This volume contains the papers presented at the symposium on Biophysics and Physiology of Carbon Dioxide held at Regensburg, April 17-20, 1979. The manuscripts represent the full or even an extended account of the oral presentations. We have decided not to include any part of the discussions which took place after the lectures because this would have led to an undue enlargement of the already substantial volume. The symposium brought together some 60 scientists of various disciplines including biophysicists, chemists, biochemists, physiologists, pharmacologists, as well as clinicians whose research activities are cen tered around the various aspects of the reactions and the regulatory role of CO within the body. 2 In view of the fact that numerous textbooks and Proceedings of Symposia deal expertly with the role of CO in acid-base balance, it 2 was decided not to include this aspect in the present symposium. This holds also for the biochemistry of carboxylation and decarboxylation reactions. Particular emphasis was placed on the following subjects: (1) Chemical reactions of CO in water and facilitated diffusion of CO2 , 2 (2) CO adducts to proteins, in particular hemoglobin, and peptide 2 hormones, (3) structure and function of carbonic anhydrase, (4) CO 2 exchange and carbonic anhydrase activity in respiratory and nonrespi ratory systems. Each section contains at least one introductory paper that presents the current knowledge in a more general framework.

Inhalt
Chemical Reactions of CO2 in Water.- Chemical Reactions of CO2 in Water.- Facilitated Diffusion of CO2.- Facilitation of CO2 Through Layers with a Spatial Distribution of Carbonic Anhydrase.- Facilitated Diffusion of CO2 and Carbonic Anhydrase Activity.- Mechanisms of Facilitated CO2 and H+ Diffusion in Protein Solutions.- The Effect of Diffusion Potentials on Facilitated CO2 Diffusion.- Evidence for Facilitated Transport of CO2 in Muscle Tissue.- Carbamate Reactions of Proteins.- The Binding of CO2 to Human Deoxyhemoglobin: An X-Ray Study Using Low-Salt Crystals.- The Determination of CO2 Bound to Hemoglobin as Carbamate.- Phylogeny and Physiological Significance of Oxygen-Linked CO2 Binding in Hemoglobin.- The Carbamate Reaction with Proteins: Observation by 13C-NMR and Evaluation of Structural Consequences.- The Measurement of the CO2 Hb Binding Curve of Human Hemoglobin by 13C-NMR Spectrometry.- Formation and Physiological Role of Carbamino Adducts of Angiotensin, Bradykinin, and S-Methylglucagon.- Interaction Between Hemoglobins, CO2 and Anions.- The Influence of CO2 on the First Binding Constant of Oxygen to Human Hemoglobin A0.- Carbonic Anhydrase Structure and Function.- Current Concepts of the Mechanism of Action of Carbonic Anhydrase.- Some Structural Aspects of Carbonic Anhydrase.- Primary Structure of Carbonic Anhydrases.- Evolution of Structure and Function in the Carbonic Anhydrase Isozymes of Mammals.- Carbonic Anhydrase Activity in Intact Red Cells as Measured by Means of 18O Exchange Between CO2 and Water.- Crystal Structure of Carbonic Anhydrase.- Kinetics and Mechanistic Implications of CO2 Hydration Activity of Human Erythrocyte Carbonic Anhydrases.- Models for Metal Ion Function and Evolution of the Catalytic Step in Carbonic Anhydrase.-Consequences of Metal Ion Substitutions in Human Carbonic Anhydrase B. A Carbon-13 Nuclear Magnetic Resonance Comparative Study.- Rate-Limiting Steps in the Catalytic Action of Carbonic Anhydrase.- The pH-Independence of Carbonic Anhydrase Activity: Apparent pKa Due to Inhibition by HSO4?.- Role of Buffer in Catalysis of the Hydration of CO2 by Carbonic Anhydrase.- 35CI and 81Br Nuclear Magnetic Resonance Studies of Carbonic Anhydrase.- NMR-Studies of Carbonic Anhydrase.- CO2 Exchange and Carbonic Anhydrase in Respiratory Systems.- Cl?and HCO3? Movements Across the Red Blood Cell Membrane.- The Rate Limiting Event in the Depletion of 18O from CO2 in Red Cell Suspensions.- Kinetics of CO2 Uptake by Red Cells.- Intravascular End-Capillary CO2-H+ Disequilibrium.- Changes in pH and $${{\text{P}}{C{O2}}}$$ with Time in Pulmonary Post-Capillary Blood in Cats.- Kinetics of Acid-Base Parameters of Blood After Respiratory and Metabolic Disturbances.- Carbonic Anhydrase in Lung Tissue.- Pulmonary Capillary Carbonic Anhydrase.- Can CO2 Be Actively Eliminated by the Lungs?.- Experimental Results on Gas-Blood CO2 Equilibrium in Lungs.- Intracapillary CO2 Gradients.- Contribution of Red Cell-Plasma H+ Disequilibrium to Alveolar-Blood $${{\text{P}}{C{O2}}}$$ Differences During Rebreathing.- Diffusion Limitation in Alveolar-Capillary CO2 Transfer in Human Lungs: Experimental Evidence from Rebreathing Equilibration.- Physiological Consequences of Carbonic Anhydrase Inhibition During Rest and Exercise, and on the Bohr Effect.- CO2 Transport and Carbonic Anhydrase in Placenta, Muscle and Calcium-Mobilizing Tissues. Localization of Carbonic Anhydrase.- Placental CO2 Exchange.- Transfer of Bicarbonate in a Hemochorial Placenta.- Recent Developments in Carbonic AnhydraseLocalization: Occurrence of Carbonic Anhydrase in Calcium-Mobilizing Tissues.- Arguments for and Against the Histochemical Carbonic Anhydrase Test.- Activity and Properties of Carbonic Anhydrase in Striated Muscle.- CO2 Transport and Carbonic Anhydrase in Kidney and Brain.- Significance of Carbonic Anhydrase for HCO3? Absorption and H+ Secretion in Renal Tubules.- Formation and Ionic Composition of Cerebrospinal Fluid: The Role of Carbonic Anhydrase.- Autoregulation of CSF H+ Activity.- Transients and Steady State of Chloride-Bicarbonate Relationships of Brain Extra-Cellular Fluid.- List of Participants.