Two dimensional NOESY

Fig. 3.3 A contour plot of a 750 MHz two-dimensional NOESY spectrum of the mating pheromone Er-22 adapted from Ref. [6]. B Cross section along to, displaying strong artifacts at multiples of A=340 Hz corresponding to a time variation of...

Figure 6.48 Two-dimensional NOESY spectrum (mixing time = 2 s) of the ether glucuronide of 3-methoxy-paracetamol at 600 MHz in a 3-mm cryogenic probe head (total experiment time 20 h). The sample was recovered from a conventional 3-mm LC probe head after a triple trapping SPE-NMR run (result shown in Eigure 6.41). Reproduced from [59] with permission from Elsevier.

Fig. 18. The pulse sequence used for the two-dimensional NOESY experiment for measuring H- H cross-relaxation rates in soft polymers. The entire experiment is conducted under magic-angle spinning. Gradient pulses are used to remove unwanted coherences, as this allows for much faster experiments than phase cycling.

Chen, Y.Y. and Bleam, W.F., Two-dimensional NOESY nuclear magnetic resonance study of pH-dependent changes in humic acid conformation in aqueous solution,... 

Figure 4. F NMR spectra of (A) two-dimensional NOESY exchange of 3 mM 4-fluoro-4-deoxy-galactose and 2 mM receptor at 25°C. Diagonal peaks show the one-dimensional spectrum which is projected on the top of the map. (B) 1.6 mM 4-fluoro-4-deoxy glucose and 0.8 mM receptor at 25°C and (C) 2°C. (D) 1 mM 4-fluoro-4-deoxy-galactose and 2 mM receptor at 2° C.

The resolntion that is gained by the additional freqnency dimension (N in this case) is illnstrated in Figure 3.6. The two-dimensional NOESY spectrnm of a 50 residne a-helical protein is shown in the left part of this fignre. In this experiment, the magnetization is transferred from proton H to proton Hy by dipolar coupling. The first freqnency dimension corresponds to the chemical shift of H and the second frequency dimension corresponds to the chemical shift of Hy. As with the NOESY-HSQC described previously, the intensity of the peak is related to the distance between H and Hy. Note the large number of unresolved overlapping peaks in the... 

Zumbulyadis et al. [86] selected a fluorinated polyphosphazene, containing CF3CF2CF2CF2CH2O side chains (attached to phosphorus atoms in the polymer backbone) to explore the potential of F MAS/NOESY experiments. MAS at 3.82 kHz sufficed to resolve all four F sites, though effects of isotropic indirect coupling were obscured by the linewidths. Cross peaks are seen in the two-dimensional NOESY spectrum. The authors argue that these arise from NOE processes and not from spin diffusion. 

Two-dimensional NOESY allows detection of spatial proximity between protons that are separated by less than 4.5 A. By the correlated spectroscopy method (COSY) scalar couplings between protons, which are separated by at most three (in some exceptions four) chemical bonds, are used. In the case of ribooligonucleotides such couplings consequently can only be observed between the protons of the ribose rings and the C5 and C6 protons of the pyrimidine bases of a given nucleotide. The NOESY method, however, permits the detection of contacts between the protons of different nucleotides. 

Figure 3.26 The two-dimensional NOESY spectra for 38 wt% 50 50 mixtures of poly(vinyl chloride) and poly(methyl methacrylate) in deuterated THF. Intermolecular cross-peaks are marked in (a). A small amount of water is added in (b), leading to a disappearance of the intermolecular cross-peaks. Reprinted with permission from ref. 29.

They are most often combined with traditional two-dimensional experiments such as NOESY and TOC-SY to yield a three-dimensional experiment. For example, in the case of an HSQC-NOESY spectrum of a protein, two of the axes represent the heteronuclei such as and the protons which are directly attached to the nitrogen nuclei, while the third axis contains chemical shifts of protons which share an NOE effect with the amide proton. This offers a significant increase in resolution compared to a traditional two-dimensional NOESY. A large array of these types of three-dimensional, heteronuclear-edit-ed experiments have been designed to extract structural information in various situations. 

The solutions to equation (1) may be written down immediately in terms of a matrix exponential. For the two-dimensional NOESY experiment, with appropriate normalization, the initial conditions (at the beginning of the mixing period ) can be written as a unit matrix, i.e., the two-dimensional pulse sequence is equivalent to repeated relaxation experiments in which each spin in turn is displaced from equilibrium. The two-dimensional NOE cross-peak intensity at chemical shifts corresponding to spins i and j is then related to the magnetization of spin i for the experiment in which spin j was initially perturbed. After a mixing time tm, this is just exp(—Rrm),. ... 

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