The soluble methane monooxygenase (sMMO) is a multiprotein complex and one of two enzymes in nature capable of converting methane into methanol. Therefore, the protein and its capabilities are of great interest for fuel conversion technology.
The Q intermediate of methane monooxygenase is particularly important and interesting in the conversion process. Q has the unique ability to oxidize the very strong C-H bond of methane and then introduce an oxygen atom to form methanol. This very basic chemical reaction is not yet well characterized.
A team of scientists led by Prof. Serena DeBeer, director of the department 'Inorganic Spectroscopy' at the MPI CEC, hopes to gain a better understanding of the structure of the Q intermediate and has used X-ray absorption spectroscopy to look more closely at the structure and, in particular, the distance between two iron atoms. The exact naming of the distance can help to determine whether Q has a "diamond" diiron core structure or an open core structure.
Previous EXAFS analyses showed that the two irons of the active site were very close to each other (2.46 Å). Using high-resolution EXAFS spectroscopy, the scientists were now able to determine, without influencing background signals, that there is no evidence of a short Fe-Fe distance, but rather a long 3.4 Å diiron distance, as observed in open synthetic model complexes.
This finding, published in November in JACS, contributes significantly to the understanding of biological methanol production. In addition, Prof. DeBeer's research shows that unwanted background signals contaminated previous data and thus misled analyses. New, ultra-modern EXAFS spectroscopy makes it possible to suppress the interfering background signals. This has broad implications for EXAFS studies on all diluted ferrous samples.
Publication: Cutsail III, G.E., Banerjee, R., Zhou, A., Que, L., Lipscomb, J.D., DeBeer, S. (2018). High-Resolution EXAFS Provides Evidence for a Longer Fe•••Fe Distance in the Q Intermediate of Methane Monooxygenase Journal of American Chemical Society https://doi.org/10.1021/jacs.8b10313