Dataset Information

Interfacial Ca²⁺ environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced ⁴³Ca NMR spectroscopy.

ABSTRACT: The interfaces within bones, teeth and other hybrid biomaterials are of paramount importance but remain particularly difficult to characterize at the molecular level because both sensitive and selective techniques are mandatory. Here, it is demonstrated that unprecedented insights into calcium environments, for example the differentiation of surface and core species of hydroxyapatite nanoparticles, can be obtained using solid-state NMR, when combined with dynamic nuclear polarization. Although calcium represents an ideal NMR target here (and de facto for a large variety of calcium-derived materials), its stable NMR-active isotope, calcium-43, is a highly unreceptive probe. Using the sensitivity gains from dynamic nuclear polarization, not only could calcium-43 NMR spectra be obtained easily, but natural isotopic abundance 2D correlation experiments could be recorded for calcium-43 in short experimental time. This opens perspectives for the detailed study of interfaces in nanostructured materials of the highest biological interest as well as calcium-based nanosystems in general.

SUBMITTER: Lee D

PROVIDER: S-EPMC5290151 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Publications

Interfacial Ca<sup>2+</sup> environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced <sup>43</sup>Ca NMR spectroscopy.

Lee Daniel D Leroy César C Crevant Charlène C Bonhomme-Coury Laure L Babonneau Florence F Laurencin Danielle D Bonhomme Christian C De Paëpe Gaël G

Nature communications 20170127

The interfaces within bones, teeth and other hybrid biomaterials are of paramount importance but remain particularly difficult to characterize at the molecular level because both sensitive and selective techniques are mandatory. Here, it is demonstrated that unprecedented insights into calcium environments, for example the differentiation of surface and core species of hydroxyapatite nanoparticles, can be obtained using solid-state NMR, when combined with dynamic nuclear polarization. Although c ...[more]

PMID: 28128197

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Project description:Calcium ion complexation in aqueous solutions is of paramount importance in biology as it is related to cell signaling, muscle contraction, or biomineralization. However, Ca2+-complexes are dynamic soluble entities challenging to describe at the molecular level. Nuclear magnetic resonance appears as a method of choice to probe Ca2+-complexes. However, 43Ca NMR exhibits severe limitations arising from the low natural abundance coupled to the low gyromagnetic ratio and the quadrupolar nature of 43Ca, which overall make it a very unreceptive nucleus. Here, we show that 43Ca dynamic nuclear polarization (DNP) NMR of 43Ca-labeled frozen solutions is an efficient approach to enhance the NMR receptivity of 43Ca and to obtain structural insights about calcium ions complexed with representative ligands including water molecules, ethylenediaminetetraacetic acid (EDTA), and l-aspartic acid (l-Asp). In these conditions and in combination with numerical simulations and calculations, we show that 43Ca nuclei belonging to Ca2+ complexed to the investigated ligands exhibit rather low quadrupolar couplings (with CQ typically ranging from 0.6 to 1 MHz) due to high symmetrical environments and potential residual dynamics in vitrified solutions at a temperature of 100 K. As a consequence, when 1H→43Ca cross-polarization (CP) is used to observe 43Ca central transition, "high-power" νRF(43Ca) conditions, typically used to detect spin 1/2 nuclei, provide ∼120 times larger sensitivity than "low-power" conditions usually employed for detection of quadrupolar nuclei. These "high-power" CPMAS conditions allow two-dimensional (2D) 1H-43Ca HetCor spectra to be readily recorded, highlighting various Ca2+-ligand interactions in solution. This significant increase in 43Ca NMR sensitivity results from the combination of distinct advantages: (i) an efficient 1H-mediated polarization transfer from DNP, resembling the case of low-natural-abundance spin 1/2 nuclei, (ii) a reduced dynamics, allowing the use of CP as a sensitivity enhancement technique, and (iii) the presence of a relatively highly symmetrical Ca environment, which, combined to residual dynamics, leads to the averaging of the quadrupolar interaction and hence to efficient high-power CP conditions. Interestingly, these results indicate that the use of high-power CP conditions is an effective way of selecting symmetrical and/or dynamic 43Ca environments of calcium-containing frozen solution, capable of filtering out more rigid and/or anisotropic 43Ca sites characterized by larger quadrupolar constants. This approach could open the way to the atomic-level investigation of calcium environments in more complex, heterogeneous frozen solutions, such as those encountered at the early stages of calcium phosphate or calcium carbonate biomineralization events.

Dataset Information

Interfacial Ca²⁺ environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced ⁴³Ca NMR spectroscopy.

Publications

Interfacial Ca<sup>2+</sup> environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced <sup>43</sup>Ca NMR spectroscopy.

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Dataset Information

Interfacial Ca2+ environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced 43Ca NMR spectroscopy.

Publications

Interfacial Ca<sup>2+</sup> environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced <sup>43</sup>Ca NMR spectroscopy.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Interfacial Ca²⁺ environments in nanocrystalline apatites revealed by dynamic nuclear polarization enhanced ⁴³Ca NMR spectroscopy.