@article {2034,
	title = {Single molecule force spectroscopy reveals engineered metal chelation is a general approach to enhance mechanical stability of proteins},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {105},
	number = {32},
	year = {2008},
	note = {ISI Document Delivery No.: 339EKTimes Cited: 16Cited Reference Count: 44Cao, Yi Yoo, Teri Li, Hongbin},
	month = {Aug},
	pages = {11152-11157},
	type = {Article},
	abstract = {Significant mechanical stability is an essential feature shared by many elastomeric proteins, which function as molecular springs in a wide variety of biological machinery and biomaterials of superb mechanical properties. Despite the progress in understanding molecular determinants of mechanical stability, it remains challenging to rationally enhance the mechanical stability of proteins. Using single molecule force spectroscopy and protein engineering techniques, we demonstrate that engineered bi-histidine metal chelation can enhance the mechanical stability of proteins significantly and reversibly. Based on simple thermodynamic cycle analysis, we engineered a bi-histidine metal chelation site into various locations of the small protein, GB1, to achieve preferential stabilization of the native state over the mechanical unfolding transition state of GB1 through the binding of metal ions. Our results demonstrate that the metal chelation can enhance the mechanical stability of GB1 by as much as 100 pN. Since bi-histidine metal chelation sites can be easily implemented, engineered metal chelation provides a general methodology to enhance the mechanical stability of a wide variety of proteins. This general approach in protein mechanics will enable the rational tuning of the mechanical stability of proteins. It will not only open new avenues toward engineering proteins of tailored nanomechanical properties, but also provide new approaches to systematically map the mechanical unfolding pathway of proteins.},
	keywords = {BINDING SITES, charge, DESIGN, DOMAINS, ELASTICITY, engineering, EXTRACELLULAR-MATRIX PROTEIN, mechanical unfolding, PROTEIN, protein mechanics, rational design, SIMULATIONS, STABILIZATION, STRENGTH, THERMOSTABILITY, TITIN},
	isbn = {0027-8424},
	url = {<Go to ISI>://000258560700024},
	author = {Cao, Y. and Yoo, T. and Li, H. B.}
}
@article {ISI:000227764700020,
	title = {Spectroscopy of non-heme iron thiolate complexes: insight into the electronic structure of the low-spin active site of nitrile hydratase.},
	journal = {Inorg. Chem.},
	volume = {44},
	number = {6},
	year = {2005},
	month = {mar},
	pages = {1826{\textendash}36},
	abstract = {Detailed spectroscopic and computational studies of the low-spin iron complexes [Fe(III)(S2(Me2)N3 (Pr,Pr))(N3)] (1) and [Fe(III)(S2(Me2)N3 (Pr,Pr))]1+ (2) were performed to investigate the unique electronic features of these species and their relation to the low-spin ferric active sites of nitrile hydratases. Low-temperature UV/vis/NIR and MCD spectra of 1 and 2 reflect electronic structures that are dominated by antibonding interactions of the Fe 3d manifold and the equatorial thiolate S 3p orbitals. The six-coordinate complex 1 exhibits a low-energy S(pi) {\textendash}> Fe 3d(xy) (approximately 13,000 cm(-1)) charge-transfer transition that results predominantly from the low energy of the singly occupied Fe 3d(xy) orbital, due to pure pi interactions between this acceptor orbital and both thiolate donor ligands in the equatorial plane. The 3d(pi) {\textendash}> 3d(sigma) ligand-field transitions in this species occur at higher energies (>15,000 cm(-1)), reflecting its near-octahedral symmetry. The Fe 3d(xz,yz) {\textendash}> Fe 3d(xy) (d(pi) {\textendash}> d(pi)) transition occurs in the near-IR and probes the Fe(III)-S pi-donor bond; this transition reveals vibronic structure that reflects the strength of this bond (nu(e) approximately 340 cm(-1)). In contrast, the ligand-field transitions of the five-coordinate complex 2 are generally at low energy, and the S(pi) {\textendash}> Fe charge-transfer transitions occur at much higher energies relative to those in 1. This reflects changes in thiolate bonding in the equatorial plane involving the Fe 3d(xy) and Fe 3d(x2-y2) orbitals. The spectroscopic data lead to a simple bonding model that focuses on the sigma and pi interactions between the ferric ion and the equatorial thiolate ligands, which depend on the S-Fe-S bond angle in each of the complexes. These electronic descriptions provide insight into the unusual S = 1/2 ground spin state of these complexes: the orientation of the thiolate ligands in these complexes restricts their pi-donor interactions to the equatorial plane and enforces a low-spin state. These anisotropic orbital considerations provide some intriguing insights into the possible electronic interactions at the active site of nitrile hydratases and form the foundation for further studies into these low-spin ferric enzymes.},
	keywords = {BINDING SITES, Computational Biology, ELECTROCHEMISTRY, Ferric Compounds, Ferric Compounds: chemical synthesis, Ferric Compounds: chemistry, Hydro-Lyases, Hydro-Lyases: chemistry, iron, Iron: chemistry, models, MOLECULAR, Molecular Conformation, molecular structure, PhD, SPECTROPHOTOMETRY, Sulfhydryl Compounds, Sulfhydryl Compounds: chemistry},
	issn = {0020-1669},
	doi = {10.1021/ic0487068},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/15762709},
	author = {Kennepohl, Pierre and Neese, Frank and Schweitzer, Dirk and Jackson, Henry L and Kovacs, Julie A and Solomon, Edward I}
}
