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Single cell fragmentation spectra on TOF instruments aren't any worse than other TOF spectra.

ABSTRACT: I evaluated TIMSTOF single cell fragmentation spectra (real human single cells) for previously reported y-ion fragment issues. While I see these in Orbitrap data as previously reported, I do not see these at the same levels in TOF spectra.

INSTRUMENT(S): timsTOF SCP

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Benjamin C Orsburn

PROVIDER: MSV000090635 | MassIVE | Thu Nov 03 03:29:00 GMT 2022

REPOSITORIES: MassIVE

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Project description:Isopeptide crosslinked proteins can be the product of transglutaminase or of exposure to organophosphorus toxicants (OP). Transglutaminase links glutamine to lysine with loss of ammonia. OP toxicants induce a link between glutamic acid and lysine with loss of water. Our goal was to establish criteria to distinguish real from false isopeptide crosslinks reported by software searches of mass spectrometry data. We used fragmentation spectra of tryptic peptides from MAP-rich tubulin Sus scrofa as a test system for detection of naturally-occurring isopeptide crosslinks. Data were analyzed with Protein Prospector. Criteria for the assignments included the presence of at least 1 crosslink specific product ion, fragment ions from both peptides, Protein Prospector scores ≥20, and best fit of the MS/MS data to the crosslinked peptide as opposed to a linear peptide. Out of 301,364 spectra, 15 potential transglutaminase-type crosslinked peptide candidates were identified. Manual evaluation of these MS/MS spectra reduced the number to 1 valid crosslink between Q112 of NFH and K368 of Tau. Immunopurification with anti-isopeptide 81D1C2 confirmed that MAP-rich tubulin contained only one isopeptide. Support for this isopeptide bond was obtained by showing that transglutaminase was capable of incorporating dansyl-aminohexyl -QQIV into K368. A model of the KIETHK-QLEAHNR isopeptide was synthesized with the aid of transglutaminase. MS/MS spectra of the model validated our interpretation of the native isopeptide. An OP-induced isopeptide bond between K163 of tubulin alpha-1A and E158 of tubulin beta-4B was induced by treating MAP-rich tubulin with 100 µM chlorpyrifos oxon. This crosslink was supported by the criteria described above and by the presence of diethoxyphospho-lysine 163 in the tubulin alpha-1A peptide. The information obtained in this work is valuable for future studies that aim to understand why exposure to OP is associated with increased risk of neurodegenerative disease.

Project description:Purpose: Delonix regia or Gulmohor commonly grows here and there in Indian villages as well as it is used for megacity beautification and environmental management due to its evergreen nature and vibrant flower colour. However, an increasing incidence of seasonal pollinosis was observed among the inhabitants living in close vicinity to this tree suggesting a possible link between the airborne pollen load and the concomitant respiratory hazards. This prompted us to investigate the allergens in the pollen of this dominant avenue tree. Methodology: Allergenicity of D. regia pollen grains was first checked by Skin Prick Test (SPT) and further confirmed by in vitro tests, such as, ELISA, Dot Blot and histamine release assay. The total proteome profiling was done by 2D PAGE and it was confronted with the pooled sera of 10 patients. The IgE reactive proteins were identified by MALDI TOF/TOF in Autoflex speed (Bruker,Germany). The raw spectra were searched against NCBInr database using MASCOT search engine. Result: Delonix regia, pollen grains have been found in considerable amount in the air during its flowering season (May to July). Approximately 31% of atopic individuals were found allergic to D. regia, pollen with elevated level of specific IgE and histamine in the serum. Total 8 IgE reactive proteins have been identified by homology driven proteomics. These proteins are ATP synthase beta subunit (spot no 5), Actin (spot no 6), Hypothetical actin like protein (spot no 7), Recombinant S-adenosylmethionine synthase 2 (spot no 9), UDP-arabinopyranose mutase (spot no 13), Luminal-binding 5 (spot no 2), ELF3-like protein (spot no 8) and hypothetical protein OsJ_04810 (spot no 11). Among these eight identified allergenic proteins, five were previously reported as allergen from different sources whereas the rest three have been reported for the first time as novel allergens. Conclusion: Novelty of this study was to identify 8 allergens from D.regia for the first time using immune-biochemical and proteomic techniques. Further studies will open up new avenues in component resolved diagnosis of pollen allergy.

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Single cell fragmentation spectra on TOF instruments aren't any worse than other TOF spectra.

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