Soft-landing ion mobility has applicability in a variety of areas. The ability to produce material and collect a sufficient amount for further analysis and applications is the key goal of this technique. Soft-landing ion mobility has provided a way to deposit material in a controllable fashion, and can be tailored to specific applications. Changing the conditions at which soft-landing ion mobility occurs effects the characteristics of the resulting particles (size, distribution/coverage on the surface). Longer deposition times generated more material on the surface; however, higher pressures increased material loss due to diffusion. Larger particles were landed when using higher pressures, and increased laser energy at ablation. The utilization of this technique for the deposition of silver clusters has provided a solvent free matrix application technique for MALDI-MS. The low kinetic energy of incident ions along with the solvent free nature of soft-landing ion mobility lead to a technique capable of imaging sensitive samples and low mass analysis. The lack of significant interference as seen by traditional organic matrices is avoided with the use of metallic particles, providing a major enhancement in the ability to analyze low mass compounds by MALDI.

No description available.

L’identification des micro-organismes reposait jusqu’à présent sur l’étude des caractères culturaux et biochimiques de chaque espèce. Depuis quelques années, la spectrométrie de masse de type Matrix Assisted Laser Desorption/Ionization Time Of Flight (MALDI-TOF) s’est développée dans les laboratoires de microbiologie clinique. Cette nouvelle technologie permet de réaliser très rapidement et à moindre coût un diagnostic d’espèce sur des colonies de bactéries ou de champignons isolées sur des milieux de culture solides.Dans un premier temps, nous avons montré que cette technologie permet de réaliser une identification des germes isolés en milieu liquide, comme les flacons d’hémoculture au cours des bactériémies par exemple. Ce dépistage se fait directement à partir du flacon positif, sans attendre l’isolement des colonies sur milieu solide. Ce diagnostic disponible dès le premier jour permet d’adapter l’antibiothérapie au phénotype de résistance habituel de l’espèce.Dans un deuxième temps, nous avons cherché à identifier la nature des biomarqueurs utilisés pour l’identification des espèces bactériennes, en prenant comme exemple la bactérie pathogène Neisseria meningitidis. La comparaison du génome et du protéome des souches entièrement séquencées a permis de mettre en évidence la nature exacte des protéines impliquées dans le diagnostic d’espèce. Par ailleurs, les protéines ribosomales étant majoritaires et pouvant servir d’outil épidémiologique, nous avons constaté que la mise en évidence de leurs variations sur le spectre de masse rend la différenciation de souches au sein d’une même espèce possible, en adaptant la méthode d’analyse. Enfin, nous avons présenté des résultats préliminaires encourageants sur l’exploitation du caractère constant de certaines protéines ribosomales visibles directement sur le spectre de masse, permettant de différencier des espèces très proches, comme Streptococcus pneumoniae et Streptococcus mitis. / Until now, bacterial and fungal identification has been based on biochemical characterization of microorganisms. The Matrix-Assisted Laser Desorption/Ionization Time of Flight Spectrometry (MALDI-TOF MS) has recently been developed in clinical microbiology laboratories. This new technology allows a rapid, accurate and less expensive identification of bacterial and fungal colonies grown on agar media. First, we have shown that the direct identification of bacteria grown in liquid media such as blood cultures was possible, without waiting for a subculture on solid media. Since the diagnosis is available on the first day, the presumptive antimicrobial treatment can be rapidly adapted according to the usual resistance phenotype of the microorganism. We have then searched to identify the biomarkers used for the identification of bacteria, using Neisseria meningitidis as a model. Comparing the genome and the proteome of sequenced strains allowed us to identify the ribosomal proteins as thoses involved in the MALDI-TOF MS diagnosis. Ribosomal proteins are very abundant and are very often used as epidemiological tools : their variations on the bacteria mass spectrum allows an intra-species differentiation of several strains. Finally we present encouraging preliminary results based on the detection of consistent ribosomal proteins directly visible on the mass spectrum that lead to the accurate identification of some very close species such as Streptococcus pneumoniae and Streptococcus mitis.

No description available.

Li, Gang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 102-108). / Abstracts in English and Chinese. / TABLE OF CONTENTS --- p.v / LIST OF FIGURES --- p.viii / LIST OF TABLES --- p.xi / ABBREVIATIONS --- p.xii / Chapter Chapter One --- Introduction / Chapter 1.1 --- Matrix-assisted Laser Desorption/Ionization (MALDI) --- p.2 / Chapter 1.1.1 --- Laser Desorption --- p.2 / Chapter 1.1.2 --- Matrix-assisted Laser Desorption/Ionization --- p.2 / Chapter 1.2 --- Time-of-flight Mass Spectrometry --- p.6 / Chapter 1.2.1 --- Linear Time-of-flight Mass Spectrometer --- p.6 / Chapter 1.2.2 --- Reflectron Time-of-flight Mass Spectrometer --- p.7 / Chapter 1.2.2.1 --- Linear-field Reflectron --- p.9 / Chapter 1.2.2.2 --- Nonlinear-field Reflectron --- p.12 / Chapter 1.3 --- Structural Analysis Using Time-of-flight Mass Spectrometer --- p.13 / Chapter 1.4 --- Project Objectives --- p.17 / Chapter Chapter Two --- Instrumentation and Experimental / Chapter 2.1 --- Instrumentation --- p.20 / Chapter 2.1.1 --- Laser system --- p.20 / Chapter 2.1.2 --- Flight Tube and Vacuum System --- p.20 / Chapter 2.1.3 --- Ion source --- p.22 / Chapter 2.1.4 --- Deflector and Time Ion Selector --- p.24 / Chapter 2.1.5 --- Two-stage Gridless Reflectron --- p.28 / Chapter 2.1.6 --- "Detectors, Digitizer and Computer System" --- p.28 / Chapter 2.2 --- Experimental --- p.31 / Chapter 2.2.1 --- Sample preparation --- p.32 / Chapter 2.2.2 --- PSD calibration --- p.32 / Chapter Chapter Three --- "Simulation Studies of Time Ion Selector, Collision cells and Curved-field Reflectron" / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Time Ion selector --- p.37 / Chapter 3.3 --- Collision cell --- p.46 / Chapter 3.3.1 --- Simulation of Collision Induced Dissociation (CID) Conditions --- p.46 / Chapter 3.3.2 --- Design and Performance Evaluation of Different Collision Cells --- p.48 / Chapter 3.4 --- Curved-field reflectron (CFR) --- p.58 / Chapter 3.4.1 --- Introduction --- p.58 / Chapter 3.4.2 --- Derivation of Analytical Equations --- p.58 / Chapter 3.4.3 --- Effect of Floating Potential of the Collision Cell --- p.65 / Chapter 3.4.4 --- Effect of R and θ Parameters --- p.65 / Chapter 3.4.5 --- Effect of Length of the Reflectron --- p.70 / Chapter 3.5 --- Conclusions --- p.73 / Chapter Chapter Four --- Construction and Performance Evaluation of Modified Time-of-flight Mass Spectrometer / Chapter 4.1 --- Benchmark Results for the Origin Reflectron Time-of-flight Mass Spectrometer --- p.75 / Chapter 4.2 --- Hardware Modifications of Reflectron Time-of-flight Mass Spectrometer --- p.75 / Chapter 4.2.1 --- Collision Cell --- p.75 / Chapter 4.2.2 --- Curved-field Reflectron --- p.79 / Chapter 4.3 --- Evaluation of the Curved-field Reflectron --- p.81 / Chapter 4.4 --- Evaluation of the field-shaped cylindrical collision cell --- p.85 / Chapter 4.5 --- Conclusions --- p.95 / Chapter Chapter Five --- Concluding Remarks / Chapter 5.1 --- Concluding Remarks --- p.100 / References --- p.101 / Appendix / Appendix 1 User program for time ion selection --- p.108 / Appendix 2 User program for gas collision --- p.111 / Appendix 3 MATHEMATICA program used in calculation for curved-fleld reflectron --- p.114

Since the introduction of electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI), there has been an unprecedented growth of biomolecule analysis using mass spectrometry (MS). One of the most popular applications for mass spectrometry is the field of proteomics, which has emerged as the next scientific challenge in the post-genome era. One critical step in proteomic analysis is sample preparation, a major bottleneck that is attributed to many time consuming and labor-intensive steps involved. Microfluidics can play an important role in proteome sample preparation due to its ability to handle small volumes of sample and reagent, and its capability to integrate multiple processes on a single chip with the potential for high-throughput analysis. However, to utilize microfluidic systems for proteome analysis, an efficient interface between microfluidic chip and mass spectrometry is required. This thesis presents several methods for coupling of microfluidic chips with ESI-MS and MALDIMS. III Three microfluidic-ESI interfaces were developed. The first interface involves fabricating a polymer based microchannel at the rectangular corners of the glass substrates using a single photolithography step. The second interface was build upon the previous interface in which a digital microfluidic platform was integrated with the microchannel in a “top-down” format. The integrated microfluidic system was used for inline quantification of amino acids in dried blood spots that have been processed by digital microfluidics. The third interface was formed by sandwiching a pulled glass capillary emitter between two digital microfluidic substrates. This method is a simpler and more direct coupling of digital microfluidics with ESI-MS as compared to the method used for second interface. Finally, a strategy using a removable plastic “skin” was developed to interface digital microfluidics with MALDI-MS for offline sample analysis. We demonstrated the utility of this format by implementing on-chip protein digestion on immobilized enzyme depots.

Since the introduction of electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI), there has been an unprecedented growth of biomolecule analysis using mass spectrometry (MS). One of the most popular applications for mass spectrometry is the field of proteomics, which has emerged as the next scientific challenge in the post-genome era. One critical step in proteomic analysis is sample preparation, a major bottleneck that is attributed to many time consuming and labor-intensive steps involved. Microfluidics can play an important role in proteome sample preparation due to its ability to handle small volumes of sample and reagent, and its capability to integrate multiple processes on a single chip with the potential for high-throughput analysis. However, to utilize microfluidic systems for proteome analysis, an efficient interface between microfluidic chip and mass spectrometry is required. This thesis presents several methods for coupling of microfluidic chips with ESI-MS and MALDIMS. III Three microfluidic-ESI interfaces were developed. The first interface involves fabricating a polymer based microchannel at the rectangular corners of the glass substrates using a single photolithography step. The second interface was build upon the previous interface in which a digital microfluidic platform was integrated with the microchannel in a “top-down” format. The integrated microfluidic system was used for inline quantification of amino acids in dried blood spots that have been processed by digital microfluidics. The third interface was formed by sandwiching a pulled glass capillary emitter between two digital microfluidic substrates. This method is a simpler and more direct coupling of digital microfluidics with ESI-MS as compared to the method used for second interface. Finally, a strategy using a removable plastic “skin” was developed to interface digital microfluidics with MALDI-MS for offline sample analysis. We demonstrated the utility of this format by implementing on-chip protein digestion on immobilized enzyme depots.

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This paper, contain three parts, focus on develop synthesis method for novel functional nanocluster, base on its special optical and reactive property. In the first part, lysozyme VI was mixed with HAuCl4 under acidic condition(pH~3) and yield blue fluorescent Au8 nanocluster. When this Au8 cluster was incubate under alkaline condition (pH~12) a size evolution from Au8 to Au25 took place and monitored with fluorescence spectrum, MALDI MS, DLS. On the other hand, on the role of structural characteristic, fluorescence of Au8 cluster can be quenched by GSH as GSH induced core-etching reaction took place. Take advantage of this reaction, GSH in RBC can be quantitatively analysis by Au8 cluster. Compare with standard medical analysis method, this assay got comparable quantitative result and advantage in environmental friendly, low cost and low sample demand. Follow the first part, it was knowing that Hg2+quench fluorescence of Au25 but Au8 cluster. The second part of research development a ratiometric fluorescence assay for Hg2+ in drinking water sample, by control size evolution of nanocluster mentioned in first part by adding Ag+ into protein direct synthesis nanocluter process. Under optimize condition of bimetallic nanocluster synthesis, two separately fluorescence peak locate under 613 nm and 471 nm represent bigger size and smaller nanoclusters. Using fluorescence intensity ratio of two wavelength, concentration of Hg2+ in water sample can be determined by standard addition method with high reproducibility. Limit of detection was determined to be 0.1 and 0.4 nM, both lower than EPA permitted level in drinking water. On the third part, SA and HAuCl4 was mixed under water contained acetonitrile solution and SA caped nanocluster was form. This nanocluster after self essemble possess special crystalline and surface phenomenon and fit matrix for high reproducible laser desorption/ionization mass spectrometry. Compare with traditional matrix SA, the cluster matrix show 6.6% in RSD with 33%. And the desorption/ionization efficiency of nanocluster matrix is also much higher. Insulin, myoglobin and HSA sample can be quantitative with this matrix with mean RSD lower than 10%.

A method for the oxidation of lipoproteins in vitro was developed using the free radical initiator, 2,2?-azobis-(2-amidinopropane) dihydrochloride (AAPH). Following in vitro oxidation, the susceptibility to oxidation of the serum samples was studied using density gradient ultracentifugation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Shifts in mean buoyant density of the lipoprotein particles, specifically low density lipoprotein (LDL) and high density lipoprotein (HDL), were observed in the density profile following centrifugation. The degree of shift in the density proved to be proportional to the extent of oxidation. Changes in apolipoproteins were studied with MALDI-TOF-MS. Observed variations in the mass spectra include m/z shifts due to chemical modifications and change in isoform distributions. The oxidation procedure and analysis techniques were applied to a clinical application to study the effects of table grape consumption on lipoprotein susceptibility to oxidation. The main objective of the research, to show feasibility that these methods could be used in a clinical setting, was achieved.