While extracting dynamics parameters from backbone 15N relaxation measurements in proteins has become routine over the past two decades, it is increasingly recognized that accurate quantitative analysis can remain limited by the potential presence of systematic errors associated with the measurement of 15N R1 and R2 or R1Ï? relaxation rates as well as heteronuclear 15N-{1H} NOE values. We show that systematic errors in such measurements can be far larger than the statistical error derived from either the observed signal-to-noise ratio, or from the reproducibility of the measurement. Unless special precautions are taken, the problem of systematic errors is shown to be particularly acute in perdeuterated systems, and even more so when TROSY instead of HSQC elements are used to read out the 15N magnetization through the NMR-sensitive 1H nucleus. A discussion of the most common sources of systematic errors is presented, as well as TROSY-based pulse schemes that appear free of systematic errors to the level of
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Measurement of 15N relaxation rates in perdeuterated proteins by TROSY-based methods
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