Molecular Photobiology

Molecular Photobiology: Inactivation and Recovery describes the deleterious photochemical reactions occurring in biological systems. This book is composed of 10 chapters that specifically tackle light interactions in the ultraviolet region of the spectrum resulting to damaged proteins and nucleic acids in living systems. This book deals first with the kinds of photochemical reactions that can occur and the possible effects of photochemistry on molecular, cellular, and organismal levels. The succeeding chapters highlight the principle of recovery mechanisms, wherein evidence shows that cells can repair their damaged genetic material, and thus recover from the otherwise inactivating effects of light. The remaining chapters are devoted to the comparison and contrast of some biological effects of ionizing radiation and those of ultraviolet radiation. This book is of value to molecular photobiologists, photochemists, biochemists, and radiation scientists and researchers.

Preface

Glossary

1. Introduction: Basic Principles

1-1. Effects of Ultraviolet Radiation upon Biological Systems

1-2. Laws of Photochemistry

1-3. Absorption Spectra

1-4. Action Spectra

General References

2. Experimental Procedures

2-1. Light Sources

2-2. Wavelength Selection

2-3. Measurement of Energy Output

2-4. General Problems in Dosimetry

2-5. Flash Photolysis

General References

3. Quantum Photochemistry

3-1. Properties of Photons and Electrons

3-2. Covalent Bonds

3-3. Photon Effects on Orbital Electrons

3-4. Dissipation of Photon Energy

3-5. Role of Molecular Orientation

3-6. Hypochromicity

3-7. Energy Transfer

General References

4. Photochemistry of the Nucleic Acids

4-1. Introduction

4-2. Effects of UV on Ribose and Deoxyribose

4-3. Effects of UV on Purines

4-4. Hydration Products of the Pyrimidines

4-5. Cyclobutane-Type Dimers of Thymine, Cytosine, and Uracil

4-6. Other Photochemical Reactions of the Pyrimidines

4-7. Effect of UV on the Molecular Weight of DNA (Chain Breakage)

4-8. DNA-DNA Cross-Links

4-9. The Cross-Linking of DNA to Protein

4-10. The Effect of Base Composition on the Intrinsic Sensitivity of DNA to UV

4-11. The Effect of Substitution by Halogenated Pyrimidines on the Intrinsic Sensitivity of DNA to UV

4-12. The Influence of the Environment during Irradiation on the Intrinsic Sensitivity of DNA

4-13. Photochemistry of RNA

4-14. Summary

General References

5. Photochemistry of Amino Acids and Proteins

5-1. Introduction

5-2. Relative Photochemical Sensitivity of the Amino Acids

5-3. General Comments on the Photochemistry of Proteins

5-4. Photochemical Inactivation of Enzymes

General References

6. Photoinactivation of Biological Systems

6-1. Introduction

6-2. Simple Survival Curves

6-3. Biphasic Survival Curves

6-4. Multihit and Multitarget Survival Curves

6-5. Bacterial Viability

6-6. Macromolecular Synthesis

6-7. Bacteriophage

6-8. Induction of Prophage

6-9. Plant Viruses

6-10. Animal Viruses

6-11. Eucaryotic Cells

General References

7. Recovery from Photochemical Damage

7-1. Introduction

7-2. Fortuitous Recovery

A. Biologically Undetectable Damage

B. Polyploidy

C. Multiplicity Reactivation

D. Cross Reactivation (Marker Rescue)

E. Suppression of Prophage Induction

7-3. Reversal of Damage by Repair in Situ

A. Decay of Photoproducts

B. Direct Photoreversal of Pyrimidine Dimers

C. Enzyme-Catalyzed Photoreactivation

7-4. Reconstruction of Damaged DNA

A. Evidence for Excision-Repair

B. The Steps in Excision-Repair

C. Generality of Excision-Repair

7-5. DNA Synthesis on Unrepaired Templates

7-6. Physiological and Environmental Effects on Repair and Recovery

A. New Repair Mechanisms (or Indirect Effects on Known Ones)

B. Liquid Holding Recovery

C. UV Sensitivity and the DNA Replication Cycle

D. Indirect Photoreactivation

E. Photoprotection

F. UV Reactivation

G. Filament Formation and Recovery of Cell Division

7-7. Genetic Control of Repair Processes

General References

8. Ultraviolet Mutagenesis

8-1. Introduction

8-2. Early Observations on Bacterial Systems

8-3. Nature of the Mutants Produced by UV

8-4. Role of Repair Processes in Mutagenesis

General References

9. Photodynamic Action

9-1. Introduction

9-2. Structure of Photodynamic Dyes

9-3. Mechanisms of Photodynamic Action

9-4. Photodynamic Action on Cells

9-5. Photodynamic Action on Viruses

9-6. Photodynamic Action on Proteins and Nucleic Acids

9-7. Photosensitized Reactions Not Requiring Oxygen

9-8. Photosensitized Reactions in Whole Animals

General References

10. Comparison of UV and Ionizing Radiation

10-1. Introduction

10-2. The Target of Primary Radiobiological Importance Is DNA

10-3. The Effects of DNA Base Composition, DNA Content, Ploidy, and Strandedness of the DNA on the Radiation Sensitivity of Cells

10-4. The Biochemical Effects of X-Irradiation

10-5. General Discussion of Radiation Chemistry

A. Introduction

B. Direct and Indirect Effects

C. Chemical Protection against Radiation Damage

D. Oxygen Effect

E. Types of Damage Expected

F. Energy Migration

10-6. Radiation Chemistry of Water

10-7. Radiation Chemistry of the Purines and Pyrimidines

10-8. Radiation Chemistry of DNA

10-9. The Interaction of X-Rays and UV

General References

Subject Index