Structural biology engages ever larger biomolecular systems in ever more complex environments. EPR spectroscopy offers for such studies methods that allow determining structures and structural changes on the nanometer scale by measuring the dipolar coupling between spin-centers. Promising are in this context Pulsed-Electron-Electron-Double-Resonance (PELDOR) or Double-Quantum- Coherence-(DQC) experiments. Many of the interesting systems are diamagnetic, which requires that they are spin-labelled with nitroxides. However, the chemical and EPR spectroscopic properties of these nitroxides lead to several limitations. In this project, we will functionalise trityl radicals in such a way that they can be used as spin labels for proteins. On model systems we will optimize the pulsesequences and measuring protocols for trityl-based distance measurements. We will use the one order of magnitude narrower spectral width to increase the signal intensity, to increase the PELDOR modulation depth to 100% and to enable routine DQC experiments. The TM-relaxation time on the microsecond time scale will enable us to perfome distance measurements under sample cooling with liquid nitrogen instead of liquid helium and in the long run allow for distance measurements in liquid solution at room temperature, meaning under truly biological conditions. The superior chemical stability of the trityl radicals, will be used for more sensitive in-cell experiments.