One Dimensional Experiments

In the context of the NMR-SIM simulation, the recording of a one-dimensional experiment consists of the definition of the spin system, the pulse sequence and the experiment parameters. The result of the simulation is a FID that is loaded into the ID WIN-NMR processing program. Both the time domain and the frequency domain data may be processed using a variety of domain specific mathematical functions. 

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These assignments are confirmed by the HH TOCS Y diagram b and the selective one-dimensional experiment on top of b with the H NMR subspectrum of the 2-A/-acetylamino-2-deoxygluco-pyranosyl- residue. 

In on-line multidimensional HPLC (MDHPLC) two relatively high-efficiency columns are coupled in an instrument, via the use of valves, traps and other means. In LC-LC the precolumn is used for sample cleanup and prefractionation, before introduction of the fraction of interest to the analytical column. Much of the instrumentation for MDHPLC is the same as that in conventional one-dimensional experiments. However, the additional complexity of MDHPLC experiments leads to greater difficulties than those found in conventional HPLC ... 

The idea of back transformation of a three-dimensional NMR experiment involving heteronuclear 3H/X/Y out-and-back coherence transfer can in principle be carried to the extreme by fixing the mixing time in both indirect domains. Even if one-dimensional experiments of this kind fall short of providing any information on heteronuclear chemical shifts, they may still serve to obtain isotope-filtered 3H NMR spectra. A potential application of this technique is the detection of appropriately labelled metabolites in metabolism studies, and a one dimensional variant of the double INEPT 111/X/Y sequence has in fact been applied to pharmacokinetics studies of doubly 13C, 15N labelled metabolites.46 Even if the pulse scheme relied exclusively on phase-cycling for coherence selection, a suppression of matrix signals by a factor of 104 proved feasible, and it is easily conceivable that the performance can still be improved by the application of pulsed field gradients. 

Although the parabolic rate law has the same form as the mean square displacement (see Section 4.3.1), its physical background is quite different. Parabolic growth is always observed in a one dimensional experiment when due to a gradient-driven flux and where the boundaries are kept at constant potentials. 

NMR spectroscopic analysis of cyclic peptides has the greatest potential for providing quantitative indication and/or proof of the presence of (3-sheet structure in these molecules. NMR evidence can range from qualitative information from simple one-dimensional experiments to quantitative as well as actual structure determinations from more complex two-dimensional experiments. 

From simple one-dimensional experiments, qualitative information regarding secondary structure can be obtained. Shown in Figure 5a are the regions of the ID NMR spectrum containing the amide and aromatic proton resonances for GSM (2) and one GS14 diaste-reomer, GS14K2J12 The GSM spectrum shows 12 well-resolved amide resonances (each is a... 

In Figure 23b, the gel has been exchanged twice with D2O and dried at 100 °C, with considerable care being taken to avoid subsequent water adsorption. As can be seen from the figure, there is a very marked decrease in the intensity of the heteronuclear connectivity, but there is still a residual interaction arising from the trace amounts of hydroxy protons indicated in the projection of FI. It is this situation that leads to the possible ambiguities in the one-dimensional experiments described above. 

Bryce, D. L., Bernard, G. M., Gee, M., Lumsden, M. D., Eichele, K., and Wasylishen, R. (2001). Practical aspects of modern routine solid-state multinuclear magnetic resonance spectroscopy One-dimensional experiments. Can. J. Anal. Sci. Spectrosc. 46,46-82. 

The delay time between successive scans in a 2D experiment is, of course, of major importance for the sensitivity that can be obtained per unit time. For the case of a one-dimensional experiment in which a single 90° pulse is applied to a spin system and time averaging is used, we saw in Section 3.11 that the optimum time A between consecutive pulses is 1.27T, or alternatively that the Ernst flip angle can be used with more rapid repetition. For most 2D experiments, A = 1.27Tj is also close to optimum for a 90° pulse. This repetition time... 

For the common one-dimensional experiment in which the signs of the concentration gradient and of velocity are different. 

It is important to realize that double Fourier transformation is not an essential part of two-dimensional NMR spectroscopy. This was made clear by Ernst in his early article (26) and when the spin system is simple there may be no particular advantage in using it. This approach was adopted in studies of C-enriched methyl formate in which various selective H and/or pulses were applied to individual transitions and it was found possible to deduce an accurate value for v( C) and draw conclusions about relaxation behaviour. (164-166) Detailed analysis (167) also shows that the sensitivity of two-dimensional Fourier transform spectroscopy can be as good as half that achieved in ordinary one-dimensional experiments. In this connection we should note that the time-saving gain of Fourier transformation... 

D EXSY is also important for cases where one-dimensional experiments are feasible (i) more extensive data sets of rate constants as a function of temperature become available which ultimately improves the quality of data of activation energies determined from Arrhenius plots (ii) an independent check is possible if the assumed model of exchange chosen for lineshape analysis of variable-temperature one-dimensional CP/MAS spectra is indeed correct... 

With the very large data sets currently used in one-dimensional experiments (32 or 64 K), digital resolution is seldom a problem. Equation 2-3 also demonstrates that SR and DR are the same. Both are derived from eq. 2-1 in Section 2-4d. DR, however, provides the entry to zero filling and the recovery of lost data points (Section 2-5b). Again, for the previous SR example, with one level of zero filling to 65,536 total points, we have... 

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