Prof. Dr. Serena DeBeer | |
---|---|
Born | 1973 |
Nationality | American |
Other names | Serena DeBeer George |
Education | Southwestern University, TX B.S. Chemistry (1995) Stanford University Ph.D. Chemistry (2002) |
Known for | X-ray spectroscopy nitrogenase photosystem II hydrogenase Methane monooxygenase |
Scientific career | |
Fields | Chemistry |
Institutions | SSRL SLAC Stanford University (2001–2009) Cornell University (2009-present) Ruhr University Bochum (2014–present) Max Planck Institute for Chemical Energy Conversion (2011–present) |
Doctoral advisor | Edward I. Solomon Keith O. Hodgson |
Serena DeBeer (born 1973) is an American chemist. She is currently a W3-Professor and the director at the Max Planck Institute for Chemical Energy Conversion in Muelheim an der Ruhr, Germany, where she heads the Department of Inorganic Spectroscopy. Her expertise lies in the application and development of X-ray based spectroscopic methods as probes of electronic structure in biological and chemical catalysis.
Serena DeBeer studied at Southwestern University, Georgetown, Texas (US), where she completed her bachelor program in chemistry, with minor in mathematics in 1995 (with honors). She received her doctorate from Stanford University in 2002, working under the guidance of Edward I. Solomon and Keith O. Hodgson. She then moved to SLAC National Accelerator Laboratory, where she worked first as a beamline scientist (2001–2003) at the Stanford Synchrotron Radiation Laboratory, and later as staff scientist (2003–2009). In the Fall of 2009, she relocated to Cornell University in Ithaca, NY (USA), where she accepted a faculty position as assistant professor at the department of chemistry and chemical biology. [1] In the Summer of 2011, she moved to Germany and started to work as a W2-Professor and research group leader at the Max Planck Institute for Bioinorganic Chemistry (since 2012 Max Planck Institute for Chemical Energy Conversion, MPI CEC) in Mülheim an der Ruhr, Germany. Since 2012 she has held the position of an adjunct professor at Cornell University as well as an honorary faculty position at Ruhr University Bochum since 2014. [2] DeBeer headed the research group "X-ray Spectroscopy" at MPI CEC until 2017 when she was appointed director at this institute and promoted to a W3-Professor. Currently she leads the department of "Inorganic Spectroscopy" [3] at MPI CEC. Additionally, she is the group leader of the PINK beamline [4] project at the Energy and Materials In-Situ Laboratory [5] at the Helmholtz Zentrum Berlin, Germany. Since 2024, Serena has held an honorary faculty position at University Duisburg-Essen. [6]
Research in the DeBeer group focuses on answering fundamental questions in energy research. Namely, how does one reversibly store and release energy from chemical bonds using earth abundant transition metals? And how is this done most efficiently? Her research group studies homogeneous, heterogeneous and biological catalysts in order to answer these questions, with a primary focus on enzymatic catalysis. She is an expert in the application of advanced X-ray spectroscopy to understand catalytic transformations.
A strong focus of her research is to study the enzyme that is responsible for the conversion of dinitrogen (N2) to ammonia (NH3)—Nitrogenase. Serena DeBeer and her group study this remarkable system comprising a FeMo cofactor (FeMoco) as its active site, and structural model complexes utilizing high-resolution X-ray absorption (XAS) and X-ray emission spectroscopy (XES). Through this work, great progress has been made in understanding the structure of this active site. A key contribution was a spectroscopic identification of the central atom in the active site as a carbide. [7] Moreover, the application of high-resolution XAS spectroscopy supported with theoretical calculations, allowed her group to succeed in the assignment of the oxidation state of the Mo atom in the FeMoco as Mo(III). [8] This study was followed up later with the experimental evidence of a non-Hund spin configuration at the Mo atom by means of X-ray Magnetic Circular Dichroism (XMCD) spectroscopy. [9] Another approach in this field concerns comparative studies of different forms of nitrogenase enzymes with FeMoco and FeVco active sites, [10] Selenium-incorporated FeMoco, [11] as well as spectroscopic characterization of the first intermediate state of the nitrogenase catalytic cycle (E1). [12] [13]
Another important chemical conversion studied by her group is the catalytic oxidation of methane to methanol. Nature utilizes a group of enzymes called methane monooxygenase (MMOs). The active site of this enzyme that enables the cleavage of the C-H of methane is a dinuclear Fe(IV) intermediate Q found in the hydroxylase protein (MMOH) of MMO. Spectroscopic studies in the DeBeer group have provided new insights into the structure of this diiron complex. Through applications of advanced X-ray spectroscopic studies like high-resolution XAS they characterized the key intermediate in biological methane oxidation as an open-core diiron structure (with FeIV=O motif). [14] Additional EXAFS studies confirmed this finding by showing no evidence for a short Fe-Fe distance but rather a long diiron distance consistent with an open-core structure. [15]
Recent work of DeBeer's group has focused on developing the full information content of various X-ray spectroscopic methods and their application to biological catalysts.
Among these methods are:
In this method (also known as VtC XES = Valence-to-Core X-ray Emission Spectroscopy), one monitors the resultant fluorescence after a valence electron refills the ionized metal 1s core hole. As such, valence XES spectra provide a map of ligand ionization energies, and provides information on both ligand identity and protonation state. A prominent application of this method its use to identify the central carbon atom in FeMo cofactor of Nitrogenase (see section Nitrogenase). [7]
The DeBeer group is actively involved in the development and application of RXES/RIXS based methods in both the hard and soft X-ray regime. These include 1s-Valence RIXS as a means to obtain ligand-selective XAS [16] and 2p3d RIXS as a means to map out the d-d excitations. [17] [18] [19] [20] [21] [22]
This method has been extensively used in solid-state materials, to determine the magnetic properties. Past applications to (bio-)inorganic or protein systems were lacking proper qualitative and quantitative interpretations. DeBeer's group expanded the information that can be obtained from XMCD of covalent systems. [23] To date, this been the only one method able to provide evidence for the proposed non-Hund configuration at the Mo atom in Nitrogenase [9] (see section Nitrogeanse).
The group of Serena DeBeer in collaboration with the group of Prof. Birgit Kangießer at TU Berlin, developed an in-house dispersive X-ray Emission Spectroscopy (XES) setup. The setup that utilizes a laboratory X‑ray source (Metal Jet) in combination with a von Hamos full cylinder optic with Highly Annealed Pyrolytic Graphite (HAPG) crystal and a CCD detector. This allows obtaining spectra in the 2.4-9 keV range. Moreover, this spectrometer is an alternative to synchrotron-based beamlines for concentrated samples. [24]
The DeBeer group is also leading the development of the PINK beamline [4] at the Energy Materials In-situ Laboratory [5] at the Helmholtz Zentrum Berlin. Dr. Sergey Peredkov is the lead designer and instrument scientist for this project. This beamline operates in 2-10 keV energy regime, either in a “pink” beam mode with multilayer mirror or with monochromatic beam (by addition of a double crystal monochromator). The beamline is presently in a commissioning phase.
Nitrogenases are enzymes (EC 1.18.6.1EC 1.19.6.1) that are produced by certain bacteria, such as cyanobacteria (blue-green bacteria) and rhizobacteria. These enzymes are responsible for the reduction of nitrogen (N2) to ammonia (NH3). Nitrogenases are the only family of enzymes known to catalyze this reaction, which is a step in the process of nitrogen fixation. Nitrogen fixation is required for all forms of life, with nitrogen being essential for the biosynthesis of molecules (nucleotides, amino acids) that create plants, animals and other organisms. They are encoded by the Nif genes or homologs. They are related to protochlorophyllide reductase.
The Max Planck Institute for Chemical Energy Conversion is a research institute of the Max Planck Society. It is located in the German town of Mülheim.
Methane monooxygenase (MMO) is an enzyme capable of oxidizing the C-H bond in methane as well as other alkanes. Methane monooxygenase belongs to the class of oxidoreductase enzymes.
In chemistry, a (redox) non-innocent ligand is a ligand in a metal complex where the oxidation state is not clear. Typically, complexes containing non-innocent ligands are redox active at mild potentials. The concept assumes that redox reactions in metal complexes are either metal or ligand localized, which is a simplification, albeit a useful one.
FeMoco (FeMo cofactor) is the primary cofactor of nitrogenase. Nitrogenase is the enzyme that catalyzes the conversion of atmospheric nitrogen molecules N2 into ammonia (NH3) through the process known as nitrogen fixation. Because it contains iron and molybdenum, the cofactor is called FeMoco. Its stoichiometry is Fe7MoS9C.
Abhik Ghosh is an Indian inorganic chemist and materials scientist and a professor of chemistry at UiT – The Arctic University of Norway in Tromsø, Norway.
Lawrence Que Jr. is a chemist who specializes in bioinorganic chemistry and is a Regents Professor at the University of Minnesota, Twin Cities. He received the 2017 American Chemical Society (ACS) Award in Inorganic Chemistry for his contributions to the field., and the 2008 ACS Alfred Bader Award in Bioinorganic Chemistry.
Karl Wieghardt is a German inorganic chemist and emeritus director of the Max Planck Institute for Chemical Energy Conversion in Mülheim. He was active in the preparation and detailed characterization of models for iron and manganese metalloenzymes, metal complexes of noninnocent ligands, and magnetic interactions in polynuclear metal complexes.
Julia A. Kovacs is an American chemist specializing in bioinorganic chemistry. She is professor of chemistry at the University of Washington. Her research involves synthesizing small-molecule mimics of the active sites of metalloproteins, in order to investigate how cysteinates influence the function of non-heme iron enzymes, and the mechanism of the oxygen-evolving complex (OEC).
An oxyhydride is a mixed anion compound containing both oxide O2− and hydride ions H−. These compounds may be unexpected as the hydrogen and oxygen could be expected to react to form water. But if the metals making up the cations are electropositive enough, and the conditions are reducing enough, solid materials can be made that combine hydrogen and oxygen in the negative ion role.
The selenide iodides are chemical compounds that contain both selenide ions (Se2−) and iodide ions (I−) and one or metal atoms. They are in the class of mixed anion compounds or chalcogenide halides.
The iodate fluorides are chemical compounds which contain both iodate and fluoride anions (IO3− and F−). In these compounds fluorine is not bound to iodine as it is in fluoroiodates.
Borate sulfides are chemical mixed anion compounds that contain any kind of borate and sulfide ions. They are distinct from thioborates in which sulfur atoms replace oxygen in borates. There are also analogous borate selenides, with selenium ions instead of sulfur.
The borate bromides are mixed anion compounds that contain borate and bromide anions. They are in the borate halide family of compounds which also includes borate fluorides, borate chlorides, and borate iodides.
Connie C. Lu is a Taiwanese-American inorganic chemist and a professor of chemistry at the University of Bonn. She was previously a professor of chemistry at the University of Minnesota, Twin Cities. Lu's research focuses on the synthesis of novel bimetallic coordination complexes, as well as metal-organic frameworks. These molecules and materials are investigated for the catalytic conversion of small molecules like as N2 and CO2 into value-added chemicals like ammonia and methanol. Lu is the recipient of multiple awards for her research, including the National Science Foundation CAREER Award and the Sloan Research Fellowship in 2013, and an Early Career Award from the University of Minnesota's Initiative for Renewable Energy and the Environment in 2010.
Selenogallates are chemical compounds which contain anionic units of selenium connected to gallium. They can be considered as gallates where selenium substitutes for oxygen. Similar compounds include the thiogallates and selenostannates. They are in the category of chalcogenotrielates or more broadly chalcogenometallates.
Pentaphenylantimony is an organoantimony compound containing five phenyl groups attached to one antimony atom. It has formula Sb(C6H5)5 (or SbPh5).
Inverted ligand field theory (ILFT) describes a phenomenon in the bonding of coordination complexes where the lowest unoccupied molecular orbital is primarily of ligand character. This is contrary to the traditional ligand field theory or crystal field theory picture and arises from the breaking down of the assumption that in organometallic complexes, ligands are more electronegative and have frontier orbitals below those of the d orbitals of electropositive metals. Towards the right of the d-block, when approaching the transition-metal–main group boundary, the d orbitals become more core-like, making their cations more electronegative. This decreases their energies and eventually arrives at a point where they are lower in energy than the ligand frontier orbitals. Here the ligand field inverts so that the bonding orbitals are more metal-based, and antibonding orbitals more ligand-based. The relative arrangement of the d orbitals are also inverted in complexes displaying this inverted ligand field.
Zirconium acetate usually refers to the chemical formula Zr6O4(OH)4(O2CCH3)12. It forms by the reaction of zirconyl chloride and acetate. Claims of Zr(O2CCH3)4 have been superseded by experiments using X-ray crystallography.
An oxalate chloride or oxalato chloride is a mixed anion compound contains both oxalate and chloride anions.