Kinetics Magnetization transfer

F. Du, X.-H. Zhu, H. Qiao, X. Zhang and W. Chen, Efficient in vivo P magnetization transfer approach for noninvasively determining multiple kinetic parameters and metabolic fluxes of ATP metabolism in the human brain. Magn. Reson. Med., 2007, 57, 103-114. 

The corresponding parameters for the BS process in these systems cannot be evaluated using 19F NMR experiments because the rate is too slow. However, kinetic parameters for the BS process in heptafluorocycloocta-1,3,5,7-tetraene 116 have been shown by magnetization transfer techniques to be... 

Line-shape analysis, magnetization transfer experiments, 2D NOESY etc. can be used for kinetic studies of CTI, but they require relatively high peptide concentrations (Fig. 8.7) [53]. Mainly used for the investigation of model systems, they can also be utilized in complex cases for the determination of individual rate constants and for the monitoring of protein folding. 

More recent mechanistic studies have been able to distinguish between pathways (b) and (c), and all results indicate that (c) is operative [87]. The initial ligand dissociation and substitution steps have been studied using NMR magnetization transfer experiments, NMR and UV-vis kinetics, and mass spectrometry [87,88]. These investigations indicate that both phosphine/phosphine (Fig. 4.31a) and phosphine/olehn (Fig. 4.31b) substitution reactions in (L)(PR3)(X)2Ru= CHR complexes proceed by a dissociative mechanism involving a 14-electron intermediate (L)(X)2Ru=CHR (A). Although this proposed intermediate has not been observed in solution, presumably due to its low concentration, it has been identihed in the gas phase [88]. 

The advent and popularization of more sophisticated NMR experiments, such as magnetization transfer techniques [43], was a great asset for kinetic studies. Using these techniques the equilibrium involving insertion/deinsertion in the complex [RhH(C2H4)(PPr3)2] has been studied in detail [44]. A hydride complex is the only species observed by NMR from —90 to 0°C. Its resonances... 

We have developed a model for the esp in PJyqQ which includes contributions of both PjyQl and PjyQp" interactions to the esp of PJyqQ . We can show how factors such as kinetics, magnetic interactions, and structure affect the esp. This model can then be applied to assess the esp in PSI in terms of primary electron transfer steps. 

Additional studies were performed using BuVE in order to obtain the initiation kinetics of complexes 35 and 36 independent of any propagation steps. For 35, was found to be dependent on the alkene concentration, while 36 was independent of the alkene concentration. The alkene dependence suggests another mechanism of initiation is occurring for 35 compared to the benzyhdene counterpart 2, while 36 proceeds through a typical dissociative pathway. The thermodynamic parameters obtained from the BuVE study were consistent with the values previously obtained from the magnetization transfer experiments. 

---