiency and internal energy transfer was in opposite order. Substrate that transferred more internal energy to ions did not show higher ion desorption efficiency. This result could not be explained by the Thermal Desorption model which was a generally believed mechanism of the SALDI desorption process. A non-thermal model, the Phase Transition model is proposed to account for the
SALDI desorption process. The Phase Transition model suggests that the substrate is melted/ restructured upon laser irradiation, and this will assist ion desorption. The Phase Transition model is supported by the morphological change of carbon substrates after SALDI and high initial velocity of ions desorbed by carbon-based SALDI (> 1,000 ms-1).
SALDI-MS is useful for small molecule analysis due to the relatively clean
background in the low mass region. SALDI-IMS is developed and applied to the imaging of spatial distribution of small molecules in forensic and biological samples. Gold nanoparticles (AuNPs) was selected as the substrate from several other noble metal NPs. A solvent-free method, argon ion sputtering, was employed for coating AuNPs on sample surface prior to SALDI-IMS analysis. Fine details of the samples, such as the fine pattern of latent fingerprints and handwriting on questioned documents can be preserved and imaged reliably by avoiding the use of solvent. Fatty acids, drugs and ink components can be imaged in forensic samples including latent fingerprints, banknotes and checks. The solvent-free SALDI-IMS method was also applied to image the distribution of metabolites in intact animal tissues. Spatial distributions of neurotransmitters, nucleobases and fatty acids can be imaged from mouse brain and tumor tissue sections.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
20
Smith, Donna M. "Matrix Assisted Laser Desorption Ionization Quadrupole Time-of-Flight Mass Spectrometry of Poly(2-Vinylpyridine)." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1110337309.
Повний текст джерела
21
Fiorentino, Michael Armond. "Immediate observation of matrix assisted laser desorption ionization products in a Fourier transform mass spectrometer /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004264.
Повний текст джерела
22
Moyer, Susanne Catharine. "Phosphotyrosine peptide fragmentation by atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3080729.
Повний текст джерела
23
An, Hyun Joo. "Characterization of protein-bound oligosaccharides using matrix-assisted laser desorption/ionization Fourier transform mass spectrometry /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
Повний текст джерела
24
Ochoa, Mariela L. "Forensic and Proteomic Applications of Thermal Desorption Ion Mobility Spectrometry and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry." Ohio University / OhioLINK, 2005. http://www.ohiolink.edu/etd/view.cgi?ohiou1113585811.
Повний текст джерела
25
Krutchinsky, Andrew. "A collisional damping interface for a time-of-flight mass spectrometer with both electrospray ionization and matrix assisted laser desorption ionization." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0009/NQ31999.pdf.
Повний текст джерела
26
Chen, Yanfeng. "Analysis of Biological Molecules Using Stimulated Desorption Photoionization Mass Spectrometry." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14620.
Повний текст джерелаАнотація:
Surface-assisted laser desorption/ionization mass spectrometry (SALDI MS) is a novel technique for direct analysis of organic and biological molecules. Amino acids, dipeptides, and organoselenium compounds were successfully detected by SALDI on carbon and silicon surfaces. Surface effects, solvent effects, temperature effects and pH effects were studied. A possible mechanism of SALDI is proposed based on observed results.
In general, stimulated desorption results in neutral yields that are much larger than ion yields. Thus, we have exploited and further developed laser desorption single photon ionization mass spectrometry (LD/SPI MS) as a means of examining biomolecules. The experimental results clearly demonstrate that LD/SPI MS is a very useful and fast analysis method with uniform selectivity and high sensitivity.
Selenium (Se) is an essential ultra-trace element in the human body. In efforts to obtain more useful information of selenium metabolites in human urine, mass determination of unknown organoselenium compounds in biological matrices using SALDI MS was investigated. In another approach, several selenium metabolites in human urine were successfully detected by LD/SPI MS. A HPLC-MS/MS method was also developed for a quantitative case study of selenium metabolites in human urine after ingestion of selenomethionine.
Low-energy electrons (LEE, 3-20 eV) have been shown to induce single and double strand breaks (SSB and DSB) in plasmid DNA. To understand the genotoxic effects due to secondary species of high-energy radiation, we investigate the role of transient negative ions and the specificity in LEE-DNA damage by examining the neutral product yields using low electron stimulated dissociation SPI MS. The neutral yields as a function of incident electron energy are also correlated with the SSBs and DSBs measured using post-irradiation gel electrophoresis. The results provide further insight concerning the mechanisms of LEE-induced damage to DNA.
Overall, this research provided an in-depth understanding of non-thermal surface processes and the development of new mass spectrometric techniques for the analysis of biomolecules.
27
Zhang, Jinhua. "Characterization and structural elucidation of oligosaccharides by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
Повний текст джерела
28
SUH, MOO-JIN. "MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRY OF BACTERIAL RIBOSOMAL PROTEINS AND RIBOSOMES." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1106583486.
Повний текст джерела
29
Abell, Darcy Cameron. "Analysis of potato glycoalkaloids by ELISA and matrix assisted laser desorption/ionization time-of-flight mass spectroscopy /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22940.pdf.
Повний текст джерела
30
Ratcliffe, Lucy Vivien. "Proteomic strategies for protein and biomarker identification by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)." Thesis, Nottingham Trent University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431885.
Повний текст джерелаАнотація:
This thesis describes the development of novel strategies for the analysis of peptides by MALDI mass spectrometry. The developed techniques are applied to the identification of protein and proteomic biomarkers for melanoma. A commercial atmospheric pressure (APMALDI) source (MassTechnologies, Burtonsville, MD, USA) was modified to allow operation with a high powered nitrogen laser and independent PC control of the sample stage. A software interface was developed using LabVIEW 6.1 that allows full control of the target position with respect to the laser fibre optic interface, allowing the target to be adjusted within any point within a particular sample spot to enhance signal quality. The modified AP-MALDI-QIT interface was evaluated for the analysis of standard peptide mixtures and tryptic digests of proteins. AP-MALDI-QIT analysis of tryptic peptides following capillary liquid chromatographic (LC) separation and direct analysis of a protein digest is reported. Peptide fragments were identified by peptide mass fingerprinting from mass spectrometric data and sequence analysis obtained by tandem mass spectrometry of the principal mass spectral peaks using a data-dependent scanning protocol. These data were compared with those from mass spectrometric analysis using capillary LC/MALDI-time-of-flight (TOF) and capillary LC/electrospray ionisation (ESI)-quadrupole TOF. For all three configurations the resulting data were searched against the MSDB database, using MASCOT and the sequence coverage compared for each technique. Complementary data were obtained using the three techniques. A bottom-up proteomic methodology for the peptide profiling of human serum samples using MALDI mass spectrometry was developed. Reproducibility studies were carried out to define the MALDI measurement precision. Pre-analytical sample handling factors, such as room temperature incubation and freeze thaw cycles have also been investigated. The methodology developed was applied to the analysis of serum peptides from stage IV melanoma patients and healthy control subjects. Prediction of human melanoma metastatic cancer from peptide profiling using artificial neural networks (ANNs) model classified 98 % of samples correctly. The identification of three out of six ions predicted by the ANNs model to be indicative biomarkers that have good predictive performance were identified using MALDI PSD, AP-MALDI MSIMS and LC-ESI-MS/MS. Two of the ions were shown to belong to the same identified peptide, u-l-acid glycoprotein precursor (l, 2) which correctly predicted 95 % (i.e. 45/50) of metastatic melanoma patients.
31
Eng, Tony Liang. "De novo peptide sequencing from matrix-assisted laser desorption/ionization-time of flight post-source-decay spectra." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86584.
Повний текст джерела
32
Hoteling, Andrew J. "MALD/I TOF PSD and CID : understanding precision, resolution, and mass accuracy and MALD/I TOFMS : investigation of discrimination issues related to solubility /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/318.
Повний текст джерела
33
Holcomb, April M. Owens Kevin G. "Investigation into the ionization mechanism occurring in matrix assisted laser desorption ionization and factors affecting ion flight time in MALDI time-of-flight mass spectrometry /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3161.
Повний текст джерела
34
Sorensen, Christina M. "ESI-MS and MALDI-TOF-MS for the characterization and analysis of metallo-oligomers and proteins." Laramie, Wyo. : University of Wyoming, 2005. http://proquest.umi.com/pqdweb?did=1031044031&sid=4&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Повний текст джерела
35
Driedger, Darcy R. "Analysis of potato glycoalkaloids by immunoassay coupled to capillary electrophoresis or matrix-assisted laser desorption/ionization mass spectrometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0011/NQ59948.pdf.
Повний текст джерела
36
Lam, Sze-ki Clare, and 林思琪. "Matrix-assisted laser desorption ionization time-of-flight mass spectrometry for identification and antifungal susceptibility of penicillium marneffei." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206605.
Повний текст джерелаАнотація:
Penicillium marneffei is the most important thermal dimorphic fungus causing systemic mycosis in HIV-infected patients in Southeast Asia. However, laboratory diagnosis based on microscopic morphology and mycelial-to-yeast conversion is time-consuming and expertise-dependent. The performance of the Bruker MALDI-TOF MS system for identification of mold and yeast cultures of 59 P. marneffei strains were evaluated by using the direct transfer method. Using the Bruker databases, BDAL v4.0.0.1 and Filamentous Fungi Library 1.0, the 59 P. marneffei strains grown in mold and yeast phase were identified as P. funiculosum (score <1.7) and P. purpurogenum (<1.7) respectively. When the combined database was expanded with inclusion of spectra from 20 P. marneffei strains grown in mold, yeast or both phases, all the remaining 39 P. marneffei strains grown in both mold and yeast phase were correctly identified to the species level with score >2.0. The spectra of P. marneffei exhibited significant difference to those of the closely related species, P. brevi-compactum, P. chrysogenum, Talaromyces aurantiacus and T. stipitatus (one strain included for each species). P. brevi-compactum was identified to the genus level (as P. brevi-compactum but with score <2.0) and P. chrysogenum was unidentified (as P. chrysogenum but with score <1.7) using the combined database with or without spectra from P. marneffei. Both T. aurantiacus and T. stipitatus were unidentified (as wrong species with score <1.7). MALDI-TOF MS is useful for rapid identification of both yeast and mold cultures of P. marneffei, but this requires expansion of the database using P. marneffei strains.
Since the susceptibilities of P. marneffei to the newer antifungal drugs are not well studied, their in vitro antifungal activities against the 59 isolates of P. marneffei were also investigated in accordance with CLSI M27-A3 microdilution method. MICs of itraconazole, voriconazole, posaconazole and anidulafungin for yeast form of P. marneffei were determined. The MICs of itraconazole, voriconazole, posaconazole and anidulafungin were 0.00128-0.00256 μg/ml, 0.01565-0.0625 μg/ml, 0.000978-0.001956 μg/ml, 2-8 μg/ml respectively. The results suggested that the azoles have similarly good activities against P. marneffei, whereas anidulafungin was the least active.published_or_final_version
Microbiology
Master
Master of Medical Sciences
37
Dunn, Jamie D. "Polymer-modified plates for enrichment of phosphopeptides prior to analysis by matrix-assisted laser desorption/ionization mass spectrometry." Diss., Connect to online resource - MSU authorized users, 2007.
Знайти повний текст джерела
38
Chen, Cheng-Tai, and 陳振泰. "Study of TiO2-sol-gel assisted desorption/ionization mass spectrometry." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/11145021475112867836.
Повний текст джерелаАнотація:
碩士國立交通大學
應用化學系碩博士班
91
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been widely used in the analysis for various types of analytes. The analysis results mainly rely on the selections of MALDI matrices. The solubility and co-crystallization between analytes and matrices are the major concerns in MALDI analysis. A new matrix system was developed to replace the usage of conventional MALDI matrix to avoid these problems. The TiO2 sol-gel-deposited thin film was employed as the sample substrate to assist the UV laser desorption/ionization of analytes in laser desorption/ionization mass spectrometric analysis. Only one step of sample preparation by simply depositing the analytes on the TiO2 film was required before sending the sample into the mass spectrometer. Thus, the concerns about the solubility and co-crystallization between analytes with matrices do not arise in this approach. The detectable molecule with the greatest molecular weight was about 8.5 kDa. Owing to the strong interference contributed by the TiO2 film in the low-mass region, this approach is only suitable for molecular sizes with masses larger than 500 Da. It was also found that the roughness on the surface of the TiO2 film might affect the detection limit in the analysis. Various amounts of polyethylene glycol (PEG) were added into the TiO2 sol during sol-gel process. The TiO2 sol-gel/PEG hybrid material was spin-coated on a glass slide. PEG in the TiO2 film was removed during heated at a temperature of 500℃, which resulted in generating a rough surface for the TiO2 film. Furthermore, the absorption capacities of the TiO2 films were increased as the degree of the roughness increased at a wavelength of 337 nm. The intensities of analytes signals in the MALDI mass spectra were enhanced when the analytes was desorbed from a TiO2 film with a rougher surface. Additionally, owing to the characteristic of TiO2-sol-gel being a good molecularly imprinted material, a molecular recognition-based mass spectrometry based on using TiO2-sol-gel as the molecular-imprinting material was developed. α-Cyclodextrin (CD) was selected as the template molecule and doped into the TiO2-sol-gels in a sol-gel reaction. The molecularly imprinted TiO2 sol was spin-coated on a glass slide, and appropriate template cavities in the TiO2 sol-gel material were formed after the template molecules were removed. This modified glass slide can be used to select α-CD from a sample solution; α-CD was directly detected from the modified glass slide by TiO2 sol-gel assisted laser desorption/ionization mass spectrometry. In addition to size complementarity between α-CD and the cavities imprinted in the TiO2 film, it is believed that the hydroxyl groups located around the binding pocket are involved in discriminating between analytes through significant hydrogen bonding interactions, The detectable concentration for α-CD was about 50 ppb for an 18mL of sample solution.
39
Chiang, Ni-Chen, and 江妮蓁. "Nanomaterials for Bioanalysis in Surface-Assisted Laser Desorption/Ionization Mass Spectrometry." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/72763000084814143996.
Повний текст джерелаАнотація:
碩士國立臺灣大學
化學研究所
97
This thesis is divided into two parts. In the first part, we have employed two sets of differently sized (average diameters: 3.5 and 14 nm) gold nanoparticles (Au NPs) as selective probes and matrices for the determination of aminothiols in biological samples using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Because of their higher ionization efficiency, the 3.5-nm-diameter Au NPs exhibited greater desorption/ionization efficiency toward the aminothiols than did the larger Au NPs; centrifugation of these small Au NPs was, however, difficult. To solve this problem, we investigated the use of mixtures of the 3.5- and 14-nm Au NPs; in this case, the analyte-induced Au NP aggregates were readily centrifuged, providing greater concentration efficiency. When using 38 and 150 pM solutions of the 3.5- and 14-nm Au NPs, respectively, as the probe and matrix, SALDI-MS provided limits of detection (signal-to-noise ratio = 3) of 2, 20, and 44 nM for 1.0-mL solutions of glutathione (GSH), cysteine (Cys), and homocysteine, respectively. We validated the practicality of this approach—with its advantages of sensitivity, reproducibility, rapidity, and simplicity—through the analysis of GSH in MCF-7 cell lysates and Cys in plasma. In the second part, we have synthesized and investigated the uses of nanomaterials, including Au NPs, Pt nanosponges (NSP), Fe3O4 NPs, TiO2 NPs, Se NPs, and CdTe quantum dots (QDs), as SALDI-MS matrixes for the analysis of small molecules, peptides and proteins. Although those nanomaterials served as useful inorganic matrixes in the SALDI-MS measurements, SALDI-MS performance with respect to sensitivity, reproducibility, and mass range is highly dependent on the nature and concentrations of NPs. Thus, our aim of this study is to evaluate different NP matrixes for analyzing biomolecules in those optimum conditions. We found that for small solutes (e.g. glutathione), Au NPs provided the lowest (140 fmol) limit of detection (LOD) at signal-to-noise ration 3. And the upper detectable mass range is approximately 25 kDa by using Pt NSPs and Fe3O4 NPs as the SALDI-MS matrix. For efficient desorption and ionization, nanomaterials need to have a strong absorption of laser energy and an efficient proton energy transfer to the analytes, while their interactions with analytes can not be too strong. With respect to sensitivity, the nanomaterials must be stable under laser irradiation; minimum formation of clusters from the nanomaterials such as Au clusters. Although Fe3+ and Cd2+ have strong interactions with proteins, leading to improved ionization efficiency (sensitivity), they cause peak broadening (loss in mass resolution).
40
Wang, Yu-Wen, and 王鈺雯. "Development of Electrode-Assisted Desorption Electrospray Ionization and Its biomedical Applications." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/67738758668009086608.
Повний текст джерелаАнотація:
碩士臺灣大學
化學研究所
98
Ambient ionization mass spectrometry has recently played an important role in Biological Mass Spectrometry because pre-treatment of samples is not required. It can be used for direct analysis of solid and liquid samples with a simple mass spectrometer. We developed the novel Electrode-Assisted Desorption Electrospray Ionization (EADESI) method for quick biomedical sample analysis. EADESI is a novel ambient ionization method which can be used as detection of samples on nearly any type of substrate. The instrument consists of three major parts: a three-dimensional movable sample plate with ground potential, a high voltage electrode, and a spray source. The spray source and electrode are positioned at about 45° with respect to each other and directly above the sample plate. Solvent nebulized by gas was used as a spray device to spray onto the sample, and then the desorbed analyte ions were introduced into the mass spectrometer. Our results indicated that EADESI can have space resolution of 25 μm. EADESI also has a wide dynamic range for different types of biomedical compounds.
41
Chen, Wen-Tsen, and 陳玟岑. "Bioanalysis of Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Using Nanomaterials." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/07053806639731332071.
Повний текст джерелаАнотація:
博士國立臺灣大學
化學研究所
101
This thesis focuses on synthesizing nanomaterials through surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) for the analysis of captopril and catechins in urines and tea samples, respectively, and for the investigation of protein-protein interaction in addition to the detection of single- and double-stranded oligodeoxynucleotides (ss- and ds-ODNs, respectively). The thesis is divided into five parts. Chapter one introduces the framework and background of basic principles of mass spectrometry, the soft ionization method, MALDI, SALDI, generally applied in MS, and analysis of captopril, tea catechins, proteins and protein-protein complexes, and ODNs. In chapter two, an internal standard comprised captopril (CAP) mixed with 14-nm-diameter gold nanoparticles (Au NPs) was introduced. The analytes were first captured using the unmodified 14-nm Au NPs; followed by addition of the internal standard (CAP-Au NPs) and the analysis of the sample using SALDI-MS. This approach provided linearity for CAP over the concentration range 2.5–25 μM, with a limit of detection (signal-to-noise ratio = 3) of 1 μM. This approach provided good quantitative linearity and reproducibility (relative standard deviations: <10%) of CAP for the determination of the levels of CAP in human urine samples. In chapter three, SALDI-MS using titanium dioxide nanoparticles (TiO2 NPs) as the matrix and captopril (CAP) as internal standard were used for the determination of the concentrations of theanine and four catechins—catechin, (_)-epigallocatechin (EGC), (_)-epicatechin gallate (ECG), and (_)-epigallocatechin gallate (EGCG). This SALDI-MS approach provides good quantitative linearity and sensitivity (LOD at the femtomole-to-picomole level) for these five analytes. It also provides good reproducibility, spot-to-spot and batch-to-batch variations of less than 10 and 13%, respectively, for the analysis of tea samples, with identified peaks for theanine and four catechins. Tea samples from Taiwan and four other countries have various SALDI-MS profiles, showing their potential for differentiation of tea samples from different sources. The result also shows that tea samples harvested in different seasons and counties in Taiwan provide significantly different MS profiles. The fourth chapter utilizes the mercury-tellurium (HgTe) nanomaterials chosen as SALDI-MS matrices in the detection of proteins and weak protein–protein complexes, such as a1-antitrypsin–trypsin and IgG–protein G complexes, in the presence of stabilizing Brij 76 surfactant and Zn(II) ions. This soft and sensitive technique allows the detection of weak protein complexes at the picomole level under mild conditions. In addition, we observed multiple charged states for these two complexes, respectively. This simple and reproducible (RSD <25%) approach holds great potential for the detection of other proteins and their complexes for various omics such as proteomics. The fifth chapter describes the use of SALDI-MS with HgTe nanostructures acting as the matrix for the detection of ss- and ds-ODNs. The present approach provides good sensitivity (LOD at the femtomole-to-picomole level) and reproducibility (variation: <23%) for the detection of ss-ODNs (up to 50-mer) and ds-ODNs (up to 30 base pairs). Furthermore, the practicality of this approach was applied for the analysis of a single nucleotide polymorphism (SNP) that determines the fate of the valine residue in the b-globin of sickle cell megaloblasts. This simple and reproducible approach employing HgTe nanostructures as matrices appears to hold great potential for use in genomic diagnosis.
42
Lee, Chuping, and 李竹平. "Mechanism of Matrix-Assisted Laser Desorption/Ionization (MALDI) and Its Applications." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3gjhd5.
Повний текст джерелаАнотація:
博士國立臺灣大學
化學研究所
106
Matrix-assisted laser desorption/ionization (MALDI) is one of the important methods in mass analysis for biomolecules. To improve the application of MALDI in bioanalysis, it is vital to understand the ionization mechanism. Here we study the three topics, which are the mechanism of protonated ion, the mechanism of metal-related ion separately, and then we compare some softer ionization methods to find out the method soft enough for some fragile molecules in MALDI. In the first topic of the protonated ion generation mechanism in MALDI, generating the first ions remains the most controversial part of the ionization mechanism. Several mechanisms have been proposed to explain the mechanism of ion generation in MALDI. However, the truthfulness of each mechanism in MALDI are difficult to determine because it is not easy to quantitatively measure the contributions of these mechanisms. The ionization mechanism of UV-MALDI was investigated by measuring the total cation intensity (not including sodiated and potasiated ions) as a function of analyte concentration (arginine, histidine, and glycine) in matrix of 2,4,6-trihydroxyacetophenone (THAP) using time-of-flight (TOF) mass spectrometer. The total ion intensity increased up to 55 times near the laser fluence threshold as the arginine concentration increased from 0% to 1%. The increscent were small for the case of histidine, and almost no increase occurred regarding for glycine. The increases became small for all analytes mentioned at high laser fluence. Here, thermal proton transfer model was used to predict the ion intensity as a function of analyte concentration. The increase of ion intensity can be explained by the thermal proton transfer model in the primary ion generation in MALDI. In the second topic of the metal-related ion generation mechanism in MALDI, preformed ions are generally accepted as a unspoken mechanism. Three separate experiments were demonstrated that thermally induced dissolution of salts can make significant contribution in metal ion generation in MALDI. In the first experiment, ion intensities from two different types of samples were measured. Several single crystals were grown from the solution containing 2,5-DHB matrix and salt (LiCl and NaCl). One group of crystals was washed by deionized water before sending into mass spectrometer. The other group of crystals was used directly. The intensities of metal ion and metal adducts of the matrix ion obtained from unwashed crystals were higher than those from crystals washed with deionized water, indicating that metal ion and metal adducts of the matrix ion mainly generated from the surface, not inside the 2,5-DHB crystal. The contributions of preformed metal ions and metal adducts of the matrix ions inside the matrix crystals were minor. In the second experiment, mass spectra of MALDI from two groups of samples were measured for comparison. One group of samples was the mixture of dried matrix powder, salt (LiCl and NaCl) and analyte powder. No solvent was used in this sample preparation method. The other group of samples was powder from the crystal of dried droplet, which the solution of droplet contained matrix, salt and analyte. Metal adducts of the matrix and analyte ion intensities generated from these two samples are similar, indicating that the contribution of the preformed metal adducts of the matrix and analyte ions were insignificant. In the third experiment, the correlation between the metal-related ion intensity fluctuation and the protonated ion intensity fluctuation was observed, indicating that the generation mechanism of the metal-related ions is similar to that of the protonated ions. The thermally induced proton transfer model effectively describes the generation of the protonated ions; we suggest that metal-related ions are mainly generated from the salt dissolution in the matrix melted by the laser. In the final topic, MALDI is one of the soft ionization methods in mass analysis for protein and glycan, but some fragile glycans with sulfate or sialic acid tend to lose the sulfate and sialic acid during the ionization process. The intensity of intact ion is usually small, and sometime no intact ions are observed at all. In recent years, many studies purposed new matrices to reduce the in-source and post-source decays as well as to increase the sensitivity of intact molecules. These matrices include (1) frozen sample (2) trilayer sample (3) HgTe nanostructures (4) 5-methoxysalicylic acid (MSA) (5) 2,5-dihydroxybenzoic acid butylamine (DHBB) (6) matrix-assisted ionization (MAI). Because different analytes were used in these studies, it is difficult to compare the softness of ionization for these matrices. In this study, we used these matrices and several fragile analytes to investigate softness of these matrices in the ionization process. These analytes include heparin disaccharide I-S, ganglioside GD1a, pullulan and dextran. We proved that frozen sample provide soft ionization and enhanced ion intensity.
43
Kuo, Shan-Jen, and 郭善仁. "Nanoparticle mass spectrometry with electrospray ionization and matrix-assisted laser desorption/ionization as the ion source." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/64788027228962549777.
Повний текст джерелаАнотація:
碩士國立臺灣大學
化學研究所
90
The quadrupole ion trap (QIT) was first invented by Paul and Steinwedel in 1960. It has been used in various fields, for instance, mass analysis of atomic, molecular, and cluster ions. In commercially available ion trap mass spectrometer (ITMS), a radio-frequency (RF) ac field (typically 1MHz)is applied between the ring and the end-cap electrodes of the trap. This frequency limits the mass analysis range of ITMS. Traditionally, most of the ITMS are combined with microchannel plates (MCP) or channeltron electron multiplier (CEM) detectors. These kinds of mass spectrometers are particularly suitable for smaller ions detection, because large charged particles have the lower impact velocities on the detector elements. We adopt electrospray ionization (ESI) and matrix assisted laser desorption/ionization (MALDI) as two different ionization methods to produce high mass charged particles, and an audio-frequency ion trap for trapping these large charged particles. We used a photomultiplier tube (PMT) to collect scattered laser light from charged particles as the detecting method and also to calibrate such mass spectra. The mass spectrometer is suitable for interrogating high-mass particles, that are heavier than 1000000 Daltons (particle sizes ranged from 100nm to several micrometer).
44
Luehr, Teesha Crystal. "Multiplexed matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) biomarker discovery." Thesis, 2017. https://dspace.library.uvic.ca//handle/1828/8913.
Повний текст джерелаАнотація:
The work presented herein is a method optimization for biomolecule detection and identification using Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging (MALDI-MSI). MALDI-MSI is a unique form of mass spectrometry that is highly multiplexed; it can simultaneously retain location information of the mass of multiple ions, allowing for correlation of morphology or pathology to reconstructed ion heat maps. There were three main objectives for the research - 1) A method optimization of sample preparation techniques for bottom-up proteomic MALDI-MSI was performed. This included the optimization of tissue wash steps, trypsin digestion incubation times, and matrix deposition techniques. The results included identifying the appropriate pH for the wash steps to optimize trypsin digestion, an overnight trypsin incubation to allow for complete digestion, and the inclusion of MCAEF – Matrix Coating Assisted by an Electric Field – during matrix coating for enhanced spectra. 2) An unbiased statistical data processing workflow for simultaneous processing of multiple datasets was performed. This was done using a thyroid hormone treated tadpole dataset to gain insight into the metabolism of anuran metamorphosis. Results found included a finalized data processing workflow that detected 5000 metabolite features from five organs were detected in pre-metamorphic tadpoles. Of these detected metabolites, 136 were significantly affected upon exposure to thyroid hormone and 64 metabolites were putatively identified. 3) A sample preparation technique for metabolomic analysis of formalin-fixed paraffin embedded (FFPE) colorectal liver metastasis samples was performed. Results included the importance of using a high mass resolution mass spectrometer while emphasizing more appropriate use of fresh-frozen tissue sections for metabolomic analysis.Graduate
45
Huang, Yu-Hui, and 黃郁惠. "Nanomaterials Based Surface-Assisted Laser Desorption/Ionization Mass Spectrometry for Oligodeoxynucleotide-Drug Complexes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/43683345685577175283.
Повний текст джерелаАнотація:
碩士國立臺灣大學
化學研究所
103
A surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using HgTe nanostructures as the matrix has been employed for the detection of four 15-base oligodeoxynucleotides (ODNs) and their complexes with mitoxantrone (MTX) that is a common drug for treatment of acute myeloid leukemia (AML) patients. The major peaks for the four tested ODNs are genes found in AML patients at m/z values of 4571, 4586, 4610, and 4635, while they are at m/z values of 5017, 5031, 5055, and 5079 for their corresponding complexes with MTX. The ODN with m/z value of 4610 is assigned for a normal gene of AML, while the other three are single-base mutant ODNs. This approach allows detection of the tested ODNs at the concentrations down to 2 nM, showing their potential for diagnosis of AML. The dissociation constants values of the four tested ODN-MTX complexes determined by the SALDI-MS approach are similar and all in the μM level, which agree with that determined by applying a conventional absorption approach. Relative to the conventional approach, the SALDI-MS approach has advantages of simplicity, rapidity, reproducibility, and use of smaller amounts of ODNs and MTX.
46
Griffin, Timothy J. "Genetic analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry." 1999. http://catalog.hathitrust.org/api/volumes/oclc/43651475.html.
Повний текст джерела
47
Hsieh, Yi-Ting, and 謝依婷. "Detection of Monophosphate Nucleotides ThroughSurface-Assisted Laser Desorption/Ionization MassSpectrometry Using Gold Nanoparticles." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/73621759268878091646.
Повний текст джерелаАнотація:
碩士臺灣大學
化學研究所
98
This thesis is that we demonstrated the determination of monophosphate nucleotides through the surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using hexadecyltrimethylammonium bromide (CTAB) adsorbed gold nanoparticles (CTAB-Au NPs). The binding of four monophosphate nucleotides — adenosine 5’-monophosphate (5’-AMP), guanosine 5’-monophosphate (5’-GMP),uridine 5’-monophosphate (5’-UMP) and cytidine 5’-monophosphate (5’-CMP) — to the surfaces of these CTAB-Au NPs induced their aggregation, which allowed selective concentration of the four analytes from sample solutions. The analytes adsorbed CTAB-Au NPs were directly subjected to SALDI-MS measuremen, preventing a need of mixing the analytes with organic matrices. Our results revealed that CTAB was effective to improve ionization efficiency of the analytes and to suppress the MS background from Au clusters. By using CTAB-Au NPs that were prepared by mixing 0.4 μM CTAB with 1.8 nM Au NPs, our SALDI-MS approach provided the detection of limits at a signal-to-noise ratio of 3 of 25, 25, 5 and 10 nM for 5’-CMP, 5’-UMP, 5’-AMP and 5’-GMP, respectively. We have successfully validated the practicality of this approach through the analyses of 5’-AMP, 5’-GMP, 5’-UMP and 5’-CMP in the mushrooms extracts and of 5’-GMP in monosodium glutamate. Our approach provides advantages of simplicity, sensitivity, and reproducibility (shot-to-shot variation less than 20%) for the the determination of the concentrations of the analytes in the biological samples。
48
Wu, Chen-I., and 吳偵憶. "Using Matrix-Assisted Laser Desorption Ionization/Time-of-Flight Mass Spectrometry for the Rapid Diagnosis of Occult Blood in Feces by Matrix-Assisted Laser Desorption Ionization/Time-of-Flight Mass Spectrometry." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/21585363718662964254.
Повний текст джерелаАнотація:
碩士國立中山大學
化學系研究所
94
Abstract In this paper we demonstrate that matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry can be used to rapidly detect occult blood in human feces. The water-soluble hemoglobins, which are the most predominant proteins found in blood, were used as protein biomarkers for the presence of occult blood. The proteins were best extracted from feces using a small amount of pure water and then separated from the feces through centrifugation. We found that saturated 4-hydroxy-α-cyanocinnamic acid (α-CHC) solution was the best MALDI matrix for hemoglobin analysis; this matrix was mixed with the aqueous solution extracted from the feces at a volumetric ratio of 1:1. Although the MALDI-TOF MS results obtained using real samples were consistent with those provided through conventional chemical analysis, the detection limit of occult blood (0.1–1 μg/mg of feces) in feces when using MALDI MS was approximately 10–100 times lower than that of the conventional approach. In addition, materials that commonly interfere with the conventional chemical assaying of occult blood in feces—such as foods containing animal blood—do not interfere with the detection of the hemoglobin biomarkers during MALDI-TOF MS analysis.
49
Fitzgerald, Michael C. "The analysis of nucleic acids by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry." 1994. http://catalog.hathitrust.org/api/volumes/oclc/31943244.html.
Повний текст джерела
50
Wu, Hsin-pin, and 吳欣頻. "The applications of metal nanoparticles : Biosensor and surface assisted laser desorption/ionization mass spectrometry." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/5dm8kk.
Повний текст джерелаАнотація:
碩士國立中山大學
化學系研究所
96
The thesis is divided into four sections. 1. Sample-first preparation: A method for surface-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of cyclic oligosaccharides：In this work, we report the application of a sample first preparation method for the analysis of cyclic oligosaccharides when using bare AuNPs as the assisted matrix. In the sample first method, the analyte is deposited first and then followed by the bare AuNPs. The cyclic oligosaccharides, including α-, β-, andγ-cycodextrin (CD), are difficult to ionize by MALDI-MS, but they could be cationized very efficiently using bare AuNPs as matrixes in combination with a sample first preparation method. The sample first method not only provides high sensitivity for the measurement of neutral carbohydrate but also improves the spot homogeneity. This practical method was further validated by the analyses of biological samples, including neutral carbohydrate, neutral steroid, aminothiols, and peptides. 2. Gold nanoparticles as assisted matrix for detecting small biomolecules from high salt solutions through laser desorption/ionization mass spectrometry：The neutral steroid and carbohydrates, which are difficult to be ionized by using MALDI, but cationized very efficiently by SALDI coupled with the sample first preparation method even if they are dissolved in a high-concentration NaCl solution. Under identical conditions, this practical method was further validated by the analysis of indolamines and peptides. It has also been utilized to analyze the small biomolecules in urine samples. 3. Phosphate-modified TiO2 nanoparticles for selective detection of dopamine, levodopa, adrenaline, and catechol based on fluorescence quenching：In contrast to these studies, we report a simple approach for the selective detection of DA, L-DOPA, and adrenaline by phosphate-modified TiO2 (P-TiO2) NPs in the presence of fluorescein. After the binding of DA, the P-TiO2 NPs become neutral and even positively charged. The adsorption of fluorescein on the particles results in the quenching of fluorescein by TiO2-DA complexes, which have strong absorption at 428 nm. By monitoring the decreases in fluorescence at 520 nm for fluorescein, we calculated the limits of detection (LODs) for DA, L-DOPA, and adrenaline at a signal-to-noise (S/N) ratio of 3, which were 33.5, 81.8, and 20.3 nM, respectively. The results imply that the proposed methods have great potential for use in the selective analysis of catecholamines in biological samples and clinical applications. 4. Sodium hydroxide as pretreatment and fluorosurfactant-capped gold nanoparticles as sensor for the highly selective detection of cysteine： Under acidic conditions, fluorosurfactant (FSN)-capped AuNPs are aggregated in the presence of homocysteine (HCys) and cysteine (Cys) but not in the presence of cysteinylglycine, glutathione, and γ-glutamycysteine. When adding NaOH to a solution of HCys, the five-membered ring transition state is formed through intramolecular hydrogen abstraction. By contrast, it is difficult for Cys to form a fourmembered ring transition state after Cys has been pretreated with NaOH. As a result, the HCys-induced aggregation of the FSN-capped AuNPs is suppressed because the five-membered ring transition state exhibits relatively larger steric hindrance and has stronger interaction with the FSN molecules. Thus, we can discriminate between Cys and HCys on the basis of different aggregation kinetics. Under the optimum condition, we have validated the applicability of our method through the analyses of Cys in urine samples. It is believed that this approach has great potential for the detection of Cys in biological samples.