Measurement of N 15 - T 1 relaxation rates in a perdeuterated protein by magic angle spinning solid-state nuclear magnetic resonance spectroscopy

In this paper, we present the measurement of N 15 - T 1 relaxation times in the solid state for a perdeuterated protein for which exchangeable protons are back substituted during recrystallization using a buffer which contains 10% H 2 O and 90% D 2 O . We find large variations of the N 15 relaxation time, even within the same β sheet. By comparing N 15 - T 1 relaxation times measured for a protonated and a deuterated protein (using the above mentioned approach), we conclude that H 1 driven N 15 , N 15 spin diffusion has a significant impact on the absolute N 15 relaxation time in protonated proteins. This effect is important for a quantitative analysis of relaxation data in terms of molecular dynamics.