Download or read book X ray Absorption Spectroscopy of Heme and Non heme Iron written by Samuel Aaron Wilson and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In biological systems dioxygen serves two essential functions, one as a terminal electron acceptor, and two as a biosynthetic agent. The latter role will be primarily the focus of this thesis, which will look at the role of dioxygen in specific mononuclear iron metalloenzyme and biomimetic model systems. During enzymatic turnover, the use of dioxygen as a biosynthetic agent involves the binding of dioxygen and the formation of one or more iron-peroxo (Fe-OO) or hydroperoxo (Fe-OOH) intermediates. This is followed by the controlled cleavage of the oxygen-oxygen double bond, a highly energetically favorable and exothermic process, to form a high-valent iron-oxo intermediate. For many enzymatic systems, these iron-oxygen species and high-valent intermediates are represent a significant obstacle as they are often difficult to trap and isolate in pure form, making them very challenging to study. Thus, biomimetic model complexes offer an excellent way to understand the mechanisms for reactivity and how the enzyme may tune the ligand environment around the iron center in order to govern the electronic structure of many of these key intermediate species. Chapter 1 will introduce the fields of iron non-heme enzymes, heme enzymes, and biomimetic model studies that play a key role in understanding the enzyme systems that they represent. Chapter 1 will also introduce the methodology of X-ray absorption spectroscopy, a specialized spectroscopic technique that has been invaluable in understanding these difficult to study systems. Chapter 2 looks at the enzyme tyrosine hydroxylase, a pterin-dependent non-heme iron enzyme that utilizes dioxygen to catalyze the hydroxylation of L-tyr to L-DOPA in the rate-limiting step of catecholamine neurotransmitter biosynthesis. X-ray absorption spectroscopy (XAS) and variable-temperature-variable-field magnetic circular dichroism (VTVH MCD) spectroscopy are combined with single-turnover kinetic experiments to investigate the geometric and electronic structure of the wild-type tyrosine hydroxylase and two mutants, S395A and E332A, and their interactions with substrates. This research showns that all three forms of tyrosine hydroxylase undergo 6-coordinate (6C) → 5-coordinate (5C) conversion with tyr + pterin, consistent with the general mechanistic strategy established for O2-activating non-heme iron enzymes. When the FeII site is 6C, the two-electron reduction of O2 to peroxide by FeII and pterin is favored over individual one-electron reactions demonstrating that both a 5C FeII and a redox-active pterin are required for coupled O2 reaction. When the FeII is 5C, the O2 reaction is accelerated by at least 2 orders of magnitude. Comparison of the kinetics of wild-type tyrosine hydroxylase, which produces FeIV=O + 4a-OH-pterin, and the E332A mutant, which does not, shows that the E332 residue plays an important role in directing the protonation of the bridged FeII-OO-pterin intermediate in wild-type to productively form the FeIV=O intermediate, which is responsible for the hydroxylation of L-tyr to L-DOPA. Chapter 3 uses a combination of nuclear resonance vibrational spectroscopy (NRVS) and extended X-ray absorption fine structure spectroscopy (EXAFS) to define the natures of ferric (FeIIIBLM) and activated bleomycin (ABLM), an important glycopeptide anticancer drug capable of effecting single- and double-strand DNA cleavage, as (BLM)FeIII-OH and (BLM)FeIII([eta]1-OOH) species, respectively. These spectroscopically defined species are then used in a series of density functional theory (DFT) calculations to show that the direct H-atom abstraction by ABLM is the most thermodynamically favored reaction pathway. Chapter 4 reports the first high-resolution x-ray crystal structure of an side-on ferric peroxide species in a non-heme iron biomimetic complex, [FeIII(OO)(TMC)]+, and a series of spectroscopic studies which looks at the pathway of interconversion from a iron(III)-peroxo complex to a iron(III)-hydroperoxo complex, followed by the homolytic O-O bond cleavage to an iron(IV)-oxo intermediate species. This work is followed by a series of reactivity studies that show that the iron(III)-hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes, and has a similar reactivity to the iron(IV)--oxo complex in the C--H bond activation of alkylaromatics. These three species represent the three most biologically relevant iron-oxygen intermediates, and have all been synthesized utilizing the same macrocyclic ligand, which has allowed for the elucidation of key differences at the iron center and its bonding interactions with dioxygen, while the ligand environment remains fixed. Chapter 5 focuses in more detail on the high-valent FeIV=O species with the spectroscopic characterization of a new iron-oxo complex [FeIV=O(BQEN)]2+. This non-heme iron(IV)-oxo complex is shown to activate the C-H bonds of both alkanes and alcohols via a hydrogen-atom (H-atom) abstraction mechanism. This work also presents evidence for the formation of an additional high-valent iron-oxo intermediate species, [FeV=O(BQEN)]3+, which exhibits high reactivity in oxidation reactions and fast oxygen exchange with H218O. This FeV=O species is proposed as a possible active oxidant in the catalytic oxidation of alkanes and alcohols. Chapter 6 takes a more detailed look at the role of the equatorial ligand in the tuning in the iron-oxo unit by comparing the reactivity differences between two S = 1 non-heme iron-oxo species, [FeIV=O(TBC)(CH3CN)]2+ and [FeIV=O(TMC)(CH3CN)]2+. TBC, 1,4,8,11-tetrabenzyl-1,4,8,11-tetraazacyclotetradecane, is a equatorially constrained cyclam ligand which exhibits a greater than two orders of magnitude reactivity increase over TMC for both H-atom abstraction and oxo-transfer reactions. In this study, the S = 1 ground states of [FeIV=O(TBC)(CH3CN)]2+ and [FeIV=O(TMC)(CH3CN)]2+ are first structurally defined using XAS. Next, this structural information is utilized in a series of DFT calculations to look at what structural differences are responsible for the reactivity differences between these two very similar complexes and the mechanistic reactivity differences between the S = 1 and S = 2 surface for the biologically relevant H-atom abstraction and oxo-transfer reactions. Chapter 7 considers the electronic structure of the Fe--O2 bond in oxy-hemoglobin and oxy-myoglobin which is a long-standing issue in the field of bioinorganic chemistry. Here, spectroscopic studies have been complicated by the highly delocalized electronic structure of the porphyrin and calculations require interpretation of multi-determinant wavefunctions of a highly covalent site. Iron L-edge X-ray absorption spectroscopy (XAS) is used with a valence bond configuration interaction (VBCI) multiplet model to directly probe the electronic structure of the iron in the biomimetic FeO2 heme complex [Fe(pfp)(1-MeIm)O2] (pfp = meso-tetra([alpha], [alpha], [alpha], [alpha]-o-pivalamidophenyl)porphyrin). This method allows separate estimates of [sigma]-donor, [pi]-donor, and [pi]-acceptor interactions through ligand to metal charge transfer (LMCT) and metal to ligand charge transfer (MLCT) mixing pathways. The L-edge spectrum of [Fe(pfp)(1-MeIm)O2] is further compared to those of [FeII(pfp)(1-MeIm)2], [FeII(pfp)], and [FeIII(tpp)(ImH)2]+ (tpp = meso-tetraphenylporphyrin) which have FeII S = 0, FeII S = 1 and FeIII S = 1/2 ground states, respectively. These serve as the expected references for the three contributions to the ground state of oxy-pfp. This FeO2 S = 0 site is found to have significant [sigma]-donation and a strong [pi]-interaction of the O2 with the iron.

Download or read book X ray Absorption Spectroscopic Investigations of Non heme Iron Active Sites written by Erik Christopher Wasinger and published by . This book was released on 2003 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Absorption Spectroscopic Studies of Mononuclear Non heme Iron Enzymes written by and published by . This book was released on 1996 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s-->3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.

Download or read book X ray Absorption Studies of Non heme Iron containing Proteins and Their Models written by Clayton Robert Randall and published by . This book was released on 1993 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Absorption Spectroscopic Studies of Non heme Iron Proteins and Model Complexes written by Ekaterina Y. Shishova and published by . This book was released on 2003 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Absorption Spectroscopic Studies of Mononuclear Non heme Iron Enzymes written by Tami E. Westre and published by . This book was released on 1996 with total page 674 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Absorption Spectroscopic Studies of Binuclear Non heme Iron Complexes and Their Dioxygen Adducts written by Heather Bufford and published by . This book was released on 1995 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Absorption Spectroscopic Studies of Nonheme Iron containing Oxygen Activating Enzymes written by Lijin Shu and published by . This book was released on 1997 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X Ray Absorption and X Ray Emission Spectroscopy written by Jeroen A. van Bokhoven and published by John Wiley & Sons. This book was released on 2016-01-08 with total page 896 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last two decades, remarkable and often spectacular progress has been made in the methodological and instrumental aspects of x–ray absorption and emission spectroscopy. This progress includes considerable technological improvements in the design and production of detectors especially with the development and expansion of large-scale synchrotron reactors All this has resulted in improved analytical performance and new applications, as well as in the perspective of a dramatic enhancement in the potential of x–ray based analysis techniques for the near future. This comprehensive two-volume treatise features articles that explain the phenomena and describe examples of X–ray absorption and emission applications in several fields, including chemistry, biochemistry, catalysis, amorphous and liquid systems, synchrotron radiation, and surface phenomena. Contributors explain the underlying theory, how to set up X–ray absorption experiments, and how to analyze the details of the resulting spectra. X-Ray Absorption and X-ray Emission Spectroscopy: Theory and Applications: Combines the theory, instrumentation and applications of x-ray absorption and emission spectroscopies which offer unique diagnostics to study almost any object in the Universe. Is the go-to reference book in the subject for all researchers across multi-disciplines since intense beams from modern sources have revolutionized x-ray science in recent years Is relevant to students, postdocurates and researchers working on x-rays and related synchrotron sources and applications in materials, physics, medicine, environment/geology, and biomedical materials

Download or read book Iron containing Enzymes written by Sam P. De Visser and published by Royal Society of Chemistry. This book was released on 2011 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mononuclear iron containing enzymes are important intermediates in bioprocesses and have potential in the industrial biosynthesis of specific products. This book features topical review chapters by leaders in this field and its various sub-disciplines.

Download or read book X ray Absorption Studies on Heme Proteins Using Synchrotron Radiation written by Cindy Hsiao-Ching Yuen and published by . This book was released on 1977 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Spectroscopic Studies of Highly Covalent Iron Centers written by James Jie Yan and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Resolution EPR written by Graeme Hanson and published by Springer Science & Business Media. This book was released on 2009-06-19 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metalloproteins comprise approximately 30% of all known proteins, and are involved in a variety of biologically important processes, including oxygen transport, biosynthesis, electron transfer, biodegradation, drug metabolism, proteolysis, and hydrolysis of amides and esters, environmental sulfur and nitrogen cycles, and disease mechanisms. EPR spectroscopy has an important role in not only the geometric structural characterization of the redox cofactors in metalloproteins but also their electronic structure, as this is crucial for their reactivity. The advent of x-ray crystallographic snapshots of the active site redox cofactors in metalloenzymes in conjunction with high-resolution EPR spectroscopy has provided detailed structural insights into their catalytic mechanisms. This volume was conceived in 2005 at the Rocky Mountain Conference on Analytical Chemistry (EPR Symposium) to highlight the importance of high-resolution EPR spectroscopy to the structural (geometric and electronic) characterization of redox active cofactors in metalloproteins. We have been fortunate to have enlisted internationally recognized experts in this joint venture to provide the scientific community with an overview of high-resolution EPR and its application to metals in biology. This volume, High-Resolution EPR: Applications to Metalloenzymes and Metals in Medicine, covers high-resolution EPR methods, iron proteins, nickel and copper enzymes, and metals in medicine. An eloquent synopsis of each chapter is provided by John Pilbrow in the Introduction. A second volume, Metals in Biology: Applications of High-Resolution EPR to Metalloenzymes, will appear later this year covering the complement of other metalloproteins. One of the pioneers in the development of pulsed EPR and its application to metalloproteins was Arthur Schweiger, whose contribution we include in this volume. Unfortunately, he passed away suddenly during the preparation of this volume. The editors and coauthors are extremely honored to dedicate this volume to the memory of Arthur Schweiger in recognition of his technical advances and insights into pulsed EPR and its application to metalloproteins. Arthur was extremely humble and treated everyone with equal respect. He was a gifted educator with an ability to explain complex phenomena in terms of simple intuitive pictures, had a delightful personality, and continues to be sadly missed by the community. It is an honor for the editors to facilitate the dissemination of these excellent contributions to the scientific community. Suggestions for future volumes are always appreciated.

Download or read book Metallomics and the Cell written by Lucia Banci and published by Springer Science & Business Media. This book was released on 2013-04-18 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metallomics and the Cell provides in an authoritative and timely manner in 16 stimulating chapters, written by 37 internationally recognized experts from 9 nations, and supported by more than 3000 references, several tables, and 110 illustrations, mostly in color, a most up-to-date view of the "metallomes" which, as defined in the "omics" world, describe the entire set of biomolecules that interact with or are affected by each metal ion. The most relevant tools for visualizing metal ions in the cell and the most suitable bioinformatic tools for browsing genomes to identify metal-binding proteins are also presented. Thus, MILS-12 is of relevance for structural and systems biology, inorganic biological chemistry, genetics, medicine, diagnostics, as well as teaching, etc.

Download or read book Ultrafast X ray Spectroscopy of Heme Proteins written by Dominik Kinschel and published by . This book was released on 2020 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'auteur: Proteins ; Myoglobin ; Time-resolved ; X-ray Emission Spectroscopy ; X-ray Absorption Spectroscopy X-ray Free electron laser ; femtosecond ; Spin Dynamics ; Heme proteins.

Download or read book Spectroscopic Probes of the Non heme Iron Active Sites written by Yan Zhang and published by . This book was released on 1992 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metalloporphyrins Advances in Research and Application 2013 Edition written by and published by ScholarlyEditions. This book was released on 2013-06-21 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metalloporphyrins—Advances in Research and Application: 2013 Edition is a ScholarlyEditions™ book that delivers timely, authoritative, and comprehensive information about Chlorophyll. The editors have built Metalloporphyrins—Advances in Research and Application: 2013 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Chlorophyll in this book to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Metalloporphyrins—Advances in Research and Application: 2013 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.