NMR hardware

The major components of an NMR spectrometer include a with a magnet, probe, rf electronics, and a desktop computer as depicted in Fig. 12.3 and further described in Table 12.2. Significant advancements in NMR hardware over the years have yielded dramatic increases in experimental sensitivity and resolution. One such advancement has been the recent introduction of the shielded 900 MHz magnet. A 900 MHz magnet results in an 84% improvement in sensitivity and a 150% improvement in resolution relative to a standard 600 MHz magnet (Kupce, 2001). The shielded aspect of the magnet reduces the 

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Smaller diameter probes reduce sample volumes from 500 to 600 pi typical with a 5 mm probe down to 120-160 pi with a 3 mm tube. By reducing the sample volume, the relative concentration of the sample can be correspondingly increased for non-solubility limited samples. This dramatically reduces data acquisition times when more abundant samples are available or sample quantity requirements when dealing with scarce samples. At present, the smallest commercially available NMR tubes have a diameter of 1.0 mm and allow the acquisition of heteronuclear shift correlation experiments on samples as small as 1 pg of material, for example in the case of the small drug molecule, ibu-profen [5]. In addition to conventional tube-based NMR probes, there are also a number of other types of small volume NMR probes and flow probes commercially available [6]. Here again, the primary application of these probes is the reduction of sample requirements to facilitate the structural characterization of mass limited samples. Overall, many probe options are available to optimize the NMR hardware configuration for the type and amount of sample, its solubility, the nucleus to be detected as well as the type and number of experiments to be run. 

Aside from the basic components of the spectrometer as mentioned above, there are many optional accessories that should be considered for establishing an appropriate NMR hardware configuration. Variable... 

From the biological viewpoint, glycosaminoglycans (GAGS) are one of the most relevant oligo- and polysaccharides. The access to new NMR hardware and software, as well as the employment of new synthetic and molecular biology protocols have permitted important advances in the comprehension of their structural and conformational properties, as well as deeply study different examples of their interaction with receptors. 

Since investigators continuously strive to extract increasing amounts of data from shrinking sample sizes, much commercial and academic research on NMR hardware focuses on optimizing RF probe sensitivity to allow the analysis of trace materials. Significant advances have been achieved through several distinct modifications of instrumentation. This present chapter provides a review of the characterization of nanoliter volumes via static NMR spectroscopy and emphasizes some of the more relevant developments in probe technology that have enabled such measurements. 

Now let s look in detail at each process, so that we can understand the NMR acquisition parameters needed to set up the experiment. After the pulse, we will follow through the hardware devices in a block diagram and try to understand a little about the NMR hardware. It turns out that processing of the NMR signal in the hardware is strictly analogous to the theoretical steps we will use in viewing the NMR experiment with the vector model, so it is essential to understand it in general. 

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