The Science

Peptoids are a class of biomimetic polymers with increased stability and extensive design flexibility, which can aid in the synthesis of complex bio-inspired materials with novel functions. Researchers took inspiration from carbonic anhydrases (CAs) and designed histidine-containing peptoids to facilitate the formation of carbonate materials. These peptoids can coordinate with zinc ions in solution, mimicking the function of naturally occurring CAs. By coordinating with the zinc, the peptoids help convert bicarbonate into carbonate and reorganize water layers on calcite surfaces. These processes ultimately lower the energy barrier required for calcite growth. This study highlights a new approach for creating precision-designed polymers to control carbonate mineralization, with potential application to the synthesis of other mineral products from dilute sources.

The Impact

This research introduces a new approach to precisely controlling mineral formation using synthetic materials inspired by natural processes. Researchers developed specialized synthetic polymers that mimic the function of carbonic anhydrase enzymes to accelerate the growth of calcite, a widely occurring mineral. The peptoid materials work in combination with zinc ions to lower energy barriers, deprotonate bicarbonate, and reorganize water layers on the mineral surface, enabling more efficient acceleration of calcite growth. The findings pave the way for designing synthetic materials that can regulate mineralization processes and provide the scientific foundation for the development of functional materials and new technologies.

Summary

Carbonate mineralization is the conversion of CO₂ into stable, thermodynamically favorable carbonate minerals. Researchers have taken design inspiration from a zinc-containing enzyme family, CA, that catalyzes the hydration of CO₂ to bicarbonate and promotes carbonate precipitation. They created a class of histidine-containing peptoids that can coordinate with Zn²⁺ ions and act as CA mimetics for accelerating calcite step growth. In situ atomic force microscopy measurements revealed that these peptoids significantly enhance step advancement. The effect is more pronounced when the peptoids are combined with Zn²⁺ ions or under higher calcium-to-carbonate activity ratios. These results indicate that peptoids facilitate the incorporation of CO₃^2- ions at step edges. Solution nuclear magnetic resonance spectroscopy and 3-D atomic force microscopy analyses showed that the coordination of peptoids with Zn²⁺ promotes both the deprotonation of HCO₃^- to CO₃^2- and the restructuring of the interfacial hydration layers of calcite, collectively lowering the activation barrier for step growth. These findings establish a design framework for sequence-defined polymers to accelerate carbonate formation processes, providing new opportunities in materials science for the design and synthesis of complex bio-inspired structures.

Contact

Chun-Long Chen, Pacific Northwest National Laboratory, chunlong.chen@pnnl.gov 

Funding

This work was supported by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, Biomolecular Materials Program, under award FWP 80124 at Pacific Northwest National Laboratory.