Engineering of crystal surfaces and subsurfaces by framework biomineralization protein phases

Abstract

A nacre protein, n16.3, forms phases that introduce textured mineral overgrowth and subsurface nanoporosities within calcite crystals.

Polymorphs, Proteins, and Nucleation Theory: A Critical Analysis

“…These reported studies utilized mole protein quantities, Ca(II) potentiometric methods, and parallel mineralization assay systems to study the early and later events in calcite-based calcium carbonate nucleation and monitor the formation and stabilization of PNCs and ACC in a time-dependent fashion. What was discovered was very informative: these proteins are distinguishable in terms of what mineral species or steps in the non-classical scheme they affect (Figure 4) [58][59][60][61][62][63][64][65][66][67]. Further, using mineralization assays which overlap with the time periods of the potentiometric titrations and utilize similar solution and supersaturation conditions [58][59][60][61][62][63][64][65][66][67] these studies demonstrated that these proteins form hydrogels that can capture, assemble, and organize mineral nanoparticles ( Figure 5) [62,65] consistent with CPA theory [15].…”

“…As we are starting to see, a common theme that emerges from proteome studies is that these proteins share common traits, such as intrinsic disorder or unfolded structure [69] and aggregation propensity [69] that leads to protein phase or hydrogel formation that provides volume confinement and a pathway to particle assembly and organization [58][59][60][61][62][63][64][65][66][67]. Yet, the sequences of these proteins are unalike [58][59][60][61][62][63][64][65][66][67] and so genetic variation is permissible and even welcomed in biological organisms so long as specific nucleation goals are being met. AP7 is a hydrogelator that forms aggregating gels that contain mineral nanoparticles.…”

“…What was discovered was very informative: these proteins are distinguishable in terms of what mineral species or steps in the non-classical scheme they affect (Figure 4) [58][59][60][61][62][63][64][65][66][67]. Further, using mineralization assays which overlap with the time periods of the potentiometric titrations and utilize similar solution and supersaturation conditions [58][59][60][61][62][63][64][65][66][67] these studies demonstrated that these proteins form hydrogels that can capture, assemble, and organize mineral nanoparticles ( Figure 5) [62,65] consistent with CPA theory [15]. The major conclusions one can draw from these studies are the following: (1) nacre [58][59][60][61][62][63][64][65][66] and sea urchin spicule matrix proteins [67,68] perform seminal tasks that would be critical for eventual polymorph selection and stabilization; (2) the functionalities of these six nacre proteins [58][59][60][61][62][63][64]…”

“…As an example, recent in vitro studies involving five recombinant mollusk shell nacre-associated proteins [58][59][60][61][62][63][64][65][66] and ACC-stabilizing sea urchin spicule matrix proteins [67,68] have utilized mineralization assay conditions identical to those employed in non-classical nucleation studies [29][30][31][32][33]. What links these different biomineralization proteins together are two common molecular themes [69,70]: intrinsic disorder, or absence of folding protein structure, and amyloid-like aggregation-prone domains, which promote protein-protein association leading to the formation of protein phases or hydrogels [58][59][60][61][62][63][64][65][66][67][68]. These reported studies utilized mole protein quantities, Ca(II) potentiometric methods, and parallel mineralization assay systems to study the early and later events in calcite-based calcium carbonate nucleation and monitor the formation and stabilization of PNCs and ACC in a time-dependent fashion.…”

“…Further, using mineralization assays which overlap with the time periods of the potentiometric titrations and utilize similar solution and supersaturation conditions [58][59][60][61][62][63][64][65][66][67] these studies demonstrated that these proteins form hydrogels that can capture, assemble, and organize mineral nanoparticles ( Figure 5) [62,65] consistent with CPA theory [15]. The major conclusions one can draw from these studies are the following: (1) nacre [58][59][60][61][62][63][64][65][66] and sea urchin spicule matrix proteins [67,68] perform seminal tasks that would be critical for eventual polymorph selection and stabilization; (2) the functionalities of these six nacre proteins [58][59][60][61][62][63][64][65] are consistent with either non-classical [29][30][31][32][33] or CPA [16] theories [15]. Note that since these protein assay studies were calcite-based, there were no opportunities to study metastable aragonite or vaterite formation and stabilization.…”