Contents

List of Symbols and Abbreviations xix

1 Tracing Life's Origin: From Amino Acids to Space Mission ROSETTA 1

1.1 The Origin of Life 1

1.2 The Asymmetry of Life 2

1.3 How Life's Asymmetry Originated 5

1.3.1 Random Mechanisms 5

1.3.2 Determinate Mechanisms 7

1.3.3 Chirogenesis in Outer Space 10

2 Stereochemistry for the Study of the Origin of Life 17

2.1 Amino Acids and Chemical Reactions: A Guided Tour 17

2.2 Optical Activity 24

2.3 Stereochemical Nomenclature 25

2.3.1 The Cahn-Ingold-Prelog Notation: R- and S-Enantiomers... 25

2.3.3 D- and L-Enantiomers 26

2.3.4 d- and /-Enantiomorph Crystals 27

2.3.5 P- and M-Descriptors 27

2.3.6 A-andA-Descriptors 27

2.4 Optical Rotation Dispersion and Cotton Effect 28

2.5 Through the Eye of a Chromophore: CD Spectroscopy 31

2.6 Miscellaneous Techniques 34

2.7 "Chiral Light" and the Stokes Parameters 36

2.8 Chromatographic Resolution of Enantiomers 39

3 Minority Report: Life's Chiral Molecules of Opposite Handedness... 47

3.1 Sympathy for the Devil: How D-Amino Acids Make Organisms Work 48

3.1.1 D-Amino Acids in Plants and Human Food 48

3.1.2 D-Amino Acids in Peptides 49

3.1.3 Do D-Amino Acids Affect Grey Matter? 50

3.2 The Dark Side of D-Amino Acids 51

3.3 "What Time was it?" Ask the Amino Acid Clock! 52

3.4 Biotic Origin: Were D-Life and L-Life Contemporaries? 54

3.4.1 Biotic and Selection Theories 54

3.4.2 How Polypeptides Form 55

3.4.3 Counterarguments Against the Biotic Theory 56

4 When Crystals Deliver Chirality to Life 61

4.1 Spontaneous Crystallization of Chiral Minerals 63

4.2 Heated Debate: Which Amino Acid Enantiomer Precipitates First? . 67

4.3 Turning World: The Direction of Stirring 72

4.4 Deposits of Enantiomorphous Quartz on Earth 74

4.5 Adsorption of Chiral Organic Molecules on Enantiomorphous Crystals 76

5 When Parity Falls: The Weak Nuclear Interaction 79

5.1 The Fall of Parity: "I Couldn't Understand It" 80

5.2 Asymmetric Radiolysis by Polarized Electrons 84

5.3 The Vester-Ulbricht Process 86

5.3.1 Circularly Polarized Bremsstrahlung in the VU Process 87

5.3.2 In Search of the Ultimate VU Experiment:

California Dreaming? 88

5.3.3 What Are the Next VU Experiments? 90

5.4 Parity Non-Conserving Energy Differences 90

5.4.1 The Electroweak Interaction 91

5.4.2 Characteristics of Electromagnetic and Weak Interaction . . . 92

5.4.3 Difference Matters: Energies of Enantiomers 93

5.4.4 Calculated Energy Differences of Amino Acid Enantiomers 95

5.4.5 Calculated Energy Differences of Sugar Enantiomers 97

5.4.6 Never Say Never: Measuring Parity Non-Conserving

Energy Differences 99

5.4.7 Implications of Parity Non-Conserving Energy Differences . 102

6 Chiral Fields: Light, Magnetism, and Chirality 103

6.1 Magneto-Optical Effects 104

6.2 Photochirogenesis 107

6.2.1 Asymmetric Photolysis of Racemic Organic Molecules 107

6.2.2 Asymmetric Photolysis of Amino Acids 108

6.2.3 Asymmetric Photoisomerization 117

6.2.4 Asymmetric Synthesis 119

6.2.5 'Natural' Sources of Circularly Polarized Light 120

7 Key to the Prebiotic Origin of Amino Acids 125

7.1 Amino Acid Formation Under Atmospheric Conditions 125

7.2 Amino Acid Formation Under Hydrospheric Conditions 127

7.3 Amino Acid Formation Under Interstellar Conditions 127

7.3.1 Photochemistry in the Interstellar Medium 127

7.3.2 Simulation of Interstellar Chemistry in the Lab 128

7.3.3 Fresh in the Ice: Amino Acid Structures 131

7.3.4 Illumination with Circularly Polarized Light 140

8 A New Record for Chiral Molecules in Meteorites 145

8.1 Chiral Organic Molecules in Meteorites? 145

8.1.1 Amino Acids in Meteorites 146

8.1.2 The Untold Story of Diamino Acids in Meteorites 148

8.2 Diamino Acids as Gene Trigger 154

8.3 Survival of Organic Molecules After Impact on Earth 157

8.4 Space Exploration and Chirality: What Next? 158

9 The New Space Race: Chiral Molecules on Comets and on Mars 161

9.1 In Search of Chiral Molecules in Comets 161

9.1.1 Comet Formation: Theory and Experimental Results 162

9.1.2 ROSETTA: A Cometary Mission Full of Answers 163

9.1.3 The Chirality-Module of Mission ROSETTA 165

9.2 Chiroptical Techniques and the SETH Project 178

9.3 The Search for Chiral Molecules on Mars 179

9.3.1 Space Invaders: Traces of Life in Martian Meteorites 179

9.3.2 Chirality and Mission ExoMars 180

10 Accelerating the Carousel: Amplification Mechanisms 185

10.1 Some Amplification Needed: The Bifurcation Theory 187

10.2 Amplification by Kinetic Reaction Sequences 189

10.3 Amplification by Progressive Accumulation 194

10.4 Amplification by the Soai Reaction 195

10.5 Transfer, Memory, and Switching of Chiral Properties 197

10.6 Concluding Remarks 198

Appendix 199

Bibliography 207

Index 229

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