Magnetization-exchange experiment

Figure 6. Magnetization Exchange Experiment for microtubule-bound 74 (solid lines represent curves for distance markers).

Fig. 12. The magnetization-exchange experiment.(a) magnetization-exchange pulse sequence (b) = 3 C magnetization-exchange spectra of doubly C-labelled zinc acetate at different mixing times Tm (c) simulated (solid lines) and experimental ( ) magnetization-exchange curves on (top) and off (bottom) the R condition. (Parts (b) and (c) reproduced from ref. 75, 1988, with permission from Elsevier Science.)...

This can be done by carrying out lineshape simulations. However, in general this is not done because a Zeeman magnetization exchange experiment is more... 

Figure 4 Pulse sequence for carrying out the RR experiment (see text). In the case of the magnetization exchange experiment, CP of the rare spins is followed by a flipback pulse on the rare spin channel, selective inversion of a particular resonance, and a variable delay before acquisition.

Di Bari L, Kowalewski J and Bodenhausen G 1990 Magnetization transfer modes in scalar-coupled spin systems investigated by selective 2-dimensional nuclear magnetic resonance exchange experiments J. Chem. Rhys. 93 7698-705... 

Abstract This review reports on the study of the interplay between magnetic coupling and spin transition in 2,2 -bipyrimidine (bpym)-bridged iron(II) dinuclear compounds. The coexistence of both phenomena has been observed in [Fe(bpym)(NCS)2]2(bpym), [Fe(bpym)(NCSe)2]2(bpym) and [Fe(bt)(NCS)2]2(bpym) (bpym = 2,2 -bipyrimidine, bt = 2,2 -bithiazoline) by the action of external physical perturbations such as heat, pressure or electromagnetic radiation. The competition between magnetic exchange and spin crossover has been studied in [Fe(bpym)(NCS)2]2(bpym) at 0.63 GPa. LIESST experiments carried out on [Fe(bpym)(NCSe)2]2(bpym) and [Fe(bt)(NCS)2]2(bpym) at 4.2 K have shown that it is possible to generate dinuclear molecules with different spin states in this class of compounds. A special feature of the spin crossover process in the dinuclear compounds studied so far is the plateau in the spin transition curve. Up to now, it has not been possible to explore with a microscopic physical method the nature of the species... 

Peralkylated tetracarba-mdo-hexaboranes(6) 56 [72] are extremely stable, and almost inert in air and stable towards H20, in contrast with the parent carbaborane [73], nB/nB magnetization transfer experiments performed at 140 °C for the per-ethyl derivative show that exchange reactions between boron atoms in positions 1 and 6 are very slow. 

The steady-state heteronuclear 15N 1H NOEs are determined as a ratio of cross-peak intensities in two experiments, with and without presaturation of amide 1H nuclear spins, usually referred to as NOE and NONOE experiments, respectively. Magnetization exchange between amide protons and water protons could affect the equilibrium 1H magnetization in the NONOE experiment, and thereby increase the measured NOE values. 

Modern NMR techniques such as quantitative analysis of multisite exchange using either ID magnetization transfer experiments (JOS) or the 2D exchange spectroscopy (EXSY) method (104,105) promise to be of great help in unraveling the complex stereochemical exchange networks involved in cluster fluxionality. The usefulness of EXSY in the context of this article is illustrated by the phase-sensitive 13C 1H EXSY spectrum (255 K, tm = 0.5 sec)... 

---