Q-Band FT-EPR Spektrometer

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Hereby we apply for a dedicated Q-band pulsed spectrometer equipped with: (i) a 150 W TWT amplifier, providing the highest commercially available microwave power; (ii) the newly developed technology of Arbitrary Waveform Generators (AWG), providing all waveform features that can be described mathematically - a true breakthrough for pulsed-EPR experiments. This spectrometer will be mainly used for DEER on spin-labeled membrane proteins. In the case of nitroxide-based DEER, the high-power Q-band setup together with an available home-made resonator will allow (i) an increase of about 20 in signal-to-noise with respect to conventional X-band DEER on the same amount of sample; (ii) determination of interspin distances on samples with spin concentrations down to 20 micromolar in a 12-24 h measurement time; (iii) biophysical studies on complex biosystems in physiological environments without orientation selection and proton modulation artifacts. All these achievements are otherwise impossible using conventional X-band or low-power Q-band DEER. For probes other than nitroxides, e.g. metal centers, the new AWG setup will allow the use of dedicated pulsesequences to improve sensitivity in DEER experiments. Therefore, the study of orthogonally-labeled proteins and protein networks in cellular environments will become possible.