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News Article | October 4, 2016
Site: www.rdmag.com

Life has always played by its own set of molecular rules. From the biochemistry behind the first cells, evolution has constructed wonders like hard bone, rough bark and plant enzymes that harvest light to make food. But our tools for manipulating life—to treat disease, repair damaged tissue and replace lost limbs—come from the nonliving realm: metals, plastics and the like. Though these save and preserve lives, our synthetic treatments are rooted in a chemical language ill-suited to our organic elegance. Implanted electrodes scar, wires overheat and our bodies struggle against ill-fitting pumps, pipes or valves. A solution lies in bridging this gap where artificial meets biological—harnessing biological rules to exchange information between the biochemistry of our bodies and the chemistry of our devices. In a paper published Sept. 22 in Scientific Reports, engineers at the University of Washington unveiled peptides—small proteins which carry out countless essential tasks in our cells—that can provide just such a link. The team, led by UW professor Mehmet Sarikaya in the Departments of Materials Science & Engineering, shows how a genetically engineered peptide can assemble into nanowires atop 2-D, solid surfaces that are just a single layer of atoms thick. These nanowire assemblages are critical because the peptides relay information across the bio/nano interface through molecular recognition—the same principles that underlie biochemical interactions such as an antibody binding to its specific antigen or protein binding to DNA. Since this communication is two-way, with peptides understanding the "language" of technology and vice versa, their approach essentially enables a coherent bioelectronic interface. "Bridging this divide would be the key to building the genetically engineered biomolecular solid-state devices of the future," said Sarikaya, who is also a professor of chemical engineering and oral health sciences. His team in the UW Genetically Engineered Materials Science and Engineering Center studies how to coopt the chemistry of life to synthesize materials with technologically significant physical, electronic and photonic properties. To Sarikaya, the biochemical "language" of life is a logical emulation. "Nature must constantly make materials to do many of the same tasks we seek," he said. The UW team wants to find genetically engineered peptides with specific chemical and structural properties. They sought out a peptide that could interact with materials such as gold, titanium and even a mineral in bone and teeth. These could all form the basis of future biomedical and electro-optical devices. Their ideal peptide should also change the physical properties of synthetic materials and respond to that change. That way, it would transmit "information" from the synthetic material to other biomolecules—bridging the chemical divide between biology and technology. In exploring the properties of 80 genetically selected peptides—which are not found in nature but have the same chemical components of all proteins—they discovered that one, GrBP5, showed promising interactions with the semimetal graphene. They then tested GrBP5's interactions with several 2-D nanomaterials which, Sarikaya said, "could serve as the metals or semiconductors of the future." "We needed to know the specific molecular interactions between this peptide and these inorganic solid surfaces," he added. Their experiments revealed that GrBP5 spontaneously organized into ordered nanowire patterns on graphene. With a few mutations, GrBP5 also altered the electrical conductivity of a graphene-based device, the first step toward transmitting electrical information from graphene to cells via peptides. In parallel, Sarikaya's team modified GrBP5 to produce similar results on a semiconductor material—molybdenum disulfide—by converting a chemical signal to an optical signal. They also computationally predicted how different arrangements of GrBP5 nanowires would affect the electrical conduction or optical signal of each material, showing additional potential within GrBP5's physical properties. "In a way, we're at the flood gates," said Sarikaya. "Now we need to explore the basic properties of this bridge and how we can modify it to permit the flow of 'information' from electronic and photonic devices to biological systems."

Seker U.O.S.,Genetically Engineered Materials Science and Engineering Center | Seker U.O.S.,Technical University of Istanbul | Seker U.O.S.,Massachusetts Institute of Technology | Wilson B.,Genetically Engineered Materials Science and Engineering Center | And 7 more authors.
Biomacromolecules | Year: 2014

Adsorption behavior of a gold binding peptide was experimentally studied to achieve kinetics and thermodynamics parameters toward understanding of the binding of an engineered peptide onto a solid metal surface. The gold-binding peptide, GBP1, was originally selected using a cell surface display library and contains 14 amino acid residues. In this work, single- and three-repeats of GBP1 were used to assess the effects of two parameters: molecular architecture versus secondary structure on adsorption on to gold substrate. The adsorption measurements were carried out using surface plasmon resonance (SPR) spectroscopy at temperatures ranging from 10 to 55 °C. At all temperatures, two different regimes of peptide adsorption were observed, which, based on the model, correspond to two sets of thermodynamics values. The values of enthalpy, ΔHads, and entropy, ΔSads, in these two regimes were determined using the van't Hoff approach and Gibbs-Helmholtz relationship. In general, the values of enthalpy for both peptides are negative indicating GBP1 binding to gold is an exothermic phenomenon and that the binding of three repeat gold binding peptide (3l-GBP1) is almost 5 times tighter than that for the single repeat (l-GBP1). More intriguing result is that the entropy of adsorption for the 3l-GBP1 is negative (-43.4 ± 8.5 cal/(mol K)), while that for the l-GBP1 is positive (10.90 ± 1.3 cal/(mol K)). Among a number of factors that synergistically contribute to the decrease of entropy, long-range ordered self-assembly of the 3l-GBP1 on gold surface is the most effective, probably through both peptide-solid and peptide-peptide intermolecular interactions. Additional adsorption experiments were conducted in the presence of 2,2,2-trifluoroethanol (TFE) to determine how the conformational structures of the biomolecules responded to the environmental perturbation. We found that the peptides differ in their conformational responses to the change in solution conditions; while l-GBP does not fold in the presence of TFE, 3l-GBP1 adopted two types of secondary structure (β-strand, α-helix) and that peptide's binding to the solid is enhanced by the presence of low percentages of TFE solvent. Not only do these kinetics and thermodynamics results provide adsorption behavior and binding of genetically engineered peptides for inorganics (GEPI), but they could also provide considerable insights into fundamental understanding peptide molecular recognition and their selective specificity for the solids. Moreover, comprehensive work described herein suggests that multiple repeat forms of the solid binding peptides possess a conformational component that can be exploited to further tailor affinity and binding of a given sequence to a solid material followed by ordered assembly as a convenient tool in future practical applications. © 2014 American Chemical Society.

Hnilova M.,Genetically Engineered Materials Science and Engineering Center | Hnilova M.,University of Washington | Liu X.,University of Washington | Yuca E.,Genetically Engineered Materials Science and Engineering Center | And 10 more authors.
ACS Applied Materials and Interfaces | Year: 2012

This study demonstrates a biological route to programming well-defined protein-inorganic interfaces with an arrayed geometry via modular peptide tag technology. To illustrate this concept, we designed a model multifunctional fusion protein, which simultaneously displays a maltose-binding protein (MBP), a green fluorescence protein (GFPuv) and an inorganic-binding peptide (AgBP2C). The fused combinatorially selected AgBP2C tag controls and site-directs the multifunctional fusion protein to immobilize on silver nanoparticle arrays that are fabricated on specific domain surfaces of ferroelectric LiNbO 3 via photochemical deposition and in situ synthesis. Our combined peptide-assisted biological and ferroelectric lithography approach offers modular design and versatility in tailoring surface reactivity for fabrication of nanoscale devices in environmentally benign conditions. © 2012 American Chemical Society.

Lee J.S.,Genetically Engineered Materials Science and Engineering Center | Kuroha T.,Genetically Engineered Materials Science and Engineering Center | Kuroha T.,Nagoya University | Hnilova M.,Genetically Engineered Materials Science and Engineering Center | And 9 more authors.
Genes and Development | Year: 2012

Valves on the plant epidermis called stomata develop according to positional cues, which likely involve putative ligands (EPIDERMAL PATTERNING FACTORS [EPFs]) and putative receptors (ERECTA family receptor kinases and TOO MANY MOUTHS [TMM]) in Arabidopsis. Here we report the direct, robust, and saturable binding of bioactive EPF peptides to the ERECTA family. In contrast, TMM exhibits negligible binding to EPF1 but binding to EPF2. The ERECTA family forms receptor homomers in vivo. On the other hand, TMM associates with the ERECTA family but not with itself. While ERECTA family receptor kinases exhibit complex redundancy, blocking ERECTA and ERECTA-LIKE1 (ERL1) signaling confers specific insensitivity to EPF2 and EPF1, respectively. Our results place the ERECTA family as the primary receptors for EPFs with TMM as a signal modulator and establish EPF2-ERECTA and EPF1-ERL1 as ligand-receptor pairs specifying two steps of stomatal development: initiation and spacing divisions. © 2012 by Cold Spring Harbor Laboratory Press.

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