Large-scale analysis of peptide sequence variants : the case for high-field asymmetric waveform ion mobility spectrometry

[Image: see text] Large scale analysis of proteins by mass spectrometry is becoming increasingly routine; however, the presence of peptide isomers remains a significant challenge for both identification and quantitation in proteomics. Classes of isomers include sequence inversions, structural isomers, and localization variants. In many cases, liquid chromatography is inadequate for separation of peptide isomers. The resulting tandem mass spectra are composite, containing fragments from multiple precursor ions. The benefits of high-field asymmetric waveform ion mobility spectrometry (FAIMS) for proteomics have been demonstrated by a number of groups, but previously work has focused on extending proteome coverage generally. Here, we present a systematic study of the benefits of FAIMS for a key challenge in proteomics, that of peptide isomers. We have applied FAIMS to the analysis of a phosphopeptide library comprising the sequences GPSGXVpSXAQLX(K/R) and SXPFKXpSPLXFG(K/R), where X = ADEFGLSTVY. The library has defined limits enabling us to make valid conclusions regarding FAIMS performance. The library contains numerous sequence inversions and structural isomers. In addition, there are large numbers of theoretical localization variants, allowing false localization rates to be determined. The FAIMS approach is compared with reversed-phase liquid chromatography and strong cation exchange chromatography. The FAIMS approach identified 35% of the peptide library, whereas LC–MS/MS alone identified 8% and LC–MS/MS with strong cation exchange chromatography prefractionation identified 17.3% of the library

Prospects in Analytical Atomic Spectrometry

Tendencies in five main branches of atomic spectrometry (absorption, emission, mass, fluorescence and ionization spectrometry) are considered. The first three techniques are the most widespread and universal, with the best sensitivity attributed to atomic mass spectrometry. In the direct elemental analysis of solid samples, the leading roles are now conquered by laser-induced breakdown and laser ablation mass spectrometry, and the related techniques with transfer of the laser ablation products into inductively-coupled plasma. Advances in design of diode lasers and optical parametric oscillators promote developments in fluorescence and ionization spectrometry and also in absorption techniques where uses of optical cavities for increased effective absorption pathlength are expected to expand. Prospects for analytical instrumentation are seen in higher productivity, portability, miniaturization, incorporation of advanced software, automated sample preparation and transition to the multifunctional modular architecture. Steady progress and growth in applications of plasma- and laser-based methods are observed. An interest towards the absolute (standardless) analysis has revived, particularly in the emission spectrometry.Comment: Proofread copy with an added full reference list of 279 citations. A pdf version of the final published review may be requested from Alexander Bol'shakov <[email protected]

Measurements of π+\pi^+, π−\pi^-, pp, pˉ\bar{p}, K+K^+ and K−K^- production in 120 GeV/cc p + C interactions

This paper presents multiplicity measurements of charged hadrons produced in 120 GeV/$c$ proton-carbon interactions. The measurements were made using data collected at the NA61/SHINE experiment during two different data-taking periods, with increased phase space coverage in the second configuration due to the addition of new subdetectors. Particle identification via $dE/dx$ was employed to obtain double-differential production multiplicities of $\pi^+$, $\pi^-$, $p$, $\bar{p}$, $K^+$ and $K^-$. These measurements are presented as a function of laboratory momentum in intervals of laboratory polar angle covering the range from 0 to 450 mrad. They provide crucial inputs for current and future long-baseline neutrino experiments, where they are used to estimate the initial neutrino flux

Measurements of π±\pi ^\pm , K±K^\pm , p and pˉ\bar{p} spectra in 7^7Be+9^9Be collisions at beam momenta from 19A to 150A GeV ⁣/ ⁣c{\mathrm{Ge} \mathrm{V}}\!/\!c with the NA61/SHINE spectrometer at the CERN SPS

The NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) studies the onset of deconfinement in hadron matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of π ± π± , K ± K± , p and p ¯ p¯ produced in the 20% most central 7 7 Be+ 9 9 Be collisions at beam momenta of 19A, 30A, 40A, 75A and 150A GeV/c GeV/c . The energy dependence of the K ± K± /π ± π± ratios as well as of inverse slope parameters of the K ± K± transverse mass distributions are close to those found in inelastic p+p reactions. The new results are compared to the world data on p+p and Pb+Pb collisions as well as to predictions of the Epos, Urqmd, Ampt, Phsd and Smash models