Chemistry Commons^™

Lysine Biosynthesis In Bacteria: A Metallodesuccinylase As A Potential Antimicrobial Target, Danuta Gillner, Daniel P. Becker, Richard C. Holz

Chemistry Faculty Research and Publications

In this review, we summarize the recent literature on dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) enzymes, with an emphasis on structure–function studies that provide insight into the catalytic mechanism. Crystallographic data have also provided insight into residues that might be involved in substrate and hence inhibitor recognition and binding. These data have led to the design and synthesis of several new DapE inhibitors, which are described along with what is known about how inhibitors interact with the active site of DapE enzymes, including the efficacy of a moderately strong DapE inhibitor.

Protein Control Of S-Nitrosothiol Reactivity: Interplay Of Antagonistic Resonance Structures, Marat R. Talipov, Qadir K. Timerghazin

Chemistry Faculty Research and Publications

There is currently great interest in S-nitrosothiols (RSNOs) because formation of protein-based RSNOs—protein S-nitrosation—has been recently recognized as a major pathway of the biological function of nitric oxide, NO. Despite the growing number of S-nitrosated proteins identified in vivo, enzymatic processes that control reactions of biological RSNOs are still not well understood. In this article, we use a range of models to computationally demonstrate that specific interactions of RSNOs with charged and polar residues in proteins can result in dramatic modification of RSNO structure, stability, and reactivity. This unprecedented sensitivity of the −SNO group toward interactions with …

Generation Of Molecular Complexity From Cyclooctatetraene: Preparation Of Optically Active Protected Aminocycloheptitols And Bicyclo[4.4.1]Undecatriene, Mohamed F. El-Mansy, Anobick Sar, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

The racemic (6-cyclo-heptadienyl)Fe(CO)₃⁺ cation ((±)-7), prepared from cyclooctatetraene, was treated with a variety of carbon and heteroatom nucleophiles. Attack took place at the less hindered C¹ dienyl carbon and decomplexation of the (cycloheptadiene)Fe(CO)₃ complexes gave products rich in functionality for further synthetic manipulation. In particular, a seven-step route was developed from racemic (6-styryl-2,4-cycloheptadien-1-yl)phthalimide ((±)-9 d) to afford the optically active aminocycloheptitols (−)-20 and (+)-20.

Concerted And Sequential Pathways Of Proton-Coupled Electron Transfer In Hydrogen Halide Elimination, Aimable Kalume, Lisa George, Nicole Cunningham, Scott A. Reid

Chemistry Faculty Research and Publications

Proton-coupled electron transfer (PCET) is a key reaction in a diverse array of chemical and biochemical processes. Concerted PCET, a single step process where no intermediates are expected, is often difficult to distinguish from sequential electron transfer/proton transfer (or proton transfer/electron transfer) events that involve one or more reactive intermediates. Here we demonstrate that in an apparently simple and fundamental organic reaction, hydrogen halide elimination (dehydrohalogenation), both mechanisms occur, with concerted PCET kinetically favored over sequential ET/PT. The latter involves a well-defined reactive intermediate, the corresponding iso-halon.

"Molecular Spectroscopy And Dynamics Of Reactive Chemical Intermediates Studied Using Laser Induced Fluorescence (Lif), Single Vibronic Level (Svl) Emission And Resonance Enhanced Multiphoton Ionization (Rempi) Spectrometry.", Lloyd Godfrey Muzangwa

Dissertations (1934 -)

ABSTRACT

"MOLECULAR SPECTROSCOPY AND DYNAMICS OF REACTIVE CHEMICAL INTERMEDIATES STUDIED USING LASER INDUCED FLUORESCENCE (LIF), SINGLE VIBRONIC LEVEL (SVL) EMISSION AND RESONANCE ENHANCED MULTIPHOTON IONIZATION (REMPI) SPECTROMETRY"

Lloyd Muzangwa, B.Sc. (Hons, Biochemistry).

Marquette University, 2013

In the studies of complex chemical processes, it is necessary to postulate mechanisms involving transient intermediates such as radicals, ions, and pre-reactive complexes. The detection and characterization of these intermediates affords in ideal cases determination of the detailed chemical mechanism, which, in turn, can permit the development of rational strategies for removing undesired products and enhancing the yield of the desired species. This dissertation describes …

Matrix-Isolation And Computational Studies Of Transient Polyhalogenated Intermediates And Weakly-Bound Complexes., Aimable Kalume

Dissertations (1934 -)

As time goes by and new innovations are brought up to improve living conditions, the human impact on the environment becomes more significant. It has been shown that man-made halogenated compounds play a key role in many real-world chemical processes. For example, in combustion, these compounds are used as fire retardant agents, and in atmospheric chemistry, they initiate ozone depletion reactions.

However little is known about the mechanisms governing these processes and many intermediates involved in these processes have been elusive to researchers for diverse reasons such as short lifetime and difficulty in distinguishing products from parents molecules. The studies …

Molecular Tweezers: Studies Directed Towards The Preparation Of Effective Charge Transport Materials, Khushabu Thakur

Dissertations (1934 -)

ABSTRACT

MOLECULAR TWEEZERS: STUDIES DIRECTED TOWARDS THE PREPARATION OF EFFECTIVE CHARGE TRANSPORT MATERIALS

Khushabu Thakur, B.Sc, M.Sc.

Marquette University, 2013

An important focus of the modern areas of photovoltaics and molecular electronics is to identify molecules or molecular assemblies that can promote effective charge/exciton transport over long distances. In order to be able to exert control and establish necessary structural parameters for reproducible production of self-assembled structures for long-distance charge transport, our laboratory has been actively engaged towards the preparation of a variety of well-defined, cofacially-arrayed polybenzenoid nanostructures in which aromatic donors are cofacially stacked.

Herein, we undertake the design …

No Longer A Complex, Not Yet A Molecule: A Challenging Case Of Nitrosyl O-Hydroxide, Hoon, Majher I. Sarker, Tasnuva Shahrin, Mark G. Steinmetz, Qadir K. Timerghazin

Chemistry Faculty Research and Publications

N-(9-Oxothioxanthenyl)benzothiophene carboxamides bearing leaving groups (LG⁻ = Cl⁻, PhS⁻, HS⁻, PhCH₂S⁻) at the C-3 position of the benzothiophene ring system photochemically cyclize with nearly quantitative release of the leaving group, LG⁻. The LG⁻ photoexpulsions can be conducted with 390 nm light or with a sunlamp. Solubility in 75% aqueous CH₃CN is achieved by introducing a carboxylate group at the C-6 position of the benzothiophene ring. The carboxylate and methyl ester derivatives regiospecifically cyclize at the more hindered C-1 position of the thioxanthone ring. …

Photochemical Electrocyclic Ring Closure And Leaving Group Expulsion From N-(9-Oxothioxanthenyl)Benzothiophene Carboxamides, Majher I. Sarker, Tasnuva Shahrin, Mark G. Steinmetz, Qadir K. Timerghazin

Chemistry Faculty Research and Publications

N-(9-Oxothioxanthenyl)benzothiophene carboxamides bearing leaving groups (LG⁻ = Cl⁻, PhS⁻, HS⁻, PhCH₂S⁻) at the C-3 position of the benzothiophene ring system photochemically cyclize with nearly quantitative release of the leaving group, LG⁻. The LG⁻ photoexpulsions can be conducted with 390 nm light or with a sunlamp. Solubility in 75% aqueous CH₃CN is achieved by introducing a carboxylate group at the C-6 position of the benzothiophene ring. The carboxylate and methyl ester derivatives regiospecifically cyclize at the more hindered C-1 position of the thioxanthone ring. …

Global Permutationally Invariant Potential Energy Surface For Ozone Forming Reaction, Mehdi Ayouz, Dmitri Babikov

Chemistry Faculty Research and Publications

We constructed new global potential energy surface for O + O₂ → O₃ reaction. It is based on high level electronic structure theory calculations and employs fitting by permutationally invariant polynomial functions. This method of surface construction takes full advantage of permutation symmetry of three O nuclei and allows reducing dramatically the number of ab initio data points needed for accurate surface representation. New potential energy surface offers dramatic improvement over older surface of ozone in terms of dissociation energy and behavior along the minimum energy path. It can be used to refine the existing theories of ozone …

Frozen Rotor Approximation In The Mixed Quantum/Classical Theory For Collisional Energy Transfer: Application To Ozone Stabilization, Alexander Teplukhin, Mikhail V. Ivanov, Dmitri Babikov

Chemistry Faculty Research and Publications

A frozen-rotor approximation is formulated for the mixed quantum/classical theory of collisional energy transfer and ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys.134, 144107 (Year: 2011)]. Numerical tests are conducted to assess its efficiency and accuracy, compared to the original version of the method, where rotation of the molecule in space is treated explicitly and adiabatically. New approach is considerably faster and helps blocking the artificial ro-vibrational transitions at the pre- and post-collisional stages of the process. Although molecular orientation in space is fixed, the energy exchange between rotational, vibrational, and translational digresses of freedom still occurs, …

Equivalence Of The Ehrenfest Theorem And The Fluid-Rotor Model For Mixed Quantum/Classical Theory Of Collisional Energy Transfer, Alexander Semenov, Dmitri Babikov

Chemistry Faculty Research and Publications

The theory of two seemingly different quantum/classical approaches to collisional energy transfer and ro-vibrational energy flow is reviewed: a heuristic fluid-rotor method, introduced earlier to treat recombination reactions[M. Ivanov and D. Babikov, J. Chem. Phys.134, 144107 (Year: 2011)10.1063/1.3576103], and a more rigorous method based on the Ehrenfest theorem. It is shown analytically that for the case of a diatomic molecule + quencher these two methods are entirely equivalent. Notably, they both make use of the average moment of inertia computed as inverse of average of inverse of the distributed moment of inertia. Despite this equivalence, each of the two formulations …

Identification Of A Histidine Metal Ligand In The Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade C. Mcgregor, Danuta Gillner, Sabina I. Swierczek, Dali Liu, Richard C. Holz

Chemistry Faculty Research and Publications

The H355A, H355K, H80A, and H80K mutant enzymes of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were prepared, however, only the H355A enzyme was found to be soluble. Kinetic analysis of the Co(II)-loaded H355A exhibited activity levels that were 380-fold less than Co(II)-loaded WT ArgE. Electronic absorption spectra of Co(II)-loaded H355A-ArgE indicate that the bound Co(II) ion resides in a distorted, five-coordinate environment and Isothermal Titration Calorimetry (ITC) data for Zn(II) binding to the H355A enzyme provided a dissociation constant (K_d) of 39 μM. A three-dimensional homology model of ArgE was generated using the …

Molecular Docking And Nmr Binding Studies To Identify Novel Inhibitors Of Human Phosphomevalonate Kinase, Pornthip Boonsri, Terrence S. Neumann, Andrew Lawrence Olson, Sheng Cai, Timothy J. Herdendorf, Henry M. Miziorko, Supa Hannongbua, Daniel S. Sem

Chemistry Faculty Research and Publications

Phosphomevalonate kinase (PMK) phosphorylates mevalonate-5-phosphate (M5P) in the mevalonate pathway, which is the sole source of isoprenoids and steroids in humans. We have identified new PMK inhibitors with virtual screening, using autodock. Promising hits were verified and their affinity measured using NMR-based ¹H–¹⁵N heteronuclear single quantum coherence (HSQC) chemical shift perturbation and fluorescence titrations. Chemical shift changes were monitored, plotted, and fitted to obtain dissociation constants (K_d). Tight binding compounds with K_d’s ranging from 6–60 μM were identified. These compounds tended to have significant polarity and negative charge, similar to the natural …

Mixed Quantum/Classical Theory Of Rotationally And Vibrationally Inelastic Scattering In Space-Fixed And Body-Fixed Reference Frames, Alexander Semenov, Dmitri Babikov

Chemistry Faculty Research and Publications

We formulated the mixed quantum/classical theory for rotationally and vibrationally inelastic scattering process in the diatomic molecule + atom system. Two versions of theory are presented, first in the space-fixed and second in the body-fixed reference frame. First version is easy to derive and the resultant equations of motion are transparent, but the state-to-state transition matrix is complex-valued and dense. Such calculations may be computationally demanding for heavier molecules and/or higher temperatures, when the number of accessible channels becomes large. In contrast, the second version of theory requires some tedious derivations and the final equations of motion are rather complicated …

Ro-Vibrational Quenching Of Co (V = 1) By He Impact In A Broad Range Of Temperatures: A Benchmark Study Using Mixed Quantum/Classical Inelastic Scattering Theory, Alexander Semenov, Mikhail V. Ivanov, Dmitri Babikov

Chemistry Faculty Research and Publications

The mixed quantum/classical approach is applied to the problem of ro-vibrational energy transfer in the inelastic collisions of CO(v = 1) with He atom, in order to predict the quenching rate coefficient in a broad range of temperatures 5 < T < 2500 K. Scattering calculations are done in two different ways: direct calculations of quenching cross sections and, alternatively, calculations of the excitation cross sections plus microscopic reversibility. In addition, a symmetrized average-velocity method of Billing is tried. Combination of these methods allows reproducing experiment in a broad range of temperatures. Excellent agreement with experiment is obtained at 400 < T < 2500 K (within 10%), good agreement in the range 100 < T < 400 K (within 25%), and semi-quantitative agreement at 40 < T < 100 K(within a factor of 2). This study provides a stringent test of the mixed quantum/classical theory, because the vibrational quantum in CO molecule is rather large and the quencher is very light (He atom). For heavier quenchers and closer to dissociation limit of the molecule, the mixed quantum/classical theory is expected to work even better.

Probing Radical Pathways In Electrophilic Addition Of Halogens: Classical Vs. Bridged Intermediates, Lisa George, Aimable Kalume, Scott A. Reid

Chemistry Faculty Research and Publications

We examine radical mediated pathways in electrophilic addition to the simplest alkene, ethylene, where the structure of the radical intermediate has been extensively debated. Starting from the π-complex with a dihalogen, C₂H₄⋯I₂, isolated in an inert matrix, we initiate reaction by photolytically cleaving the I₂ bond. We succeed in trapping and spectroscopically interrogating the symmetrically bridged radical complex, which calculations confirm is the global minimum on the C₂H₅I Potential Energy Surface (PES). Consistent with the participation of a bridged intermediate, radical addition preferentially but not exclusively yields the anti …

Spectral Data For "Reactivity Of Acyclic (Pentadienyl)Iron(1+) Cations: Synthetic Studies Directed Toward The Frondosins", Do W. Lee, Rajesh K. Pandey, Sergey V. Lindeman, William A. Donaldson

Natural Products Synthesis via Organoiron Methodology

Spectral data created in the course of the research project. Supports specific findings in "Reactivity of acyclic (pentadienyl)iron(1+) cations: Synthetic studies directed toward the frondosins".

A short, 4-step route to the scaffold of frondosin A and B is reported. The [1-methoxycarbonyl-5-(2′,5′-dimethoxyphenyl)pentadienyl]Fe(CO)₃⁺ cation was prepared in two steps from (methyl 6-oxo-2,4-hexadienoate)Fe(CO)₃. Reaction of this cation with isopropenyl Grignard or cyclohexenyllithium reagents affords (2-alkenyl-5-aryl-1-methoxycarbonyl-3-pentene-1,5-diyl)Fe(CO)₃ along with other addition products. Oxidative decomplexation of these (pentenediyl)iron complexes, utilizing CuCl₂, affords 6-aryl-3-methoxycarbonyl-1,4-cycloheptadienes via the presumed intermediacy of a cis-divinylcyclopropane.

On Pi-Stacking, Ch/Pi, And Halogen Bonding In Halobenzene Clusters: Resonant 2-Photon Ionization Studies Of Chlorobenzene, Lloyd Muzangwa, Silver Nyambo, Brandon Uhler, Scott A. Reid

Chemistry Faculty Research and Publications

Noncovalent interactions such as hydrogen bonding, π-π stacking, CH/π interactions, and halogen bonding play crucial roles in a broad spectrum of chemical and biochemical processes, and can exist in cooperation or competition. Here we report studies of the homoclusters of chlorobenzene, a prototypical system where π-π stacking, CH/π interactions, and halogen bonding interactions may all be present. The electronic spectra of chlorobenzene monomer and clusters (Clbz)_n with n = 1-4 were obtained using resonant 2-photon ionization in the origin region of the S₀–S₁ (ππ*) state of the monomer. The cluster spectra show in all cases a …

On The Electronic Spectroscopy Of The Iso-Polyhalomethanes, Aimable Kalume, Lisa George, Scott A. Reid

Chemistry Faculty Research and Publications

The iso-polyhalomethanes are important reactive intermediates, displaying intense near-UV absorption bands that have been assigned to the S₀ → S₃ transition on the basis of Time-Dependent Density Functional Theory (TDDFT) calculations. In this work, theory and multi-dimensional Franck–Condon (FC) analysis are used to model the electronic spectra of selected iso-polyhalomethanes. The S₀ → S₃ transition approximately corresponds to a π–π^∗ transition on the halocarbocation subunit, which induces significant geometry changes. The calculated multimode FC profiles capture features of the experimental spectra of the matrix-isolated species, and are compared with the results of previous Resonance Raman …

Electronic Communication Across Diamagnetic Metal Bridges: A Homoleptic Gallium(Iii) Complex Of A Redox-Active Diarylamido-Based Ligand And Its Oxidized Derivatives, Brendan J Liddle, Sarath Wanniarachchi, Jeewantha S. Hewage, Sergey Lindeman, Sergey V. Lindeman, James R. Gardinier

Chemistry Faculty Research and Publications

Complexes with cations of the type [Ga(L)₂]ⁿ⁺ where L = bis(4-methyl-2-(1H-pyrazol-1-yl)phenyl)amido and n = 1, 2, 3 have been prepared and structurally characterized. The electronic properties of each were probed by electrochemical and spectroscopic means and were interpreted with the aid of density functional theory (DFT) calculations. The dication, best described as [Ga(L^–)(L⁰)]²⁺, is a Robin-Day class II mixed-valence species. As such, a broad, weak, solvent-dependent intervalence charge transfer (IVCT) band was found in the NIR spectrum in the range 6390–6925 cm^–1, depending on the solvent. Band shape …

Spectroscopic And Computational Studies Of Matrix-Isolated Iso-Cxbr3 (X=F,Cl,Br): Structure, Properties, And Photochemistry Of Substituted Iso-Tribromomethanes, Lisa George, Aimable Kalume, Scott A. Reid, Brian J. Esselman, Robert J. Mcmahon

Chemistry Faculty Research and Publications

Iso-polyhalomethanes are important reactive intermediates in the condensed and gas-phase chemistry of halomethanes. Building upon our recent study of iso-bromoform, in this work the substituted iso-tribromomethanes (iso-CXBr₃; X = F, Cl, Br) were characterized by matrix isolation infrared and UV/Vis spectroscopy, supported by ab initio calculations, to further probe the structure, spectroscopy, properties, and photochemistry of these important intermediates. Selected wavelength laser irradiation of CXBr₃ samples in an inert rare gas (typically Ar; mixing ratio 1:500) held at ∼5 K yielded iso-CXBr₃ (XBrC–Br–Br or Br₂C–Br–X). The observed infrared and UV/Vis absorptions are in excellent …

Photochemical Eilmination Reactions Via Zwitterionic Intermediates Generated By Electrocyclic Ring Closures, Majher Ibna Mannan Sarker

Dissertations (1934 -)

The research focuses on the design of photoremovable protecting groups that can be used to deprotect biological substrates of an organic compound by photolysis. The deprotection of the protecting group via photolysis requires heterolysis of a bond to the substrate. Heterolysis of a C-O or C-S σ-bonds in a zwitterionic intermediate is proposed. The photochemical electrocyclic reactions studied involve acrylanilides, benzothiophene carboxanilides, and N-(9-oxothioxanthenyl) benzothiophene carboxamides. α,β-Unsaturated anilides bearing leaving groups at the allylic position of the α-methylacrylamide group undergo photochemical electrocyclic ring closure with release of leaving group which could occur directly from a photochemically produced zwitterionic intermediate or …

Spectral Characterization Of Cytochromes P450 Active Site And Catalytic Intermediates, Daniel Kaluka

Dissertations (1934 -)

Cytochromes P450 (P450s) have been the subject of intense research for over six decades. Though it is widely accepted that a highly reactive Fe(IV)=O π-cation radical, or the so called compound I, facilitates the oxidation of relatively inert hydrocarbons, spectroscopic characterization of this putative intermediate has eluded detection under turnover conditions, presumably due to its very short lifetime. In this work, chemically inert substrates of P450s have been utilized in a new approach to capture and stabilize this transient intermediate and characterize it with resonance Raman (RR) spectroscopy, which is a well established tool for studying heme proteins. Specifically, perfluorodecanoic …

Syntheses And Electronic Properties Of Rhodium(Iii) Complexes Bearing A Redox-Active Ligand, Sarath Wanniarachchi, Brendan J Liddle, Brandon Kizer, Jeewantha S. Hewage, Sergey V. Lindeman, James R. Gardinier

Chemistry Faculty Research and Publications

A series of rhodium(III) complexes of the redox-active ligand, H(L = bis(4-methyl-2-(1H-pyrazol-1-yl)phenyl)amido), was prepared, and the electronic properties were studied. Thus, heating an ethanol solution of commercial RhCl3·3H2O with H(L) results in the precipitation of insoluble [H(L)]RhCl3, 1. The reaction of a methanol suspension of [H(L)]RhCl3 with NEt4OH causes ligand deprotonation and affords nearly quantitative yields of the soluble, deep-green, title compound (NEt4)[(L)RhCl3]·H2O, 2·H2O. Complex 2·H2O reacts readily with excess pyridine, triethylphosphine, or pyrazine (pyz) to eliminate NEt4Cl and give charge-neutral complexes trans-(L)RhCl2(py), trans-3, trans-(L)RhCl2(PEt3), trans- 4, or trans-(L)RhCl2(pyz), trans-5, where the incoming Lewis base is trans- to the amido …

Chemical Proteomics-Based Analysis Of Off-Target Binding Profiles For Rosiglitazone And Pioglitazone: Clues For Assessing Potential For Cardiotoxicity, Brian R. Hoffmann, Mohamed F. El-Mansy, Daniel S. Sem, Andrew S. Greene

Chemistry Faculty Research and Publications

Drugs exert desired and undesired effects based on their binding interactions with protein target(s) and off-target(s), providing evidence for drug efficacy and toxicity. Pioglitazone and rosiglitazone possess a common functional core, glitazone, which is considered a privileged scaffold upon which to build a drug selective for a given target—in this case, PPARγ. Herein, we report a retrospective analysis of two variants of the glitazone scaffold, pioglitazone and rosiglitazone, in an effort to identify off-target binding events in the rat heart to explain recently reported cardiovascular risk associated with these drugs. Our results suggest that glitazone has affinity for dehydrogenases, consistent …

Structural, Spectroscopic, And Electrochemical Properties Of Nonheme Fe(Ii)-Hydroquinonate Complexes: Synthetic Models Of Hydroquinone Dioxygenases, Amanda E. Baum, Heaweon Park, Denan Wang, Sergey V. Lindeman, Adam T. Fiedler

Chemistry Faculty Research and Publications

Using the tris(3,5-diphenylpyrazol-1-yl)borate (^Ph2Tp) supporting ligand, a series of mono- and dinuclear ferrous complexes containing hydroquinonate (HQate) ligands have been prepared and structurally characterized with X-ray crystallography. The monoiron(II) complexes serve as faithful mimics of the substrate-bound form of hydroquinone dioxygenases (HQDOs) – a family of nonheme Fe enzymes that catalyze the oxidative cleavage of 1,4-dihydroxybenzene units. Reflecting the variety of HQDO substrates, the synthetic complexes feature both mono- and bidentate HQate ligands. The bidentate HQates cleanly provide five-coordinate, high-spin Fe(II) complexes with the general formula [Fe(^Ph2Tp)(HL^X)] (1X), where HL^X is …

Experimental Documentation Of The Structural Consequences Of Hydrogen-Bonding Interactions To The Proximal Cysteine Of A Cytochrome P450, Piotr J. Mak, Yuting Yang, Sangchoul Im, Lucy A. Waskell, James R. Kincaid

Chemistry Faculty Research and Publications

Resonance Raman spectroscopy is used to document, for the first time, a 6 cm−1 decrease of the Fe-S stretch by introducing an H-bond donor into the proximal pocket of a cytochrome P450, which interacts with the key cysteine thiolate axial ligand. The anticipated trans-effect on bound exogenous ligands is also confirmed and evidence is obtained supporting intimate interaction of the new histidyl-imidazole fragment with the heme periphery.

Fe(Ii) Complexes That Mimic The Active Site Structure Of Acetylacetone Dioxygenase: O2 And No Reactivity, Heoweon Park, Michael M. Bittner, Jacob Baus, Sergey V. Lindeman, Adam T. Fiedler

Chemistry Faculty Research and Publications

Acetylacetone dioxygenase (Dke1) is a bacterial enzyme that catalyzes the dioxygen-dependent degradation of β-dicarbonyl compounds. The Dke1 active site contains a nonheme monoiron(II) center facially ligated by three histidine residues (the 3His triad); coordination of the substrate in a bidentate manner provides a five-coordinate site for O₂ binding. Recently, we published the synthesis and characterization of a series of ferrous β-diketonato complexes that faithfully mimic the enzyme–substrate intermediate of Dke1 (Park, H.; Baus, J.S.; Lindeman, S.V.; Fiedler, A.T. Inorg. Chem.2011, 50, 11978–11989). The 3His triad was modeled with three different facially coordinating N3 supporting ligands, and …

The Fe-Type Nitrile Hydratase From Comamonas Testosteroni Ni1 Does Not Require An Activator Accessory Protein For Expression In Escherichia Coli, Misty L. Kuhn, Salette Martinez, Natalie Gumataotao, Uwe Bornscheuer, Dali Liu, Richard C. Holz

Chemistry Faculty Research and Publications

We report herein the functional expression of an Fe-type nitrile hydratase (NHase) without the co-expression of an activator protein or the Escherichia coli chaperone proteins GroES/EL. Soluble protein was obtained when the α- and β-subunit genes of the Fe-type NHase Comamonas testosteroni Ni1 (CtNHase) were synthesized with optimized E. coli codon usage and co-expressed. As a control, the Fe-type NHase from Rhodococcus equi TG328–2 (ReNHase) was expressed with (ReNHase^+Act) and without (ReNHase^−Act) its activator protein, establishing that expression of a fully functional, metallated ReNHase enzyme requires the …