Influence of cross-correlation between the chemical shift anisotropies of pairs of nuclei on multiple-quantum relaxation rates in macromolecules
Introduction
Recent years have seen an increase in interest in the measurement and analysis of NMR relaxation, much of it stimulated by the increasing availability of - and -labelled proteins. In addition to the conventional measurement of nuclear Overhauser enhancement to determine internuclear distances [1], relaxation studies of proteins in particular have been used to probe molecular dynamics 2, 3. More recently, measurements of the cross-correlation of different dipolar interactions have been used to determine the angle between them as well as to investigate local motion 4, 5, and measurements of dipolar–chemical shift anisotropy (CSA) cross-correlation have been used to measure chemical shift anisotropy 6, 7, 8, 9, 10, 11. Dipolar–CSA cross-correlation is also responsible for the production of relatively narrow linewidths in spectra produced by the TROSY experiment [12]compared with those produced by competing techniques. CSA–CSA cross-correlation has been predicted for zero- and double-quantum coherence [13]but has not been measured experimentally.
We report here experimental measurement and analysis of CSA–CSA cross-correlation in the heteronuclear zero- and double-quantum coherences arising from Glutamine 27 of perdeuterated -labelled protein hdlc1. It has come to our notice that Boyd is undertaking similar studies [14].
Section snippets
Theory
The time dependence of the density operator can be written in matrix form as 15, 16:where H is the time-independent nuclear spin superoperator, Γ is the relaxation superoperator, σ(t) is the density operator at a time t, and σ0 is the density operator at equilibrium. For convenience the density operator is often expanded as either single-transition operator, or the product of shift operators. Here we adopt the latter approach. The diagonal elements of Γ give the
Experimental methods and results
The pulse sequence used to measure the relaxation of heteronuclear zero- and double-quantum coherence is shown in Fig. 1. Sensitivity is maximised by both exciting and detecting magnetisation. The essential features of CSA–CSA cross-correlation may be demonstrated by the transverse relaxation behaviour of the backbone group of Glutamine 27 of a fully -labelled and perdeuterated, except for the amide protons, sample of the protein hdlc1 in H2O [24]. Glutamine 27 is in an
Discussion
The calculation of values for both ΓklC and ΔσH has been made by making a number of approximations. The model free spectral density function given in Eq. (14)makes the assumption that molecular motion is isotropic; this is often not the case and consequently J(ω) may vary with orientation [27]. However, since the angle between the vector and the principal axis of the CSA tensor is relatively small (∼220) any variation of J(ω) between the two will also be small and can usually be
References (28)
- et al.
J. Magn. Reson.
(1992) - et al.
J. Magn. Reson. Ser. A
(1994) - et al.
J. Magn. Reson.
(1998) - et al.
Chem. Phys. Lett.
(1990) - et al.
Chem. Phys. Lett.
(1991) - et al.
J. Magn. Reson.
(1998) - et al.
Chem. Phys. Lett.
(1993) - et al.
J. Magn. Reson. Ser. A
(1996) J. Magn. Reson.
(1997)- D. Neuhaus, M. Williamson, The Nuclear Overhauser Effect, VCH, Weinheim,...
Biochemistry
J. Am. Chem. Soc.
J. Am. Chem. Soc.
J. Am. Chem. Soc.
Cited by (23)
Solution NMR spin relaxation methods for characterizing chemical exchange in high-molecular-weight systems
2005, Methods in EnzymologyUse of chemical shifts in macromolecular structure determination
2002, Methods in EnzymologyCitation Excerpt :The origins of this variability (as with the isotropic 15N shift itself) have so far eluded generally applicable structural interpretations.67 Carbon CSA effects are also receiving increasing attention in protein NMR, probing CSA-dipolar cross-correlated relaxation along the Cα–Hα bond,133 or along Cα–C′ or H–C′, where C′ is the carbonyl carbon.134–136 In measuring the Cα CSA one uses an (HA)CA(C)NH experiment to detect intensity differences in 13Cα–1Hα doublets caused by relaxation interference between 13Cα dipolar and CSA effects.
NMR studies of Brownian tumbling and internal motions in proteins
2001, Progress in Nuclear Magnetic Resonance SpectroscopyCross-correlations in NMR
2000, Progress in nuclear magnetic resonance spectroscopyInterpretation of chemical shifts and coupling constants in macromolecules
2000, Current Opinion in Structural BiologyDetection of chemical exchange in methyl groups of macromolecules
2019, Journal of Biomolecular NMR