Biological methane formation is a microbial process that is catalyzed by microbes called methanogens. Methanogens belong to the third kingdom of life, the Archaea, and are found in most anaerobic environments. Methane is an important and widely used energy source but is also a potent greenhouse gas. The global atmospheric methane burden has doubled over the past 200 years and continues to increase. Methyl Coenzyme M Reductase (MCR) catalyzes the final step in the formation of methane and is a hexameric (homodimer of heterotrimer) enzyme with subunit stochiometry of α2β2γ2. Each dimer binds one molar equivalent of an essential Ni containing cofactor, F₄₃₀. MCR is only active when the Ni is in the +1 redox state, called MCR_red1. Using the most potent inhibitor known so far, bromopropane sulfonate (BPS) (Ki - 50 nM) forms an absorption maximum at 420 nm, called MCR_ps. The absorbtion maxima of MCR_red1 is at 385nm. Studies using BPS analogues of varying chain lengths were used to explore the active site and catalytic mechanism of MCR.