Investigations of the oxygen carriers range from the characterization of natural populations to measurements of tenths of nanometer distances between atoms. The scope is so great that few biologists and biochemists can fully comprehend the primary literature in its entirety. In addition, the findings of the past two or three decades have advanced the field so rapidly that a truly current account is not readily accessible to a general audience. In recognition of the problem a symposium was held and its proceedings published in the American Zoologist in 1980. Although it included several research reports, most of the contributions were intended to summarize then state-of-the-art information on molecular structure and respiratory function at a level that could be understood by biologists and biochemists who are not experts on our subject. Judging from the reprint requests with which the authors were inundated, the assessment of need had been accurate. I believe that the need for an update, which is wholly focused on communication to the general audience, is even greater in 1992. I therefore asked the authors of this volume to address individuals who might otherwise turn in vain to an advanced textbook of physiology or biochemistry. I have, of course, requested a more comprehensive coverage than would be possible in a general text, but one that is not more parochial. Just as textbooks differ vastly in the level at which their subject matter is presented, so the level of non-expertise was conceived differently by the contributors to this volume.

1 Oxygen Carriers as Molecular Models of Allosteric Behavior.- 1 Introduction and Outline.- 2 Properties of Respiratory Proteins.- 3 Features and Properties of Allosteric Proteins.- 4 Derivation of Oxygen-Saturation Functions: The Generating Function.- 5 Oxygen Binding by Human Hemoglobin.- 6 Oxygen Binding by High Molecular Weight Invertebrate Hemoglobins.- 7 Oxygen Binding by Arthropod Hemocyanins.- 8 Oxygen Binding by Molluscan Hemocyanins.- 9 Concluding Remarks.- References.- 2 Plant Hemoglobins.- 1 Introduction.- 2 Distribution and Physiological Function of Plant Hemoglobins.- 3 Structures and Reactions of Plant Hemoglobins.- 4 Biosynthesis and Degradation of Plant Hemoglobins.- References.- 3 Functions of Cytoplasmic Hemoglobins and Myohemerythrin.- 1 Structure.- 2 Function of Cytoplasmic Hemoglobin and Myohemerythrin at High Concentration: Hemoglobin-Facilitated Oxygen Diffusion.- 3 Functions of Cytoplasmic Hemoglobin at Low Concentration: Myoglobin-Mediated Oxidative Phosphorylation.- 4 Hemoglobin as a Terminal Oxidase.- 5 Hemoglobin-Associated Iron.- 6 Oxygen Storage in Large Domains: The Insect Tracheal Organ.- 7 Oxygen Storage in Very Small Domains.- 8 Nerve Hemoglobins.- 9 Nematode and Trematode Hemoglobins.- 10 Hemoglobin-Mediated Sulfide Utilization.- 11 Summary.- 12 Conclusion.- References.- 4 Structures of Red Blood Cell Hemoglobins.- 1 Introduction.- 2 Invertebrate Hemoglobins.- 3 Vertebrate Hemoglobins.- 4 Conclusions.- References.- 5 Respiratory Function of the Red Blood Cell Hemoglobins of Six Animal Phyla.- 1 Introduction.- 2 RBC Distribution, Hematology, and Morphology.- 3 Respiratory Design.- 4 O2 Binding of RBCs and Purified Hb Components.- 5 Respiratory Functions of RBC Hbs.- 6 Evolution of the RBC.- References.- 6 Molecular Structure/Function Relationships of Hemerythrins.- 1 Introduction.- 2 Structure of the Protein.- 3 Structure of the Diiron Site and O2-Binding Properties.- 4 Allosteric Effectors and Cooperativity in O2 Binding.- 5 Comparisons to O2 Binding in Myoglobin/Hemoglobin and Hemocyanin.- 6 Redox Chemistry of the Diiron Site.- 7 An Unexamined Problem: Protein Folding and Iron Site Assembly.- 8 Relationships to Nonheme Diiron Sites in Other Proteins.- References.- 7 Physiological Function of the Hemerythrins.- 1 Introduction.- 2 Respiratory Design of Hemerythrin-Containing Animals.- 3 In Vitro Respiratory Properties.- 4 In Vivo Respiratory Properties.- 5 Physiological Significance of the Temperature Dependence of the Hemerythrins.- 6 Conclusions.- References.- 8 Molecular Structure of the Extracellular Heme Proteins.- 1 Introduction.- 2 Annelid Extracellular Hemoglobins.- 3 Annelid Extracellular Chlorocruorins.- 4 Pogonophore and Vestimentiferan Extracellular Hemoglobins.- 5 Nematode Extracellular Hemoglobins.- 6 Arthropod Extracellular Hemoglobins.- 7 Molluscan Extracellular Hemoglobins.- 8 Biosynthesis of Invertebrate Hemoglobins.- 9 Conclusions.- References.- 9 Properties and Functions of Extracellular Heme Pigments.- 1 Introduction.- 2 Distribution and Localization.- 3 Oxygen-Binding Properties.- 4 Functions of Extracellular Heme Pigments.- 5 Transport, Transfer, and Storage Functions.- 6 Other Functions.- 7 Summary and Conclusion.- References.- 10 Molluscan Hemocyanins: Structure and Function.- 1 Introduction: The Nature and Distribution of Molluscan Hemocyanins.- 2 Structure of the Native Molluscan Hemocyanin Molecule.- 3 Subunits of Molluscan Hemocyanins.- 4 Primary Structure and Evolution of Molluscan Hemocyanins.- 5 The Active Site and Oxygen Binding.- References.- 11 Respiratory Functionof the Molluscan Hemocyanins.- 1 Distribution and Phylogeny of the Molluscan Hemocyanins.- 2 Molecular Size and Structure.- 3 Oxygen-Carrying Capacity of Molluscan Bloods.- 4 Oxygen Equilibrium Properties of Molluscan Hemocyanins.- 5 Physiological Functioning of the Molluscan Hcs.- 6 Summary and Conclusions.- References.- 12 Molecular Structure of the Arthropod Hemocyanins.- 1 Introduction.- 2 The Quaternary Structure.- 3 On the Relationship Between Structure and Function.- 4 Heterogeneity of the Subunits.- 5 Molecular Structure of the Subunit and the Hexamer.- 6 Biosynthesis.- 7 Evolution.- References.- 13 Respiratory Function of Arthropod Hemocyanins.- 1 Introduction.- 2 Hemolymph Oxygen-Binding Properties.- 3 Oxygen Transport: The Functioning of Hemocyanin in Vivo.- 4 Modulation of Hemocyanin O2-Carrying Function.- References.- 14 Structure-Function Relationships of the Ectothermic Vertebrate Hemoglobins.- 1 Introduction.- 2 Hemoglobins of the Agnatha.- 3 Hemoglobin Heterogeneity.- 4 Root Effect Hemoglobins.- 5 Changes in Hemoglobins During Ontogeny.- 6 Methemoglobin.- 7 Summary.- References.- 15 Respiratory Functions of Avian and Mammalian Hemoglobins.- 1 Introduction.- 2 Oxygen Capacity of Blood.- 3 The Affinity of Hemoglobin for Oxygen - Whole Blood.- 4 Cooperativity of Oxygen Binding.- 5 The Bohr Effect in Whole Blood.- 6 Molecular Basis for Differences in Respiratory Properties of Hb.- 7 Modulation of the Respiratory Functions of Hb.- References.