Recent trends of capillary electrophoresis-mass spectrometry in proteomics research.

Progress in proteomics research has led to a demand for powerful analytical tools with high separation efficiency and sensitivity for confident identification and quantification of proteins, posttranslational modifications, and protein complexes expressed in cells and tissues. This demand has significantly increased interest in capillary electrophoresis-mass spectrometry (CE-MS) in the past few years. This review provides highlights of recent advances in CE-MS for proteomics research, including a short introduction to top-down mass spectrometry and native mass spectrometry (native MS), as well as a detailed overview of CE methods. Both the potential and limitations of these methods for the analysis of proteins and peptides in synthetic and biological samples and the challenges of CE methods are discussed, along with perspectives about the future direction of CE-MS. @ 2019 Wiley Periodicals, Inc. Mass Spec Rev 00:1-16, 2019.

Clinical implementation of molecular methods in detection of microorganisms from blood with a special focus on PCR electrospray ionization mass spectrometry.

INTRODUCTION: The ongoing improvement and development of state-of-the-art diagnostic methods indicate that we are in an era of revolution in clinical microbiological diagnosis of infectious diseases. Non-culture-based methods have the possibility to play a central role in delivering personalized microbiological diagnoses of severe infections. The PCR electrospray ionization mass spectrometry (PCR/ESI-MS) system is built on the principle of universal detection and specific identification. The performance studies using PCR/ESI-MS on whole blood samples, as well as our experiences, indicate that this method provides useful clinical information. These types of modern molecular methods deserve further development for broad implementation into clinical practices. Areas covered: The review describes briefly hitherto developed molecular assays in detection of microorganisms directly from whole blood and focuses on the clinical implementation of PCR/ESI-MS. Expert opinion: The detection of an extensive broad-spectrum of microorganisms directly from whole blood samples with a series of tests that are run automatically with a turn-around time of 8 h would be a desirable diagnostic tool for the clinical microbiology laboratories. We believe that the clinical experience with PCR-ESI MS may guide the development and establishment of similar state-of-the-art diagnostic technologies in medicine in the future.

Mass spectrometry-based shotgun lipidomics - a critical review from the technical point of view.

Over the past decade, mass spectrometry (MS)-based "shotgun lipidomics" has emerged as a powerful tool for quantitative and qualitative analysis of the complex lipids in the biological system. The aim of this critical review is to give the interested reader a concise overview of the current state of the technology, focused on lipidomic analysis by mass spectrometry. The pros and cons, and pitfalls associated with each available "shotgun lipidomics" method are discussed; and the new strategies for improving the current methods are described. A list of important papers and reviews that are sufficient rather than comprehensive, covering all the aspects of lipidomics including the workflow, methodology, and fundamentals is also compiled for readers to follow. Graphical abstract ᅟ.

Recent advances in coupling capillary electrophoresis-based separation techniques to ESI and MALDI-MS.

Coupling CE-based separation techniques to MS creates a powerful platform for analysis of a wide range of biomolecules from complex samples because it combines the high separation efficiency of CE and the sensitivity and selectivity of MS detection. ESI and MALDI, as the most common soft ionization techniques employed for CE and MS coupling, offer distinct advantages for biomolecular characterization. This review is focused primarily on technological advances in combining CE and chip-based CE with ESI and MALDI-MS detection in the past five years. Selected applications in the analyses of metabolites, peptides, and proteins with recently developed CE-MS platforms are also highlighted.

From protein complexes to subunit backbone fragments: a multi-stage approach to native mass spectrometry.

Native mass spectrometry (MS) is becoming an important integral part of structural proteomics and system biology research. The approach holds great promise for elucidating higher levels of protein structure: from primary to quaternary. This requires the most efficient use of tandem MS, which is the cornerstone of MS-based approaches. In this work, we advance a two-step fragmentation approach, or (pseudo)-MS(3), from native protein complexes to a set of constituent fragment ions. Using an efficient desolvation approach and quadrupole selection in the extended mass-to-charge (m/z) range, we have accomplished sequential dissociation of large protein complexes, such as phosporylase B (194 kDa), pyruvate kinase (232 kDa), and GroEL (801 kDa), to highly charged monomers which were then dissociated to a set of multiply charged fragmentation products. Fragment ion signals were acquired with a high resolution, high mass accuracy Orbitrap instrument that enabled highly confident identifications of the precursor monomer subunits. The developed approach is expected to enable characterization of stoichiometry and composition of endogenous native protein complexes at an unprecedented level of detail.

Recent advances of electrochemical mass spectrometry.

This review article surveys some recent developments of electrochemistry (EC) in combination with mass spectrometry (MS) including instrumentation and bioanalytical applications.

CE-MS for metabolomics: developments and applications in the period 2010-2012.

CE-MS has emerged as a powerful technique for the profiling of (highly) polar and charged metabolites in biological samples. This review provides an update of the most recent developments in CE-MS for metabolomics covering the scientific literature from July 2010 to June 2012. The present paper is an update of two previous review papers covering the years 2000-2010 (Electrophoresis 2009, 30, 276-291; Electrophoresis 2011, 32, 52-65). Emerging technological developments used in CE-MS for metabolomics are discussed, such as the use of novel interfacing techniques for coupling CE to MS. Representative examples illustrate the applicability of CE-MS in the fields of biomedical, clinical, microbial, plant, environmental and food metabolomics. Concerning targeted and non-targeted approaches, a comprehensive overview of recent CE-MS-based metabolomics studies is given in a table. Information on sample type and pretreatment, capillary coatings and MS detection mode is provided. Finally, general conclusions and perspectives are provided.

New advances in amino acid profiling by capillary electrophoresis-electrospray ionization-mass spectrometry.

Capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) offers a selective, sensitive yet robust approach for amino acid profiling in complex biological samples with minimal sample pretreatment. Direct analysis of amino acids and their analogs is routinely performed using strongly acidic buffer conditions under positive-ion mode ESI-MS with a coaxial sheath liquid interface. New advances in online sample preconcentration, chemical derivatization, and/or ESI interface designs can further improve assay performance allowing for resolution of amino acid stereoisomers and labile aminothiols with low nanomolar detection limits. Accurate prediction of the electromigration behavior of amino acids offers a convenient approach for their qualitative identification complementary to ESI-MS. Simultaneous analysis of amino acids together with other classes of cationic metabolites can be realized by CE-ESI-MS for comprehensive metabolite profiling applications relevant to disease prognosis, drug efficacy, and food safety/quality control.

Bio-electrosprays: from bio-analytics to a generic tool for the health sciences.

Electrosprays or electrospraying is a process by which an aerosol is generated between two charged electrodes. This aerosol generation methodology has been known for well over a century, and has undergone exploration in aerosol and materials sciences, to many other areas of research and development. In one such exploration, electrosprays were partnered with mass spectrometry for the accurate characterisation of molecules. This technology now widely referred to as electrospray ionisation mass spectrometry (ESI MS) significantly contributes to molecular analysis and cancer biology to name a few. In fact these findings were recognised by the Chemistry Nobel Committee in 2002, and have catapulted electrosprays to many areas of research and development. In this review, the author wishes to introduce and discuss another such recent discovery, where electrosprays have been investigated for directly handling living cells and whole organisms. Over the past few years these electrosprays now referred to as "bio-electrosprays" have undergone rigorous developmental studies both in terms of understanding all the associate physical, chemical and biological sciences for completely assessing their effects, if any on the direct handling of living biological materials. Therefore, the review will bring together all the work that has contributed to fully understanding that bio-electrosprays are an inert technology for directly handling living biological materials, while elucidating some unique features they possess over competing technologies. Hence, demonstrating this approach as a flexible methodology for a wide range of applications spanning bio-analytics, diagnostics to the possible creation of synthetic tissues, for repairing and replacing damaged/ageing tissues, to the targeted and controlled delivery of personalised medicine through experimental and/or medical cells and/or genes. Therefore, elucidating the far reaching ramifications bio-electrosprays have to our health sciences and well-being.

A review of recent trends in electrospray ionisation-mass spectrometry for the analysis of metal-organic ligand complexes.

Electrospray ionisation-mass spectrometry (ESI-MS) is used in a wide variety of fields to examine the formation, stoichiometry and speciation of complexes involving metals and organic ligands. This article reviews the literature in this area over the past 5 years, examining trends in ESI-MS use and novel applications that enhance the scope of the technique. ESI-MS can provide direct information on changes in speciation with metal:ligand ratio and pH, identify metal oxidation state directly and allow insight into competitive interactions in ternary systems. However, both the instrumental set-up and artefacts in the electrospraying process can affect the species distribution observed, and changes in solution chemistry can affect the relative ion intensity of species. Therefore, ESI-MS data is at its most powerful when corroborated by data from other experimental techniques, such as pH potentiometry. The challenges in interpreting direct ESI-MS data quantitatively are discussed in detail, with reference to differences in the ion intensities of species, signal suppression and quantifying species distributions. The use of HPLC-ESI-MS is also reviewed, highlighting challenges and applications. Overall, the need for more standard reporting of quality assurance data is discussed, to strengthen the applications of ESI-MS to metal-organic ligand complexes further.

Cluster secondary ion mass spectrometry of polymers and related materials.

Cluster secondary ion mass spectrometry (cluster SIMS) has played a critical role in the characterization of polymeric materials over the last decade, allowing for the ability to obtain spatially resolved surface and in-depth molecular information from many polymer systems. With the advent of new molecular sources such as C(60)(+), Au(3)(+), SF(5)(+), and Bi(3)(+), there are considerable increases in secondary ion signal as compared to more conventional atomic beams (Ar(+), Cs(+), or Ga(+)). In addition, compositional depth profiling in organic and polymeric systems is now feasible, without the rapid signal decay that is typically observed under atomic bombardment. The premise behind the success of cluster SIMS is that compared to atomic beams, polyatomic beams tend to cause surface-localized damage with rapid sputter removal rates, resulting in a system at equilibrium, where the damage created is rapidly removed before it can accumulate. Though this may be partly true, there are actually much more complex chemistries occurring under polyatomic bombardment of organic and polymeric materials, which need to be considered and discussed to better understand and define the important parameters for successful depth profiling. The following presents a review of the current literature on polymer analysis using cluster beams. This review will focus on the surface and in-depth characterization of polymer samples with cluster sources, but will also discuss the characterization of other relevant organic materials, and basic polymer radiation chemistry.

The synergy of elemental and biomolecular mass spectrometry: new analytical strategies in life sciences.

The application of mass spectrometry with soft ionization techniques (ESI, electrospray ionization, and MALDI, matrix-assisted laser desorption ionization) in the life sciences for the detection and identification of biomolecules is already well established, whereas the application of elemental mass spectrometry and in particular inductively coupled plasma mass spectrometry (ICP-MS) for the determination of metals, metalloids and non-metals in biomolecules is rather new and there is some hesitation in accepting this analytical method, although it offers many advantages. Therefore, it is the aim of this tutorial review to highlight new analytical strategies consisting of the combined applications of elemental and molecular mass spectrometric techniques. In fact, elemental and biomolecular mass spectrometric methods are highly complementary: elemental mass spectrometry methods, such as ICP-MS, offer very sensitive element analysis in the trace and ultra-trace concentration range with multielement capability and the excellent and uniform sensitivity is structure-independent and can be used analytically for accurate quantification as well as for fast screening of specific elements even in complex samples. Laser ablation (LA) ICP-MS, as a solid state mass spectrometric technique, allows the direct determination of trace elements in biological and environmental samples and is applied for microlocal analysis with spatial resolution in the mum range. In contrast, molecular weight determination and structural information is completely lost during the ionization step so that these features have to be provided by biomolecular mass spectrometry and in particular by ESI- and MALDI-MS. On the basis of selected examples, it will be shown that only the combination of different elemental and biomolecular mass spectrometric techniques can solve analytical problems in the life sciences and environmental research in a synergistic way where neither technique alone would be successful. This synergy will be demonstrated by selected applications from various areas: food and nutrition, toxicology, clinical and pharmaceutical research, biochemistry and in particular proteomics. Future developments and trends will be discussed concerning instrumental developments of new mass spectrometric techniques providing high sensitivity with lower detection limits for many elements measured quasi-simultaneously so that new analytical information about biological systems can be drawn from isotopic information and the application of stable non-radioactive isotopic tracers. In addition, elemental labels enable the development of new high-throughput screening techniques based on multiplexed biomarkers. Advanced powerful surface mass spectrometric techniques are required for the imaging of elemental and molecular information in order to analyse tissue samples and to develop novel array-based biochips.

Chip-mass spectrometry for glycomic studies.

The introduction of micro- and nanochip front end technologies for electrospray mass spectrometry addressed a major challenge in carbohydrate analysis: high sensitivity structural determination and heterogeneity assessment in high dynamic range mixtures of biological origin. Chip-enhanced electrospray ionization was demonstrated to provide reproducible performance irrespective of the type of carbohydrate, while the amenability of chip systems for coupling with different mass spectrometers greatly advance the chip/MS technique as a versatile key tool in glycomic studies. A more accurate representation of the glycan repertoire to include novel biologically-relevant information was achieved in different biological sources, asserting this technique as a valuable tool in glycan biomarker discovery and monitoring. Additionally, the integration of various analytical functions onto chip devices and direct hyphenation to MS proved its potential for glycan analysis during the recent years, whereby a new analytical tool is on the verge of maturation: lab-on-chip MS glycomics. The achievements until early beginning of 2007 on the implementation of chip- and functional integrated chip/MS in systems glycobiology studies are reviewed here.

Microorganism characterization by single particle mass spectrometry.

In recent years a major effort by several groups has been undertaken to identify bacteria by mass spectrometry at the single cell level. The intent of this review is to highlight the recent progress made in the application of single particle mass spectrometry to the analysis of microorganisms. A large portion of the review highlights improvements in the ionization and mass analysis of bio-aerosols, or particles that contain biologically relevant molecules such as peptides or proteins. While these are not direct applications to bacteria, the results have been central to a progression toward single cell mass spectrometry. Developments in single particle matrix-assisted laser desorption/ionization (MALDI) are summarized. Recent applications of aerosol laser desorption/ionization (LDI) to the analysis of single microorganisms are highlighted. Successful applications of off-line and on-the-fly aerosol MALDI to microorganism detection are discussed. Limitations to current approaches and necessary future achievements are also addressed.

Dodging matrix effects in liquid chromatography tandem mass spectrometric assays--compilation of key learnings and perspectives.

Triple quad liquid chromatography mass spectrometric assays (LC/MS/MS) have revolutionized the analysis of drug(s)/metabolite(s) with exceptional speed, sensitivity and selectivity features. From inception to date, several new and innovative features have been regularly proposed by researchers to further enhance the value in the applicability of this analytical tool. However, owing to such compressed run times and scanty sample preparation procedures, LC/MS/MS assays that are not fully optimized generally have issues of matrix effects, where ionization potential is either suppressed or enhanced due to the presence of other materials (endogenous/exogenous) in the matrix. By definition, even co-medications, isomeric or isobaric impurities, and drug excipients used in dosing solutions could also potentially contribute to matrix effects. This article captures some of the interesting work carried out by researchers to understand and handle matrix effects. Additionally, it provides perspectives to effectively deal with matrix effects.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004.

This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.

Advances in imaging secondary ion mass spectrometry for biological samples.

Imaging mass spectrometry combines the power of mass spectrometry to identify complex molecules based on mass with sample imaging. Recent advances in secondary ion mass spectrometry have improved sensitivity and spatial resolution, so that these methods have the potential to bridge between high-resolution structures obtained by X-ray crystallography and cyro-electron microscopy and ultrastructure visualized by conventional light microscopy. Following background information on the method and instrumentation, we address the key issue of sample preparation. Because mass spectrometry is performed in high vacuum, it is essential to preserve the lateral organization of the sample while removing bulk water, and this has been a major barrier for applications to biological systems. Recent applications of imaging mass spectrometry to cell biology, microbial communities, and biosynthetic pathways are summarized briefly, and studies of biological membrane organization are described in greater depth.

Orbitrap mass spectrometry: instrumentation, ion motion and applications.

Since its introduction, the orbitrap has proven to be a robust mass analyzer that can routinely deliver high resolving power and mass accuracy. Unlike conventional ion traps such as the Paul and Penning traps, the orbitrap uses only electrostatic fields to confine and to analyze injected ion populations. In addition, its relatively low cost, simple design and high space-charge capacity make it suitable for tackling complex scientific problems in which high performance is required. This review begins with a brief account of the set of inventions that led to the orbitrap, followed by a qualitative description of ion capture, ion motion in the trap and modes of detection. Various orbitrap instruments, including the commercially available linear ion trap-orbitrap hybrid mass spectrometers, are also discussed with emphasis on the different methods used to inject ions into the trap. Figures of merit such as resolving power, mass accuracy, dynamic range and sensitivity of each type of instrument are compared. In addition, experimental techniques that allow mass-selective manipulation of the motion of confined ions and their potential application in tandem mass spectrometry in the orbitrap are described. Finally, some specific applications are reviewed to illustrate the performance and versatility of the orbitrap mass spectrometers.

Is charge reduction in ESI really necessary?

The technique of charge reduction electrospray mass spectrometry (CREMS), which can reduce the charge state complexity produced in electrospray ionization (ESI), is discussed.