Characterization of Phosphorylated Peptides by Electron-Activated and Ultraviolet Dissociation Mass Spectrometry: A Comparative Study with Collision-Induced Dissociation.

Mass-spectrometry-based methods have made significant progress in the characterization of post-translational modifications (PTMs) in peptides and proteins; however, room remains to improve fragmentation methods. Ideal MS/MS methods are expected to simultaneously provide extensive sequence information and localization of PTM sites and retain labile PTM groups. This collection of criteria is difficult to meet, and the various activation methods available today offer different capabilities.

Specific detection of protein carbonylation sites by 473 nm photodissociation mass spectrometry.

The study of protein oxidation remains a challenge despite the biomedical interest in reliable biomarkers of oxidative stress. This is particularly true for carbonylations although, recently, liquid chromatography-mass spectrometry techniques (LC-MS) have been proposed to detect this non-enzymatic and poorly distributed oxidative modification of proteins using untargeted or carbonyl-reactive probe methods. These methods proved to be feasible but could not preserve the dynamic range of the protein sample, making it impossible to quantify oxidatively modified proteoforms compared with native proteoforms.

High performance {NbTaX}@PVP (X = Cl, Br) cluster-based nanocomposites coatings for solar glazing applications.

The development of highly ultraviolet (UV) and near-infrared (NIR) absorbent transparent coatings is an important enabling technology and area of research for environmental sustainability and energy conservation. Different amounts of K[{NbTaX }X ] cluster compounds (X = Cl, Br) dispersed into polyvinylpyrrolidone matrices were prepared by a simple, nontoxic and low-cost wet chemical method. The resulting solutions were used to fabricate visibly transparent, highly UV and NIR absorbent coatings by drop casting.

Controlling the Deposition Process of Nanoarchitectonic Nanocomposites Based on {NbTaX} Octahedral Cluster-Based Building Blocks (X = Cl, Br; 0 ≤ x ≤ 6, n = 2, 3, 4) for UV-NIR Blockers Coating Applications.

The antagonism between global energy needs and the obligation to slow global warming is a current challenge. In order to ensure sufficient thermal comfort, the automotive, housing and agricultural building sectors are major energy consumers. Solar control materials and more particularly, selective glazing are part of the solutions proposed to reduce global energy consumption and tackle global warming.

Nanoarchitectonics of Glass Coatings for Near-Infrared Shielding: From Solid-State Cluster-Based Niobium Chlorides to the Shaping of Nanocomposite Films.

The high potential of [{NbCl}L] cluster-based building blocks as near-infrared radiation blockers for energy saving applications is exposed in the present paper (i = inner edge-bridging ligand, a = apical ligand of the Nb; L = HO and/or Cl). To do so, a combined experimental and theoretical investigation of edge-bridged [{NbCl}Cl(HO)] cluster unit series ( = 0, 4, 6; = 2, 3, 4; = 2, 3, 4) has been carried out. By using the K[{NbCl}Cl] starting solid-state precursor, we explored the behavior of the [{NbCl}Cl] cluster unit during the different steps of its integration as a building block into a polyvinylpyrrolidone (PVP) matrix to form a glass coating composite denoted {NbCl}@PVP ( = 2 or 3).

Photo-control of bimolecular reactions: reactivity of the long-lived Rhodamine 6G triplet excited state with ˙NO.

Photo-chemistry provides a non-intuitive but very powerful way to probe kinetically limited, sometimes thermodynamically non-favored reactions and, thus, access highly specific products. However, reactivity in the excited state is difficult to characterize directly, due to short lifetimes and challenges in controlling the reaction medium. Among photo-activatable reagents, rhodamine dyes find widespread uses due to a number of favorable properties including their high absorption coefficient.

Ionization and Photofragmentation of Isolated Metalloporphyrin Cations Investigated by VUV Action Spectroscopy*.

We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX with M=Fe, Co, Zn) by means of vacuum-ultraviolet (VUV) action spectroscopy in the energy range of 8.5-35 eV. Experiments were carried out in the gas phase by interfacing an electrospray ionization tandem mass spectrometer with a synchrotron beamline.

Revisiting properties of edge-bridged bromide tantalum clusters in the solid-state, in solution and vice versa: an intertwined experimental and modelling approach.

Edge-bridged halide tantalum clusters based on the {TaBr} core have been the topic of many physicostructural investigations both in solution and in the solid-state. Despite a large number of studies, the fundamental correlations between compositions, local symmetry, electronic structures of [{TaBr}L] cluster units (L = Br or HO, in solution and in the solid-state), redox states, and vibrational and absorption properties are still not well established. Using K[{TaBr}Br] as a starting precursor (i: inner and a: apical), we have investigated the behavior of the [{TaBr}Br] cluster unit in terms of oxidation properties and chemical modifications both in solution (water and organic solvent) and after recrystallization.

Bringing Molecular Dynamics and Ion-Mobility Spectrometry Closer Together: Shape Correlations, Structure-Based Predictors, and Dissociation.

Unfolding of proteins gives detailed information about their structure and energetics and can be probed as a response to a change of experimental conditions. Ion mobility coupled to native mass spectrometry is a gas-phase technique that can observe such unfolding in the gas phase by monitoring the collision cross section (CCS) after applying an activation, for example, by collisions (collision-induced unfolding, CIU). The structural assignments needed to interpret the experiments can profit from dedicated modeling strategies.

Radical Anions of Oxidized vs. Reduced Oxytocin: Influence of Disulfide Bridges on CID and Vacuum UV Photo-Fragmentation.

The nonapeptide oxytocin (OT) is used as a model sulfur-containing peptide to study the damage induced by vacuum UV (VUV) radiations. In particular, the effect of the presence (or absence in reduced OT) of oxytocin's internal disulfide bridge is evaluated in terms of photo-fragmentation yield and nature of the photo-fragments. Intact, as well as reduced, OT is studied as dianions and radical anions.

Ion mobility resolved photo-fragmentation to discriminate protomers.

Rationale: Among the sources of structural diversity in biomolecular ions, the co-existence of protomers is particularly difficult to take into account, which in turn complicates structural interpretation of gas-phase data.

Methods: We investigated the sensitivity of gas-phase photo-fragmentation measurements and ion mobility spectrometry (IMS) to the protonation state of a model peptide derivatized with chromophores. Accessible interconversion pathways between the different identified conformers were probed by tandem ion mobility measurement.

Photo-induced linkage isomerization in the gas phase probed by tandem ion mobility and laser spectroscopy.

Ruthenium complexes involving sulfoxide ligands can undergo linkage isomerization upon light absorption, accompanied by dramatic changes in their optical properties. These remarkable photochromic properties are sensitive to the nature of the ligand as well as to that of the solvent. We used tandem ion mobility spectrometry coupled to mass spectrometry to gain direct experimental insight into the isomerization pathways connecting the different linkage isomers of an isolated ruthenium complex with two dimethyl-sulfoxide ligands.

Combining Structural Probes in the Gas Phase - Ion Mobility-Resolved Action-FRET.

In the context of native mass spectrometry, the development of gas-phase structural probes sensitive to the different levels of structuration of biomolecular assemblies is necessary to push forward conformational studies. In this paper, we provide the first example of the combination of ion mobility (IM) and Förster resonance energy transfer (FRET) measurements within the same experimental setup. The possibility to obtain mass- and mobility-resolved FRET measurements is demonstrated on a model peptide and applied to monitor the collision-induced unfolding of ubiquitin.

Ultraviolet, Infrared, and High-Low Energy Photodissociation of Post-Translationally Modified Peptides.

Mass spectrometry-based methods have made significant progress in characterizing post-translational modifications in peptides and proteins; however, certain aspects regarding fragmentation methods must still be improved. A good technique is expected to provide excellent sequence information, locate PTM sites, and retain the labile PTM groups. To address these issues, we investigate 10.

Visible Multiphoton Dissociation of Chromophore-Tagged Peptides.

The visible photodissociation mechanisms of QSY7-tagged peptides of increasing size have been investigated by coupling a mass spectrometer and an optical parametric oscillator laser beam. The experiments herein consist of energy resolved collision- and laser-induced dissociation measurements on the chromophore-tagged peptides. The results show that fragmentation occurs by similar channels in both activation methods, but that the branching ratios are vastly different.

Combining Time-of-Flight Secondary Ion Mass Spectrometry Imaging Mass Spectrometry and CARS Microspectroscopy Reveals Lipid Patterns Reminiscent of Gene Expression Patterns in the Wing Imaginal Disc of Drosophila melanogaster.

Using label-free ToF-SIMS imaging mass spectrometry, we generated a map of small molecules differentially expressed in the Drosophila wing imaginal disc. The distributions of these moieties were in line with gene expression patterns observed during wing imaginal disc development. Combining ToF-SIMS imaging and coherent anti-Stokes Raman spectroscopy (CARS) microspectroscopy allowed us to locally identify acylglycerols as the main constituents of the pattern differentiating the future body wall tissue from the wing blade tissue.

Action-Self Quenching: Dimer-Induced Fluorescence Quenching of Chromophores as a Probe for Biomolecular Structure.

To obtain a more detailed understanding of how structure influences the function and interaction of biomolecules, it is important to develop structure sensitive techniques to probe these relationships. Alongside in vivo and in vitro techniques, it is instructive to consider in vacuo methodologies: for example native mass spectrometry, ion mobility mass spectrometry, and FRET. Here, we propose a novel technique for probing biomolecular structure based on the changes in photophysics of a chromophore upon dimer formation.

Conformational Dynamics in Ion Mobility Data.

The shape of the spectral features in arrival time distributions (ATDs) recorded by ion mobility spectrometry (IMS) can often be interpreted in terms of the coexistence of different isomeric species. Interconversion between such species is also acknowledged to influence the shape of the ATD, even if no general quantitative description of this effect is available. We present an analytical model that allows simulating ATDs resulting from interconverting species.

Action-FRET of a Gaseous Protein.

Mass spectrometry is an extremely powerful technique for analysis of biological molecules, in particular proteins. One aspect that has been contentious is how much native solution-phase structure is preserved upon transposition to the gas phase by soft ionization methods such as electrospray ionization. To address this question-and thus further develop mass spectrometry as a tool for structural biology-structure-sensitive techniques must be developed to probe the gas-phase conformations of proteins.

Excited States of Xanthene Analogues: Photofragmentation and Calculations by CC2 and Time-Dependent Density Functional Theory.

Action spectroscopy has emerged as an analytical tool to probe excited states in the gas phase. Although comparison of gas-phase absorption properties with quantum-chemical calculations is, in principle, straightforward, popular methods often fail to describe many molecules of interest-such as xanthene analogues. We, therefore, face their nano- and picosecond laser-induced photofragmentation with excited-state computations by using the CC2 method and time-dependent density functional theory (TDDFT).

Combined Infrared Multiphoton Dissociation with Ultraviolet Photodissociation for Ubiquitin Characterization.

Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds.

The Gas-Phase Photophysics of Eosin Y and its Maleimide Conjugate.

The use of the xanthene family of dyes as fluorescent probes in a wide range of applications has provided impetus for the studying of their photophysical properties. In particular, recent advances in gas-phase techniques such as FRET that utilize such chromophores have placed a greater importance on the characterization of these properties in the gas phase. Additionally, the use of synthetic linker chains to graft the chromophores in a site-specific manner to their target system is ubiquitous.

Sequential Proton Coupled Electron Transfer (PCET): Dynamics Observed over 8 Orders of Magnitude in Time.

Charge transfer mechanisms lay at the heart of chemistry and biochemistry. Proton coupled electron transfers (PCET) are central in biological processes such as photosynthesis and in the respiratory chain, where they mediate long-range charge transfers. These mechanisms are normally difficult to harness experimentally due to the intrinsic complexity of the associated biological systems.

The structure of chromophore-grafted amyloid-β(12-28) dimers in the gas-phase: FRET-experiment guided modelling.

We present theoretical modelling, ion mobility spectrometry and action-FRET experiments for chromophore-grafted amyloid-β(12-28) dimers. A first-principles global minimum search based on replica-exchange molecular dynamics (REMD) leads to a compact structure with strong interstrand interactions. We use REMD with a distance restraint that implements an adaptive effective bias upon average FRET-efficiencies and thus guides the sampling by the action-FRET measurement.

Correction: Conformational changes in amyloid-beta (12-28) alloforms studied using action-FRET, IMS and molecular dynamics simulations.

[This corrects the article DOI: 10.1039/C5SC01463H.].