Copper-Dioxygen Coordination Chemistry Relevant to Copper Proteins
Monday March 31st, 4 p.m.
Salle R
ENS site, 24 rue Lhomond
Professor Kenneth D. Karlin
Department of Chemistry
Ira Remsen Chair in Chemistry
213 NCB
Johns Hopkins University
Baltimore, MD 21218 USA
http://sites.krieger.jhu.edu/karlin/
http://chemistry.jhu.edu/
Email: karlin@jhu.edu
Ph: 410-516-8027
Copper ion is a vital constituent of metalloprotein active sites, those supporting the aerobic organisms. Biological roles include electron shuttling/trafficking and the processing of the critical small molecule nitrogen oxides NO, NO2– and N2O, as well as O2 (dioxygen). For the latter, copper proteins participate in O2-transport, oxygenase activity (i.e., O-atom(s) insertion) and O2-reduction to H2O2 or water accompanied by substrate dehydrogenation. Functions include pigment production, neurotransmitter and hormone generation, conversion of methane to methanol, oxidative cleavage of recalcitrant polysaccharides as well as scavenging of reactive oxygen species (ROS). Copper biochemistry encompasses one-electron (e−) redox shuttling within the CuII/CuI oxidation states.
A major theme of our long-term research program has focused on ligand (L) design, systematic ligand variation and the use of cryogenic solution handling, enabling the generation and investigation of (L)CuIn/O2(g) (n = 1, 2) derived species. Through such approaches, one may identify factors such as donor atom type or number, coordination geometry, metal complex redox potential, and second coordination sphere composition, those which significantly contribute to Cu-protein active site structure & generation of reactive intermediates, all providing insights into reaction mechanism(s).
Prior to our research efforts, no synthetically derived well-characterized CuIn-(O2(g)) species existed. Success in this area has come from carefully considered ligand design and application of cryogenic solution handling. Use of tripodal tetradentate N4 ligands leads to the generation of superoxo-copper(II) {(ligand)CuII(O2•–)} complexes and/or peroxo-dicopper(II) analogs which have been characterized structurally/spectroscopically and have been examined with respect to scope of reaction. Binucleating ligands hold two copper(I) ions may undergo reversible O2(g)-binding and/or ‘activation’ of the bound peroxo (O22–) ligand leading to hydroxylation of unactivated arene C–H bonds, chemistry which has relevance to the tyrosinase enzyme reaction mechanism. Study of phenolato-bridged dicopper complexes leads to new kinds of superoxo, peroxo or hydroperoxo dicopper(II) complexes which can be reversibly interconverted with oxidants/reductants and/or acids-bases, thus leading us to elucidate thermodynamic interrelationships. Most recently we described peroxo-dicopper(II) complex nucleophilic oxidative aldehyde deformylation chemistry, a dioxygenase reaction.
Results obtained from the present research presented provides insights into biological copper ion mediated O2-processing and thus also possibly can apply to practical organic oxidation chemistry and/or energy related fuel-cell technologies.
Recent relevant publications:
Karlin, Kenneth D.; Hota, Pradip Kumar; Kim, Bohee; Panda, Sanjib; Phan, Hai “Synthetic Copper-(Di)oxygen Complex Generation and Reactivity Relevant to Copper Protein O2-Processing” Bull. Jpn. Soc. Coord. Chem. 2024, 83, 16-27.
Kim, Bohee.; Karlin, Kenneth D. “Ligand–Copper(I) Primary O2-Adducts: Design, Characterization, and Biological Significance of Cupric–Superoxides” Acc. Chem. Res. 2023, 56, 2197-2212.
Quist, David. A.; Ehudin, Melanie A.; Schaefer, A. W.; Schneider, G. L.; Solomon, Edward I.; Karlin, Kenneth D. “Ligand Identity-Induced Generation of Enhanced Oxidative Hydrogen Atom Transfer Reactivity for a CuII2(O2•−) Complex Driven by Formation of a CuII2(−OOH) Compound with a Strong O−H Bond”. J. Am. Chem. Soc. 2019, 141, 12682.
Quist, David A.; Diaz, Daniel E.; Liu, Jeffrey J.; Karlin, Kenneth D. Activation of dioxygen by copper metalloproteins and insights from model complexes. J. Biol. Inorg. Chem. 2017, 22, 253-288.
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Kenneth D. Karlin is the Ira Remsen Professor of Chemistry at Johns Hopkins University in Baltimore, Maryland, USA. He was educated at Stanford University (cum laude, B.S. 1970) and at Columbia University, New York (Ph.D. 1975; Preceptor, Stephen J. Lippard). He was a N.A.T.O. postdoctoral fellow at Cambridge University in England, before being appointed Assistant Professor of Chemistry at the State University of New York at Albany (SUNY Albany) in 1977. He moved to The Johns Hopkins University as Professor in 1990, where he was appointed as Ira Remsen Chair in Chemistry in 1999. He (recently) led the Johns Hopkins University Chemistry department, serving as Chair from 2014-1017. Dr. Karlin served as Editor-in-Chief of Progress in Inorganic Chemistry (John Wiley & Sons) from 1992-2018 (Volumes 41-59) and has throughout his career has served on various journal Editorial or Advisory Boards. He also has served in advisory or administrative positions with the Society for Biological Inorganic Chemistry (SBIC), the Petroleum Research Fund (PRF) (of the American Chemical Society (ACS)) and the Division of Inorganic Chemistry (DIC) of the ACS, most recently as 2013 DIC Chair (elected)). He is also a Fellow of the American Association for the Advancement of Science and was elected as an ACS Fellow in 2014. For additional research accomplishments/recognitions, he won a 2009 ACS National Award, the F. Albert Cotton Award in Synthetic Inorganic Chemistry. Most recently he was announced as the 2021 winner of the ACS Award for Distinguished Service in the Advancement of Inorganic Chemistry, a recognition for a career full of outstanding research, as well as service to the (bio)inorganic chemistry community. Other recognitions include the 2019 KAIST Distinguished Lectureship Award for 2019 (Dajeon, Korea). The 10th Sunney Chan Lectureship (2014, Academia Sinica, Taiwan), the Maryland Chemistry of the Year Award (2011) and the ACS Sierra Nevada Distinguished Chemist Award (2009). Dr. Karlin has been Organizer/Chair of a number of international meetings on copper and/or bioinorganic chemistry (2017, 2005, 1992, 1984, 1982), the 1998 Metals in Biology Gordon Research Conference (elected as Chair) and the 1989 International Conference on Bioinorganic Chemistry (ICBIC-4; ~ 750 participants). In the bioinorganic chemistry realm, he has served in various capacities for the Society of Biological Inorganic Chemistry (SBIC), as Treasurer and for 16 years was Chair of the SBIC’s International Organizing Committee, the body that oversees the series of biennial ICBIC meetings. Dr. Karlin’s bioinorganic research focuses on the design, synthesis and study of coordination complexes whose chemistry is relevant to biological processes, mainly metalloenzyme active site chemistry, involving copper and/or heme (porphyrin-iron) complexes and their chemistry with molecular oxygen, its reduced derivatives, and nitrogen oxide compounds. He has published over 380 papers in peer-reviewed journals.