@article {2695,
	title = {Modulating the Mechanical Stability of Extracellular Matrix Protein Tenascin-C in a Controlled and Reversible Fashion},
	journal = {Journal of Molecular Biology},
	volume = {390},
	number = {4},
	year = {2009},
	note = {ISI Document Delivery No.: 477KYTimes Cited: 2Cited Reference Count: 45Zhuang, Shulin Peng, Qing Cao, Yi Li, Hongbin},
	month = {Jul},
	pages = {820-829},
	type = {Article},
	abstract = {Stretching force can induce conformational changes of proteins and is believed to be an important biological signal in the mechanotransduction network. Tenascin-C is a large extracellular matrix protein and is subject to stretching force under its physiological condition. Regulating the mechanical properties of the fibronectin type III domains of tenascin-C will alter its response to mechanical stretching force and thus may provide the possibility of regulating the biological activities of tenascin-C in living cells. However, tuning the mechanical stability of proteins in a rational and systematic fashion remains challenging. Using the third fibronectin type III domain (TNfn3) of tenascin-C as a model system, here we report a successful engineering of a mechanically stronger extracellular matrix protein via engineered metal chelation. Combining steered molecular dynamics simulations, protein engineering and single-molecule atomic force microscopy, we have rationally engineered a bihistidine-based metal chelation site into TNfn3. We used its metal chelation capability to selectively increase the unfolding energy barrier for the rate-limiting step during the mechanical unfolding of TNfn3. The resultant TNfn3 mutant exhibits enhanced mechanical stability. Using a stronger metal chelator, one can convert TNfn3 back to a state of lower mechanical stability. This is the first step toward engineering extracellular matrix proteins with defined mechanical properties, which can be modulated reversibly by external stimuli, and will provide the possibility of using external stimuli to regulate the biological functions of extracellular matrix proteins. (C) 2009 Elsevier Ltd. All rights reserved.},
	keywords = {DYNAMICS, ELASTICITY, ENGINEERING PROTEINS, FNIII DOMAIN, FRAGMENTS, MECHANICAL STABILITY, mechanical unfolding, microscopy, MOLECULE FORCE SPECTROSCOPY, MUSCLE, rational design, recombination, SINGLE PROTEIN, single-molecule force spectroscopy, tenascin},
	isbn = {0022-2836},
	url = {<Go to ISI>://000268519200019},
	author = {Zhuang, S. L. and Peng, Q. and Cao, Y. and Li, H. B.}
}
@article {2149,
	title = {Configurational entropy modulates the mechanical stability of protein GB1},
	journal = {Journal of Molecular Biology},
	volume = {379},
	number = {4},
	year = {2008},
	note = {ISI Document Delivery No.: 314NITimes Cited: 10Cited Reference Count: 39Li, Hongbin Wang, Hui-Chuan Cao, Yi Sharma, Deepak Wang, Meijia},
	month = {Jun},
	pages = {871-880},
	type = {Article},
	abstract = {Configurational entropy plays important roles in defining the thermodynamic stability as well as the folding/unfolding kinetics of proteins. Here we combine single-molecule atomic force microscopy and protein engineering techniques to directly examine the role of configurational entropy in the mechanical unfolding kinetics and mechanical stability of proteins. We used a small protein, GB1, as a model system and constructed four mutants that elongate loop 2 of GB1 by 2, 5, 24 and 46 flexible residues, respectively. These loop elongation mutants fold properly as determined by far-UV circular dichroism spectroscopy, suggesting that loop 2 is well tolerant of loop insertions without affecting GB1{\textquoteright}s native structure. Our single-molecule atomic force microscopy results reveal that loop elongation decreases the mechanical stability of GB1 and accelerates the mechanical unfolding kinetics. These results can be explained by the loss of configurational entropy upon closing an unstructured flexible loop using classical polymer theory, highlighting the important role of loop regions in the mechanical unfolding of proteins. This study not only demonstrates a general approach to investigating the structural deformation of the loop regions in mechanical unfolding transition state, but also provides the foundation to use configurational entropy as an effective means to modulate the mechanical stability of proteins, which is of critical importance towards engineering artificial elastomeric proteins with tailored nanomechanical properties. (C) 2008 Elsevier Ltd. All rights reserved.},
	keywords = {configurational entropy, DISULFIDE BONDS, FORCE, FORCE SPECTROSCOPY, FRAGMENT RECONSTITUTION, IMMUNOGLOBULIN BINDING DOMAIN, length, LOOP, MECHANICAL STABILITY, mechanical unfolding, MODULES, resistance, single molecule atomic force microscopy, SINGLE PROTEIN, SPECTROSCOPY, TITIN, TRANSITION-STATE},
	isbn = {0022-2836},
	url = {<Go to ISI>://000256815700018},
	author = {Li, H. B. and Wang, H. C. and Cao, Y. and Sharma, D. and Wang, M.}
}
@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 = {<Go to ISI>://000259401900019},
	author = {Balamurali, M. M. and Sharma, D. and Chang, A. and Khor, D. and Chu, R. and Li, H. B.}
}
@article {2247,
	title = {Stabilization provided by neighboring strands is critical for the mechanical stability of proteins},
	journal = {Biophysical Journal},
	volume = {95},
	number = {8},
	year = {2008},
	note = {ISI Document Delivery No.: 352NMTimes Cited: 5Cited Reference Count: 37Sharma, Deepak Feng, Gang Khor, Dingyue Genchev, Georgi Z. Lu, Hui Li, Hongbin},
	month = {Oct},
	pages = {3935-3942},
	type = {Article},
	abstract = {Single-molecule force spectroscopy studies and steered molecular dynamics simulations have revealed that protein topology and pulling geometry play important roles in determining the mechanical stability of proteins. Most studies have focused on local interactions that are associated with the force-bearing beta-strands. Interactions mediated by neighboring strands are often overlooked. Here we use Top7 and barstar as model systems to illustrate the critical importance of the stabilization effect provided by neighboring beta-strands on the mechanical stability. Using single-molecule atomic force microscopy, we showed that Top7 and barstar, which have similar topology in their force-bearing region, exhibit vastly different mechanical-stability characteristics. Top7 is mechanically stable and unfolds at similar to 150 pN, whereas barstar is mechanically labile and unfolds largely below 50 pN. Steered molecular dynamics simulations revealed that stretching force peels one force-bearing strand away from barstar to trigger unfolding, whereas Top7 unfolds via a substructure-sliding mechanism. This previously overlooked stabilization effect from neighboring beta-strands is likely to be a general mechanism in protein mechanics and can serve as a guideline for the de novo design of proteins with significant mechanical stability and novel protein topology.},
	keywords = {BARSTAR, DYNAMICS SIMULATIONS, IMMUNOGLOBULIN DOMAINS, MICROSCOPE, MOLECULE FORCE SPECTROSCOPY, resistance, SINGLE PROTEIN, TITIN, TOPOLOGY, UBIQUITIN},
	isbn = {0006-3495},
	url = {<Go to ISI>://000259503900036},
	author = {Sharma, D. and Feng, G. and Khor, D. and Genchev, G. Z. and Lu, H. and Li, H. B.}
}
@article {1555,
	title = {Engineering proteins with novel mechanical properties by recombination of protein fragments},
	journal = {Angewandte Chemie-International Edition},
	volume = {45},
	number = {34},
	year = {2006},
	note = {ISI Document Delivery No.: 082MRTimes Cited: 20Cited Reference Count: 51Sharma, Deepak Cao, Yi Li, Hongbin},
	pages = {5633-5638},
	type = {Article},
	keywords = {AFM, ATOMIC-FORCE MICROSCOPY, ELASTICITY, EVOLUTION, IG DOMAIN, IMMUNOGLOBULIN DOMAINS, MOLECULAR-DYNAMICS SIMULATIONS, protein engineering, protein structures, scanning probe microscopy, SINGLE PROTEIN, single-molecule studies, SPECTROSCOPY, STABILITY, TITIN},
	isbn = {1433-7851},
	url = {<Go to ISI>://000240391400016},
	author = {Sharma, D. and Cao, Y. and Li, H. B.}
}
@article {1349,
	title = {Nonmechanical protein can have significant mechanical stability},
	journal = {Angewandte Chemie-International Edition},
	volume = {45},
	number = {4},
	year = {2006},
	note = {ISI Document Delivery No.: 004RFTimes Cited: 30Cited Reference Count: 44},
	pages = {642-645},
	type = {Article},
	keywords = {ADHESION, cell, DISULFIDE BONDS, DYNAMICS, ELASTICITY, mechanical properties, microscopy, MOLECULE FORCE-SPECTROSCOPY, protein unfolding, resistance, scanning probe microscopy, SIMULATION, SINGLE PROTEIN, single-molecule studies, TITIN IMMUNOGLOBULIN DOMAINS},
	isbn = {1433-7851},
	url = {<Go to ISI>://000234769200026},
	author = {Cao, Y. and Lam, C. and Wang, M. J. and Li, H. B.}
}
