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Abstract RationaleThe use of secondary ion mass spectrometry (SIMS) to perform micrometer‐scalein situcarbon isotope (δ13C) analyses of shells of marine microfossils called planktic foraminifers holds promise to explore calcification and ecological processes. The potential of this technique, however, cannot be realized without comparison to traditional whole‐shell δ13C values measured by gas source mass spectrometry (GSMS). MethodsPaired SIMS and GSMS δ13C values measured from final chamber fragments of the same shell of the planktic foraminiferOrbulina universaare compared. The SIMS–GSMS δ13C differences (Δ13CSIMS‐GSMS) were determined via paired analysis of hydrogen peroxide‐cleaned fragments of modern cultured specimens and of fossil specimens from deep‐sea sediments that were either untreated, sonicated, and cleaned with hydrogen peroxide or vacuum roasted. After treatment, fragments were analyzed by a CAMECA IMS 1280 SIMS instrument and either a ThermoScientific MAT‐253 or a Fisons Optima isotope ratio mass spectrometer (GSMS). ResultsPaired analyses of cleaned fragments of cultured specimens (n = 7) yield no SIMS–GSMS δ13C difference. However, paired analyses of untreated (n = 18) and cleaned (n = 12) fragments of fossil shells yield average Δ13CSIMS‐GSMSvalues of 0.8‰ and 0.6‰ (±0.2‰, 2 SE), respectively, while vacuum roasting of fossil shell fragments (n = 11) removes the SIMS–GSMS δ13C difference. ConclusionsThe noted Δ13CSIMS‐GSMSvalues are most likely due to matrix effects causing sample–standard mismatch for SIMS analyses but may also be a combination of other factors such as SIMS measurement of chemically bound water. The volume of material analyzed via SIMS is ~105times smaller than that analyzed by GSMS; hence, the extent to which these Δ13CSIMS‐GSMSvalues represent differences in analyte or instrument factors remains unclear.
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Decoding the Fucose Migration Product during Mass‐Spectrometric analysis of Blood Group Epitopes
Abstract Fucose is a signaling carbohydrate that is attached at the end of glycan processing. It is involved in a range of processes, such as the selectin‐dependent leukocyte adhesion or pathogen‐receptor interactions. Mass‐spectrometric techniques, which are commonly used to determine the structure of glycans, frequently show fucose‐containing chimeric fragments that obfuscate the analysis. The rearrangement leading to these fragments—often referred to as fucose migration—has been known for more than 25 years, but the chemical identity of the rearrangement product remains unclear. In this work, we combine ion‐mobility spectrometry, radical‐directed dissociation mass spectrometry, cryogenic IR spectroscopy of ions, and density‐functional theory calculations to deduce the product of the rearrangement in the model trisaccharides Lewis x and blood group H2. The structural search yields the fucose moiety attached to the galactose with anα(1→6) glycosidic bond as the most likely product.
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- Award ID(s):
- 1904577
- PAR ID:
- 10418509
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 62
- Issue:
- 24
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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