Preface.Radical Mechanisms of S-Adenosylmethionine-Dependent Enzymes,P.A. Frey and S.J. Booker.Molybdopterin from Molybdenum and Tungsten Enzymes,H. Schindelin, C. Kisker, and K.V. Rajagopalan.Pyrroloquinoline Quinone (PQQ) from Methanol Dehydrogenase and Tryptophan Tryptophylquinone (TTQ) from Methylamine Dehydrogenase,V.L. Davidson.Trihydroxyphenylalanine Quinone (TPQ) from Copper Amine Oxidases and Lysyl Tyrosylquinone (LTQ) from Lysyl Oxidase,J.E. Dove and J.P. Klinman.Methylidene-Imidazolone (MIO) from Histidine and Phenylalanine Ammonia-Lyase,B. Langer, M. Langer, and J. Retey.Structural, Redox, and Mechanistic Parameters for Cysteine-Sulfenic Acid Function in Catalysis and Regulation,A. Claiborne, T.C. Mallett, J.I. Yeh, J. Luba, and D. Parsonage.Stable Glycyl Radical from Pyruvate Formate-Lyase and Ribonucleotide Reductase (III),J. Knappe and A.F. Volker Wagner.Tyrosyl Radical Cofactors,R.P. Pesavento and W.A. van der Donk.Posttranslationally Modified Tyrosines from Galactose Oxidase and Cytochrome c Oxidase,M.S. Rogers and D.M. Dooley.Author Index.Subject Index.