Tieqiao Zhang

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Coiled-coil sequences in proteins consist of heptad repeats containing two characteristic hydrophobic positions. The role of these buried hydrophobic residues in determining the structures of coiled coils was investigated by studying mutants of the GCN4 leucine zipper. When sets of buried residues were altered, two-, three-, and four-helix structures were(More)
Cardiomyocytes contract against a mechanical load during each heartbeat, and excessive mechanical stress leads to heart diseases. Using a cell-in-gel system that imposes an afterload during cardiomyocyte contraction, we found that nitric oxide synthase (NOS) was involved in transducing mechanical load to alter Ca(2+) dynamics. In mouse ventricular myocytes,(More)
The Thermus thermophilus 3-isopropylmalate dehydrogenase (IPMDH) and Escherichia coli isocitrate dehydrogenase (ICDH) are two functionally and evolutionarily related enzymes with distinct substrate specificities. To understand the determinants of substrate specificities of the two proteins, the substrate and coenzyme in IPMDH were docked into their(More)
To examine the relationship between polypeptide chain synthesis and protein folding, we have constructed a circularly permuted variant of phage T4 lysozyme. The permuted protein begins at residue 37 of the wild-type sequence and ends at residue 36. The normal chain termini are joined by a six-residue linker, Ser-Gly4-Ala. The permuted lysozyme folds(More)
To measure the thermodynamic consequences of the reduction in the number of polypeptide-chain conformations that accompanies protein folding, we developed a method called loop permutation analysis. In this approach, the stabilizing contributions of three engineered disulphide bonds were compared in extended and circularly permutated mutants of phage T4(More)
A computational method for estimating the relative binding free energies of enzyme-substrate complexes is described that combines electrostatic and solvation models and X-ray crystallographic data. The polar contribution is evaluated by the Poisson-Boltzman equation. The nonpolar contribution is evaluated by solvent transfer data and surface area(More)
Tumor adaptive resistance to therapeutic radiation remains a barrier for further improvement of local cancer control. SIRT3, a member of the sirtuin family of NAD(+)-dependent protein deacetylases in mitochondria, promotes metabolic homeostasis through regulation of mitochondrial protein deacetylation and plays a key role in prevention of cell aging. Here,(More)
Third-order nonlinear optical properties of two series of self-assembled porphyrin wires, one being terminated by zinc porphyrin and the other by free base porphyrin, were measured by femtosecond time-resolved optical Kerr effect. The hyperpolarizability values of the latter series were extremely large ranging from 10-30 to 10-29 esu, 10 times larger than(More)
The CO ligation process in a mutant (H77G) of CooA, the CO-sensing transcriptional regulator in Rhodospirillum rubrum, is studied with femtosecond time-resolved transient absorption spectroscopy in the mid-infrared region. Following photolyzing excitation, a transient bleach in the vibrational region of bound CO due to the CO photodissociation is detected.(More)
X Ž . The photophysics and isomerization dynamics in the excited state of a cyanine dye, 3,3 -di 3-sulfopropyl -thiacyanine triethylaminium salt was investigated. Using the femotosecond time-resolved fluorescence up-conversion technique, wavelength-dependent fluorescence dynamics was observed and the theoretical prediction of the dual fluorescence behavior(More)