1. INTRODUCTION 68

1.1 Receptor patterns in the plasma membrane 68

1.2 Different types of receptor patterns 71

2. METHODS TO INVESTIGATE NON-RANDOM RECEPTOR CLUSTERING 73

2.1 Fluorescence resonance energy transfer 73

2.2 Flow cytometric energy transfer measurement 78

2.3 Fluorescence anisotropy and energy transfer 79

2.4 Photobleaching energy transfer on single cells 81

2.5 Two-dimensional mapping of receptor superstructures 82

2.6 Detecting single receptor molecules 85

2.7 Chemical identification of receptor clusters 86

2.8 Electron microscopy 87

2.9 Scanning force microscopy 88

3. CONFORMATIONAL STATES OF RECEPTORS 90

3.1 Multi-subunit receptor structures 90

3.2 Physical parameters influencing conformational states 91

3.3 Chemical interactions and receptor conformations 92

4. ON THE ORIGIN OF NATURALLY OCCURRING RECEPTOR CLUSTERS 93

4.1 Synthesis of receptors and their localization in the plasma membrane 93

4.2 Lipid domain structure of the plasma membrane 94

4.3 The validity of the SingerNicolson model 94

5. CONCLUSIONS 96

6. ACKNOWLEDGEMENTS 96

7. REFERENCES 97