1 General Introduction ......................................... 1
References ................................................... 4
2 Electron Paramagnetic Resonance Theory ....................... 7
2.1 Historical Review ....................................... 7
2.2 EPR Fundamentals ........................................ 8
2.2.1 Preface .......................................... 8
2.2.2 Resonance Phenomenon ............................. 9
2.2.3 Magnetization ................................... 10
2.2.4 Bloch Equations ................................. 11
2.2.5 Continuous Microwave Irradiation ................ 12
2.3 Types of Interactions and Spin Hamiltonian ............. 14
2.3.1 Electron Zeeman Interaction ..................... 15
2.3.2 Nuclear Zeeman Interaction ...................... 16
2.3.3 Hyperfine Interaction ........................... 16
2.3.4 Nuclear Quadrupole Interaction .................. 17
2.3.5 Nuclear Spin-Spin Interaction ................... 18
2.3.6 Zero-Field Splitting ............................ 18
2.3.7 Weak Coupling Between Electron Spins ............ 18
2.4 Anisotropy in EPR Spectra .............................. 20
2.4.1 g Anisotropy .................................... 20
2.4.2 Combined Anisotropics in Real Spectra ........... 22
2.5 Dynamic Exchange ....................................... 23
2.6 Nitroxides as Spin Probes .............................. 26
2.6.1 Spin Probe Versus Spin Label .................... 27
2.6.2 Quantum Mechanical Description .................. 27
2.6.3 Nitroxide Dynamics .............................. 28
2.6.4 Environmental Influences ........................ 30
2.7 CW Spectral Analysis via Simulations ................... 31
2.8 Time Evolution of Spin Ensembles ....................... 33
2.8.1 The Density Matrix .............................. 33
2.8.2 Product Operator Formalism ...................... 35
2.8.3 Application to EPR .............................. 36
2.8.4 The Vector Model ................................ 37
2.8.5 The (S = 1/2, I = 1/2) Model System ............. 37
2.9 Pulse EPR Methods Based on the Primary Echo ............ 39
2.9.1 ESE Detected Spectra ............................ 40
2.9.2 2-Pulse Electron Spin Echo Envelope Modulation
(ESEEM) ......................................... 41
2.10 Pulse EPR Methods Based on the Stimulated Echo ......... 42
2.10.1 3-Pulse ESEEM ................................... 42
2.10.2 Hyperfine Sublevel Correlation (HYSCORE)
Spectroscopy .................................... 44
2.10.3 Blind Spots ..................................... 44
2.10.4 Phase Cycling ................................... 45
2.11 Double Electron-Electron Resonance (DEER) .............. 46
References .................................................. 50
3 The Functional Structure of Human Serum Albumin ............. 53
3.1 Introduction ........................................... 54
3.2 The Distribution of Fatty Acids in Human Serum
Albumin in Solution .................................... 56
3.2.1 Results ......................................... 56
3.2.2 Discussion ...................................... 59
3.3 Multispin Contributions to DEER Spectra ................ 62
3.3.1 Spin Counting ................................... 62
3.3.2 Quantification of Multispin Artifacts ........... 65
3.4 Orientation Selectivity in DEER: Beyond Distances ...... 68
3.5 Conclusions ............................................ 76
3.6 Materials and Methods .................................. 76
References .................................................. 79
4 Copper Complexes of Star-Shaped Cholic Acid Oligomers With
1,2,3-Triazole Moieties ..................................... 83
4.1 Introduction ........................................... 84
4.2 Triazole-Substituted Oligomer T3t as Metal Ion
Sensor ................................................. 87
4.2.1 Fluorescence Quenching Enhancement by T3t ....... 87
4.2.2 T3t: A Tridentate Ligand for Copper ............. 88
4.2.3 Deriving a Molecular Picture From the EPR
Results ......................................... 93
4.2.4 Comparative Fluorescence Quenching Studies
of T3t and T0 ................................... 93
4.2.5 Summary ......................................... 95
4.3 Influence of the Molecular Structure on the Metal
Ion Complexation ....................................... 95
4.3.1 Fluorescence Quenching of T3b ................... 95
4.3.2 Copper Coordination in T3b ...................... 96
4.3.3 Influence of a Fourth Cholic Acid Arm .......... 100
4.3.4 Observation of a Fourth Species in a 2:1
Mixture of CuCl2 and Q8tb ...................... 102
4.3.5 Summary ........................................ 103
4.4 Self-Assembly of Monomeric Cholic Acid Derivatives .... 103
4.4.1 Cu2+ Coordination by S2 ........................ 103
4.4.2 Cu2+ Mediated Spatial Assembly of Single
Cholic Acid Chains ............................. 105
4.5 Conclusions ........................................... 109
4.6 Materials and Methods ................................. 110
References ................................................. 111
5 Nano-Inhomogeneities in Structure and Reactivity of
Thermoresponsive Hydrogels ................................. 115
5.1 Introduction .......................................... 116
5.2 Results ............................................... 118
5.2.1 The Temperature Induced Hydrogel Collapse
as Seen by Probe Molecules ..................... 118
5.2.2 Chemical Decomposition of Spin Probes in
Hydrophilic Regions of the Hydrogel ............ 121
5.3 Discussion ............................................ 124
5.3.1 The Hydrogel Collapse on a Molecular Level ..... 124
5.3.2 Hydrogel Inhomogeneities on the Nanoscale
Lead to Nanoreactors and Nanoshelters .......... 126
5.3.3 Nanoreactors With Localized Acid Groups ........ 127
5.4 Conclusions ........................................... 129
5.5 Materials and Methods ................................. 129
References ................................................. 131
6 Thermoresponsive Spin-Labeled Hydrogels as Separable DNP
Polarizing Agents .......................................... 133
6.1 Introduction .......................................... 134
6.2 Theory of Overhauser DNP .............................. 136
6.3 Results and Discussion ................................ 137
6.3.1 Strategy for the Preparation of
Thermoresponsive Spin-Labeled Hydrogels ........ 137
6.3.2 CW EPR Characterization of the Spin-Labeled
Hydrogels ...................................... 138
6.3.3 Characteristic DNP Factors and 1H Relaxation
Times .......................................... 139
6.3.4 Temperature-Dependent DNP Performance of
Spin-Labeled Hydrogels ......................... 141
6.4 Conclusions ........................................... 143
6.5 Outlook ............................................... 143
6.6 Materials and Methods ................................. 144
References ................................................. 146
7 Local Nanoscopic Heterogeneities in Thermoresponsive
Dendronized Polymers ....................................... 149
7.1 Introduction .......................................... 150
7.2 Local Heterogeneities Above the Critical
Temperature ........................................... 151
7.3 Pre-Collapse of the Dendronized Polymers Below the
Critical Temperature .................................. 157
7.4 Formation and Influence of a Dense Peripheral
Polymeric Layer ....................................... 159
7.4.1 Results ........................................ 159
7.4.2 Discussion ..................................... 162
7.5 Conclusions ........................................... 167
7.6 Materials and Methods ................................. 169
References ................................................. 170
8 Conclusion ................................................. 173
Appendix ...................................................... 177
Curriculum Vitae .............................................. 209
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