Nuclear resonance vibrational spectroscopy and electron paramagnetic resonance spectroscopy of 57Fe-enriched [FeFe] hydrogenase indicate stepwise assembly of the H-cluster. by Kuchenreuther, J, Guo, Y, Wang, H, Myers, W, George, S, Boyke, C, Yoda, Y, Alp, E, Zhao, J, Britt, R, Swartz, JR, Cramer, S