Advances in Quantum Chemistry (eBook)

Cover 1
Copyright page 5
Contents 6
Contributors 10
Preface 12
Chapter 1. Theoretical Studies of the Interaction of Radiation with Biomolecules 14
References 16
Chapter 2. Free-Radical-Induced DNA Damage as Approached by Quantum-Mechanical and Monte Carlo Calculations: An Overview from the Standpoint of an Experimentalist 18
1. Introduction 18
2. The various types of DNA damage 19
3. DNA damage by ionizing radiation-general aspects and modeling 20
4. Pattern of •OH attack on DNA 22
5. Ionization potentials and electron affinities of the nucleobases (reduction potentials) 23
6. Hole and electron transfer through DNA 23
7. Tautomerization and isomerization reactions of DNA radicals 24
8. Regioselectivity of •OH attack on the nucleobases 26
9. Selectivity of free-radical attack at the sugar moiety 27
10. Reactions of alkyl radicals 28
11. Reduction potentials of DNA radicals 28
12. Assignment of transients by quantum-chemical calculations of their electronic transitions 29
13. DNA stability and repair 30
References 31
Chapter 3. Energy Deposition Models at the Molecular Level in Biological Systems 34
1. Introduction 35
2. Cross sectional data 36
3. Monte Carlo simulation 60
4. Conclusions 67
References 68
Chapter 4. DFT Treatment of Radiation Produced Radicals in DNA Model Systems 72
1. Introduction 72
2. Electron affinities of DNA bases (valence and diffuse states) [11] 73
3. Effect of base pairing and proton transfer [12,13] 78
4. Electron induced dehalogenation reactions of halouracils and effect of base pairing 14,15 83
5. Hydrogen atom loss in pyrimidine DNA bases [16,17] 88
6. Electron induced DNA strand breaks [18] 91
7. Energetics of base release in nucleoside anion radicals [90] 94
References 98
Chapter 5. Computational Studies of Radicals Relevant to Nucleic Acid Damage 102
1. Introduction 102
2. Computational methods 103
3. Nucleobase cation radicals 105
4. Nucleobase radicals 111
5. Deoxyribose and ribose radicals 122
6. Conclusions and outlook 127
Acknowledgements 128
References 128
Chapter 6. Radical Cations of the Nucleic Bases and Radiation Damage to DNA: Ab Initio Study 134
1. Introduction 134
2. Computational methods 137
3. Isolated DNA bases 141
4. Clusters of DNA bases 147
5. Conclusion 155
Acknowledgements 156
References 156
Chapter 7. Charge Exchange and Fragmentation in Slow Collisions of He2+ with Water Molecules 162
1. Introduction 163
2. Experimental methods 164
3. Theoretical approach 168
4. Experimental and theoretical results 172
5. Conclusions 181
Acknowledgements 181
References 181
Chapter 8. How Very Low-Energy (0.1-2 eV) Electrons Cause DNA Strand Breaks 184
1. Introduction 184
2. Where do very low-energy electrons attach to DNA and what bonds are broken? 185
3. Methods used to characterize the energies of the metastable anions 191
4. Summary 199
Acknowledgements 200
References 200
Chapter 9. Electron-Driven Molecular Processes Induced in Biological Systems by Electromagnetic and Other Ionizing Sources 202
1. Introduction 202
2. Electron-impact experiments in biological environments: Current state of the art 204
3. Recent theoretical modelling of resonant states in biomolecules 208
4. The present approach: The symmetry adapted-single centre expansion (SA-SCE) method 211
5. The present results on gas-phase biomolecules 223
6. Conclusions 238
Acknowledgements 239
References 239
Chapter 10. Electron Attachment to DNA Base Complexes 244
1. Overview 244
2. Introduction 245
3. Experimental methods 247
4. Theoretical methods 249
5. Covalent bound anions 249
6. Dipole-bound anions 255
7. AISE systems 258
8. Summary and future directions 262
Acknowledgements 262
References 262
Chapter 11. Accelerating Multiple Scattering of Electrons by Ion Impact: Contribution to Molecular Fragmentation and Radiation Damages 266
1. Introduction 266
2. Fast electron emission and Fermi-shuttle acceleration 268
3. First experimental indications-two step processes 270
4. Theoretical considerations 274
5. Higher order electron scattering sequences 280
6. Conclusions and outlook 286
Acknowledgements 287
References 287
Chapter 12. Total Electron Stopping Powers and CSDA-Ranges from 20 eV to 10 MeV Electron Energies for Components of DNA and RNA 290
1. Introduction 290
2. Theory 291
3. Calculated results and discussion 293
4. Concluding remarks 300
References 300
Chapter 13. The Influence of Stopping Powers upon Dosimetry for Radiation Therapy with Energetic Ions 302
1. Introduction 303
2. Stopping power 304
3. I values for water and air 307
4. Stopping power ratios for dosimetry 312
5. Discussion 316
6. Conclusions 317
Acknowledgement 318
References 318
Subject index 320