Designer proteins form wires and arrays on a mineral surface

The purpose of the research, published July 11 in the newspaper Nature, was to design artificial proteins to self-assemble on a crystalline surface by creating an exact match between the amino acid motif in the protein and the atoms of the crystal. The possibility of programming these interactions could allow the design of new biomimetic materials with customized colors, chemical reactivity or mechanical properties, or serve as scaffolds for nanoscale filters, solar cells or electronic circuits.

"Biology has an amazing ability to organize matter from the atomic scale up to that of blue whales," said co-first author Harley Pyles, a graduate student of the Institute for Protein Design of the UW Medicine. "Now, using protein design, we can create new biomolecules that fit at scales from atomic length to millimeter.In this case, mica, a natural crystal, acts as a large plaque. Lego base on which we are assembling new protein architectures. "

The design of the new mineral-binding molecules has been inspired by proteins that interact with ice. At the molecular level, the ice is flat and contains an atomically accurate pattern of rigid water molecules. In nature, the proteins correspond to these models to allow them to stick to the ice.

The team used a computer-based molecular design to design new proteins with custom electric charge models on their surfaces, as well as it's made of nanoscale Lego blocks perfectly matched to the plate. mica base. Synthetic genes encoding these synthetic proteins were placed in bacteria, which then produced these proteins en masse in the laboratory.

The researchers discovered that different patterns formed different patterns on the surface of the mica. By redrawing parts of the proteins, the team was able to produce honeycomb networks in which it could numerically adjust the pore diameter by a few nanometers only, which corresponds to the width of a single single molecule of double helix DNA.

"This is an important step in the study of protein-material interfaces," said David Baker, director of the IPD, professor of biochemistry at the Faculty of Medicine at the University of Michigan. University of Washington and co-lead author of the research. "We have reached an unprecedented degree of order by designing units that self-assemble into aligned rows of nanorods, precise hexagonal lattices, and exquisite nanowires of a width of one to one." molecule."

The research was made possible by the use of atomic force microscopy, which uses a small needle to map molecular surfaces, much like the needle of a disk drive reads the information in the grooves of a vinyl record. AFM results show that architectures formed by proteins are controlled by a subtle balance between the expected interactions with the surface of the mica and the forces that appear only when a large number of proteins act in concert, like logs on a river.

"Even though we have designed specific interactions at the atomic level, we are getting these structures, in part because the proteins are drowned in water and are forced to cluster," said James De Yoreo, a science scientist at the PNNL and co-director. NW IMPACT, a joint research initiative of PNNL and UW to promote discoveries and advances in the field of materials. "This behavior was unexpected and demonstrated the need to better understand the role of water in the control of proteins in molecular – scale systems.

Being able to create functional filaments and protein networks from scratch could also create entirely new, unique materials. The results could lead to new strategies for semiconductor circuit and metal nanoparticle synthesis for photovoltaic or energy storage applications. Or, protein honeybee nests could be used as extremely accurate filters, according to the co-first author, Shuai Zhang, a PNNL postdoctoral researcher. "The pores would be small enough to filter drinking water viruses or to filter out airborne particles," Zhang said.

The design and synthesis of proteins forming a honeycomb network have been supported by the DOE Science Bureau, and imaging and AFM analysis by the Center for Synthesis Science on a scale, an Energy Frontier Research Center funded by the DOE. The design and synthesis of nanorod and nanowire proteins have been supported by the IPD Research Grant Fund, the Michelson Medical Research Foundation and the Protein Design Initiative Fund. The development of AFM imaging protocols was supported by Synthesis of Materials and Simulations on Multiple Scales, an initiative funded internally by PNNL.

The researchers created synthetic proteins, represented in orange, that form honeycomb structures on the atomic surface of the mica, presented here in the form of tan spheres.