Effects of Lorentz invariance violation on cosmic ray photon emission and gamma ray decay processes

In this work, we use Lorentz invariance violation (LIV) introduced as a generic modification to particle dispersion relations to study some consequences of single photon emission, known as vacuum Cherenkov radiation, and photon decay processes in cosmic and gamma rays. These processes are forbidden in a Lorentz invariant theory but allowed under the hypothesis of LIV. We show that the emission rate have a dependency on the cosmic ray primary mass and the electric charge that could modify the UHECR spectrum. Furthermore, LIV dramatically enhances photon decay into an electro-positron pair above certain energy threshold. This last effect can then be used to set limits to the LIV energy scale from the direct observation of very high energy cosmic photon events by telescopes of gamma-rays.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan, Kore

Structural Analysis of an Intact Monoclonal Antibody by Online Electrochemical Reduction of Disulfide Bonds and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Structural confirmation and quality control of recombinant monoclonal antibodies (mAbs) by top-down mass spectrometry is still challenging due to the size of the proteins, disulfide content, and post-translational modifications such as glycosylation. In this study we have applied electrochemistry (EC) to overcome disulfide bridge complexity in top-down analysis of mAbs. To this end, an electrochemical cell was coupled directly to an electrospray ionization (ESI) source and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer (MS) equipped with a 15 T magnet. By performing online EC-assisted reduction of interchain disulfide bonds in an intact mAb, the released light chains could be selected for tandem mass spectrometry (MS/MS) analysis without interference from heavy-chain fragments. Moreover, the acquisition of full MS scans under denaturing conditions allowed profiling of all abundant mAb glycoforms. Ultrahigh-resolution FTICR-MS measurements provided fully resolved isotopic distributions of intact mAb and enabled the identification of the most abundant adducts and other interfering species. Furthermore, it was found that reduction of interchain disulfide bonds occurs in the ESI source dependent on capillary voltage and solvent composition. This phenomenon was systematically evaluated and compared with the results obtained from reduction in the electrochemical cell

Top-Down MALDI-In-Source Decay-FTICR Mass Spectrometry of Isotopically Resolved Proteins

An accurate mass measurement of a known protein provides information on potential amino acid deletions and post-translational modifications. Although this field is dominated by strategies based on electrospray ionization, mass spectrometry (MS) methods using matrix-assisted laser desorption/ionization (MALDI) have the advantage of yielding predominantly singly charged precursor ions, thus avoiding peak overlap from different charge states of multiple species. Such MALDI-MS methods require mass measurement at ultrahigh resolution, which is provided by Fourier transform ion cyclotron resonance (FTICR) mass analyzers. Recently, using a MALDI-FTICR-MS platform equipped with a 15 T magnet, we reported on the mass analysis of intact human serum peptides and small proteins with isotopic resolution up to ∼15 kDa and identified new proteoforms from an accurate measurement of mass distances. In the current study, we have used this FTICR system after an upgrade with a novel dynamically harmonized ICR cell, i.e., ParaCell, for mapping isotopically resolved intact proteins up to about 17 kDa and performed top-down MALDI in-source decay (ISD) analysis. Standard proteins myoglobin (<i>m</i>/<i>z</i>-value 16 950) and ribonuclease B (<i>m</i>/<i>z</i>-value 14 900) were measured with resolving powers of 62 000 and 61 000, respectively. Furthermore, it will be shown that (singly charged) MALDI-ISD fragment ions can be measured at isotopic resolution up to <i>m</i>/<i>z</i>-value 12 000 (e.g., resolving power 39 000 at <i>m</i>/<i>z</i>-value 12 000) providing more reliable identifications. Moreover, examples are presented of pseudo-MS³ experiments on ISD fragment ions from RNase B by collisional-induced dissociation (CID)

Identification of New Apolipoprotein-CIII Glycoforms with Ultrahigh Resolution MALDI-FTICR Mass Spectrometry of Human Sera

Apolipoprotein-CIII (apoCIII) is an abundant blood glycoprotein associated with lipoprotein particles. Three different glycoforms have been described, all containing a mucin-type core-1 <i>O</i>-glycosylation with either zero, one or two sialic acids. Changes in the relative abundance of these glycoforms have been observed in a variety of different pathologies. In this study, ultrahigh resolution 15T MALDI Fourier transform ion cyclotron resonance (FTICR) MS was used to analyze apoCIII isoforms in serum protein profiles. For this purpose, serum proteins were purified using both a fully automated RPC18-based magnetic bead method and an RPC4 cartridge-based solid phase extraction method. Six new apoCIII isoforms were identified with low-ppm mass measurement errors and ultrahigh precision. These were characterized by more complex glycan moieties that are fucosylated instead of sialylated. To confirm the glycan moiety and localize the glycosylation site, top-down ESI-FTICR-MS/MS and bottom-up LC-ion trap MS/MS were used. A large variation in the presence and abundance of the fucosylated isoforms was found in a set of 96 serum samples. These findings of fucosylated apolipoprotein-CIII isoforms warrant further research to elucidate the implications these glycoforms may have for the plethora of studies where alterations in apoCIII have been linked to the development of many different pathologies

Additional file 3: of IgA N- and O-glycosylation profiling reveals no association with the pregnancy-related improvement in rheumatoid arthritis

Supplementary figures. Figures S1 and S2 Values depicted in graphs from data in Additional file 2: Table S3. (DOCX 248 kb

Top-Down FTICR MS for the Identification of Fluorescent Labeling Efficiency and Specificity of the Cu-Protein Azurin

Fluorescent protein labeling has been an indispensable tool in many applications of biochemical, biophysical, and cell biological research. Although detailed information about the labeling stoichiometry and exact location of the label is often not necessary, for other purposes, this information is crucial. We have studied the potential of top-down electrospray ionization (ESI)-15T Fourier transform ion cyclotron resonance (FTICR) mass spectrometry to study the degree and positioning of fluorescent labeling. For this purpose, we have labeled the Cu-protein azurin with the fluorescent label ATTO 655-N-hydroxysuccinimide­(NHS)-ester and fractionated the sample using anion exchange chromatography. Subsequently, individual fractions were analyzed by ESI-15T FTICR to determine the labeling stoichiometry, followed by top-down MS fragmentation, to locate the position of the label. Results showed that, upon labeling with ATTO 655-NHS, multiple different species of either singly or doubly labeled azurin were formed. Top-down fragmentation of different species, either with or without the copper, resulted in a sequence coverage of approximately 50%. Different primary amine groups were found to be (potential) labeling sites, and Lys-122 was identified as the major labeling attachment site. In conclusion, we have demonstrated that anion exchange chromatography in combination with ultrahigh resolution 15T ESI-FTICR top-down mass spectrometry is a valuable tool for measuring fluorescent labeling efficiency and specificity

Typing <i>Pseudomonas aeruginosa</i> Isolates with Ultrahigh Resolution MALDI-FTICR Mass Spectrometry

The introduction of standardized matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) platforms in the medical microbiological practice has revolutionized the way microbial species identification is performed on a daily basis. To a large extent, this is due to the ease of operation. Acquired spectra are compared to profiles obtained from cultured colonies present in a reference spectra database. It is fast and reliable, and costs are low compared to previous diagnostic approaches. However, the low resolution and dynamic range of the MALDI-TOF profiles have shown limited applicability for the discrimination of different bacterial strains, as achieved with typing based on genetic markers. This is pivotal in cases where certain strains are associated with, e.g., virulence or antibiotic resistance. Ultrahigh resolution MALDI-FTICR MS allows the measurement of small proteins at isotopic resolution and can be used to analyze complex mixtures with increased dynamic range and higher precision than MALDI-TOF MS, while still generating results in a similar time frame. Here, we propose to use ultrahigh resolution 15T MALDI-Fourier transform ion cyclotron resonance (FTICR) MS to discriminate clinically relevant bacterial strains after species identification performed by MALDI-TOF MS. We used a collection of well characterized <i>Pseudomonas aeruginosa</i> strains, featuring distinct antibiotic resistance profiles, and isolates obtained during hospital outbreaks. Following cluster analysis based on amplification fragment length polymorphism (AFLP), these strains were grouped into three different clusters. The same clusters were obtained using protein profiles generated by MALDI-FTICR MS. Subsequent intact protein analysis by electrospray ionization (ESI)-collision-induced dissociation (CID)-FTICR MS was applied to identify protein isoforms that contribute to the separation of the different clusters, illustrating the additional advantage of this analytical platform