There can hardly be any doubt that radiation will continue to be an im­ portant factor in our lives. Present and future advances in atomic tech­ nology urgently require further work on research and development in the field of radiation biology if the maximum benefit is to be obtained at minimal risk from the various kinds of radiation that form a major by­ product of nuclear processes. Consequently, it is also necessary to prepare students and younger scientists for doing such work. The present book originates from teaching experience gained in lectures, seminars, and discussion groups started by the undersigned in 1957 and more recently held together with Drs. Dertinger and Jung. The friendly comments given to the German edition made us feel that it might be worth­ while to put the results of our efforts at the disposal of those to whom English is more familiar. In agreement with the view, based on well-known facts, that most if not aIl of the more striking practical achievements have resulted from patient and careful investigations into some basic problem, the book aims at introducing the reader to the methods of thought and experiment used in molecular radiation biology as weIl as to the results obtained thereby.

Inhalt

1. Introduction.- 1.1. Historical Survey.- 1.2. Dose-Response Curves and Special Aspects of Radiation Action.- 1.3. The Temporal Stages of Radiation Action.- 1.4. The Significance of Molecular Radiation Biology.- 1.5. An Introduction to Molecular Radiation Biology.- References.- 2. The Hit Theory.- 2.1. Basic Concepts.- 2.2. Single and Multiple Hit Phenomena.- 2.3. Dose-Response Curves of Multiple Target Systems.- 2.4. The Influence of Biological Variability on the Form of Dose-Response Curves.- 2.5. The "Relative Steepness" of the Dose-Response Curve.- 2.6. Possibilities of Deception by Single-Hit Curves.- References.- 3. The Stochastics of the Action of Radiation.- 3.1. Kinetic Interpretation of the Dose-Response Curve.- 3.2. Multi-Hit Curves.- 3.3. Reverse Processes.- 3.4. A Formalistic Description of Dose-Response Curves.- 3.5. Dose-Response Curves of Colony Formation.- References.- 4. Primary Processes of Energy Absorption.- 4.1. X- and Gamma-Radiation.- 4.2. Neutrons.- 4.3. Charged Particles.- 4.4. Uptake of Energy by Molecules.- 4.5. The Energy Distribution of Secondary Electrons.- 4.6. Energy Deposited per Primary Interaction.- References.- 5. Target Theory and Action Cross Section.- 5.1. Establishment of a Rigid Concept of a "Hit".- 5.2. Target Theory.- 5.3. Theory of the Action Cross Section.- 5.4. Relative Biological Effectiveness.- References.- 6. Direct and Indirect Action of Radiation.- 6.1. The Direct Effect.- 6.2. Indirect Effect in Solutions.- 6.3. Indirect Effect in Cells.- 6.4. Indirect Effect in the Dry State.- 6.5. Protective and Sensitizing Agents.- References.- 7. The Temperature Effect.- 7.1. Experimental Observations.- 7.2. Temperature Effect and the Indirect Action of Radiation..- 7.3. LET-Dependence of the Temperature Effect.- 7.4. The "Thermal Spike" Model.- References.- 8. The Oxygen Effect.- 8.1. The Oxygen Effect in Macromolecules.- 8.2. An Oxygen Effect Hypothesis.- 8.3. The Oxygen Effect in Bacteria.- 8.4. Oxygen Effect and LET.- References.- 9. The Action of Radiation on Enzymes: The Example of Ribonuclease.- 9.1. Structure and Function of Ribonuclease.- 9.2. Inactivation Kinetics.- 9.3. Radiation-Induced Radicals.- 9.4. Changes in Irradiated Enzyme Molecules.- 9.5. Separation and Identification of Irradiation Products.- 9.6. Amino Acid Analysis.- 9.7. Mechanisms of Inactivation.- References.- 10. Physico-Chemical Changes in Irradiated Nucleic Acids.- 10.1. The Structure of DNA.- 10.2. Radiation-Induced Radicals.- 10.3. Chemical Changes in Irradiated DNA.- 10.4. Breaks in the Polynucleotide Chains.- 10.5. Intermolecular Cross-Linking.- 10.6. Rupture of Hydrogen Bonds.- References.- 11. Inactivation of Nucleic Acid Functions.- 11.1. Functions of Nucleic Acids.- 11.2. Infectivity.- 11.3. Transformation.- 11.4. Priming Activity of DNA.- 11.5. Enzyme Induction.- 11.6. DNA-mRNA Hybrids.- 11.7. Translation.- References.- 12. The Action of Radiation on Viruses.- 12.1. Basic Properties of Viruses.- 12.2. Inactivation of Viruses containing Single-Stranded Nucleic Acids.- 12.3. Inactivation of Viruses containing Double-Stranded DNA.- 12.4. Repair of Radiation Damage in Viral DNA.- 12.5. BU Effect.- References.- 13. The Action of Radiation on Bacteria.- 13.1. Some Basic Properties of Bacteria.- 13.2. Inactivation of Bacteria.- 13.3. Bacterial DNA as the Critical Target.- 13.4. Repair of UV Damage.- 13.5. Repair of Damage caused by Ionizing Radiation.- 13.6. Genetic Control of Repair in Bacterium E. coli.- 13.7. Micrococcus Radiodurans.- References.- 14. Radiation Sensitivity and Biological Complexity.- 14.1. Attempts at a Systematic Approach.- 14.2. What is Radiation Sensitivity?.- References.