Carr Group


We use a combination of X-ray crystallography, electron microscopy, biophysical methods and biochemistry to investigate how a variety of different enzymes achieve catalysis.

Biological catalysis underpins all cellular processes and is reliant on the activity of many different enzymes, whose functions allow complex chemistry to be performed in water at ambient temperatures. We use a combination of X-ray and neutron diffraction methods, electron microscopy, biophysical and biochemical techniques to investigate how a variety of different enzymes work. Areas of interest include protein-protein and protein-DNA interactions and the structure and function of metalloproteins that active small inorganic molecules (H2, N2, CO, CO2).

We have pioneering a technique for investigating catalysis by metalloenzymes that couples single-crystal Infra-Red spectroscopy with electrochemical control of the redox state of the crystallised protein.  This allows specific intermediates of catalysis to be trapped prior to structure determination, ultimately producing molecular movies detailing exactly how atomic positions change during turnover of these biologically and biotechologically important enzymes.  Proteins currently under investigation include [NiFe]-hydrogenases, CO Dehydrogenase and Nitrogenase.


[NiFe]-Hydrogenases are complex metalloenzymes containing nickel and iron atoms at their active site, which allow bacteria to use hydrogen as an energy source. This is achieved by enzymatic splitting of hydrogen gas into protons and electrons. We use structural biology, electrochemistry and IR spectroscopy (in collaboration with Professor Kylie Vincent, University of Oxford and Dr Philip Ash, University of Leicester) to understand how the enzyme influences the properties of nickel and iron ions bound within the protein in order to split or produce hydrogen. Analysis of variant proteins containing mutated amino acids at the active site of the protein has allowed us to propose a novel mechanism for how [NiFe]-hydrogenases can achieve this and electrochemical poising is providing the most comprehensive understanding of catalysis to date.


Carbon monoxide dehydrogenase catalyses the reversible reduction of CO2 to CO a biotechnologically important reaction for the sequestration of CO2 from the atmosphere and production of CO, an important feedstock for chemical synthesis. The enzyme contains a Nickel-Iron cluster at the active site and we are investigating how the cluster and protein matrix interact to activate gas molecules to allow oxygen addition to CO or abstraction from CO2.


Nitrogen is an essential element for life and the largest reservoir on the planet is atmospheric dinitrogen (N2) a highly inert molecule.  Industrial nitrogen fixation via the Haber-Bosch process requires high temperatures and pressures accounting for 2-3% of global energy consumption.  On the other hand biological nitrogen fixation by nitrogenase converts nitrogen into ammonia, a biologically available form of nitrogen, and employs a highly complex metal cluster containing Iron and molybdenum atoms.  We are using electrochemical poising to observe changes in the cluster during the initial reduction stage, visualise how nitrogen binds and what happens during reduction of the N-N triple bond. 

More recently work in the Carr group has shifted focus to investigate the molecular mechanisms of gas activation and metabolism by metalloproteins.  These proteins convert simple inorganic building blocks such as hydrogen, nitrogen and carbon monoxide into the building blocks of life.  Investigating how the interplay between the metal cofactor and the surrounding protein matrix achieve rates of reaction that are rarely matched by synthetic catalysts is a highly interdisciplinary requiring spectroscopy, electrochemistry and structural biology and  RCaH is the ideal location for such cross-disciplinary science.