Poster Presentation 23rd International Society of Magnetic Resonance Conference 2023

Application of NMR on Biominerals (#318)

Shu-Li Li 1 , Eric Chung-Yuen Yuan 1 , Li-Han Wang 1 , Shing-Jong Huang 2 , Jerry Chun Chung Chan 1
  1. National Taiwan University, Taipei, Taiwan
  2. National Taiwan University, Instrumentation Center, Taipei, Taiwan

Magnesium-stabilized amorphous calcium carbonate (Mg-ACC) and polymer-stabilized calcium phosphate (ACP) are important precursors of biogenic Mg-calcite and bone formations. However, limited information obtained by diffraction techniques for amorphous materials has led to a poor understanding of their structures. To characterize their structural formations, we conducted a series of NMR measurements. Using the magnetic dipole-dipole interaction of 25Mg and 13C, we investigated ion clustering effects in Mg-ACC. The results showed that the localized Mg-rich and Mg-depleted domains could be distinguished by their chemical shifts in our 13C{25Mg} S-RESPDOR experiments, revealing the structural heterogeneity of Mg-ACC. To further understand the nature of the ion distribution in Mg-ACC, we used the chemical shifts of the two Mg domains to deconvolute the 13C Bloch decay spectrum. By applying the concept of mixed ions effect, we determined the localized Mg content in each domain based on their chemical shifts. Thus, we were able to determine the total Mg content in Mg-ACC, which was compared favorably with the results of ICP-MS. Additionally, PDSD experiments showed that the domain sizes of the two components in Mg-ACCs varied considerably as the Mg content increased from 16% to 23%, which might be correlated with the toughening mechanism in the lenses of brittle stars.1 In our study of ACPs, we used 31P{1H} HETCOR measurements with CP dynamics to experimentally discern the chemical states of various structural moieties and their associated motional dynamics. Our results showed that the phosphate species in ACPs had remarkable structural versatility, with HPO42- being the dominant species in polymer-stabilized ACP. This finding highlights the importance of HPO42- in bone formations.2

  1. Polishchuk, I.; Bracha, A. A.; Bloch, L.; Levy, D.; Kozachkevich, S.; Etinger-Geller, Y.; Kauffmann, Y.; Burghammer, M.; Giacobbe, C.; Villanova, J.; Hendler, G.; Sun, C.-Y.; Giuffre, A. J.; Marcus, M. A.; Kundanati, L.; Zaslansky, P.; Pugno, N. M.; Gilbert, P. U. P. A.; Katsman, A.; Pokroy, B. Coherently Aligned Nanoparticles within a Biogenic Single Crystal: A Biological Prestressing Strategy. Science. 2017, 358 (6368), 1294–1298.
  2. Wang, Y.; Von Euw, S.; Fernandes, F. M.; Cassaignon, S.; Selmane, M.; Laurent, G.; Pehau-Arnaudet, G.; Coelho, C.; Bonhomme-Coury, L.; Giraud-Guille, M.-M.; Babonneau, F.; Azaïs, T.; Nassif, N. Water-Mediated Structuring of Bone Apatite. Nat. Mater. 2013, 12 (12), 1144–1153.