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Engineered Biomimetic Polymers as Tunable Agents for CaCO 3 Mineralization

Engineered non-natural polymers (peptoids) direct CaCO 3 crystal morphology (lower left). These crystals exhibit a number of unique morphologies ranging from elongated spindles and twisted paddles to crosses and spheres. Certain peptoids also dramatically accelerate CaCO3 growth by nearly 23-fold at extremely low concentrations, while others show almost no effects (lower right). These artificial polymers mimic the action of certain proteins while providing high stability.

Molecular Foundry scientists Ron Zuckermann and Jim DeYoreo have developed a suite of protein-like materials capable of enhancing or inhibiting mineralization of inorganic solids. These engineered, non-natural polymers could enable technologies applicable to industrial crystallization, including CO 2 sequestration.

One option for reducing CO2 emissions—the single largest manmade source of global warming—is capturing and storing this gas permanently in underground reservoirs. In nature, living organisms sequester carbon dioxide in the form of calcium carbonate (CaCO3 ) on a massive scale. Proteins that catalyze this transformation inspired the team to develop simpler and more robust synthetic accelerants made from biomimetic peptoid polymers.

The team used a combinatorial nanoscience approach to synthesize peptoids composed of hydrophobic and anionic monomers. These materials exhibit both a high degree of control over CaCO3 growth morphology and an unprecedented 23-fold acceleration in CaCO3 growth at an extremely low peptoid concentration. What's more, this growth can be tuned by adjusting the peptoid concentration. These findings suggest peptoids can be developed to direct the timing and rate of crystallization, a potentially useful control in locking CO2 into thermodynamically stable minerals.

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C.-L. Chen, J. Qi, R.N. Zuckermann, and J.J. DeYoreo, "Engineered Biomimetic Polymers as Tunable Agents for Controlling CaCO3 Mineralization", J. Am. Chem. Soc. 2011, dx.doi.org/10.1021/ja200595f.