@article {2033, title = {Engineered elastomeric proteins with dual elasticity can be controlled by a molecular regulator}, journal = {Nature Nanotechnology}, volume = {3}, number = {8}, year = {2008}, note = {ISI Document Delivery No.: 335WZTimes Cited: 12Cited Reference Count: 29Cao, Yi Li, Hongbin}, month = {Aug}, pages = {512-516}, type = {Article}, abstract = {Elastomeric proteins are molecular springs that confer excellent mechanical properties(1-5) to many biological tissues and biomaterials. Depending on the role performed by the tissue or biomaterial, elastomeric proteins can behave as molecular springs(1,2,6,7) or shock absorbers(3-5,8-10). Here we combine single-molecule atomic force microscopy and protein engineering techniques to create elastomeric proteins that can switch between two distinct types of mechanical behaviour in response to the binding of a molecular regulator. The proteins are mechanically labile by design and behave as entropic springs with an elasticity that is governed by their configurational entropy. However, when a molecular regulator binds to the protein, it switches into a mechanically stable state and can act as a shock absorber. These engineered proteins effectively mimic and combine the two extreme forms of elastic behaviour found in natural elastomeric proteins, and thus represent a new type of smart nanomaterial that will find potential applications in nanomechanics and material sciences.}, keywords = {BINDING, BIOLOGICAL ROLES, DESIGN, DOMAINS, FORCE-SPECTROSCOPY, MECHANICAL-PROPERTIES, STABILITY, TITINS, TOPOLOGY}, isbn = {1748-3387}, url = {://000258325800018}, author = {Cao, Y. and Li, H. B.} } @article {2148, title = {{\textquoteright}Mechanical Engineering{\textquoteright} of Elastomeric Proteins: Toward Designing New Protein Building Blocks for Biomaterials}, journal = {Advanced Functional Materials}, volume = {18}, number = {18}, year = {2008}, note = {ISI Document Delivery No.: 358QQTimes Cited: 6Cited Reference Count: 102Li, Hongbin}, month = {Sep}, pages = {2643-2657}, type = {Review}, abstract = {Elastomeric proteins are subject to stretching force under biological settings and play important roles in regulating the mechanical properties of a wide range of biological machinery. Elastomeric proteins also underlie the superb mechanical properties of many protein-based biomaterials. The developments of single molecule force spectroscopy have enabled the direct characterization of the mechanical properties of elastomeric proteins at the single molecule level and led to the new burgeoning field of research: single protein mechanics-and engineering. Combined, single molecule atomic force microscopy and protein engineering efforts are well under way to understand molecular determinants for the mechanical stability of elastomeric proteins and to develop methodologies to tune the mechanical properties of proteins in a rational and systematic fashion, which will lead to the {\textquoteright}mechanical engineering{\textquoteright} of elastomeric proteins. Here the current status of these experimental efforts is discussed and the successes and challenges in constructing novel proteins with tailored nanomechanical proteins are highlighted. The prospect of employing such engineered artificial elastomeric proteins as building blocks for the construction of biomaterials for applications ranging from material sciences to biomedical engineering is also discussed.}, keywords = {ATOMIC-FORCE MICROSCOPY, BIOLOGICAL ROLES, DIHYDROFOLATE-REDUCTASE, EXTRACELLULAR-MATRIX PROTEIN, FLUORESCENT PROTEIN, IG DOMAIN, MOLECULAR-DYNAMICS SIMULATIONS, PROTEIN, SINGLE, TITIN IMMUNOGLOBULIN DOMAINS, UNFOLDING PATHWAYS}, isbn = {1616-301X}, url = {://000259933000001}, author = {Li, H. B.} } @article {2035, title = {Protein-protein interaction regulates proteins{\textquoteright} mechanical stability}, journal = {Journal of Molecular Biology}, volume = {378}, number = {5}, year = {2008}, note = {ISI Document Delivery No.: 305IOTimes Cited: 10Cited Reference Count: 38Cao, Yi Yoo, Teri Zhuang, Shulin Li, Hongbin}, month = {May}, pages = {1132-1141}, type = {Article}, abstract = {Elastomeric proteins are molecular springs found not only in a variety of biological machines and tissues, but also in biomaterials of superb mechanical properties. Regulating the mechanical stability of elastomeric proteins is not only important for a range of biological processes, but also critical for the use of engineered elastomeric proteins as building blocks to construct nanomechanical devices and novel materials of well-defined mechanical properties. Here we demonstrate that protein-protein interactions can potentially serve as an effective means to regulate the mechanical properties of elastomeric proteins. We show that the binding of fragments of IgG antibody to a small protein, GB1, can significantly enhance the mechanical stability of GB1. The regulation of the mechanical stability of GB1 by IgG fragments is not through direct modification of the interactions in the mechanically key region of GB1; instead, it is accomplished via the long-range coupling between the IgG binding site and the mechanically key region of GB1. Although Fc and Fab bind GB1 at different regions of GB1, their binding to GB1 can increase the mechanical stability of GB1 significantly. Using alanine point mutants of GB1, we show that the amplitude of mechanical stability enhancement of GB1 by Fc does not correlate with the binding affinity, suggesting that binding affinity only affects the population of GB1/human Fc (hFc) complex at a given concentration of hFc, but does not affect the intrinsic mechanical stability of the GB1/hFc complex. Furthermore, our results indicate that the mechanical stability enhancement by IgG fragments is robust and can tolerate sequence/structural perturbation to GB1. Our results demonstrate that the protein-protein interaction is an efficient approach to regulate the mechanical stability of GB1-like proteins and we anticipate that this new methodology will help to develop novel elastomeric proteins with tunable mechanical stability and compliance. (C) 2008 Elsevier Ltd. All rights reserved.}, keywords = {BINDING, BIOLOGICAL ROLES, CRYSTAL-STRUCTURE, DIHYDROFOLATE-REDUCTASE, DOMAIN, ENGINEERING PROTEINS, FORCE SPECTROSCOPY, FRAGMENT, HUMAN-IGG, MECHANICAL STABILITY, mechanical unfolding, MOLECULAR ELASTICITY, protein-protein interaction, single molecule atomic force microscopy, STABILIZATION}, isbn = {0022-2836}, url = {://000256171900015}, author = {Cao, Y. and Yoo, T. and Zhuang, S. L. and Li, H. B.} } @article {2017, title = {Recombination of protein fragments: A promising approach toward engineering proteins with novel nanomechanical properties}, journal = {Protein Science}, volume = {17}, number = {10}, year = {2008}, note = {ISI Document Delivery No.: 351CKTimes Cited: 4Cited Reference Count: 50Balamurali, M. M. Sharma, Deepak Chang, Anderson Khor, Dingyue Chu, Ricky Li, Hongbin}, month = {Oct}, pages = {1815-1826}, type = {Article}, abstract = {Combining single molecule atomic force microscopy (AFM) and protein engineering techniques, here we demonstrate that we can use recombination-based techniques to engineer novel elastomeric proteins by recombining protein fragments from structurally homologous parent proteins. Using I27 and I32 domains from the muscle protein titin as parent template proteins, we systematically shuffled the secondary structural elements of the two parent proteins and engineered 13 hybrid daughter proteins. Although I27 and I32 are highly homologous, and homology modeling predicted that the hybrid daughter proteins fold into structures that are similar to that of parent protein, we found that only eight of the 13 daughter proteins showed beta-sheet dominated structures that are similar to parent proteins, and the other five recombined proteins showed signatures of the formation of significant alpha-helical or random coil-like structure. Single molecule AFM revealed that six recombined daughter proteins are mechanically stable and exhibit mechanical properties that are different from the parent proteins. In contrast, another four of the hybrid proteins were found to be mechanically labile and unfold at forces that are lower than the similar to 20 pN, as we could not detect any unfolding force peaks. The last three hybrid proteins showed interesting duality in their mechanical unfolding behaviors. These results demonstrate the great potential of using recombination-based approaches to engineer novel elastomeric protein domains of diverse mechanical properties. Moreover, our results also revealed the challenges and complexity of developing a recombination-based approach into a laboratory-based directed evolution approach to engineer novel elastomeric proteins.}, keywords = {ATOMIC-FORCE MICROSCOPY, BIOLOGICAL ROLES, COMPUTATIONAL DESIGN, ELASTICITY, elastomeric protein, EVOLUTION, IMMUNOGLOBULIN DOMAINS, MECHANICAL STABILITY, mechanical unfolding, MOLECULAR-DYNAMICS SIMULATION, recombination, SEQUENCE, SINGLE PROTEIN, single-molecule force spectroscopy, TITIN}, isbn = {0961-8368}, url = {://000259401900019}, author = {Balamurali, M. M. and Sharma, D. and Chang, A. and Khor, D. and Chu, R. and Li, H. B.} }