Evaluation of a Shuttle DNP Spectrometer by Calculating the Coupling and Global Enhancement Factors of l-Tryptophan |
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Authors: | Philip Lottmann Thorsten Marquardsen Alexander Krahn Andreas Tavernier Peter H?fer Marina Bennati Frank Engelke Christian Griesinger |
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Institution: | 1. NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, G?ttingen, Germany 2. Bruker BioSpin, Silberstreifen 4, 76287, Rheinstetten, Germany 3. Electron Paramagnetic Resonance, Max Planck Institute for Biophysical Chemistry, 37077, G?ttingen, Germany
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Abstract: | A liquid state shuttle dynamic nuclear polarization (DNP) spectrometer is presented, featuring several technical modifications that increase stability and improve reproducibility. For the protons of l-tryptophan, the signal enhancement and the DNP spin properties, such as relaxation, were measured and compared with each other. The calculated coupling factors suggest that the proton accessibility for the polarizer molecule has an important influence on the DNP enhancement. In general, short proton spin longitudinal relaxation times without radical reduce the detectable enhancement by decreasing the leakage factor and increasing the relaxation losses during the course of the sample transfer. The usage of a global enhancement factor gives a more complete overview of the capabilities for the described experimental setup. Global enhancements of up to ?4.2 for l-tryptophan protons are found compared to pure Boltzmann enhancements of up to ?2.4. |
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