ID NMR method

Another approach to obtain spatially selective chemical shift information is, instead of obtaining the entire image, to select only the voxel of interest of the sample and record a spectrum. This method called Volume Selective spectroscopY (VOSY) is a ID NMR method and is accordingly fast compared with a 3D sequence such as the CSI method displayed in Figure 1.25(a). In Figure 1.25(b), a VOSY sequence based on a stimulated echo sequence is displayed, where three slice selective pulses excite coherences only inside the voxel of interest. The offset frequency of the slice selective pulse defines the location of the voxel. Along the receiver axis (rx) all echoes created by a stimulated echo sequence are displayed. The echoes V2, VI, L2 and L3 can be utilized, where such multiple echoes can be employed for signal accumulation. 

One-dimensional (ID) NMR methods based on the dipolar correlation effect in combination with the Hahn and solid echoes (52,63), the stimulated echo (5), the magic echo (64), magnetization-exchange (65), and cross-relaxation dynamics (66) provide access only to the second van VIeck moment via a model which takes into accoimt the solid-like and liquid-like contributions to the spin system response (67). Model free access is given by the analysis of multiple-quantum builtup (68) and decay (69) curves recorded in the initial regime of the excitation/reconversion periods. 

Orrell K G, Sik V and Stephenson D 1990 Quantitative investigations of moieouiar stereodynamios by ID and 2D NMR methods Prog. Nucl. Magn. Reson. Specfrosc. 22 141-208... 

Structure and stereochemistry of the dibromides 2a-h were elucidated by various NMR methods including ID proton-proton NOE difference spectra and 2D... 

The method utilizing ID NMR is simple and eonvenient. Henee the NMR method diseussed here ean be applied to the systematie investigation of the membrane irug inter-aetions, elosely related to the vital function in biomembranes. It is expected that the application can be extended to the lipid-peptide interaction and protein uptake. We are now applying the method to apolipoprotein binding with lipid bilayers and emulsions. Preferential protein binding sites in membranes can be specified by NMR on the molecular level. 

Typical structure elucidation protocols using NMR methods rely on one-dimensional (ID) 1H and 13C reference spectra, when sufficient sample is available to acquire a 13C reference spectrum, in conjunction with a... 

The kinetic information for NMR experiments is contained in the line broadening observed for a nucleus that resides in two different magnetic environments, and values for rate constants can be obtained using line-shape analysis.28,68,69 Line broadening experiments obtained using ID NMR is the method of choice when analyzing the kinetics of a molecule in two sites. 2D NMR techniques, such as 2D EXYS are employed when the kinetics are sequential, i.e. more than one step, or multiple sites are analyzed.69 For example in the case of supramolecular systems this technique was employed to measure the exchange kinetics in capsules.70... 

D-NMR methods are highly useful for structure elucidation. Jeener described the principles of the first 2D-NMR experiment in 1971 [31]. In standard NMR nomenclature, a data set is referred to by one, i.e., less than the total number of actual dimensions, since the intensity dimension is implied. The 2D-data matrix therefore can be described as a plot containing two frequency dimensions. The inherent third dimension is the intensity of the correlations within the data matrix. This is the case in ID NMR data as well. The implied second dimension actually reflects the intensity of the peaks of a certain resonance... 

This ladybird is protected by hyperaspine (23) (Fig. 4), the structure of which was deduced from its ID and 2D NMR data. These spectra disclosed the presence in the molecule of a 3-oxaquinolizidine skeleton substituted by a 2-pyrro-lecarboxylate moiety, by a secondary methyl group, and by a n-pentyl side chain. The ds-fused ring conformation and the relative configuration of 23 were based on IR and 2D NMR methods [37]. 

The coupling of HPLC with NMR represents a powerful method for the high-throughput screening of peptides in mixtures run in stop-flow and continuous-flow modes. It is possible to obtain routine high-quality HPLC/NMR ID NMR data with as little as 5 pg of compound in a chromatogram peak. However, the HPLC/NMR technique cannot be favorably compared to mass spectrometry techniques (HPLC/MS) in terms of sensitivity and speed of analysis. To date, the majority of reports of the use of HPLC/NMR have been for drug metabolites.1 ... 

Wilson ID, Griffiths L, Lindon JD, Nicholson JK. HPLC/NMR and related hyphenated NMR methods. In Gorog S, ed. Identification and Determination of Impurities in Drugs. New York Elsevier, 2000 299-322. 

In Fig. 1 we have highlighted with a dark background the different types of NMR methods that are used in drug-discovery projects. These include basic ID and 2D methods that are used to confirm the identity of peptides, determine their conformation, or derive restraint information used in 3D structure calculations (left side of Fig. 1). Methods to study binding interactions (middle section of Fig. 1) can be broadly categorized as being based on NOEs, diffusion, relaxation, or chemical shift changes. NOE-based methods include the transferred NOE... 

For the investigation of the molecular dynamics in polymers, deuteron solid-state nuclear magnetic resonance (2D-NMR) spectroscopy has been shown to be a powerful method [1]. In the field of viscoelastic polymers, segmental dynamics of poly(urethanes) has been studied intensively by 2D-NMR [78, 79]. In addition to ID NMR spectroscopy, 2D NMR exchange spectroscopy was used to extend the time scale of molecular dynamics up to the order of milliseconds or even seconds. In combination with line-shape simulation, this technique allows one to obtain correlation times and correlation-time distributions of the molecular mobility as well as detailed information about the geometry of the motional process [1]. 

We will see that in 2D NMR, the sampling in the second dimension can also be done either way, except that this choice is up to the user and is not hard wired. The alternate ( Bruker-like ) sampling method is called TPPI (time proportional phase incrementation), and the simultaneous ( Varian-like ) method is called States or States-Haberkorn (after the originators of the technique). The consequences for processing and interpretation of the data are the same in the second dimension of 2D spectra as they are in ID NMR. 

Dimensional (ID) NMR, using line shape, estimating the Edwards-Anderson parameter ijEA, is applicable to systems, on the time scale of the order 10 3-10 8 s and this method fails for the direct determination of gEA on longer time scales. 

D MAS NMR techniques In the previous section, we reported applications of ID NMR spectroscopy, which enables the determination and quantitative characterisation of different phosphorus groups Q" via deconvolution of 31P resonances. Unfortunately, such an approach has at least two limitations. First, the 31P MAS NMR spectra suffer from broad and overlapping signals, and these methods fail when more complicated systems are to be analysed. Second, the structural information is significantly limited, for example the connectivities of Q group or through-space interactions cannot be established from only ID spectra. To overcome these limitations, it is necessary to apply more advanced 2D NMR techniques. 

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