AsianScientist (Jul. 14, 2015) – With the help of a specially engineered proteins, scientists have created the smallest crystal reported to date: a cadmium chloride nanocrystal just 19 atoms large. Their results have been published in Angewandte Chemie.
The researchers, led by Professor Kam Zhang at the RIKEN Center for Life Science Technologies (CLST) and Professor Jeremy Tame at Yokohama City University, used an artificial protein called Pizza6 as a scaffold to synthesize the tiny crystal.
Pizza6, thus named because it resembles a pizza cut into six identical slices, is a highly symmetrical protein not found in nature. First announced in 2014, it is anticipated that such symmetrical proteins can be used as scaffolds for the creation of new hybrid biomaterials suited to a variety of purposes such as drug packaging and delivery to cells, or even bioremediation of hazardous metals in the environment.
In the current research, the Pizza6 protein was modified by introducing a metal-binding site.
“Our initial impetus was to design metal-binding sites to control the self-assembly of our designed symmetrical proteins,” said first author Dr. Arnout Voet, who performed the work of designing and building the proteins.
“We used computational methods to find a rational way to incorporate a metal-binding site into the Pizza protein we had previously designed, based on the idea that this could allow us to control protein assembly easily. We believe that this would give us a new tool for building novel proteins from the ground up by using very cheap metal reagents.”
Indeed, when the proteins were modified to have a metal-binding site and then placed in a solution of cadmium chloride, the researchers found that trimers of the protein would spontaneously bind together. Using RIKEN’s SPring-8 synchrotron facility in Harima and other facilities, they analyzed the structure at the atomic level and discovered, interestingly, that the atoms of cadmium and chloride had formed a tiny lattice—a crystal structure—sandwiched between two ‘pizzas.’
According to Zhang, corresponding author of the present study, “We were very excited to see the formation of the crystal, as it provides insights into the process of biomineralization—the process through which nature incorporates metallic elements into tissues to form structures such as seashells, teeth, and bones.”
“Our results indicate the feasibility of using rationally-designed symmetrical proteins to biomineralize nanocrystals. Achieving this could allow us to make a wide range of nano-devices such as biopharmaceuticals, biosensors, light-driven switches, and synthetic enzymes from the bottom up.”
“We have many ideas about how this might be put to further use,” he continues, “and will continue to experiment to find novel properties in these artificially designed proteins.”
The article can be found at: Voet et al. (2015) Biomineralization of a Cadmium Chloride Nanocrystal by a Designed Symmetrical Protein.
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Source: RIKEN.
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