untargeted. Targeted metabolomics focuses on a subset of metabolites involved in one or more pathways; the chemical identities of metabolites to be measured are known, authentic standards are available in these studies. The goal of untargeted metabolomics is to observe global metabolite profiling differences between sample types, experiments are designed to maximise the coverage of metabolites....

Over the past decade, mass spectrometry has been revolutionized by access to instruments of increasingly high mass-resolving power. For small molecules up to approximately 400 Da (e.g., drugs, metabolites, and various natural organic mixtures ranging from foods to petroleum), it is possible to determine elemental compositions (C(c)H(h)N(n)O(o)S(s)P(p)...) of thousands of chemical components sim...

The integration of soft ionization technologies and ultrahigh resolution FTICR mass spectrometry (Fourier transform ion-cyclotron MS) has enabled the examination of molecules, directly from mixtures, with ultrahigh mass resolution and sub-ppm mass accuracy. This ability to observe structure and reactivity aspects of intact (macro)molecules has, in particular, contributed to the molecular-level ...

The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The “magic” that we were attempting to report was that w...

Mass spectrometers work by determining the weights and numbers of molecules in a sample. Frequently they also fragment the molecules and determine the weights of the molecular fragments. The resulting information about the weights and abundances of the molecules and molecular fragments is collected and displayed in what are called mass spectra. Like a fingerprints, mass spectra can be used to p...

A recent innovation in mass spectrometry is the ability to record mass spectra on ordinary samples, in their native environment, without sample preparation or preseparation by creating ions outside the instrument. In desorption electrospray ionization (DESI), the principal method described here, electrically charged droplets are directed at the ambient object of interest; they release ions from...

This article reviews the new physics and new applications of secondary ion mass spectrometry using cluster ion probes. These probes, particularly C(60), exhibit enhanced molecular desorption with improved sensitivity owing to the unique nature of the energy-deposition process. In addition, these projectiles are capable of eroding molecular solids while retaining the molecular specificity of mas...

4. Automated Interpretation of CID Spectra 282 5. Accurate Mass Tags 282 C. Protein Identification in Complex Mixtures 282 D. Analysis of Protein Expression 284 III. Proteomes and Post-Translational Modifications 285 A. Proteomes 285 1. The Analytical Challenge 285 2. Analysis of Protein−Protein Complexes 286 B. Post-Translational Modifications 286 1. Background 286 2. Detection and Purificatio...

THE 15TH ASILOMAR CONFERENCE on Mass Spectrometry this October was devoted to the role of mass spectrometry (MS) in proteomics. The Asilomar Conference site is in a picturesque national park in Pacific Grove, CA, overlooking the Pacific Ocean. The conference aims to bring together scientists from a cross section of disciplines that are applying MS to an emerging field. This year, that emerging ...