High resolution MALDI-TOF mass spectra of three proteins obtained using space—velocity correlation focusing

RECENT ADVANCES IN INSTRUMENTAL APPROACHES TO TIME-OF-FLIGHT MASS SPECTROMETRY

Time-of-flight mass spectrometry (TOFMS) is one of the simplest and most powerful approaches for mass spectrometry. Realization of the advantages inherent in TOFMS requires innovation in the theory and practice of the technique. Instrumental developments, in turn, create new capabilities that enable applications in chemical measurement. This review focuses on the recent advances in TOFMS instrumentation. New strategies for ion acceleration, multiplexed detection, miniaturized TOFMS instruments, approaches to extend the length of ion flight, and novel ion detection technologies are reviewed. Techniques that change the basic paradigm of TOFMS by measuring m/z based on ion flight distance are considered, as are applications at the frontiers of instrumental performance. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Time-resolved imaging of the MALDI linear-TOF ion cloud: direct visualization and exploitation of ion optical phenomena using a position- and time-sensitive detector

In this study, we describe the implementation of a position- and time-sensitive detection system (Timepix detector) to directly visualize the spatial distributions of the matrix-assisted laser desorption ionization ion cloud in a linear-time-of-flight (MALDI linear-ToF) as it is projected onto the detector surface. These time-resolved images allow direct visualization of m/z-dependent ion focusing effects that occur within the ion source of the instrument. The influence of key parameters, namely extraction voltage (E(V)), pulsed-ion extraction (PIE) delay, and even the matrix-dependent initial ion velocity was investigated and were found to alter the focusing properties of the ion-optical system. Under certain conditions where the spatial focal plane coincides with the detector plane, so-called x-y space focusing could be observed (i.e., the focusing of the ion cloud to a small, well-defined spot on the detector). Such conditions allow for the stigmatic ion imaging of intact proteins for the first time on a commercial linear ToF-MS system. In combination with the ion-optical magnification of the system (~100×), a spatial resolving power of 11–16 μm with a pixel size of 550 nm was recorded within a laser spot diameter of ~125 μm. This study demonstrates both the diagnostic and analytical advantages offered by the Timepix detector in ToF-MS.

From large analogical instruments to small digital black boxes: 40 years of progress in mass spectrometry and its role in proteomics. Part II 1985-2000

This is the continuation of a personal retrospective on the developments that since 1965 have given shape to Mass Spectrometry (MS) and taken it from a position of simply playing a role in Protein Chemistry to becoming an indispensable tool in Proteomics, all within a 40-year span. Part I covered the period from 1965 to 1984. This second part reviews the Mass Spectrometry timeline of events from 1985 to 2000, stopping at various time points where MS made significant contributions to protein chemistry or where the development of new instrumentation for MS represented a major advance for peptide and protein work. Major highlights in the field and their significance for peptide and protein characterization such as the advent and practical consequences of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) are covered, including work done with triple quads, the development of time-of-flight (TOF) instruments and new ion traps and going on to the more recent work on the full characterization of the Proteome with ion traps, TOF instruments and new ionization and tagging techniques for protein sequencing.

Mass Spectrometers for the Analysis of Biomolecules

Mass spectrometry (MS) has become a vital enabling technology in the life sciences. This chapter summarizes the fundamental aspects of MS, with reference to topics such as isotopic abundance and accurate mass and resolution. A broad and comprehensive overview of the instrumentation, techniques, and methods required for the analysis of biomolecules is presented. Emphasis is placed on describing the soft ionization methods and separation techniques employed in current state-of-the-art mass spectrometers.

Linking genome and proteome by mass spectrometry: large-scale identification of yeast proteins from two dimensional gels

The function of many of the uncharacterized open reading frames discovered by genomic sequencing can be determined at the level of expressed gene products, the proteome. However, identifying the cognate gene from minute amounts of protein has been one of the major problems in molecular biology. Using yeast as an example, we demonstrate here that mass spectrometric protein identification is a general solution to this problem given a completely sequenced genome. As a first screen, our strategy uses automated laser desorption ionization mass spectrometry of the peptide mixtures produced by in-gel tryptic digestion of a protein. Up to 90% of proteins are identified by searching sequence data bases by lists of peptide masses obtained with high accuracy. The remaining proteins are identified by partially sequencing several peptides of the unseparated mixture by nanoelectrospray tandem mass spectrometry followed by data base searching with multiple peptide sequence tags. In blind trials, the method led to unambiguous identification in all cases. In the largest individual protein identification project to date, a total of 150 gel spots-many of them at subpicomole amounts-were successfully analyzed, greatly enlarging a yeast two-dimensional gel data base. More than 32 proteins were novel and matched to previously uncharacterized open reading frames in the yeast genome. This study establishes that mass spectrometry provides the required throughput, the certainty of identification, and the general applicability to serve as the method of choice to connect genome and proteome.

Developments in matrix-assisted laser desorption/ionization peptide mass spectrometry

Most characteristics of matrix-assisted laser desorption/ionization (MALDI) are ideal for the analysis of biomolecules. New preparation techniques have dramatically increased mass accuracy and resolution, making MALDI a high-performance mass spectrometric technique for peptide mass analysis. Attempts to obtain amino acid sequence information by MALDI have been partially successful. The technique has been put to novel uses in protein primary structure characterization.