An Iterative Fitting Procedure for the Determination of Longitudinal NMR Cross-Correlation Rates

η z ∕ κ : A transverse relaxation optimized spectroscopy NMR experiment measuring longitudinal relaxation interference

“…Wang et al 18 opted to measure proton flip rates indirectly by measuring selective 1 H R 1 values from the decay of amide proton diagonals in 3D NOESY experiments. Unfortunately, the NOE approach is not suitable for large molecules either because of spectral congestion of the NOESY diagonal.…”

“…Each of these rates depends on different spectral densities, and therefore all report on ͑slightly͒ different dynamical properties. 16 One rate of modern interest [17][18][19][20][21] is z , the rate constant for longitudinal 1 H N -15 N dipole-dipole ͑DD͒ / 15 N chemical shift anisotropy ͑CSA͒ cross-correlated relaxation. The information contained in this rate helps separate the effects of CSA, chemical exchange broadening, and anisotropic tumbling on the classical relaxation rates.…”

“…17 However, z is difficult to measure accurately because an interfering effect of 1 H-1 H dipolar cross relaxation renders the rate equations strongly multiexponential. [17][18][19] At least five previous attempts have been made to resolve these issues. [17][18][19][20][21] The first three approaches, although groundbreaking, suffer from various technical difficulties that prevent them from providing reliable rate determinations for small proteins.…”

“…[17][18][19] At least five previous attempts have been made to resolve these issues. [17][18][19][20][21] The first three approaches, although groundbreaking, suffer from various technical difficulties that prevent them from providing reliable rate determinations for small proteins. The most recent experiment 21 yields reliable rates for small proteins, but cannot be used for larger protein systems due to lack of transverse relaxation optimized spectroscopy ͑TROSY͒ detection and insufficient sensitivity due to periods of fastrelaxing 15 …”

qTROSY – a novel scheme for recovery of the anti-TROSY magnetisation

“…and may either further drain or replenish it, depending on the magnetisation of the surrounding proton lattice. A more detailed description of these complex longitudinal relaxation processes goes beyond the scope of this paper and can be found elsewhere (Wang et al, 2000;Korzhnev et al, 2001), while a semi-quantitative analysis of density matrix calculations is provided in the supplementary material. The result indicates a considerable decay for both 15 N and, to a lesser extent, H N anti-TROSY polarisation during the t 1,A and t 2,A shift evolution times, respectively.…”