Effects of Ionizing Radiation on DNA

This publication presents the culmination of collaborative effort between specialists in the wide range of disciplines concerned with the effects of ionizing radiations on nucleic acids. The authors belong to a group formed under the aegis of the Com­ mission of the European Communities some eight years ago with the object of facilitating the exchange of ideas and inforrration between European scientists working in this field. The Commission'S aim was not to replace traditional information channels, but to strengthen the various links between the scien­ tists in the group, as if they were working together in a single team. In addition to the annual meetings of the group, contact was maintained by individual visits, exchanges of young scientists, experiments using mutual equipment, and the regular publication of a Newsletter, mainly to announce the availability of preprints. Bruxelles, December 1977 A. J. Bertinchamps Commission of the European Communities. Preface Mankind today is faced with a choice of cardinal importance, namely, deciding on the source and quantity of energy to be made available for tomorrow's world. If, as is probable, the energy is to be mainly of nuclear origin, we must expect a marked ex­ pansion of the nuclear industry, which could well become the world's leading industry in the not-too-distant future. This would carry with it the problems caused by the presence of enor­ mous quantities of radioactivity, despite the stringent precau­ tions taken to date and those to be taken in future.

Section I: Physical Aspects.- 1 Structure and Electronic Properties of DNA.- 1.1 Nomenclature and Primary Structure of DNA.- 1.2 Dimensions and Conformations.- 1.2.1 The Bases.- 1.2.2 The Nucleosides and Nucleotides.- 1.2.3 DNA.- 1.3 Electronic Properties.- 1.3.1 Molecular Orbital Calculations.- 1.3.2 Absorption Spectra.- 1.4 Interactions.- 1.4.1 In-Plane Interactions: The Hydrogen Bonds.- 1.4.2 Vertical Associations: The Stacking of the Bases.- 1.4.3 The Role of the Sugar-Phosphate Backbone.- 1.4.4 The Stability of the DNA Helix.- 1.4.5 Interactions with Aromatic Molecules.- 2 Interaction of Ionizing Radiation with Matter.- 2.1 Introduction.- 2.2 Ionizing Radiation.- 2.3 Degradation Spectra and Linear Energy Transfer (LET).- 2.4 Primary Processes and Primary Products.- 2.5 Activation Spectra.- 2.6 Superexcited States.- 2.7 Inner-Shell Ionizations.- 2.8 Slow Particles.- 2.9 Direct and Indirect Effects. Energy Transfer.- 2.10 Radiation Yield. G-Value.- 3 Structure of Radicals from Nucleic Acid Constituents.- 3.1 Introduction.- 3.2 Base Radicals.- 3.2.1 Hydrogen Addition to Purines.- 3.2.2 Hydrogen Addition to Pyrimidines.- 3.2.2.1 5-yl Radicals.- 3.2.2.2 6-yl Radicals.- 3.2.2.3 >?-OH Radicals.- 3.2.3 Hydrogen-Abstraction Radicals.- 3.2.3.1 Abstraction from Pyrimidine Rings.- 3.2.3.2 Abstraction from Substituent Groups to Pyrimidines and Purines.- 3.2.4 Molecular Ion Radicals.- 3.3 Sugar-Phosphate Backbone Radicals.- 3.4 Molecular Orbital Calculations.- 3.5 Radical Formation Mechanisms.- 4 Structure of Radicals from Nucleic Acids.- 4.1 Frozen Solution and Dry State.- 4.1.1 Radiolysis of DNA in Frozen Solution.- 4.1.2 Radicals from Solid Nucleic Acids.- 4.2 Oriented Fibers.- 4.2.1 The Wet Spinning Method.- 4.2.2 ESR Results.- 5 Radical Yields.- 5.1 General Aspects.- 5.2 Yields in Constituents.- 5.2.1 Solid Bases, Nucleosides and Nucleotides.- 5.2.2 Influence of Environmental, Parameters.- 5.2.2.1 Temperature.- 5.2.2.2 Crystallinity.- 5.2.2.3 Glasses.- 5.3 Yields in Nucleic Acids.- 5.3.1 Influence of Environmental Parameters.- 5.3.1.1 Effect of Moisture Content.- 5.3.1.2 Effect of Molecular Weight.- 5.3.1.3 Yields at Room Temperature.- 5.3.1.4 Effect of Temperature.- 5.3.1.5 Glasses 9.- 5.3.2 Comparison with Yields in Constituents.- 6 Radiomimetic Radical Production.- 6.1 Introduction.- 6.2 Interaction with H-Atoms and OH-Radicals.- 6.2.1 Addition and Abstraction Reactions with Nucleic Acid Bases and Sugars.- 6.2.2 Reactions with Nucleic Acids.- 6.3 Reaction with Electrons.- 6.3.1 ESR Characteristics of the Pyrimidine and Purine Anion Radicals.- 6.3.1.1 Pyrimidine Derivatives.- 6.3.1.2 Purine Derivatives.- 6.3.2 Conversion of the Anion Radicals.- 6.3.2.1 Pyrimidine Base Anions as Precursors of H-Addition Radicals.- 6.3.2.2 Dehalogenation Radicals in 5-Halouracils.- 6.3.2.3 Protonation Reactions of Purine Anions.- 6.4 Interaction with Excited Inert Gases.- 6.4.1 Purine and Pyrimidine Derivatives.- 6.4.2 DNA.- 6.4.3 Mechanisms of Radical Formation.- 7 Transfer Phenomena.- 7.1 Introduction.- 7.2 Substituent Effects.- 7.2.1 Barbituric Acid and Derivatives.- 7.2.2 5-Halogen-Substituted Uracil Bases and Nucleosides.- 7.3 Electron Transfer in ?-Irradiated DNA.- 7.3.1 Preliminary ESR Experiments on ?-Irradiated DNA.- 7.3.2 Mechanical Mixtures and Molecular Complexes of DNA Nucleotides.- 7.3.3 A Working Hypothesis for Internucleo-tide Spin-Transfer Processes.- 7.3.4 Other Examples of Intermolecular Spin-Transfer Processes.- 7.3.5 Formal Analysis of ESR Spectra of Dry DNA.- 7.4 Photosensitization by Dyes in Frozen Solutions.- 7.4.1 Nature of the Photosensitizers.- 7.4.2 Free Radicals Induced in Nucleotides.- 7.4.2.1 Description and Interpretation of the ESR Spectra.- 7.4.2.2 Mechanism of Radical Formation.- 7.4.2.3 Influence of Oxygen.- 7.4.2.4 Influence of the Relative Molar Concentration of Dye and Substrate.- 7.4.2.5 Influence of Dye Aggregation.- 7.4.3 Free Radicals Induced in DNA.- 7.4.3.1 Description and Interpretation of the ESR Spectra.- 7.4.3.2 Mechanism of Formation: Anionic Stage.- 7.4.3.3 Quantitative Influence of Oxygejn and Ionic Strength.- 7.4.4 General Conclusions.- References.- Section II: Chemical Aspects.- 1 Primary Events in the Radiolysis of Aqueous Solutions of Nucleic Acids and Related Substances.- 1.1 Reactive Species in Irradiated Aqueous Systems.- 1.2 Rates of Reaction with the Primary Species.- 1.3 Intermediates in the Radiolysis of Aqueous Solutions of Nucleic Acids and Their Components.- 1.3.1 Reaction with Hydroxyl Radicals.- 1.3.1.1 Pyrimidines.- 1.3.1.2 Purines.- 1.3.1.3 Nucleosides, Nucleotides and Polynucleotides.- 1.3.2 Reaction with Hydrogen Atoms.- 1.3.3 Reaction with the Solvated Electron.- 1.3.4 Reactions of the Intermediates with Added Solutes.- 1.3.4.1 Oxygen.- 1.3.4.2 Electron-Transfer Processes.- 2 Radiation-Induced Degradation of the Base Component in DNA and Related Substances ― Final Products.- 2.1 Introduction.- 2.2 Nucleic Acid Constituents in Aqueous Aerated Solutions.- 2.2.1 Free Bases.- 2.2.1.1 Thymine.- 2.2.1.2 Uracil.- 2.2.1.3 Cytosine.- 2.2.1.4 5-Bromouracil.- 2.2.1.5 Adenine.- 2.2.2 Nucleosides and Nucleotides.- 2.2.2.1 Thymidine.- 2.2.2.2 5-Bromo-2?-Deoxyuridine.- 2.2.2.3 Uridine.- 2.2.2.4 Deoxyadenosine.- 2.2.2.5 Nucleotides ― Thymidylic Acid and Uridylic Acid.- 2.2.2.6 Dinucleotides ― TpT.- 2.3 Nucleic Acid Constituents in Deaerated Aqueous Solutions.- 2.3.1 Free Bases.- 2.3.1.1 Thymine.- 2.3.1.2 Uracil.- 2.3.1.3 Cytosine.- 2.3.1.4 Adenine.- 2.3.2 Free Bases in the Presence of a Second Solute.- 2.3.2.1 Bases and Ethanol.- 2.3.2.2 Thymine and Radiosensitizers.- 2.3.2.3 Pyrimidine Bases and Surfactants.- 2.3.2.4 Pyrimidine Bases and Amino Acids.- 2.3.3 Nucleosides and Nucleotides.- 2.3.3.1 Thymidine.- 2.3.3.2 Purine Nucleosides and Nucleotides.- 2.4 Nucleic Acid Constituents in Solid State or in Frozen Solutions.- 2.5 DNA in Aerated and Deaerated Solutions.- 2.5.1 Modifications of the Base Moieties in the Polynucleotide Chain.- 2.5.1.1 UV Absorption and IR Spectra.- 2.5.1.2 Formic or Perchloric Acid Hydrolysis ― Base Destruction.- 2.5.1.3 Peroxidation of Pyrimidines.- 2.5.1.4 Indirect Determinations of the Fairly Stable Products.- 2.5.1.5 Direct Determinations of the Fairly Stable Products.- 2.5.2 Products Released from the Polynucleotide Chain.- 2.5.2.1 3H-H2O from DNA Thymine Methyl-(3H).- 2.5.2.2 Ammonia.- 2.5.2.3 Free Bases.- 2.5.2.4 Products of Base Component Degradation ― Release of Carbon Dioxide from the Thymine Fragment.- 3 Radiation-Induced Degradation of the Sugar in Model Compounds and in DNA.- 3.1 Introduction.- 3.2 Free Radical Reactions of Sugars and Sugar Phosphates.- 3.3 Sugars.- 3.3.1 2-Deoxy-D-Ribose.- 3.3.1.1 Aqueous Solutions.- 3.3.1.2 Crystalline State.- 3.3.2 D-Ribose.- 3.3.2.1 Aqueous Solution.- 3.3.2.2 Solid State.- 3.4 Sugar Phosphates.- 3.4.1 D-Ribose-5-Phosphate.- 3.4.1.1 Deoxygenated Solutions.- 3.4.1.2 Oxygenated Solutions.- 3.5 Nucleosides.- 3.5.1 Scission of the N-Glycosidic Linkage in Thymidine.- 3.5.1.1 Deoxygenated Solutions.- 3.5.1.2 Oxygenated Solutions.- 3.6 Nucleotides.- 3.6.1 Phosphate Release.- 3.6.1.1 Mononucleotides.- 3.6.1.2 Thymidine-3?,5?-Diphosphate.- 3.6.2 Scission of the N-Glycosidic Linkage.- 3.6.3 Formation of Cyclo-Nucleotides.- 3.7 DNA.- 3.7.1 Product Release from DNA and the Mechanism of Strand Breaks.- 3.7.1.1 Release of Malonaldehyde.- 3.7.1.2 Release of Sugars and Unaltered Bases.- 3.7.2 End Group Determinations on Broken DNA Strands.- 3.7.2.1 5? End Groups.- 3.7.2.2 3? End Groups.- 4 Changes in the Secondary and Tertiary Structures of DNA after Irradiation.- 4.1 Hyperchromicity and Melting Curves.- 4.2 Titration.- 4.3 Other Methods.- 4.4 Conclusions.- References.- Section III: Biological Aspects.- 1 Biological Functions of DNA and Methods of Testing.- 1.1 Introduction.- 1.2 Processes in which DNA is Involved.- 1.2.1 Semiconservative Replication.- 1.2.2 Transcription.- 1.2.3 Repair.- 1.2.4 Transformation.- 1.2.5 Transfection.- 1.3 Degrees of Difficulty of Testing DNA Functions.- 1.4 Description of Several Simple Systems.- 1.4.1 Transformation with Bacterial DNA.- 1.4.2 Transfection with Phage DNA.- 1.4.2.1 Transfection of Spheroplasts.- 1.4.2.2 Transfection of Competent Cells.- 2 Radiation Effects on the Biological Function of DNA.- 2.1 Introduction.- 2.1.1 Main Types of Lesions Induced in DNA by Ionizing Radiation.- 2.1.2 Calculation of the Number of Strand Breaks in DNA.- 2.1.2.1 Analytical Ultracentrifugation.- 2.1.2.2 Preparative Ultracentrifugation.- 2.2 Inactivation of Phage DNA.- 2.2.1 The Phage and Its Advantages.- 2.2.2 Irradiation of Nucleic Acids Isolated from Phage.- 2.2.2.1 Biological Inactivation of Single-Stranded DNA.- 2.2.2.2 Biological Inactivation of Double-Stranded DNA.- 2.2.3 Irradiation of Phage.- 2.2.3.1 Inactivation of Phages with Single-Stranded DNA 27.- 2.2.3.2 Inactivation of Phages with Double-Stranded DNA.- 2.2.4 Effect of Incorporated Radionuclides on the Biological Activity of Phage DNA.- 2.3 Irradiation Effects on the Transforming and Transfecting Activity of DNA.- 2.3.1 Biological Activity of Transforming DNA Irradiated in vivo.- 2.3.2 Transforming Activity of DNA Irradiated in vitro.- 2.3.3 Contribution of Strand Breakage, Base Damage, and Crosslinks to the Inactivation.- 2.3.4 Mathematical Interpretation of the Dose Effect Curves.- 2.3.5 Biological Activity of Irradiated Transfecting DNA.- 2.4 Irradiation Effects on Transcription.- 2.4.1 Transcription on Irradiated DNA in vitro.- 2.4.2 RNA Synthesis in Irradiated Cells.- 2.5 Irradiation Effects on DNA Replication.- 2.5.1 Introduction.- 2.5.2 Methods of Measuring DNA Replication in Cells.- 2.5.2.1 Radioactive Labelling.- 2.5.2.2 Autoradiography.- 2.5.2.3 Replication Synthesis Defined.- 2.5.3 Effect of Radiation on Uptake of Precursors into DNA.- 2.5.3.1 Bacteria.- 2.5.3.2 Mammalian Cells in Culture.- 2.5.3.3 Cells of Irradiated Animals.- 2.5.4 Influence of Mitotic Cycle on the Irradiation Effects on DNA Synthesis.- 2.5.5 Form and Interpretation of Dose-Effect Curves.- 2.5.6 Inhibition of DNA Synthesis and Cell Survival.- 2.5.7 Irradiation Effects on DNA Synthesis in vitro.- 3 Modification of Radiation Damage.- 3.1 Introduction.- 3.2 Factors Enhancing the Radiosensitivity of DNA.- 3.2.1 Phase State, Dehydration, and Temperature.- 3.2.2 Oxygen.- 3.2.3 Halógena ted Base Analogs.- 3.2.4 Chemical Compounds Acting on Radiation Induced DNA Transients.- 3.2.5 Chemical Compounds Combining with DNA Independently of Radiochemical Reactions.- 3.3 Sulfhydryl Compounds and Radioprotection by Radical Scavenging.- 4 Repair Processes for Radiation-Induced DNA Damage.- 4.1 Introduction.- 4.2 Repair of Single-Strand Breaks in Bacteria.- 4.2.1 Measurement of Single-Strand Breaks.- 4.2.2 Different Rejoining Processes.- 4.2.3 Slow Repair in Escherichia coli.- 4.2.3.1 Genetic Control.- 4.2.3.2 Effects of Post-Irradiation Conditions.- 4.2.4 Fast Repair in E. coli.- 4.2.5 Rejoining of SSBs in Other Bacteria.- 4.2.6 Post-Irradiation Degradation.- 4.3 Rejoining of Single-Strand Breaks in Eucaryotic Cells.- 4.3.1 Introduction.- 4.3.2 End Groups Produced.- 4.3.3 Efficiency of Break Production.- 4.3.4 Rejoining after High Doses in Cultured Cells.- 4.3.4.1 Rejoining in Different Cells.- 4.3.4.2 Effects of Inhibitors.- 4.3.4.3 Energy Requirements.- 4.3.5 Studies Using Low Doses ( and DNA Content of the Genome.- 5.3 Open Questions.- 5.4 Conclusion.- 6 Conclusions and Perspectives.- References.- 1. Dose Units.- 1.1 Exposure.- 1.2 Absorbed Dose.- 1.3 Conversion Factors.- 1.4 Radiation-Chemical Yield (G-Value).- 2. List of Abbreviations.- 2.1 Chemical Names.- 2.2 Experimental and Theoretical Methods.- 2.3 Symbols, Entities and Units.