Protein Turns Nanoparticles Into Crystals

over head view of chicken eggs of varying colors

Biological Strategy

Red junglefowl

AskNature Team

Image: Katie Bernotsky / Unsplash / Free non-commercial use

Chemically Assemble Mineral Crystals

The vast majority of biochemical assembly and break down processes––even by the most complex organisms––occur within cells. In fact, cells are able to perform hundreds, even thousands, of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). Within cells, organisms utilize organic compounds to facilitate the assembly of mineral crystals. For example, oysters utilize acidic proteins and sulfated polysaccharides to assemble layers of aragonite crystals.

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Chemically Assemble Inorganic Compounds

The vast majority of biochemical assembly and break down processes––even by the most complex organisms––occur within cells. In fact, cells are able to perform hundreds, even thousands, of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). For example, coral polyps transform dissolved calcium and carbonate ions into crystalized calcium carbonate within the calicoblastic cells.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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Eggshells of chickens are formed from amorphous calcium carbonate nanoparticles which are transformed into ordered crystals by protein mediation.

Eggshell this a thin yet relatively strong material due to its composite makeup of ordered calcium carbonate crystals and . A layer of crystalline calcite clusters overlays partially aligned calcite columns. The mineral begins as amorphous calcium carbonate nanoparticles, then is transformed to ordered crystals by the presence of C-type lectin-type proteins. The proteins attach themselves to the nanoparticles, initiating crystal transformation, and then detach while crystal growth continues.

Image: Freeman et al. 2010 /

Growing a good egg: Metadynamics simulations show that the eggshell protein ovocleidin-17 induces the formation of calcite crystals from amorphous calcium carbonate nanoparticles. Multiple spontaneous crystallization and amorphization events were simulated; these simulations suggest a catalytic cycle that explains the role of ovocleidin-17 in the first stages of eggshell formation (the picture shows one intermediate of this cycle).