Water proton spin saturation affects measured protein backbone 15N spin relaxation rates

► Different water suppression methods were adopted to measure NMR relaxation. ► Slower 15N T1 rates were identified when the water was saturated in the experiment. ► The cause for the slower T1 relaxation is the non-uniform 1HN recovery. ► Slower T1 relaxation leads to apparent lower Model-Free order parameters.