This article reviews fundamental and applied aspects of silk-one of Nature’s

This article reviews fundamental and applied aspects of silk-one of Nature’s most intriguing materials in terms of its strength toughness and biological role-in its various forms from protein molecules to webs and cocoons in the context of mechanical and biological properties. to current experimental and computational designs in the field of synthetic silklike materials are provided to assist the materials science community in engineering customized finetuned biomaterials for biomedical applications. Keywords: biomimetic silk multiscale modeling spinning materiomics Graphical abstract 1 INTRODUCTION Nature’s Building Blocks Nature is rich in structure which defines the properties of the tiniest pieces of matter atoms molecules galaxies and the universe. Amino acids are the building RETRA hydrochloride blocks of proteins the most abundant and fundamental class of biological macromolecules. There are only 20 commonly occurring amino acids in natural proteins and their properties determine the nature of the resulting protein. This limited set of building blocks i.e. amino acids gives rise to some of the most diverse material functions identified in protein materials that not only make up everything from silk to skin and many other organs such as the brain but also living materials that interact with the environment in many active dynamic and controlled ways. These features also drive the interactions and interfaces of these proteins with other materials including other RETRA hydrochloride organic matrices to inorganic components. For instance abalone shell is made of minerals of calcium carbonate platelets glued by protein1 2 and human bone is primarily composed of collagen protein and hydroxyapatite mineral.3 As we learn more about these processing in Nature we begin to appreciate the universal importance of hierarchical structures in defining how the living world works.4 This implies exciting possibilities based on the idea of transforming the understanding of these amino acid patterns to new material functions that can find diverse applications in areas of energy and sustainability health care and design of novel devices.5-9 From Sequence to Structure The 20 different chemical building blocks (amino acids) are linked by peptide bonds and dominate biological functions in Nature from molecular recognition and catalysis to structures. Fibrous proteins such as silk collagen elastin and keratin are distinguished from globular proteins (such as hemoglobin immunoglobulins) by their repetitive peptide domains which promote regularity in secondary structure control of molecular recognition and structural integrity. Fibrous proteins require interchain as well as intrachain interactions to achieve structural function which is in contrast to globular proteins where single folded chains can achieve catalysis or recognition. The chemistry of the building blocks provides modes for physical associations between chains including hydrogen bonding and electrostatic interactions and the precise control of primary sequence allows for Mouse monoclonal to ALCAM programmed self-assembly. When these features are combined with the power of biological synthesis of the proteins driven by enzymatic reactions to generate the peptide bonds control of chirality of the chains is also achieved helping to preserve registry and molecular fit to give RETRA hydrochloride additional molecular recognition and self-assembly to provide the basis for structural hierarchy.9-13 Silk Properties and Production Silk with its remarkable structure and versatility has emerged as a particularly exciting topic of study because of its physical chemical and biological properties that lend themselves to many applications while also serving as a prototype model for future material designs.14-19 Production of silk fiber starts from making polymer from amino acid building blocks. The process continues with change in concentration of the protein and ionization of the environment followed RETRA hydrochloride RETRA hydrochloride by application of an elongational flow (shear stress). The whole process of building the 3D web is similar to an advanced 3D printer that builds the final product from a digital file using an additive process by laying down successive layers of material and controlling environmental conditions (curing material). Spiders have invented multimaterial 3D printing billions of years ago. Spider web has a multiscale structure that controls mechanical properties of the fiber such as β sheet crystal size and fiber diameter (Figure 1). Silk in its natural forms and two examples of applications.