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news & events / Posters for ASMS 2008 |
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MondayDevelopment of a Novel Analytical Platform incorporating a Digital Ion Trap Interfaced with a Synchrotron Radiation Source for SAXS Experiments
Quadrupole ion traps represent the ideal devices for trapping ions in a well defined region of space. Confinement of charged particles in a three dimensional ion trap allows investigation of the nature of interactions occurring between electromagnetic radiations and trapped ions. Due to the type of the waveform used in a digital ion trap, frequency instead of amplitude is scanned during the MS analysis allowing to trap and detect protein ions up to 100 KDa. Here, a digital ion trap interfaced with a high intensity x-rays synchrotron source was build in order to study whether small-angle x-ray scattering (SAXS) can be performed in gas-phase. In this poster, design and performance of the novel analytical platform are described. Macromolecule measurement using MALDI-DITMS
Typically three dimensional quadrupole ion traps (3D-QIT) have been used to measure mainly low and medium m/z ions. Recently, Li Ding, et. al. developed a digital ion trap (DIT) using rectangular waveforms to trap low to high mass ions by changing the trapping frequency and voltage. A new post acceleration detector (PAD) able to detect trapped ions sequentially after being trapped in the DIT has been developed and cluster ions such as [3M+H]+ (m/z:450k) of IgG (M.W.:150kDa) can be detected. J. Mass Spectrom., Vol.39, p471-484 (2004) Simulations of a new mass-selected ion separation and transmission method between linear ion traps
The efficiency of tandem mass analysis is often limited by exclusion of all ions apart from the selected parent ion. The 2D MS making use of all ions for the subsequent CID and MS2 has been recently reported. In order to use two parallel linear ion traps to perform 2D MS, we studied the method for transferring a selected ion from the first trap to the second trap, while the un-selected ions are remained in the first trap for following experiment. During the transportation, the CID is achieved by accelerating the kinetic energy to hundreds eV. The parent ion as well as its fragments may be trapped in the second ion trap which scans a product mass spectrum. Detection and Characterization of Metabolites in Complex Biological Samples using Perfusion 2-D Chromatography Linear Ion Trap- Triple Quadrupole MS
Metabolite identification can be extremely difficult in complex mixtures such as bile, urine and whole blood because of the matrix effects. Identification becomes even more challenging when more than one drug is being studied at a single time. In order to detect and characterize metabolites in this complex situation, a more selective approach is required. Hybrid linear ion trap instruments combine triple quadrupole scans and ion trap scans in the same acquisition cycle. This combination allows for an ultra-high sensitivity survey scan to be coupled to automatic MS/MS generation which aids finding metabolites in complex matrices. A Poros® trap was used to trap parent drugs and metabolites present in whole blood to facilitate the analysis. Metabolite Identification of Astilpin in Biological Specimen by ESI-IT-TOF Tandem Mass Spectrometry
A mass spectrometry method that combines electrospray with an ion trap time-of-flight mass analyzer (Shimadzu LCMS-IT-TOF) was used to investigate the in vivo and in vitro metabolism of astilbin which was the main component isolated from Rhizoma Smilacis Glabrae (RSG) and showed a selective immunosuppressive feature. Up to now, the works mainly focused on the pharmacodynamic evaluation of astilbin in animal and only one metabolite was reported in recent publication. By using the MSn experiments combined with accurate mass measurement, the metabolites of astilbin were elucidated and metabolic pathways were proposed. Isolation of C-Terminal Peptides of Proteins by Exhaustive Amidation Followed by Proteolytic Digestion for Mass Spectrometric Sequencing
The C-terminal sequencing can be useful for identifying proteins, in particular, when the N-terminal amino groups are blocked by post-translational modifications. We developed a method for isolating the C-terminal peptide to be analyzed the sequence by mass spectrometry. The method uses the fact that all the peptide fragments except for the C-terminal one in proteolytic digest of a protein could have the free carboxyl groups if all the carboxyl groups of a protein have been chemically modified by either esterification or amidation. We will report the procedures of the method including the reaction conditions of chemical modification, ion-exchange chromatography to isolate the C-terminal peptide, and MALDI mass spectrometry of the C-terminal peptide thus isolated. Identification of Peptide Sequences Using Characteristics of MALDI_QIT Mass Spectral Data
A systematic study of the Shimadzu MALDI_QIT_TOF mass spectral data has been carried out to address fragmentation patterns of peptide bond cleavages from the ion trap in the tandem mass spectra. Information regarding the characteristics of fragmentation has been extracted and implemented in a computer program to assist the automatic determination of peptide sequences from the spectra. The program also uses a scoring technique to assign a confidence score to each individual amino acid in a candidate sequence. The confidence scores, along with other factors, can be used to identify high reliability tags in the sequence for use in database searching. TuesdayVacuum MALDI Linear TOF mass spectrometry of high molecular mass nanoparticles and proteins
Dendrimers are compartmentalized polymers with sizes and chemical properties (e.g.PAMAMs) comparable to proteins. These synthetic polymers, building nanospheres with defined sizes, are expected to have exactly defined molecular structures and possess functional end groups influencing their 3-dimensional structure and properties. They also have empty internal cavities making them suitable for biomedical applications, e.g.drug-delivering systems. Before in-vivo application the products of the syntheses have to be characterized and protein-dendrimer interactions should be studied, too. In our study we tried to reveal as much information as possible from high molecular mass dendrimers (e.g.exact molecular weight and size) and optimized sample preparation to get information on protein-dendrimer interactions (e.g.non-covalent complexes) by MALDI-TOF-MS with an UHM-detector. Improvement on sensitivity of high-spatial-resolution mass imaging based on MALDI-QIT-TOF-type mass spectrometer
There is a growing trend towards reliable identification of biomolecules for mass imaging. Adoption of 3D quadrupole ion trap (QIT) can give obvious identification by high-precision MSn analysis. Another trend is an enhancement of spatial resolution. To improve spatial resolution of mass microscope, laser-spot size needs to be reduced; thus amount of produced ions are considerably decreased. Our efforts towards the improvement on sensitivity with high spatial resolution for the MALDI-QIT-TOF-type mass microscope have been focused on (1) an effective ion guide to transport ions into QIT, and (2) an optimum condition of MALDI-laser irradiation. As the result of present study, the sensitivity has been improved noticeably and mass images of biological tissues have been obtained with high spatial resolution. Automatic spotting solution for MALDI Imaging: process optimization and new developments
MALDI Imaging and profiling is a powerful tool to detect and study spatial distribution of compounds in a tissue section. Actually using automatic spotting device is one of the two strategies for avoiding delocalization of molecules under matrix deposition. Piezoelectric heads can deliver with a high reproductibility nL of solution droplets. However, for insuring best reproducibility and achieve the highest resolution the piezoelectric deposition must be very well controlled and optimized. We have been interested in optimizing deposition for various solutions of matrix using very different solvents or matrix classes such as ion matrices. A Study for Quantitative Analysis of Glycans by MALDI-TOF MS without Using Stable Isotopes
Glycans have received attention as a target molecule for biomarker discovery since the structural change of glycan is known to be associated with diseases such as cancer and with cell differentiation. In this context, comparative analysis of glycans using MS is an important technique for discovery of glyco-biomarkers. MALDI-TOF MS seems to be suitable for glyco-biomarker discovery because of its easy operation and high-throughput performance. However, quantitative analysis using MS, in particular MALDI-TOF MS, is known to be problematic. To utilize a MALDI-TOF MS for comparative analysis of glycans, we here report a study on a method of relative quantification of glycans by MALDI-TOF MS without using stable isotopes. Clustering software for analysis of complex lipid profile data based on detection of fish oils by MALDI mass spectrometry
The American Heart Association recommends regular consumption of fatty fish to minimize the risks of CVD. Dietary studies indicate that supplementation with fish oils may be beneficial to balance serum levels of n-3 fatty acids in western diets traditionally overabundant in n-6 fatty acids (i.e. linoleic acid, 18:2). Numerous commercially available fish oil products (capsules) are available but their quality is hard to verify by the consumers. Methods for authenticity control and rapid monitoring are required to prevent illegal blending and to ensure constantly high quality standards. Analytical methods to survey oil quality should be straightforward and fast, while providing a high degree of discriminatory information. MALDI-MS combined with intelligent software solutions appears very promising for this topic. Detection and discrimination of extended-spectrum ß-lactamase (ESBL) producing bacteria by MALDI-TOF-MS
Antibiotic resistance in hospital-acquired infections represents a considerable burden to patients and healthcare delivered globally. ß-Lactams are the most widely administered class of antibiotics and the most common mechanism of bacterial resistance is possession of a ß-lactamase enzyme. Detection of ß-lactamase in a wide-range of bacteria is problematic due to interferences and/or unsuitability of the method for routine analysis. ESBL producing bacteria pose a serious clinical problem because of their wide antibiotic resistance (including penicillins, most cephalosporins and monobactams) and their complex and dynamic evolution and epidemiology. We have investigated MALDI-TOF MS analysis of intact-bacteria and of cell-wall extracts (enzymatic or solvent based methods), as an approach to detection and discrimination of ESBL isolates from regional hospitals in the UK. Identifying biomarkers for Rheumatiod Arthritis in the human TNF-driven Tg197 mouse model using high mass accuracy MSn analysis
The aim of the study is to identify potential biomarkers of Rheumatoid Arthritis using a TNF-driven mouse model, and employing high mass accuracy MSn analysis. To accomplish this the differences between the human tumor necrosis factor (TNF) transgenic mouse model of arthritis Tg197 and wild type mice were followed. The Tg197 is considered to be a very useful animal model, as the onset of disease is short (3rd to 4th week of age), synchronous and with complete (100%) penetrance. Mice respond uniformly to treatment and histopathological data reflect and corroborate the progress/therapy of the illness. Further to this, the impact of a monoclonal antibody (infliximab) used in the treatment of rheumatoid/psoriatic arthritis and ankylosing spondylitis, is evaluated in these mice. Multi Post-Translational Modifications analysis for a gel band using MALDI-TOF MS/MS
Gel-based analysis, including 1D/2D electrophoresis and in-gel digestion, is a widely-recognized method for proteomics and focused protein analysis, the advantages of which are high separation of proteins, differential analysis and quantification. However, current in-gel digestion protocols are easy to loss modified peptides despite of PTMs’ significance. Furthermore, while enrichment of phosphopeptide has been developed with metal-chelate, there is little preparative method for glycopeptide from gel-band even though the modification is the most abundant PTM as well as phosphorylation. Since multiple modifications occur on protein frequently, an establishment of a comprehensive method is necessary. We will report our optimization for glyco- and phospho-peptide analysis with MALDI-MS/MS, and multistep approach to obtain both the modified peptides from one gel-band. One-spot detection of oligosaccharide and peptide using a mixture of two ionic liquid matrixes with MALDI MS.
Recently, the importance of analyzing post-translational modification is increasing in the research of proteomics. Especially in the field of mass spectrometry, it is needed to develop procedures for identifying post-translational modification of proteins. Even though MALDI-MS is suitable for the analysis of protein modification, little application was developed for identifying both protein sequence and modification at the same time because existing matrixes are focused only on peptides, oligsaccharides, phosphopeptides, etc. We therefore tried to develop a procedure for analysing both oligosaccharide structure and protein sequence in the same spot using a mixture of two existing ionic liquid matrixes. SMART-directed LC-MALDI Protein Identification using a MALDI-Ion Trap-TOF Mass Spectrometer
In protein identification analyses using LC-(MALDI) MS/MS, one piece of information which is often generated but ignored in the process is the peptide retention time. Recently, algorithms which predict the retention times of peptides separated by reversed phase chromatography have been significantly improved, to the point that they can predict the retention time of unmodified peptides to within a few minutes. Unlike the typical LC-MALDI approach, in which all precursors above a user-defined threshold (or S/N) are selected for MS/MS, we present results obtained using an algorithm-directed approach for precursor selection. We propose that the lower throughput of the ion trap-TOF mass spectrometer can be offset by the reduced number of precursors required in this approach. Discovery of O-linked glycoprotein cancer biomarkers in human sera by multi-lectin enrichment and lectin microarray binding patterns with MALDI QIT
Pancreatic cancer is one of the most dangerous cancers with a 5-year survival rate of les than 4%. Discovering new biomarkers in serum with high sensitivity and specificity would increase the chance of early prognosis of the cancer. Glycosylation is the most common modification in serum and both N- and O-linked glycosylation, have been found to be detective to different kinds of cancers. Compared to N-linked glycosylation, the mapping of O-linked glycosylation is still under development. Due to lack of a general core structure in O-linked glycans, O-linked glycoproteins are more difficult to selectively enrich from serum. The coexistence of N-linked and O-linked glycan on single protein furthermore complicates this task. WednesdayDesign of a new multi-turn ion optical system for high-performance time-of-flight mass spectrometers
Multi-turn time-of-flight mass spectrometers, in which ions travel in closed flight paths, have been developed to achieve high mass resolving powers. So far, several multi-turn time-of-flight instruments have achieved high resolving powers of over 100,000 experimentally, and it has been verified that the multi-turn time-of-flight instruments are a powerful solution for a high-performance mass spectrometer. However, despite their powerfulness, there is a problem on their design. That is, it is hard to find a new multi-turn ion optical system because of too many required ion optical conditions. In this work, we have employed a new design concept based on the ion optical study, and have successfully designed a new high-performance multi-turn ion optical system. Geometrical effect on the performance of Ion Trap Array(ITA)
An Ion Trap Array(ITA) was constructed by two parallel electric plates and it contains multiple ion trapping regions. Each region in the ITA can be used as a single conventional “ion trap”. The effect of geometry and the shape of ITA electrode on the electric field distributions inside the ITA and its performance have been studied theoretically and experimentally. Eight ITAs with different dimension were analyzed. The internal electric field distributions was calculated and the mass analysis performance of each ion trap in ITA was simulated using computer software. Mass analysis properties of different dimension ITA were tested experimentally. The results of simulations and experiments are very well coincidence. Improving the analytical performance of the ESI mass spectrometer by coupling 2D and 3D digital ion traps
A 3D ion trap driven by a digital waveform and using frequency scan has found tremendous analytical advantages for high mass bimolecular tandem mass analysis. Due to the field geometry of 3D Paul trap, the trapping efficiency for the externally generated ion remains low and the capacity of single batch analysis is limited compared to that of a linear (2D) ion rap. Nevertheless, the 3D rotational symmetric ion trap can be easily made to achieve high precision geometry which in turn a high mass resolution compared with a linear ion trap. Thus a combination of a low precision 2D ion trap and high precision but low capacity 3D ion trap become a sensible approach for high performance tandem mass analysis. A dynamic pressure MALDI source interfaced to a 3D digital ion trap using a linear ion trap
The high internal and kinetic energies of ions generated by pulsed ion sources such as MALDI must be reduced before the ions can be delivered to and successfully trapped in a 3D ion trap for mass analysis. High internal energy also results in unwanted fragmentation of ions. Cooling of the ions is possible by raising the source pressure, however operation of an ion guide at this pressure then carries the risk of discharge, and the pulsed nature of the ions which is required for introduction into a 3D ion trap is lost. A pulsed pressure source was thus suggested, with storage of ions in a linear quadrupole for later ejection. A Next Generation MALDI-Ion Mobility-Surface-induced Dissociation-Time-of-Flight Mass Spectrometer with Novel Collision Source Configurations
The combination of ion mobility (IM) with surface-induced dissociation (SID) and time-of-flight mass spectrometry (TOFMS) is a high-throughput tandem technique enabling precursor and fragment ion data to be acquired in the same mobility measurement cycle. Even with simultaneous acquisition, the sensitivity of IM-SID-TOFMS instruments are low largely attributable to ion losses in uniform field drift cells. The main goal of this work is to increase the ion transmission and sensitivity of the IM-SID-TOFMS instrument by incorporating a new periodic focusing drift cell and a higher sample capacity MALDI source with improved laser/CCD camera accessibility. MADLI MSI analysis of rat hearts from animals treated with isoprenaline
Matrix assisted laser desorption ionisation mass spectrometric imaging (MALDI-MSI) has now become an established technology that has the simple concept of localising molecules of interest within tissue and providing an estimate of relative concentrations. Although many examples have been demonstrated showing tissues with highly contrasting regions such as brain sections or samples with tumours, few studies have focussed on largely homogeneous tissue. In this study rat hearts were analysed by MALDI MSI. Data was compared between control (saline treated) animals and ones treated with isoprenaline, which induces cardiomyocyte death and reparative fibrosis similar to that observed in the human heart after myocardial infarction. New Methods in Peptide de novo Sequencing Software with Manual Intervention Feature for Tandem Mass Spectral Data
An algorithm has recently been developed that automatically sequences peptides using tandem mass spectra. The algorithm uses a new search method to find the putative ion series from the given mass spectrum and scores the ion peaks in the possible ion series to rank possible candidates The features of fragmentation present in MALDI_QIT_TOF data are integrated into the algorithm and the method can be extended to handle spectra from other types of instruments. In addition to sequencing MS2 peptide spectra, MSn spectra can also be combined to provide more coverage of sequence information and better ion classification. Matrix-assisted Laser Desorption/Ionization Tandem Mass Spectra of Synthetic Polymers Using the Low and the High-energy Fragmentation
Synthetic polymers are widely used in industry as lubricants, stabilizes, removers, anti-foaming agents or raw materials. To gain a precise understanding of the physical properties of the polymers, it is important to obtain detailed structural information such as the end groups of the polymers and by-products. Structural Characterization of Pyridylaminated Oligosaccharides by High-Sensitive Capillary Electrophoresis-ESI-QIT-TOF Mass Spectrometry
Glycosphingolipids have many cellular functions such as cell-cell recognition, cell growth and signal transduction. In order to characterize the structures of carbohydrate moieties of glycosphingolipids from extremely small amount of cells, which are obtained after EGC-II digestion and pyridylamination, the development of high-sensitive analytical system has been required. Electrospray ionization (ESI)-MSn switching ion-trap time-of-flight (IT-TOF) mass spectrometry is useful for the structural characterization of pyridylaminated (PA) oligosaccharides derived from glycosphingolipids, because it can provide information on the fine structures of oligosaccharides. Here we report a high-sensitive capillary electrophoresis (CE)-ESI-MSn mass spectrometry, which consists of electrokinetic injection CE, sheathless interface, and narrow mass range selecting MSn switching IT-TOF mass spectrometry, for the structural characterization of PA-oligosaccharides derived from glycosphingolipids. Applying isotopic profile analysis to metabolite detection and identification using high mass accuracy MSn analysis.
Radiolabeling and stable isotope labelling of parent drug molecules is a widely used approach to study in vitro and in vivo disposition patterns. However, such techniques often involve considerable data interpretation to identify each metabolite positively. To help accelerate metabolite reporting a software algorithm has been developed that automatically detects labelled metabolites using isotope profile pattern matching. Once the labelled metabolite has been detected its identity is confirmed using high mass accuracy MSn to correlate between the labelled metabolite and the most likely empirical formula. This approach was applied to the analysis of tritium labelled buprenorphine and 13C labelled dichlofenac using a quadrupole ion trap-time of flight mass analyser. Mass Spectrometric Characterization of Apheresis Samples from Rheumatoid Arthritis Patients - Approaching the Principles of Function of Immunomodulation Therapy.
Rheumatoid arthritis (RA), a common autoimmune disease affecting about 1% of the population, leads to substantial disability and loss of productivity by chronic joint inflammation and subsequent progressive destruction of the articular tissue. There are several stages of treatment available encompassing analgesics as basic therapeutics, disease modifying antirheumatic drugs (DMARDs), and TNF alpha inhibitors. However, as not all patients are responding to these treatments, there is a need for alternative therapies. One alternative is apheresis treatment using PROSORBA® columns attempting to deplete / modulate disease-related proteins. Recently, also therapeutically induced B-cell depletion has emerged. Here we describe the mass spectrometric characterization of apheresis samples as an approach to understand the principles of function of immunomodulation therapy. Characterization of plasma derived and recombinant Immunoglobulins G by MALDI mass spectrometry.
Immunoglobulins G (IgG) are an important class of immunoglobulins constituting approximately 75% of the total Immunoglobulin. Their characterization at the molecular level has been investigated by mass spectrometry but most of the work done with established methods was focused on fractions of the molecules and lack overall information such as molecular weight of various parts of IgG. It is known that very large glycoproteins like IgG are highly glycosylated and carry a large amount of post translational modifications. This makes the desorption process of the entire or parts of the glycoproteins with MALDI quite difficult. The work presented here is focused on the characterization of the major active parts of IgG such as Fab, Fc, heavy chain and light chain. Identification of stable oxidative metabolites and iminium ion reactive intermediates using high mass accuracy MSn analysis
In an effort to understand and further prevent idiosyncratic or adverse drug reactions it has become important to identify compounds that have a potential to cause toxicity. Methods have employed trapping agents such as glutathione (GSH), potassium cyanide (KCN), and others for the detection and characterization of reactive metabolites in the pre-clinical phase of drug development. Using a QIT-TOF mass spectrometer, we have developed a data dependent scanning method with fast polarity switching (100msec switching time) and MSn spectra to help structural identification. This paper describes the application of high mass accuracy MSn data analysis together with an isotope pattern algorithm to detect and identify both stable oxidative metabolites and 13C and 15N labelled iminum ion reactive intermediates The comparative profiling of glycosylation in a mouse model of Human Ovarian Endometrioid Adenocarcinoma based on genetic defects using MALDI-QIT-TOF-MS.
The application of liquid separations followed by mass spectrometry was used in the analysis of four different mouse models of human ovarian endometrioid adenocarcinomas with different genetic defect. Endometrioid ovarian cancers have been known for difficulty to define characterization. The profiling of glycosylation in these mice model tissues may reflect cancer changes based on their genetic defects. Importance of Transmission Window Selection in Quadrupole-based Mass Spectrometers to Increase Signal Intensities in iTRAQ-based Quantitation
Protein identification, characterization, and quantitation by MS/MS requires analysis of a broad m/z range between m/z 100-2000 with good S/N. Informative immonium ions, marker ions for PTMs and quantitative iTRAQ reporter ions occur at the low end of this range with relatively poor S/N. However, little consideration has thus far been given to their transmission efficiency. Presumably quadrupole instruments do not have a mass cutoff as with ion-traps since they operate in scan mode to produce spectra. However, in hybrid instruments such as quad-ion traps, quad-TOFs, and quad-ion trap TOFs the quadrupoles operate in RF only mode to transmit ions simultaneously to a mass analyzer. This RF-only transmission can result in reduced signal or signal bias of the reporter ions. Gas Phase Small Angle X-ray Scattering from Trapped Ions
BRYAN J. MCCULLOUGH1; Andrew Entwistle2; Steve G. Buffey3; Francesco Brancia2; S. Samar Hasnain3; Ikuo Konishi2; J. Guenter Grossmann3; Simon J. Gaskell1 1The University of Manchester, Manchester, UNITED KINGDOM; 2Shimadzu Research Laboratory Ltd, Manchester, United Kingdom; 3STFC Daresbury Laboratory, Warrington, United Kingdom Small angle x-ray scattering (SAXS) is a well established technique for the determination of 3D conformations of solvated biomolecules at low resolution (down to ~10 Å) [1]. An inherent problem with standard SAXS experiments is the high background caused by the presence of solvent molecules. A logical progression is therefore to remove the solvent and perform the measurements in the gas phase. As part of the small angle x-ray scattering initiative for Europe (SAXIER) we have designed and built a digital ion trap mass spectrometer (DIT) which allows SAXS measurements to be carried out on trapped ions. Here we will present the first ever gas phase SAXS data, obtained at the synchrotron radiation source (Daresbury, UK) and Diamond (Oxfordshire, UK). ThursdaySimultaneous detection of a wide mass range of product ion including immonium ions in MS/MS using MALDI-DIT MS
Digital-ion-trap(DIT) is a 3D-quadrupole ion trap (QIT) driven by a rectangular wave form. One of the advantages of DIT is that the pseudo-potential well during CID in low mass range is deeper than conventional QIT. Therefore, it is considered that lower m/z product ions, such as an immonium ion, which contributes to the determination of peptide sequence, could be detected in MS/MS. In this study, we demonstrate that DIT provides to detect the immonium ions in MS/MS, and Low Mass Cut Off (LMCO) value in MS and MS/MS is also lower than a conventional QIT-MS. This means that DIT can provide more analyte-information in one measurement. Novel Calibrant Injection Method with High-Vacuum MALDI Digital Ion Trap Mass Spectrometer
We have developed the digital ion trap mass spectrometer (DIT-MS). DIT is driven by high voltage with rectangular waveform for trapping ions. For mass scan, the frequency of the waveform is scanned with fixed amplitude. Previously, we developed a high vacuum MALDI-DIT-MS and evaluated the performance. Moreover, we devised a new method of additional ion injection while keeping previously trapped ions in the ion trap. Using the method, the signal intensity of peptide ions increased according to the number of additional ion injection. Now based on this method, we devised a method of injection of calibrant ions into the ion trap while keeping previously trapped analyte ions. We evaluated the method with MS, MS/MS and MSn for protein digests. Field-Free Atmospheric Ionization: Electrospray and Atmospheric Pressure Chemical Ionization
The electric potentials required for electrospray and APCI compromise the ability to introduce ions into apertures or tubes leading into the vacuum chamber of the mass spectrometer. It has long been reported that less than 1% of the ions generated and present in the ionization chamber make it into the vacuum chamber. This phenomenon has been referred to as “the rim effect”. The majority of the ions are lost due to a combination of two forces: high electric fields at the opening of a tube or aperture, and the low flow (linear velocity) of the gas entering the opening. To remove or reduce the rim effect due to the electric potential, remote nebulizers were designed and built. A Fragmentation Study of Isomeric dihydroxyanthraquinone in Negative Electrospray Ionization by Ion Trap Time of Flight Mass Spectrometry
Anthraquinones are present in many Chinese Herbs which are medicinally important. There are many studies on anthraquinones from the crude extracts of the Chinese herbs by using different types of mass spectrometry. However, no systematic study has been reported of the fragmentation pathways of antraquinone in negative ion electrospray ionization mode by using ion trap combined with time-of-flight mass spectrometry (LCMS-IT-TOF). The aim of the present study was to elucidate the fragmentation pathways of anthraquinones with two hydroxyl substitution groups, including 1,2-dihydroxyanthraquinone, 1,4-dihtdroxyanthraquinone and 1,8-dihydroxyanthraquinone. To confirm the relationships between precursor and product ions, some fragments were traced from MS2 to MS5. The fragmentation pathways of the three compounds displayed different features from each other. Derivatization of N-linked Glycans for Sensitive Detection by MALDI-TOF MS toward Glyco-Biomarker Discovery
Glycans have received attention as a target molecule for biomarker discovery since the structural change of glycan is known to be associated with diseases such as cancer and with cell differentiation. Although Mass spectrometry (MS) is an important technique for discovery of glyco-biomarkers, its sensitivity for glycans is lower than that for peptides. This is a critical factor in glyco-biomarker discovery when using MS. Permethylation of glycans enhances sensitivity in MS detection. It has been reported that many labeling groups were applied to the reducing end of glycans to overcome this problem. We here describe a novel derivatization which combines permethylation and the reducing end labeling to achieve a high sensitive detection of N-linked glycans using MS. Identification of Impurities in the CCQM Sample by Ion Trap Time-of-Flight Mass Spectrometry
The impurities in CCQM (Consultative Committee for Amount of Substance) sample distributed by International Metrology Bureau (BIPM)were qualitative analyzed with an ion trap analyzer linked to a time-of-flight mass analyzer, the result of LC-PDA-ESI-IT-TOF indicated that the sample contain five impurity. Based on the exact masses acquired from different tandem mass spectra, four impurities were estimated respectively as 3-methyl xanthine; theobromine; caffeine and trimethyl-xanthine, and qualitative results were confirmed by other national laboratory joining the comparison. The impurity 5 was more complicated and studied in detail with the proposed structure and fragmentation pathway. Unique fragmentation pattern of EDTA-Fe(III) by ion trap time of flight mass spectrometry with Negative Electrospray Ion Source
Chelation is capture of positively-charged metal ions by a large molecule. The most widely used chelating molecule is EDTA (Ethylene Diamine Tetraacetic Acid). EDTA has the capacity to chelate almost every positive ion in the periodic table. The formation constant of EDTA-Fe(III) is the highest among all the metal ions that can chelate with EDTA. The Multistage mass spectrum (MS stage 5) of EDTA-Fe(III) was acquired by ion trap time of time equipped with an electrospray ion source. The Unique fragmentation shows that the fragmentation mechanism is quite different from what originally proposed. On-target digestion using ionic liquid matrixes for glycopeptide analysis
On-target digestion using conventional matrixes such as a-cyano-4-hydroxycinnamic acid and 2,5-dihydroxybenzoic acid (DHB) has been known as an useful method for rapid peptide/protein analysis, especially for imaging MALDI. However, the application of the solid matrixes has a problem in the surface homogeneity. Therefore, the application of ionic liquid matrixes (ILMs) in this area was expected. On the other hand, only a few reports have been presented on on-target methods for glycoproteins probably because of the complexity. So far, we reported 1,1,3,3-tetramethylguanidine (TMG) salts of p-coumaric acid as useful ILMs for oligosaccharides and glycopeptides. Here, the ILMs were used for a rapid and reproducible on-target digestion of glycoproteins for glycopeptide analysis in both positive and negative modes. |
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