DD cross-correlation

The CSA/DD cross-correlated relaxation leads to the differential attenuation of the doublet components of HN groups, thus allowing the evaluation... 

The CH-CH DD/DD cross-correlated relaxation in protein side-chains can be easily measured in HCCH experiment. For larger proteins the resolution of the experiment may not be sufficient to extract the relaxation parameters. Car-lomagno et al proposed a modification of HBHA(CBCACO)NH sequence for the measurement of C H-C H DD/DD cross-correlated relaxation in the spectra... 

H- C DD cross-correlated relaxation rates in CDH2 groups 30... 

N CSA/DD cross-correlated relaxation rate from the intensities of N 31... 

The cross-correlation effects between the DD and CSA interactions also influence the transverse relaxation and lead to the phenomenon known as differential line broadening in a doublet [40], cf Figure Bl.13.8. There is a recent experiment, designed for protein studies, that I wish to mention at tire end of this section. It has been proposed by Pervushin etal [4T], is called TROSY (transverse relaxation optimized spectroscopy) and... 

The DD-CSA cross-correlated relaxation, namely that between 13C-1H dipole and 31P-CSA, can also be used to determine backbone a and C angles in RNA [65]. The experiment requires oligonucleotides that are 13C-labeled in the sugar moiety. First, 1H-coupled, / - DQ//Q-II CP spectra are measured. DQ and ZQ spectra are obtained by linear combinations of four subspectra recorded for each q-increment. Then, the cross-relaxation rates are calculated from the peak intensity ratios of the doublets in the DQ and ZQ spectra. The observed cross-correlation rates depend on the relative orientations of CH dipoles with respect to the components of the 31P chemical shift tensor. As the components of the 31P chemical shift tensor in RNA are not known, the barium salt of diethyl phosphate was used as a model compound with the principal components values of -76 ppm, -16 ppm and 103 ppm, respectively [106]. Since the measured cross-correlation rates are a function of the angles / and e as well, these angles need to be determined independently using 3/(H, P) and 3/(C, P) coupling constants. 

For completeness, transverse relaxation-optimization is not limited to the constructive interference between DD coupling and CSA. Pervushin et al. [12] introduced the ZQ-TROSY, which is based on cross-correlated relaxation between H CSA and 15N CSA during the multiple quantum 15N-evolution period. 

The cross-correlated DD-CSA (or DD-CSR) spectral densities, giving rise to differential line broadening and to the order transfer phenomena summarized by Eq. (20), can in principle be complex functions. The line-broadening... 

Jones DD. Amino acid properties and side-chain orientation in proteins a cross correlation approach. J. Theor. Biol. 1975 50 167-183. 

The exploitation of cross-correlation effects in high magnetic fields has introduced a new form of NMR spectroscopy called transverse relaxation-optimised spectroscopy or TROSY. The cross-correlation of the optimised dipole-dipole (DD) and chemical shift anisotropy (CSA) relaxation mechanisms leads to differential transverse relaxation rates for the two components of the l5N- H doublet in undecoupled spectra of l5N-labelled proteins. For one component, DD and CSA relaxation constructively add to produce very efficient relaxation, leading to a broad line, whereas for the other component, the two relaxation mechanisms constructively interfere, leading to a narrow line when the two mechanisms are nearly equal. There is no optimum field where DD and CSA relaxation are equal for all amide bonds, because DD relaxation between the amide protons and other nearby protons differs for each residue.72 Clearly, the overall effectiveness of TROSY is optimized when the non-exchangeable protons in the macromolecule... 

The usefulness of cross-correlated relaxation measurements for deriving structural information was described previously in several publications. More examples of that appeared in the reviewed year. Kloiber and Konrat presented a method for measurement of (DD) / (CSA) cross-... 

Riek demonstrated the correlation between hydrogen bond length in Watson-Crick base pairs with (CSA)/ N--- H (DD with proton acceptor) cross-correlated relaxation rates. The measurements are performed with modified 2D N- H-ZQ TROSY experiment. The cross-correlated relaxation rates are evaluated from the cross-peaks ratio in the spectra where the relaxation is either active or deactivated with a selective pulse. The hydrogen bond length is estimated from the ratio of cross-correlated relaxation rate involving DD interaction with the acceptor to the rate of the relaxation in the reference experiment involving DD interaction with the donor. 

Backbone torsion angles a and in oligonucleotides can be estimated from the DD/ CSA cross-correlated relaxation. A modified /-resolved... 

TROSY. The number of publications in this area was substantially reduced relative to the previous year. A new TROSY element was proposed by Riek et al. The method utilises DD/ C CSA cross-correlation... 

Measurement of CSA/ H- N DD 28 cross-correlated relaxation in Watson-Crick H-bonds Measurement of H- CDD/ P 29... 

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