Spin-echo methods

Meiboom S and Gill D 1958 Modified spin-echo method for measuring nuclear relaxation times Rev. Sci. Instrum. 29 688-91... 

Self-diffusion coefficients were measured with the NMR spin-echo method and mutual diffusion coefficients by digital image holography. As can be seen from Figure 4.4-3, the diffusion coefficients show the whole bandwidth of diffusion coeffi-... 

In Fig. 11, the value of D of Na in molten NaNOj measured at 623 K by the spin-echo method is compared with those measured by some other methods. 

Fig. 2.1.16 Trabecular bone structure, muscle after removal of the soft tissue (right). Image and tendon of a mouse tail in vitro at 21.14T, parameters multi-slice spin-echo method,...

Fig. 4 shows the application of a 1-D SPRITE technique to map the distribution of coke within a model fixed bed. In this particular example two layers of coked HZSM-5 were separated by a layer of fresh HZSM-5 (Fig. 4a).21 Each layer was 3.3 cm in length. Fig. 4b shows the profile of coke within the sample recorded by 1H SPRITE imaging these data were recorded in 15 min. The coke had a EEC ratio of 0.5, as determined by elemental analysis and the T2 of the sample was 65 ps—far shorter than could be studied using conventional spin-echo methods. It is worth emphasizing that SPRITE is mapping the coke directly in this experiment, although it should be noted that since it is imaging the H signal, as the coke becomes more graphitic in nature the amount of available H species that can be imaged will...

CPMG Carr-Purcell-Meiboom-Gil 1 spin-echo method To suppress signals with short relaxation time (e.g., protein signals) Small molecules can be detected and quantified in the presence of proteins... 

Same as B, but recorded with Spin-echo method jj D... 

Figure 12.1 Clearance of small-molecule impurities from process buffers in a formulated protein product. Trace A the NMR spectrum of a control sample containing a mixture of three components (succinate, tetraethylammonium, and tetramethylammonium) in the final formulation buffer (sodium acetate). These three components were used in the recovery process for a biopharmaceutical product. Traces B and D the proton NMR spectra of the formulated protein product. No TEA or TMA were detected, but a small amount of succinate was observed in this sample. Traces C and E the proton NMR spectra of a formulated protein product spiked with 10 jag/ml of succinate, TEA, and TMA. Traces D and E were recorded with CPMG spin-echo method to reduce the protein signals. The reduction of NMR signals from the protein allows for better observation of the small-molecule signals.

Figure 12.3 Clearance of MES in a formulated protein product. Trace A the proton NMR spectrum of a formulated protein product spiked with 8 jig/ml of MES. Trace B the proton NMR spectrum of a formulated protein product. The arrows indicate the positions where MES signals would be detected if present. Trace C the difference of traces A and B (A-B). Trace D proton NMR spectrum of 8 ftg/ml of MES in the formulation buffer. The NMR spectra in traces A, B, and D were recorded with the CPMG spin-echo method to reduce protein signals. Only the region where MES signals appear is shown.

Methods for measuring Ti and T2 are discussed in Chapter 5 of reference 21. Suffice it to say here that understanding the method for measuring T2 (the Carr-Purcell pulse sequence or spin-echo method) becomes important for discussing two-dimensional NMR spectra. When spin-spin coupling is present, a modulation of spin echoes is produced, and it is this fact that is important in 2-D NMR spectroscopy. Nuclear relaxation rates and mechanisms become important when discussing the effect of paramagnetic metal centers on NMR spectroscopy. 

As in the case of the single spin-echo detection, the multiple spin-echoes method attenuates magnetization components with short 72(5 ) values and the magnitude of the attenuation increases with increasing echo... 

Self-difFusion coefficients were measured with the NMR spin-echo method and mutual diffusion coefficients by digital image holography. As can be seen from Figure 4.4-3, the diffusion coefficients show the whole bandwidth of diffusion coefficient values, from 10 m s on the methanol-rich side, down to 10 on the [BMIM][PFg]-rich side. The concentration dependence of the diffusion coefficients on the methanol-rich side is extreme, and shows that special care and attention should be paid in the dimensioning of chemical processes with ionic Hquids. 

The former is a protein of 14.7 kDa involved in the multienzyme nucleotide excision repair (NER) pathway with a determined NMR solution structure . In this protein, the Zn + possesses rather a structural than a catalytic role. Zn NMR spectra were acquired using a rather sophisticated probe (for details, see Reference 87) and operating at temperatures 5-250 K. Data acquisition was performed with the application of spin-echo methods for enhanced sensitivity . Specifically, experiments were carried out at 25 K using a combination of CP (cross-polarization) and spikelet echo pulse sequences which provide a considerable increase in signal-to-noise ratio (of the order of 30) relative to a classical quadrupole echo pulse sequence. The proton field strength applied to the above measurements was 60 kHz with a matching field of 20 kHz for zinc and a contact time... 

Field gradient spin echo method of measuring self-diffusion, encompasses SGSE and PGSE variants. 

In polymers, the field-gradient spin-echo methods of measuring self-diffusion have been useful in three more or less distinct areas, the diffusion of polymers in their own melt and in concentrated solutions, in dilute and semidilute solutions, and the diffusion of penetrants and diluents in polymer hosts. A fourth category, the diffusion of bulky or flexible molecules in polymer hosts, is useful for subject matter not closely associated with the first and third category. It should be noted that the work reviewed here represents only a small fraction of the diffusion studies in polymers, including those using other NMR methods. 

The field gradient spin echo methods appear now to have amply proven their validity and usefulness in the study of polymer systems. This early work has been understandably academic in flavor, but there seems to be no impediment to the use of FGSE measurements for routine rheological characterization, e.g., to... 

By the pulsed field gradient spin echo method (1) it is possible to measure mean diffusion lengths ( /(l2)) for molecules in a given time interval in systems without a concentration gradient. The application of the method is limited to... 

Let us now consider the data about the spatial distribution of particles generated in vitreous matrices under the influence of radiolysis and photolysis. According to the data obtained with the help of the electron spin echo method [12], the character of this distribution substantially depends on the energy of electron and quanta by which the sample is irradiated. Thus, the positively charged hole centres which are formed in concentrated vitrified... 

From the data obtained by the electron spin echo method if follows that, at doses above 1021 eV cm"3, the distribution of anion radicals, O, in water-... 

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