Polarization concatenation

Concatenation of Polarization Transfer Steps into Homonuclear Chemical Shift Correlated Experiments. Application to Oligo- and Polysaccharides... 

In a move in the opposite direction, the overlaps resulting from concatenation of different polarization transfer mechanisms in combined 2D experiments can be eliminated by reducing the dimensionality of an experiment. Similarly to the successful transformation of basic 2D NMR techniques into their ID counterparts [32-34], a conversion of combined 2D NMR techniques into their ID analogs is feasible and has been explored by several groups [35-40]. From a different perspective this process can be seen as a twofold reduction of the dimensionality in a 3D experiment. Equally, concatenation of three polarization transfer steps in a single ID experiment represents transformation of a possible 4D homonuclear experiment into its ID analog. 

These two experiments are different from previously discussed techniques, since they are concatenations of two identical polarization transfer steps. There are various reasons why these experiments are beneficial to spec-... 

If the coupling constants are known in advance, the total mixing time can be reduced in multiple-step selective coherence-transfer experiments by using the selective homonuclear analog of the optimized heteronuclear two-step Hartmann-Hahn transfer technique proposed by Majumdar and Zuiderweg (1995). In this technique [concatenated cross-polarization (CCP)] a doubly selective transfer step (DCP) is concatenated with a triple selective mking step (TCP). For the case of a linear three-spin system with effective planar coupling tensors, a CCP experiment yields complete polarization transfer between the first and the third spin and the total transfer... 

Zuiderweg, 1995). In the case of a linear ISQ system, concatenated cross-polarization (CCP Majumdar and Zuiderweg, 1995) is more efficient than two sequential double-resonance (DCP) Hartmann-Hahn transfer steps. The CCP scheme is a combination of a DCP and TCP experiment with optimized mixing times Tj and Tj that depend on the magnitudes of and J Q (Majumdar and Zuiderweg, 1995). 

The assignment of resonances to the chemical structure commences from the main chain atoms HN, N, CA, CO and CB. The experiments, i.e. the pulse sequences for this purpose, appear superficially complex but are in fact built from concatenated parts of heteronuclear polarization transfers. The magnetization is often derived from the amide proton and also from the amide nitrogen when using transverse relaxation optimized spectroscopy. Subsequently the polarization is relayed to amide nitrogen and further to carbons. Three-dimensional spectra are produced by acquiring the frequencies of the amide proton directly and recording... 

The bonds that form the skeleton have a pronounced covalent character due to the polarization interactions, while the alkaline ions are connected by the weaker ionic bond, upon the vertices of the polyhedron of KOjq coordination. The formation of the tridimensional skeleton is found to a reduced number of combinations and only for compounds able to accomplish the tridimensional concatenation of the basic structural (C, Si) units. 

The membranes of anammoxosomes and anammox bacteria have at least two unique characteristics (i) the hydro-phobic tails of these lipids comprise ladderanes formed by the cydobutane concatenation (three or five according to otu current state of knowledge) and (ii) the polar heads present at the same time as esters and ethers, as well as the nonmodified forms of glycerol. As far as is currently known, the polar parts assodated with these phospholipids are always choline and ethanolamine (Sinninghe Damste et ah, 2002, 2004, 2005 Hopf, 2003 Van Niftrik et ah, 2004 Nouri and Tantillo, 2006 Boumann et ah, 2006 Rattray et al., 2008). Some of these structures are presented in Figure 7.7. 

The second method of creating 3D-NMR experiments, concatenation of INEPT polarization transfer sequences, is... 

Figure 25 Creation of 3D-NMR experiment by concatenation of polarization transfer steps.

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