“Computational Insights into the Radical Generation Steps in B12-dependent Methylmalonyl-CoA Mutase” Renata A. Kwiecien, Ilja V. Khavrutskii, Djamaladdin G. Musaev, Keiji Morokuma, Ruma Banerjee, Piotr Paneth, J. Am. Chem. Soc. 128, 1287-92 (2006)