Download or read book Spectroscopic and Theroretical Definition of Binuclear Non heme Iron Active Sites written by Yi-Shan Yang and published by . This book was released on 1999 with total page 558 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectroscopic Studies of Mixed valent Binuclear Non heme Iron Active Sites written by James Malcolm McCormick and published by . This book was released on 1991 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectroscopic and Reactivity Studies of Binuclear Non heme Iron Complexes written by Subhasish Mukerjee and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectroscopic and Reactivity Studies of Mononuclear and Binuclear Non heme Iron Complexes written by Bala Sundari T. Kasibhatla and published by . This book was released on 1998 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bioinorganic Spectroscopy Structure function Correlations in Binuclear Non heme Iron Enzymes and Developing Nuclear Resonance Vibrational Spectroscopy for Characterization of Enzyme Intermediates written by Caleb Branson Bell and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The foci of this dissertation are: 1) combined use of spectroscopies for mechanistic understanding of the oxygen reactions of various non-heme iron enzymes and related model complexes, and 2) the development of the recently described nuclear vibrational resonance spectroscopy (NRVS) coupled with density functional calculations (DFT) for characterization of non-heme iron enzyme intermediates. Binuclear non-heme iron enzymes are involved in many medically and industrially important processes such as DNA synthesis by ribonucleotide reductase (RNR), conversion of methane to methanol by methane monooxygenase (MMO), fatty acid desaturation by [Delta]9 desaturase, iron storage and homeostasis by ferritins, degradation of aromatic compounds by various bacterial monooxygenases (ToMO, T4MO, etc.) and antibiotic biogenesis by p-aminobenzoate N-oxygenase (AurF), etc. Interestingly, these diverse reactions typically begin with O2 reacting with a biferrous active site, coordinated by highly conserved protein ligands (ExxH motifs) in four [Alpha]-helix bundles. Moreover, spectroscopically and chemically similar intermediates can be detected in many of the enzyme systems. The best studied in this family are RNRs, where biferric peroxo intermediates (P and P'), and the high-valent Fe(III)Fe(IV) intermediate X have been stabilized and spectroscopically characterized in wt and numerous variants. De novo designed four [Alpha]-helix bundles have been synthesized (the ~140 amino acid dui ferri (DF) peptide family) and are good models for binuclear non-heme iron enzymes. These systems provide a protein environment and can be viewed as a bridge between inorganic model complexes and native proteins. The pseudo-symmetric single chain version (DFsc) coordinates two ferrous ions by two His and four Glu amino acid residues. Circular dichroism (CD), magnetic CD (MCD) and variable-temperature variable-field MCD (VTVH MCD) show that this "active site" in DFsc has a 4-coordinate and 5-coordinate (4C+5C) geometry that is weakly antiferromagnetically coupled (J [approximately equal to] --2 cm-1) indicative of [Mu]1,3 carboxylate bridges, highly similar to RNR biferrous structures. Extended x-ray absorption fine structure (EXAFS) data are consistent with this assignment and show that one terminal carboxylate residue coordinates in a bidentate fashion. Changes in the CD/MCD/VTVH MCD and EXAFS spectra in the Y51L and E11D variants show that the 4C site is proximal to (but not bound by) Y51 and the bidentate carboxylate is coordinated to the 5C iron. Open coordination positions on both irons allow for dioxygen to react rapidly with the biferrous site. The reaction of biferrous DFsc with dioxygen yields a 520 nm ([Epsilon] = [weak approximation to]1200 M-1cm-1) species with a formation rate of 2 s-1, again similar to RNR (the Class Ia RNR from Escherichia coli has a dioxygen reaction rate of ~1 s-1, however the first species formed (intermediate P) has [Lambda]max = 700 nm). The resonance Raman (rR) spectrum obtained by excitation into the 520 nm feature in DFsc (and the E11D variant) proves this chromophore arises from a Tyr to ferric charge transfer (CT) transition. The 520 nm feature is lost by substitution of Y51 but not Y18, thus Y51 binds to the site after reaction with dioxygen. Subsequent binding of Y51 functions as an internal spectral probe of the dioxygen reaction and as a proton source that would promote loss of hydrogen peroxide. Coordination by a ligand that functions as a proton source could be a structural mechanism used by natural binuclear iron enzymes to drive their reactions past peroxo biferric level intermediates. RNR's can be divided into 3 major classes based on the radical generating machinery. Class I RNR's utilize a dimetal cofactor that reacts with dioxygen and can be subdivided into Classes Ia, Ib and Ic based on sequence homology and metal dependency. Class Ia enzymes are the best studied an present in higher organisms including human (host) while Class Ib enzymes are typically found in pathogens. CD, MCD and VTVH MCD data on biferrous loaded Class Ib RNR from Bacillus cereus allow assignment of the active site as 4C+5C in solution, resolving discrepancies from available crystal structures. Differences in the zero-field splitting parameters (D and E) and magnetic coupling extracted from fits to the VTVH MCD data can be ascribed to differences in the bridging carboxylate conformations. FeII loading, monitored by CD, shows cooperative binding with Kd 100 mM, significantly stronger that the metal binding in Class Ia. This provides the pathogen a competitive advantage relative to host in physiological, iron-limited environments Returning to Class Ia, the recently discovered intermediate P' notably lacks structural definition. This is mainly due to the lack of spectroscopic handles from which to obtain the needed experimental data. What is know, however, is that this species directly forms intermediate X and is directly derived from the well-defined intermediate P. Spectroscopically, P' has Mössbauer isomer shifts ([lowercase Delta] = 0.52 and 0.45 mm/s) that are significantly lower than the cis-[Mu]1,2 peroxo P ([lowercase Delta] = 0.63 mm/s) and lacks the ~700 nm peroxo to ferric CT suggesting some change in coordination mode or protonation may be involved in P -- P'. Comparisons of the reduced and oxidized crystal structures show differences in carboxylate coordination modes and water binding that must occur at some stage along the reaction coordinate. All of these potential structural perturbations were systematically incorporated into computational models of the intermediate site and correlated with experimental data using density functional theory (DFT). Two potential reaction pathways consistent with available experimental data were found. The first involves water addition to Fe1 of the cis-[Mu]-1,2 peroxo intermediate P causing opening of a bridging carboxylate to form intermediate P' which has an increased electron affinity and is activated for proton-coupled electron transfer to form the Fe(III)Fe(IV) intermediate X. While the second, more energetically favorable pathway, involves addition of a proton to a terminal carboxylate ligand in the site which increases the electron affinity and triggers electron transfer to form X. Vibrational characterization could, in principle, distinguish these pathways. However, the lack of a reasonably intense chromophore precludes rR experiments. The recently available method of nuclear vibrational resonance spectroscopy (NRVS) does not have these chromophoric constraints and can provide the needed vibrational data for P'--and many other "spectroscopically challenged" intermediates in non-heme iron biochemistry. The vibrations enhanced in NRVS are typically lower in energy and differ from those observed in rR, thus studies on well defined model complexes are needed prior to intermediate studies. A series of mononuclear Fe(IV)=O have been characterized by NRVS coupled with DFT calculations to define NRVS spectral assignments and set a foundation for vibrational characterization of non-heme iron enzyme intermediates. These studies show that the NRVS spectrum is rich in structural information. Of the four Fe(IV)=O models, supported by the 1, 4, 8, 11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMC); N, N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine (N4Py); N-benzyl-N, N', N'-tris(2-pyridylmethyl)-1,2-diaminoethane (BnTPEN); and 1,1,1-tris{2-[N(2)-(1,1,3,3-tetramethylguanidino)]ethyl}amine (TMG3tren) ligand sets, only the trigional bipyramidal geometry (relative to the 6C approximatly C4v geometry of TMC, N4Py and BnTPEN) enforced by the TMG3tren ligand affords a high-spin species. Isotope sensitive Fe-O stretches are observed for all complexes at 820 to 831 cm-1. However, at lower energy (
Download or read book Spectroscopic and Theoretical Elucidation of Structural Contributions to Reactivity in Binuclear Non heme Iron Enzymes written by Jennifer Kathleen Schwartz and published by . This book was released on 2008 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2000 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure function Correlations of Binuclear Non heme Iron Enzymes and Their de Novo Models written by Rae Ana Snyder and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Binuclear non-heme iron enzymes are pervasive in nature and catalyze a variety of biologically important reactions, including reactions relevant to the biosynthesis of DNA, fatty acid metabolism, the protection of pathogens from oxidative stress, cell signaling, iron storage, and many others. Elucidating the structures of their diiron active sites and the contributions of these structures to reactivity can provide molecular level insight into catalysis. The near IR circular dichroism (CD), magnetic circular dichroism (MCD), and variable temperature variable field (VTVH) MCD spectroscopies form a powerful methodology that allows for detailed structural understanding of the diiron active sites in these enzymes. Presented are studies that focus on myo-inositol oxygenase, an enzyme with significance to human health, and de novo designed diiron proteins that model native enzymes.
Download or read book Oxygen Intermediates of Mononuclear Non heme Iron Systems written by Andrea Decker and published by . This book was released on 2006 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Directory of Graduate Research written by American Chemical Society. Committee on Professional Training and published by . This book was released on 2005 with total page 1932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
Download or read book Theoretical Studies of Mononuclear Non heme Iron Active Sites written by Arianna Bassan and published by . This book was released on 2004 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectroscopic and Computational Studies of Heme and Nonheme Iron dependent Enzymes written by Jessica D. Gardner and published by . This book was released on 2010 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Annual Commencement written by Stanford University and published by . This book was released on 2000 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ACS Directory of Graduate Research 1993 written by American Chemical Society. Committee on Professional Training and published by . This book was released on 1993 with total page 1700 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectroscopic Definition of Electronic Structure Contributions to O2 and N2O Activation by Mononuclear Binuclear and Tetranuclear Copper Sites in Biology written by Peng Chen and published by . This book was released on 2004 with total page 1022 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 2 Oxoglutarate Dependent Oxygenases written by Christopher J Schofield and published by Royal Society of Chemistry. This book was released on 2015-05-06 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of the first examples of 2-oxoglutarate-dependent oxygenase-catalysed reactions in the 1960s, a remarkably broad diversity of alternate reactions and substrates has been revealed, and extensive advances have been achieved in our understanding of the structures and catalytic mechanisms. These enzymes are important agrochemical targets and are being pursued as therapeutic targets for a wide range of diseases including cancer and anemia. This book provides a central source of information that summarizes the key features of the essential group of 2-oxoglutarate-dependent dioxygenases and related enzymes. Given the numerous recent advances and biomedical interest in the field, this book aims to unite the latest research for those already working in the field as well as to provide an introduction for those newly approaching the topic, and for those interested in translating the basic science into medicinal and agricultural benefits. The book begins with four broad chapters that highlight critical aspects, including an overview of possible catalytic reactions, structures and mechanisms. The following seventeen chapters focus on carefully selected topics, each written by leading experts in the area. Readers will find explanations of rapidly evolving research, from the chemistry of isopenicillin N synthase to the oxidation mechanism of 5-methylcytosine in DNA by ten-eleven-translocase oxygenases.
Download or read book American Doctoral Dissertations written by and published by . This book was released on 1999 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:
