Research Guides

Mechanistic studies of structure and function by EPR Spectroscopy

Research in the Centre for Advanced Electron Spin Resonance, CÆSR, focuses on bridged metal clusters, biophysical distance measurements, transient organic radicals, electron transfer processes, and electron paramagnetic resonance (EPR) instrumentation and methods development, among many other projects from more than 40 groups across the Mathematical, Physical and Life Sciences (MPLS) division and more than 20 groups external to the university.  My first responsibility is to serve as a contact for Electron Spin Resonance, one of six platform technologies of the department, which includes running the CAESR small research facility and CAESR services in Chemistry.  Academic activities of this post involve research collaborations, supervision of Part II, D. Phil and PDRA research, co-authorship of publications and grants, organization of the undergraduate EPR practical, and serving as a reviewer.

Bioinorganic chemistry was my focus of graduate and post-doctoral research, frequently involving novel biomimetic metal complexes, but also in projects on transition metal and f-element complexes that are decidedly non-biological.  High-spin Co(II) and other complexes with unquenched orbital momentum have been an ongoing interest, both as a surrogate of the ubiquitous Zn(II) metalloenzymes and on the side of basic studies in transition metal magnetic properties,  electronic structure, and coordination chemistry. 

Figures. Left to right are rapid-passage Q-band CW-ENDOR of bistrispyrazolylboratecobalt(II) measured at 1.6 Kelvin, an electron spin echo field sweep at D-band of the first photo-excited state (S2) of photosystem II, and a finite integral method calculation of the microwave magnetic field amplitude in a transverse electric mode (011) Ka-band ENDOR resonator.

Departmental Research Themes 

Here are descriptions of work pursued under related Themes.  Almost all projects involve some theory and modeling, often to the end of kinetics, dynamics and mechanism.

1.  Energy and sustainable chemistry
  Following eons of evolution, Nature's catalysts offer benchmarks for small molecule chemistry essential to life and sustainable energy: dinitrogen to ammonia, protons to dihydrogen, and water to dioxygen.  Prior work has been on VFe & MoFe dinitrogenases, the biosynthetic mechanism of the [FeFe] Hydrogenase catalytic cluster and its electronic structure, and on the spin density distributions over substrate oxygen atoms of the Oxygen Evolving Centre (OEC) of Photosystem II.  Present collaborations are on small molecule N2 activation catalysts and [NiFe] Hydrogenase.

2.  Chemistry at the interface with biology and medicine
  Single-crystal structures of native enzymes and their substrates are an essential starting point in drug design.  However, protein dynamics in domain motions and in subunit motions of homooligomeric and heteromeric proteins can be used to generate effective drug targets.  In an ongoing study spanning more than one hundred drug candidates, the most effective compounds make use of this new paradigm, binding to sites that are only available by way of protein dynamics.

3.  Advanced functional materials and interfaces
  Electroluminescence efficiency forms the basis of next generation OLED light sources and display technology that employ Thermally-Activated Delayed Fluorescence (TADF or E-type delayed fluorescence) materials.  While molecules and polymer side-chains in the emitting layer of these devices have relied on heavy metals such as iridium, a new class of TADF molecules has been developed that is organic, utilizing heterocycles and specific structures to modulate their electronic properties.  Research with several groups in the UK and Ireland aims to identify the relevant charge-transfer and local emitter states of these molecules and understand their role in the reverse inter-system crossing (rISC).

4.  Innovative measurement and photon science
  The measurement of electron spin resonance signals is often encumbered in a trade-off between sensitivity and inhomogeneity of radiation over the sample volume, in limited excitation bandwidth to signal width, and more fundamentally, in spin interaction topology.  Building on many years of practical experience in ESR, three approaches pursued to counter these challenges are the use of pulse shaping and probe design, alternative detecting schemes such as optical detection and spin-dependent electrical detection, and computational design of new pulse sequences.

Funding: John Fell Fund (P.I., #0007019), UCB Celltech (CÆSR), Chemistry Dept., Bruker-BioSpin (CÆSR), ERC CoSuN (H. Anderson), and EPSRC (CÆSR)

A full publication list is available (link,Symplectic,ORCID).  (Google h-index 17; 1001 citations)

a. "Magnetic edge states and coherent manipulation of molecular graphene nanoribbons". Michael Slota, Ashok Keerthi, William K. Myers, Evgeny Tretyakov, Martin Baumgarten, Arzhang Ardavan, Hatef Sadeghi, Colin J. Lambert, Akimitsu Narita, Klaus Müllen, and Lapo Bogani, Nature 2018, 557, 691–695.

b. “A Protein Fold Switch Joins the Circadian Oscillator to Clock Output in Cyanobacteria”. Yong-Gang Chang, Susan E. Cohen, Connie Phong, William K. Myers, Yong-Ick Kim, Roger Tseng, Jenny Lin, Li Zhang, Joseph S. Boyd, Yvonne Lee, Shannon Kang, Sheng Li, R. David Britt, Michael J. Rust, Susan S. Golden, Andy LiWang, Science 2015, 349 (6245), 324-328.

c. “The HydG Enzyme Generates an Fe(CO)2(CN) Synthon in the Biosynthesis of [FeFe] Hydrogenase”. Jon M. Kuchenreuther†, William K. Myers†, Daniel L. M. Suess, Troy A. Stich, Vladimir Pelmenschikov, Stacey A. Shiigi, Stephen P. Cramer, James R. Swartz, R. David Britt, Simon J. George, Science 2014, 343, 424-427.

d. “Radical Intermediate in Tyrosine Scission to the CO and CN− Ligands of [FeFe] Hydrogenase”.  Jon M. Kuchenreuther^†, William K. Myers^†, Troy A. Stich, Simon J. George, Yaser NejatyJahromy, James R. Swartz, and R. David Britt, Science 2013, 342, 472-475.

e. “EPR–ENDOR Characterization of (17O, 1H, 2H) Water in Manganese Catalase and Its Relevance to the Oxygen-Evolving Complex of Photosystem II”. Iain L. McConnell, Vladimir M. Grigoryants, Charles P. Scholes, William K. Myers, Ping-Yu Chen, James W. Whittaker, and Gary W. Brudvig, J. Am. Chem. Soc. 2012, 134 (3), 1504–1512