Sensitivity enhancement of 13C T1 measurements via polarization transfer

Suppression of the effects of cross-correlation between dipolar and anisotropic chemical shift relaxation mechanisms in the measurement of spin-spin relaxation rates

“…Expanding (11), (12) and (14) yields: (17), (19) and (20) are obtained by direct differentiation of (3), (12) and (14); (18) can be derived from (11) by induction. For the initial conditions a(0) given by (7) and (8), only the diagonal elements of the matrices in (17)-(20) affect a(t).…”

“…while for the sequences of figure l(b) and l(c), Analytic or numerical expressions for the time dependence of a~ (t) and a2(t ) can be obtained by standard methods [31]; however, insight into the expected behaviour of the CPMG sequences given in figure 2 can be obtained by expanding (3), (11), (12) and (14) to second order in t. For the conventional CPMG sequence ( figure 2(a), (3)),…”

“…A resurgence of interest in characterizing intramolecular dynamics in macromolecules through studies of heteronuclear NMR relaxation [8][9][10] has been precipitated by the development of proton-detected heteronuclear NMR spectroscopic techniques [11][12][13][14][15]. At high magnetic fields, the magnitudes of the dipolar and anisotropic chemical shift coupling are comparable for 15N in a peptide group and for aromatic t3C nuclei; consequently cross correlation between these two relaxation mechanisms systematically affects relaxation rate constants measured using conventional experimental methods.…”

Protein dynamics studied by rotating frame 15N spin relaxation times

“…For such studies with ~5N, a technical advantage arises because, even in uniformly 15N-labeled proteins, measurements of relaxation times are not disturbed by scalar couplings to other heteronuclei. Two-dimensional heteronuclear NMR techniques efficiently measure longitudinal and transverse 15N relaxation times (Kay et al, 1987(Kay et al, , 1992Sklenar et al, 1987;Wagner, 1988, 1989;Peng and Wagner, 1992). Kay et al (1989) recently used relaxation times in conjunction with measurements of heteronuclear ~H-15N Overhauser effects to determine the correlation time for overall rotational tumbling and, following the model-free approach of Lipari and Szabo (1982), the order parameter, S, for a large number of backbone ~SN nuclei in staphylococcal nuclease.…”

Recent Developments in Studying the Dynamics of Protein Structures from and 15N and 13C Relaxation Time Measurements

“…In addition, high concentrations of samples were necessary in these experiments. With the application of one-and two-dimensional experiments in which the relaxation times of the heteronuclei were indirectly detected from a decrease of signal intensity of the resonances, a remarkable improvement in resolution and sensitivity was reached Wagner, 1989, 1988;Sklenar et al, 1987;Kay et al, 1987).…”