Nitrogenases are Nature's catalysts for reduction of dinitrogen to ammonia.  The cofactors responsible for this chemistry are Fe7S10M clusters, where M = Mo, V, or Fe.  The most active of these is the 'FeMo cofactor' (FeMoco).  A decade ago, X-ray crystallography revealed an insterstitial light atom �X� at the center of FeMoco.  Since then, progress in understanding nitrogenase chemistry has been impeded by the inability to definitively identify this atom.  We present evidence from Fe K� X-ray emission (XES) spectroscopy that supports the assignment of X as C. Extensions to the FeV cofactor will be discussed.

Unveiling X: X-ray emission spectroscopy of nitrogenase cofactors

243rd National Meeting (2012)

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