2D-WISE

The 2D WISE experiment [68, 71] is based on the simple pulse scheme presented in Figure 14.11. 

The pulse sequence for the 2D WISE experiment (Fig. 20a) consists of three... 

Fig. 13.2. Expansion of the aliphatic region of the 2D WISE-NMR spectrum of poly(p-phenylene pyromellitimide) having two C-16 alkoxy side chains. Also shown are the projections in the and H dimensions. (Reproduced from Ref. [68] with permission. 1992 American Chemical Society, Washington, DC.)...

Fig. 2. Traces along the proton dimension of 2D-WISE experiments performed on 10% hydrated (left) and 35% hydrated (right) onion cell wall material. The corresponding carbon resonances are given. Proton spectral widths of 150 and 70 kHz were used for the 10 and 35% hydrated samples respectively. Reprinted from Carbohydr. Res., Vol. 322(1-2), S. Hediger, L. Emsley and M. Ficher, Solid-state NMR characterization of hydration effects on polymer mobility in onion cell wall material , pp. 102-112, Copyright 1999, with permission from Elsevier Science.

Other experiments allowing inspection of dynamic processes in millisecond s to microsecond s regime are based on measurement of the dipolar line width under MAS samples. To this group belongs both 2D WISE... 

Fqpve 5.4 2D WISE NMR specrating H wideline spectra for different structural units according to their chemical shifts (a) conventional H wideUne spectrum of a blend of poly(styrene) (PS) and poly(vinylmethylether) (PVME (b) 2D H C WISE NMR spectrum indicating different mobilities of the two components [23]... 

Schmidt-Rohr K, Clauss J and Spiess H W (1992) Correlation of structure, mobility, and morphology by 2D WISE NMR, Macromolecules 25 3273-3277. 

Al-Rashed etal. (1996) and Al-Rashed and Jones (1999a,b) presented a CFD-based model to prediet the effeets of mixing during bateh-wise gas-liquid reaetive preeipitation in the flat interfaee eell used by Waehi and Jones, 1991b. A 2D flow simulation was developed for the ehemieal reaetion with... 

It is my opinion that this approach has considerable merit, provided that the questions posed in the problems are wisely selected, as indeed they are in this text. The authors themselves are well versed in natural-product chemistry, an area that presents a wide array of small molecule structural problems. They are therefore concerned that the reader reach the practical goal of applying the full power of NMR spectroscopy to problems of this type. To this end they have selected problems that address methods for solving structures as well as those that pertain to basic theory. The authors have wisely made a point of treating the more widely used ID and 2D experiments in considerable detail. Nevertheless, they also introduce the reader to many of the less common techniques. 

Fig. 1.19 Spin-echo based pulse sequence to each gradient pulse, A the separation between encode velocity change. The gradients are each pair of bipolar gradient pulses and tm the stepped pair-wise independently (2D VEXSY) mixing time between the bipolar gradient pairs, or simultaneously (1 D VEXSY). For a VEXSY The opposite polarity of the bipolar gradient experiment, 7q to k4 are usually applied along pair is realized by an inversion 180° pulse, the same spatial direction. 8 is the duration of...

In the solid, dynamics occurring within the kHz frequency scale can be examined by line-shape analysis of 2H or 13C (or 15N) NMR spectra by respective quadrupolar and CSA interactions, isotropic peaks16,59-62 or dipolar couplings based on dipolar chemical shift correlation experiments.63-65 In the former, tyrosine or phenylalanine dynamics of Leu-enkephalin are examined at frequencies of 103-104 Hz by 2H NMR of deuterated samples and at 1.3 x 102 Hz by 13C CPMAS, respectively.60-62 In the latter, dipolar interactions between the 1H-1H and 1H-13C (or 3H-15N) pairs are determined by a 2D-MAS SLF technique such as wide-line separation (WISE)63 and dipolar chemical shift separation (DIP-SHIFT)64,65 or Lee-Goldburg CP (LGCP) NMR,66 respectively. In the WISE experiment, the XH wide-line spectrum of the blend polymers consists of a rather featureless superposition of components with different dipolar widths which can be separated in the second frequency dimension and related to structural units according to their 13C chemical shifts.63... 

Table 1 MDDR Activity Classes used in this Study. MPS is the mean pair-wise similarity, computed using the Tanimoto coefficient and Unity 2D fingerprints, averaged over all of the molecules in an activity class.

The results reported below were obtained from equilibrium simulations that were performed for a single polypeptide which is either freely diffusing or surface-immobilized. The surface was assumed to be planar, and to consist of beads of diameter a that were arranged on a 2D square lattice with distance a between nearest neighbors. Surface-immobilization was introduced by fixing the position of the 40-th bead such that it lies a distance a above a surface bead. The interaction between the polypeptide and surface beads is described by a pair-wise potential of the form ... 

Among several indicators of motional state of organic solids H linewidths has been used from very beginning of solid-state NMR. However, inherently low resolution of H MAS NMR spectra caused by the very strong homonuclear interactions and relatively low MAS speed lead to a very limited application of H MAS NMR for studies of mobility.1 A 2D wideline separation (WISE) experiment correlates carbon chemical shifts recorded under MAS with broad H lines.1,24 As a result a broad ll lines are separated in the components corresponding to the 13C sites in their close proximity. For mobile domains in a sample, the H - ll coupling are relatively weak which leads to relatively narrow 11 static lines. The opposite is observed for the rigid domains. 

For elastomers and rubbery-like materials well above the T, the high molecular mobility reduces the dipolar couplings dramatically. The WISE experiment allows one to investigate site-selectively residual dipolar interactions and thus molecular dynamics by editing the corresponding proton slices of the 2D data set. 

Figure 4.5 Different binding modes of elastase inhibitors. The three inhibitors on the right-hand side have similar 2D structures but adopt distinct binding modes. By contrast, the two structures on the left (separated by the dashed vertical line) have only limited 2D similarity but share the same binding mode. MACCS Tc values are reported for pair-wise comparisons.

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