About

Dr. Hannah S. Shafaat is a Professor at UCLA with a research focus on understanding how metalloenzymes work, particularly those that catalyze small molecule activation reactions with high efficiency. Her work involves combining protein biochemistry and engineering with bioinorganic techniques such as optical, vibrational, and magnetic spectroscopies, electrochemistry, computational methods, reactivity studies, and crystallography to gain mechanistic insights into processes like hydrogen generation and oxidation, CO2 fixation, carbon-carbon bond formation, and activation of dioxygen within diverse classes of metalloproteins. Her research aims to establish fundamental structure-function relationships that mimic the highly efficient reactivity seen in nature, with applications spanning energy, environment, human health, and origins of life. Hannah S. Shafaat earned her B.S. in Chemistry from Caltech in 2006, where she developed spectroscopic assays related to endospore viability. She completed her Ph.D. at UCSD in 2011, studying amino acid radical intermediates in biological electron transfer reactions using spectroscopy. Her postdoctoral work was conducted at the Max Planck Institute in Germany under Wolfgang Lubitz, focusing on hydrogenase and oxidase enzymes and advanced EPR techniques. She began her independent research career at The Ohio State University in 2013, progressing from Assistant to Full Professor, before joining UCLA as a Professor in 2023. Her contributions have been recognized through numerous awards, including the NIH R35 MIRA Award, Sloan Research Fellowship, and NSF CAREER Award.

Research topics

• Chemistry
• Crystallography
• Photochemistry
• Stereochemistry
• Combinatorial chemistry

Selected publications

• Origin of Red Emission in Protein-Stabilized Copper Nanoparticles: Evidence for Cu ^I -Metallothionein-Like Cluster Formation

  The Journal of Physical Chemistry B · 2026-01-07

  article

  Nanoparticles (NP) produced in or added to biological milieu will spontaneously form a shell composed of biomolecules, most commonly proteins, around the NP core. The explicit interaction of the protein shell with the NP core remains poorly resolved, particularly for NP based on metals essential to life. Red emissive copper nanoclusters (RCuNC) serve as a synthetic model for the Cu0 NP-protein interface, and have been developed as biocompatible sensors, though the mechanism underlying their red emission is still unclear. Herein, we identify that the red emission from RCuNC does not originate from the Cu0 NP but instead from previously unidentified CuI-metallothionine (MT)-like clusters. Emission decay measurements, CuI-quantification assays, native polyacrylamide gel electrophoresis imaging experiments, and direct protein metalation with CuI identify at least two distinct populations of Cu that form during the reduction of CuII in the presence of proteins. Our findings reveal that approximately 47% of the total Cu in the as-prepared bovine serum albumin-stabilized RCuNC is present as CuI. Our results underscore the need for the scrutiny of the assignment of emitting species in copper-treated protein samples prepared under reducing conditions, while revealing the opportunity for the development of protein-based sensors with red-emitting embedded CuI-MT-like clusters.

  PublisherDOI

• Boron-Centered Proton-Coupled Electron Transfer

  ChemRxiv · 2026-02-09

  articleOpen access

  Proton-Coupled Electron Transfer (PCET) has been well-established in transition metal complexes, biomolecules, and organic compounds. In the majority of PCET reagent systems, hydrogen-atom equivalents are toggled predominantly at transition-metal centers or at heteroatomcontaining basic sites, most commonly amines, hydroxyl groups, or phosphines, where welldefined X-H bonds (X = N, O, P, or metal hydrides) provide the thermodynamic and kinetic framework for coupled proton-electron transfer. In this work, we demonstrate that a deliberately designed perfunctionalized redox-active boron cluster ( closo -B 6 Ph 6 2- ) can intrinsically mediate PCET, with the coupled proton and electron transfer events confined exclusively to boron atoms rather than being mediated by metals or heteroatom based functional groups, thereby representing the first unequivocal example of a purely boron-centered PCET process.

  PublisherOA PDFDOI

• A protein-based model of carbon monoxide dehydrogenase exhibits tunable covalency across cluster oxidation and ligand-bound states

  Chemical Science · 2026-01-01

  articleOpen accessSenior author

  A nickel–iron–sulfur cluster model of the CO 2 -fixing enzyme, CODH, has been studied using spectroscopy and computation. The supporting iron–sulfur fragment balances charge and spin from the nickel site across redox states to control reactivity.

  PublisherOA PDFDOI

• Correlating Protein Dynamics and Catalytic Activity of a Model Hydrogenase Using Paramagnetic and Biological Nuclear Magnetic Resonance Spectroscopy

  Journal of the American Chemical Society · 2026-01-06 · 1 citations

  articleSenior authorCorresponding

  Rational catalyst design remains a significant challenge, with electronic structure, steric, and electrostatic effects known to contribute to activity. Recently, dynamics has been recognized as another factor that impacts catalysis, though identifying and predicting these effects have remained out of reach. Nickel-substituted rubredoxin (NiRd), a protein-based mimic of a hydrogenase enzyme, serves as a model catalytic system in which dynamics can be systematically investigated with respect to activity. While over 30 secondary-sphere mutants of NiRd have been shown to be catalytically active, no significant correlation has been observed between the rates and catalytic overpotential or electronic structure, prompting questions about the protein-derived factors that modulate activity. In this work, NMR spectroscopy was used to investigate the roles of substrate accessibility, protein dynamics, and protein stability in controlling catalysis. Significant paramagnetic effects from the nickel center (S = 1) isolate the methylene proton resonances of the metal-coordinating cysteine residues. The sensitivity of resonance positions and line widths to local environment offers an opportunity to study dynamic molecular changes around the metal center with high resolution. Machine learning algorithms were employed to identify correlations between the catalytic activity and the paramagnetic NMR spectra. These analyses revealed spectroscopic features of specific cysteine protons that report on catalytic overpotential and increased turnover rates, which are further supported by the results obtained using high-field NMR techniques. Collectively, these studies indicate the potential for multifrequency NMR techniques to resolve key contributors to catalytic activity and highlight the importance of local and outer-sphere dynamics.

  PublisherDOI

• Modulation of heme peroxo nucleophilicities with axial ligands reveal key insights into the mechanistic landscape of nitric oxide synthase

  Chemical Science · 2025-01-01 · 5 citations

  articleOpen access

  Axial ligation of synthetic heme peroxo adducts result in key geometric and electronic perturbations leading to enhanced reactivities toward bioinspired substrates, as probed utilizing both spectroscopic and theoretical methods.

  PublisherOA PDFDOI

• A semisynthetic, multicofactor artificial metalloenzyme retains independent site activity

  JBIC Journal of Biological Inorganic Chemistry · 2025-02-01 · 1 citations

  articleOpen accessSenior authorCorresponding

  Abstract Native metalloenzymes are unparalleled in their ability to perform efficient small molecule activation reactions, converting simple substrates into complex products. Most of these natural systems possess multiple metallocofactors to facilitate electron transfer or cascade catalysis. While the field of artificial metalloenzymes is growing at a rapid rate, examples of artificial enzymes that leverage two distinct cofactors remain scarce. In this work, we describe a new class of artificial enzymes containing two different metallocofactors, incorporated through bioorthogonal strategies. Nickel-substituted rubredoxin (Ni Rd ), which is a structural and functional mimic of [NiFe] hydrogenases, is used as a scaffold. Incorporation of a synthetic bimetallic inorganic complex based on a macrocyclic biquinazoline ligand (M MBQ ) was accomplished using a novel chelating thioether linker. Neither the structure of the Ni Rd active site nor the M MBQ were altered upon attachment, and each site retained independent redox activity. Electrocatalysis was observed from each site, with the switchability of the system demonstrated through the use of catalytically inert metal centers. This M MBQ –Ni Rd platform offers a new avenue to create multicofactor artificial metalloenzymes in a robust system that can be easily tuned both through modifications to the protein scaffold and the synthetic moiety, with applications for redox catalysis and tandem reactivity. Graphical abstract

  PublisherOA PDFDOI

• Diverse lineages and adaptations of oxygen-adapted hydrogenases

  Trends in Biochemical Sciences · 2025-05-27 · 7 citations

  review
  PublisherDOI

• Isocyanide Ligation Enables Electrochemical Ammonia Formation in a Synthetic Cycle for N2 Fixation

  UNC Libraries · 2025-11-27

  articleOpen access

  Transition-metal-mediated splitting of N₂ to form metal nitride complexes could constitute a key step in electrocatalytic nitrogen fixation, if these nitrides can be electrochemically reduced to ammonia under mild conditions. The envisioned nitrogen fixation cycle involves several steps: N₂ binding to form a dinuclear end-on bridging complex with appropriate electronic structure to cleave the N₂ bridge followed by proton/electron transfer to release ammonia and bind another molecule of N₂. The nitride reduction and N₂ splitting steps in this cycle have differing electronic demands that a catalyst must satisfy. Rhenium systems have had limited success in meeting these demands, and studying them offers an opportunity to learn strategies for modulating reactivity. Here, we report a rhenium system in which the pincer supporting ligand is supplemented by an isocyanide ligand that can accept electron density, facilitating reduction and enabling the protonation/reduction of the nitride to ammonia under mild electrochemical conditions. The incorporation of isocyanide raises the N-H bond dissociation free energy of the first N-H bond by 10 kcal/mol, breaking the usual compensation between p<em>K</em>_a and redox potential; this is attributed to the separation of the protonation site (nitride) and the reduction site (delocalized between Re and isocyanide). Ammonia evolution is accompanied by formation of a terminal N₂ complex, which can be oxidized to yield bridging N₂ complexes including a rare mixed-valent complex. These rhenium species define the steps in a synthetic cycle that converts N₂ to NH₃ through an electrochemical N₂ splitting pathway, and show the utility of a second, tunable supporting ligand for enhancing nitride reactivity.

  PublisherDOI

• Rubredoxin covalently linked to benzo-18-crown-6

  2025-05-29

  dataset
  PublisherDOI

• Architecture, catalysis and regulation of methylthio-alkane reductase for bacterial sulfur acquisition from volatile organic compounds

  Nature Catalysis · 2025-10-23 · 2 citations

  articleOpen access

  Bacteria utilize methylthio-alkane reductase (MAR) to acquire sulfur from volatile organic sulfur compounds. Reductive cleavage of methylthio-ethanol and dimethylsulfide liberates methanethiol for methionine synthesis and concomitantly releases ethylene and methane, respectively. Here we show that the native MAR of Rhodospirillum rubrum is a two-component system composed of a MarH ATP-dependent reductase and a MarDK catalytic core, whose architecture parallels nitrogenase. MarS complexes with MarDK to downregulate MAR activity during cellular sulfate influx, based on chromatographic and activity analyses. MarDK possesses complex metallocofactors resembling, but not identical to, nitrogenase P- and iron-only M-clusters, designated as mar1 and mar2 clusters based on metal, spectroscopic and mutagenesis analyses. They exhibit electronic features similar to the iron-only nitrogenase under turnover and, remarkably, are matured by MarB or nitrogenase NifB, resulting in maturase-dependent activity profiles. Altogether, this suggests a broader scope of reactivity, mechanisms and regulation in microbial metabolism for the nitrogenase-like family of enzymes than previously considered. Insights into the mechanism of methylthio-alkane reductase (MAR)—a nitrogenase-like enzyme essential for growth under sulfate-limited conditions—have remained scarce. Now a cryo-EM structure of MAR from Rhodospirillum rubrum, along with spectroscopic investigations, reveals how it uses complex metallocofactors for catalysis.

  PublisherOA PDFDOI

Recent grants

• Elucidating mechanisms of biological hydrogen conversion through model metalloenzymes

  NSF · $281k · 2024–2026

• CAREER: Metalloenzyme mechanisms probed by resonance Raman spectroscopy

  NSF · $650k · 2015–2021

• Metallobiochemistry of Mn/Fe protein cofactors

  NIH · $2.3M · 2018–2031

• Elucidating mechanisms of biological hydrogen conversion through model metalloenzymes

  NSF · $429k · 2021–2024

Frequent coauthors

• Sean C. Marguet

  The Ohio State University

  23 shared

• Frank Neese

  16 shared

• Wolfgang Lubitz

  15 shared

• Ashlee E. Wertz

  12 shared

• Anastasia C. Manesis

  Northwestern University

  11 shared

• Peter Caravan

  11 shared

• Eric M. Gale

  11 shared

• Caitlyn R. Cobb

  The University of Texas at Austin

  10 shared

Awards & honors

• Excellence in Undergraduate Research Mentoring Award (OSU),…
• Kavli Fellow (Korean-American Kavli Frontiers of Science Sym…
• Ed Stiefel Young Investigator Award (Metals in Biology GRC),…
• National Institutes of Health R35 MIRA Award for New and Ear…
• Alfred P. Sloan Research Fellow in Chemistry, 2018