Correlative chemical and elemental nano-imaging of morphology and disorder at the nacre-prismatic region interface in Pinctada margaritifera

Brian T. O’Callahan, Amy Larsen, Sarah Leichty, John Cliff, Alex C. Gagnon, Markus B. Raschke

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Understanding biomineralization relies on imaging chemically heterogeneous organic–inorganic interfaces across a hierarchy of spatial scales. Further, organic minority phases are often responsible for emergent inorganic structures from the atomic arrangement of different polymorphs, to nano- and micrometer crystal dimensions, up to meter size mollusk shells. The desired simultaneous chemical and elemental imaging to identify sparse organic moieties across a large field-of-view with nanometer spatial resolution has not yet been achieved. Here, we combine nanoscale secondary ion mass spectroscopy (NanoSIMS) with spectroscopic IR s-SNOM imaging for simultaneous chemical, molecular, and elemental nanoimaging. At the example of Pinctada margaritifera mollusk shells we identify and resolve ~ 50 nm interlamellar protein sheets periodically arranged in regular ~ 600 nm intervals. The striations typically appear ~ 15 µm from the nacre-prism boundary at the interface between disordered neonacre to mature nacre. Using the polymorph distinctive IR-vibrational carbonate resonance, the nacre and prismatic regions are consistently identified as aragonite (ν¯ a= 860 cm−1) and calcite (ν¯ c= 880 cm−1), respectively. We observe previously unreported morphological features including aragonite subdomains encapsulated in extensions of the prism-covering organic membrane and regions of irregular nacre tablet formation coincident with dispersed organics. We also identify a ~ 200 nm region in the incipient nacre region with less well-defined crystal structure and integrated organics. These results show with the identification of the interlamellar protein layer how correlative nano-IR chemical and NanoSIMS elemental imaging can help distinguish different models proposed for shell growth in particular, and how organic function may relate to inorganic structure in other biomineralized systems in general.

Original languageEnglish
Article number21258
JournalScientific Reports
Volume13
Issue number1
DOIs
StatePublished - Dec 2023
Externally publishedYes

Funding

Part of this research was performed on a project award (10.46936/expl.proj.2019.51109/60000141) from the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility sponsored by the Biological and Environmental Research program under Contract No. DE-AC05-76RL01830. M.B.R. acknowledges support through the NSF Science and Technology Center on Real-Time Functional Imaging (STROBE) under Grant No. DMR-1548924.

FundersFunder number
National Science FoundationDMR-1548924
Office of Science
Biological and Environmental ResearchDE-AC05-76RL01830

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