Note: Intro -- Historical Development and Perspectives of the Series -- Metal Ions in Life Sciences. -- Preface to Volume 14 -- The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment -- Contents -- Contributors to Volume 14 -- Titles of Volumes 1-44 in the Metal Ions in Biological Systems Series -- Contents of Volumes in the Metal Ions in Life Sciences Series -- Volume 1 Neurodegenerative Diseases and Metal Ions -- Volume 2 Nickel and Its Surprising Impact in Nature -- Volume 3 The Ubiquitous Roles of Cytochrome P450 Proteins -- Volume 4 Biomineralization. From Nature to Application -- Volume 5 Metallothioneins and Related Chelators -- Volume 6 Metal-Carbon Bonds in Enzymes and Cofactors -- Volume 7 Organometallics in Environment and Toxicology -- Volume 8 Metal Ions in Toxicology: Effects, Interactions, Interdependencies -- Volume 9 Structural and Catalytic Roles of Metal Ions in RNA -- Volume 10 Interplay between Metal Ions and Nucleic Acids -- Volume 11 Cadmium: From Toxicity to Essentiality -- Volume 12 Metallomics and the Cell -- Volume 13 Interrelations between Essential Metal Ions and Human Diseases -- Volume 14 The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment (this book) -- Volume 15 Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases (in press) -- Volume 16 The Alkali Metal Ions: Their Role for Life (in preparation) -- Chapter 1: The Early Earth Atmosphere and Early Life Catalysts -- 1 The Early Earth Atmosphere and Lithosphere -- 1.1 Earth´s Internal Structure -- 2 Catalysts in the Early Earth -- 3 Clays as Possible Catalysts in the Synthesis of Biomolecules -- 4 General Conclusions -- Abbreviations -- References -- Chapter 2: Living on Acetylene. A Primordial Energy Source -- 1 Introduction -- 2 Acetylene -- 2.1 Properties of Acetylene. , 2.2 Sources and Bioavailability of Acetylene on Earth and Other Planets -- 3 Bacteria Living on Acetylene -- 3.1 Pelobacter acetylenicus -- 4 Acetylene Hydratase from Pelobacter acetylenicus -- 4.1 Biochemical and Spectroscopic Properties -- 4.2 Molybdenum-Substituted Enzyme -- 4.3 Crystallization -- 4.4 Structural Overview -- 4.5 Active Site Setup -- 4.6 Site-Directed Mutagenesis -- 4.7 Density Functional Theory Calculations on the Substrate Binding Mode and Amino Acid Protonation States -- 4.8 Towards the Reaction Mechanism -- 5 Conclusions -- Abbreviations and Definitions -- References -- Chapter 3: Carbon Monoxide. Toxic Gas and Fuel for Anaerobes and Aerobes: Carbon Monoxide Dehydrogenases -- 1 Introduction -- 1.1 Chemistry of Carbon Monoxide -- 1.2 Carbon Monoxide in the Biosphere -- 1.2.1 Biological Cycle of Carbon Monoxide -- 1.2.1.1 Sources of Carbon Monoxide -- 1.2.1.2 Removal of Carbon Monoxide -- 1.2.2 Use of Carbon Monoxide under Aerobic and Anaerobic Conditions -- 1.2.2.1 Fates of Carbon Monoxide under Aerobic Conditions -- 1.2.2.2 Fates of Carbon Monoxide under Anaerobic Conditions -- 2 Structure and Function of Carbon Monoxide Dehydrogenases -- 2.1 Cu,Mo-Containing Carbon Monoxide Dehydrogenases -- 2.1.1 Structure of Cu,Mo-Carbon Monoxide Dehydrogenases -- 2.1.2 Spectroscopic Investigations -- 2.1.3 Enzymatic Activity -- 2.1.4 Reaction Mechanism -- 2.2 Monofunctional Ni,Fe-Containing Carbon Monoxide Dehydrogenases -- 2.2.1 Function, Distribution, and Overall Structure -- 2.2.2 Electronic States and Structure of Cluster C -- 2.2.3 Pathways and Channels Involved in Catalysis -- 2.2.4 Inhibited States of Cluster C -- 2.2.5 Mechanism of Reversible Carbon Dioxide Reduction at Cluster C -- 2.3 Bifunctional Ni,Fe-Containing Carbon Monoxide Dehydrogenases -- 2.3.1 Classification and Distribution. , 2.3.2 Structural Characterization of Bacterial CODH/ACS -- 2.3.3 Substrate Binding and Reaction Mechanism -- 2.4 Cu,Mo versus Ni,Fe: Parallels and Differences in Catalytic Strategies -- 3 Concluding Remarks and Future Directions -- Abbreviations -- References -- Chapter 4: Investigations of the Efficient Electrocatalytic Interconversions of Carbon Dioxide and Carbon Monoxide by Nickel-C... -- 1 Direct Carbon Dioxide/Carbon Monoxide Interconversions in Biology -- 2 Nickel-Containing Carbon Monoxide Dehydrogenases -- 3 Protein Film Electrochemistry -- 4 Carbon Monoxide Dehydrogenases as Electrocatalysts -- 4.1 The Electrocatalytic Voltammograms of Class IV Enzymes -- 4.2 The Electrocatalytic Voltammograms of Class III Enzymes -- 5 Potential-Dependent Reactions with Inhibitors -- 5.1 How Class IV Carbon Monoxide Dehydrogenases Respond to Cyanide -- 5.2 How Class IV Carbon Monoxide Dehydrogenases Respond to Cyanate -- 5.3 How Class IV Carbon Monoxide Dehydrogenases Respond to Sulfide and Thiocyanate -- 6 Demonstrations of Technological Significance -- 7 Conclusions -- Abbreviations -- References -- Chapter 5: Understanding and Harnessing Hydrogenases, Biological Dihydrogen Catalysts -- 1 Introduction -- 2 Dihydrogen Cycles and Hydrogenases -- 2.1 The Global Dihydrogen Cycle -- 2.2 Dihydrogen Cycling in Microbial Communities -- 2.3 Solar Dihydrogen Economy -- 2.3.1 Hydrogenase Photoelectrolysis Devices -- 2.3.2 Photosynthetic Dihydrogen -- 3 [NiFe] Hydrogenases -- 3.1 Structure and Function -- 3.1.1 Mechanisms for Dioxygen Tolerance -- 3.1.2 [NiFeSe] Hydrogenases -- 3.2 Biosynthesis -- 4 Nickel-Free Hydrogenases: [FeFe] and [Fe] Enzymes -- 4.1 [FeFe] Hydrogenase Structure and Function -- 4.2 [FeFe] Hydrogenase Biosynthesis -- 4.3 [Fe] Hydrogenases -- 5 Insights into Hydrogenase Mechanism from Small Molecule Mimics -- 6 General Conclusions. , Abbreviations and Definitions -- References -- Chapter 6: Biochemistry of Methyl-Coenzyme M Reductase: The Nickel Metalloenzyme that Catalyzes the Final Step in Synthesis an... -- 1 Introduction -- 1.1 Nickel Enzymes Involved in Metabolism of Environment- and Energy-Relevant Gases -- 1.2 Methyl-Coenzyme M Reductase and Its Involvement in Generation and Utilization of Methane -- 1.3 Ramifications of Methanogenesis in Energy and the Environment -- 1.4 Discoveries Underpinning Recent Studies of Methyl-Coenzyme M Reductase -- 2 Structure and Properties of Methyl-Coenzyme M Reductase and Its Bound Coenzyme F430 -- 2.1 Structure, Properties, and Reactivity of Coenzyme F430 -- 2.2 Structure, Properties, and Reactivity of Methyl-Coenzyme M Reductase -- 3 Redox and Coordination Properties of the Nickel Center in Methyl-Coenzyme M Reductase -- 3.1 Coordination and Oxidation States of the Free F430 Cofactor and Its Pentamethyl Ester Derivative -- 3.2 Coordination and Oxidation States of the Nickel Center -- 4 The Catalytic Mechanism of Methyl-Coenzyme M Reductase -- 5 Summary and Prospects for Future Science and Technology -- Abbreviations -- References -- Chapter 7: Cleaving the N,N Triple Bond: The Transformation of Dinitrogen to Ammonia by Nitrogenases -- 1 Introduction -- 2 The Structural and Biochemical Properties of Mo-Nitrogenase -- 2.1 The Fe Protein and Its Associated Metal Clusters -- 2.1.1 The Polypeptide -- 2.1.2 The [Fe4S4] Cluster -- 2.2 The MoFe Protein and Its Associated Metal Clusters -- 2.2.1 The Polypeptide -- 2.2.2 The P-cluster -- 2.2.3 The FeMoco -- 3 The Catalytic Mechanism of Mo-Nitrogenase -- 3.1 The Thorneley-Lowe Model -- 3.1.1 The Fe Protein Cycle -- 3.1.2 The MoFe Protein Cycle -- 3.2 Further Development and Modifications of the Thorneley-Lowe Model -- 3.2.1 Intermediates of the MoFe Protein Cycle. , 3.2.1.1 The Substrate-Free M4 Intermediate -- 3.2.1.2 The M7 and M8 Intermediates -- 3.2.2 The Reductive Dihydrogen Elimination Mechanism -- 3.2.3 The Alternating Dinitrogen Reduction Pathway -- 4 The Distinct Structural and Catalytic Features of V-Nitrogenase -- 4.1 The Structural Features -- 4.1.1 The Fe Protein -- 4.1.2 The VFe Protein -- 4.2 The Catalytic Features -- 4.2.1 The Reduction of Dinitrogen -- 4.2.2 The Reduction of Carbon Monoxide -- 5 Conclusions -- Abbreviations -- References -- Chapter 8: No Laughing Matter: The Unmaking of the Greenhouse Gas Dinitrogen Monoxide by Nitrous Oxide Reductase -- 1 Introduction: The Biogeochemical Nitrogen Cycle -- 2 Nitrous Oxide: Environmental Effects and Atmospheric Chemistry -- 2.1 Chemical Properties of Dinitrogen Monoxide -- 2.2 Nitrous Oxide, the Greenhouse Effect, and Ozone Depletion -- 2.3 Abiotic and Biotic Sources -- 2.4 Bacterial Denitrification -- 3 Nitrous Oxide Reductase -- 3.1 Anatomy of an Unusual Copper Enzyme -- 3.1.1 Distinct Forms of the Enzyme -- 3.1.2 Three-Dimensional Structures -- 3.2 CuA: More than an Electron Transfer Center -- 3.2.1 Spectroscopic Properties of CuA -- 3.2.2 Three-Dimensional Structure(s) of CuA -- 3.2.3 Unexpected Flexibility: CuA in P. stutzeri Nitrous Oxide Reductase -- 3.3 The Tetranuclear CuZ Center -- 3.3.1 Structural Data on CuZ -- 3.3.2 States of CuZ and Catalytic Properties -- 4 Biogenesis and Assembly of Nitrous Oxide Reductase -- 4.1 The nos Operon -- 4.2 Protein Maturation and CuA Insertion -- 4.3 Assembly of CuZ -- 5 Activation of Nitrous Oxide: The Workings of Nitrous Oxide Reductase -- 5.1 Substrate Access -- 5.2 Gated Electron Transfer -- 5.3 Activation of Nitrous Oxide -- 5.4 The Fate of the Products -- 6 General Conclusions -- Abbreviations and Definitions -- References -- Chapter 9: The Production of Ammonia by Multiheme Cytochromes c. , 1 Introduction.