High-Mg calcite nanoparticles within a low-Mg calcite matrix: A widespread phenomenon in biomineralization

Bianco‐Stein, Nuphar; Polishchuk, Iryna; Lang, Arad; Portal, Lotan; Dejoie, Catherine; Katsman, A.; Pokroy, Boaz

doi:10.1073/pnas.2120177119

Cited by 21 publications

(11 citation statements)

References 63 publications

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“…Therefore, these findings suggest strong biological, rather than environmental, control over their biomineralization, which is consistent with the data implying a key role of vital effects in modulating skeletal Mg/Ca ratios in some echinoderms [46]. Given the fact that the increased contents of magnesium in calcite biominerals generally enhance their hardness and toughness ( [49,50]; see also figure 6), elevated-Mg content in the haplocrinitid skeleton might have represented an interesting strategy to further increase its mechanical properties. This unique Mg-enriched diamond microlattice in Haplocrinites thus offers an excellent example of optimized lightweight, stiff and damage-tolerant construction.…”

Section: Discussionsupporting

confidence: 87%

A Devonian crinoid with a diamond microlattice

et al. 2023

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Owing to their remarkable physical properties, cellular structures, such as triply periodic minimal surfaces (TPMS), have multidisciplinary and multifunctional applications. Although these structures are observed in nature, examples of TPMS with large length scales in living organisms are exceedingly rare. Recently, microstructure reminiscent of the diamond-type TPMS was documented in the skeleton of the modern knobby starfish Protoreaster nodosus . Here we report a similar microlattice in a 385 Myr old crinoid Haplocrinites , which pushes back the origins of this highly ordered microstructure in echinoderms into the Devonian. Despite the low Mg 2+ /Ca 2+ ratio of the ‘calcite’ Devonian sea, the skeleton of these crinoids has high-Mg content, which indicates strong biological control over biomineralogy. We suggest that such an optimization of trabecular arrangement additionally enriched in magnesium, which enhances the mechanical properties, might have evolved in these crinoids in response to increased predation pressure during the Middle Palaeozoic Marine Revolution. This discovery illustrates the remarkable ability of echinoderms, through the process of evolutionary optimization, to form a lightweight, stiff and damage-tolerant skeleton, which serves as an inspiration for biomimetic materials.

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Section: Discussionsupporting

confidence: 87%

A Devonian crinoid with a diamond microlattice

et al. 2023

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“…Alternatively, nanodomains could form as a result of spinodal decomposition of the fluid (e.g., Seknazi et al; Bianco-Stein et al). , However, spinodal decomposition would occur at high supersaturation and would, thus, lead to the formation of a metastable phase, rather than the ordered phase. Hence, a scenario of nucleation of ordered nanoparticles at the recrystallization front would better explain the finding of dolomitic nanodomains.…”

Section: Resultsmentioning

confidence: 99%

Nanoscale Pathway of Modern Dolomite Formation in a Shallow, Alkaline Lake

Meister

Frisia

Dódony

et al. 2023

Crystal Growth & Design

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Dolomite [CaMg(CO 3 ) 2 ] formation under Earth surface conditions is considered largely inhibited, yet protodolomite (with a composition similar to dolomite but lacking cation ordering), and in some cases also dolomite, was documented in modern shallow marine and lacustrine, evaporative environments. Authigenic carbonate mud from Lake Neusiedl, a shallow, episodically evaporative lake in Austria consists mainly of Mgcalcite with zoning of Mg-rich and Mg-poor regions in μm-sized crystals. Within the Mgrich regions, high-resolution transmission electron microscopy revealed < 5-nm-sized domains with dolomitic ordering, i.e., alternating lattice planes of Ca and Mg, in coherent orientation with the surrounding protodolomite. The calcite with less abundant Mg does not show such domains but is characterized by pitted surfaces and voids as a sign of dissolution. These observations suggest that protodolomite may overgrow Mg-calcite as a result of the changing chemistry of the lake water. During this process, oscillating concentrations (in particular of Mg and Ca) at the recrystallization front may have induced dissolution of Mg-calcite and growth of nanoscale domains of dolomite, which subsequently became incorporated as ordered domains in coherent orientation within less ordered regions. It is suggested that this crystallization pathway is capable of overcoming, at least at the nanoscale, the kinetic barrier to dolomite formation.

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“…The literature is proposing essentially two different mechanisms of amorphous calcium carbonate transformation: one invoking the presence of Mg ( 24 , 72 – 74 ), the other a form of ACC hydration ( 10 , 35 ). In brief, the first scenario involves an Mg-rich ACC phase transforming upon loss of Mg into a Mg-poor ACC ( 72 ).…”

Section: Discussionmentioning

confidence: 99%

“…Interestingly, the Mg-stabilization mechanism has been investigated in more detail recently. It was invoked to explain the formation of a prestressed biogenic calcite single crystal by the brittle star Ophiocoma wendtii ( 72 ) and was recently shown to be a widespread strategy of biomineralization ( 74 ). In this model, an initial Mg-rich ACC precursor undergoes a spinodal decomposition into Mg-rich amorphous nanoparticles and a Mg-depleted amorphous matrix.…”

Section: Discussionmentioning

confidence: 99%

Structure of an amorphous calcium carbonate phase involved in the formation of Pinctada margaritifera shells

Grünewald

Checchia

Dicko

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Some mollusc shells are formed from an amorphous calcium carbonate (ACC) compound, which further transforms into a crystalline material. The transformation mechanism is not fully understood but is however crucial to develop bioinspired synthetic biomineralization strategies or accurate marine biomineral proxies for geoscience. The difficulty arises from the simultaneous presence of crystalline and amorphous compounds in the shell, which complicates the selective experimental characterization of the amorphous fraction. Here, we use nanobeam X-ray total scattering together with an approach to separate crystalline and amorphous scattering contributions to obtain the spatially resolved atomic pair distribution function (PDF). We resolve three distinct amorphous calcium carbonate compounds, present in the shell of Pinctada margaritifera and attributed to: interprismatic periostracum, young mineralizing units, and mature mineralizing units. From this, we extract accurate bond parameters by reverse Monte Carlo (RMC) modeling of the PDF. This shows that the three amorphous compounds differ mostly in their Ca–O nearest-neighbor atom pair distance. Further characterization with conventional spectroscopic techniques unveils the presence of Mg in the shell and shows Mg–calcite in the final, crystallized shell. In line with recent literature, we propose that the amorphous-to-crystal transition is mediated by the presence of Mg. The transition occurs through the decomposition of the initial Mg-rich precursor into a second Mg-poor ACC compound before forming a crystal.

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High-Mg calcite nanoparticles within a low-Mg calcite matrix: A widespread phenomenon in biomineralization

Cited by 21 publications

References 63 publications

A Devonian crinoid with a diamond microlattice

A Devonian crinoid with a diamond microlattice

Nanoscale Pathway of Modern Dolomite Formation in a Shallow, Alkaline Lake

Structure of an amorphous calcium carbonate phase involved in the formation of Pinctada margaritifera shells

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