Date Published: November 15, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Jaehun Lee, Misong Ju, Ouk Hyun Cho, Younghye Kim, Ki Tae Nam.
The self‐assembly of biomolecules can provide a new approach for the design of functional systems with a diverse range of hierarchical nanoarchitectures and atomically defined structures. In this regard, peptides, particularly short peptides, are attractive building blocks because of their ease of establishing structure–property relationships, their productive synthesis, and the possibility of their hybridization with other motifs. Several assembling peptides, such as ionic‐complementary peptides, cyclic peptides, peptide amphiphiles, the Fmoc‐peptide, and aromatic dipeptides, are widely studied. Recently, studies on material synthesis and the application of tyrosine‐rich short peptide‐based systems have demonstrated that tyrosine units serve as not only excellent assembly motifs but also multifunctional templates. Tyrosine has a phenolic functional group that contributes to π–π interactions for conformation control and efficient charge transport by proton‐coupled electron‐transfer reactions in natural systems. Here, the critical roles of the tyrosine motif with respect to its electrochemical, chemical, and structural properties are discussed and recent discoveries and advances made in tyrosine‐rich short peptide systems from self‐assembled structures to peptide/inorganic hybrid materials are highlighted. A brief account of the opportunities in design optimization and the applications of tyrosine peptide‐based biomimetic materials is included.
Proteins/peptides are small biological machines whose functions are wide ranging; their functions include molecular recognition, catalysis, replication, and mechanical responsiveness.1, 2, 3, 4 In addition to their biofunctionality, peptides are also used as precursors to encode and control the growth of inorganics in many living organisms. For example, organisms such as diatoms and marine sponges use self‐assembled peptides, proteins, and organic–inorganic suprastructures as templates to control nucleation and amorphous‐to‐crystal phase transformations, which leads to the generation of crystals with unusual shapes and complexity that have controlled sizes, orientations, compositions, and hierarchical structures ranging from the nanoscale to the microscale.5, 6, 7 In the last two decades, there have been increasing research efforts focused on the production of new functional structures based on peptides and their derivatives, either by copying the functions of peptides and proteins or by using totally new design rules. The resulting nanoscale materials are expected to have many applications, including as in biomedical materials and nanotechnology.8 Peptide materials have been successfully employed as fundamental components in biological membranes, nanodevices, hydrogels for cell culture and drug delivery, biosensors, functional materials with unique biorecognition abilities, and energy‐conversion materials. All of these applications of peptide‐based materials can be attributed to the characteristic structural/chemical features of the materials, which enable their functioning in an extremely wide context of fundamental and applied sciences.9
Due to their attractive properties, especially functional flexibility and atomically defined nanostructures, peptides with specific sequences are gradually being designed for the development of new biomaterials. To enrich the applications of peptide materials and promote synergism between inorganic and peptide systems, several hybrid materials have been developed.94, 95, 96 In this section of the review, we will focus on tyrosine‐rich peptide‐based hybrid systems that can utilize the redox activity and π–π interactions of tyrosine to synthesize functional materials for catalysis and energy applications.
From the practical perspective of nanomaterials, synthesizing materials with desired bulk properties and specific nanostructures is an ongoing challenge. Peptide self‐assembly, one of the most powerful bottom‐up approaches for the biomimetic construction of elaborate structures, is continuously expanding its range of application. Recently, a large number of studies on the synthesis and application of tyrosine‐rich peptide‐based systems have proven that tyrosine units serve as not only excellent assembly motifs but also multifunctional templates. The aromatic nature and redox‐active properties of the functional group act in a collaborative fashion, contributing to π–π interactions for the self‐assembly of the motif and charge transport via the PCET mechanism. As demonstrated by the examples discussed in this review, for the first time, our group introduced tyrosine‐rich short peptides as the building blocks of a macroscale 2D assembly and achieved the hybridization of functional inorganic components, which then synergistically enhanced the proton conduction ability. Ulijn and co‐workers demonstrated the ability to control the assembly and reactivity of tyrosine‐containing sequences to obtain polymeric pigments by enzymatic oxidation reaction. A variety of different supramolecular structures, including vesicles, nanofibrils, nanosheets, nanogels, and meshed networks, can be constructed with the self‐assembly and cross‐linking of tyrosine‐rich short peptides. Additionally, dityrosine chemistry can be widely applied to enhance the mechanical properties of biomaterials. Regarding future research on tyrosine‐rich peptide‐based building blocks, the ability to efficiently create functionalized 1D, 2D, and 3D peptide materials, supramolecular peptide–metal‐ion complex structures, and peptide–inorganic composite hybrid materials via spontaneous assembly will lead to numerous applications in membrane mimetics, device and sensor fabrication, nanoscale synthesis, and catalysis. These applications will collaboratively interconnect toward the development of a new family of robust and advanced biomaterials.
The authors declare no conflict of interest.