Chemical shift spectrum

Proton chemical shift spectra over the range of 0—15 ppm ( 0.1 ppm) TFA, ttifuoroacetic acid DMSO, dimethyl sulfoxide. When complex spectra caused by second-order effects or overlapping resonances were encountered, the range was record (11,12). 

Estimated precision in the chemical shifts is 0.05 p.p.m. The chemical shifts are given relative to external 1,4-dioxane, which was introduced into some samples only to obtain chemical shifts. Spectra obtained at 258 for — 10% solutions. Spectra of compounds were obtained at 22.5 MHz see Ref. 20. Spectra of compounds were obtained at 22.5 MHz see Ref. 24.J Spectrum obtained at 100.6 MHz see Ref. 24. Data taken from Ref. 61. Chemical shifts for GalNAc only are given. The data given in the parentheses for compounds 51 and 32 refer to the carbon count. 

As regards the aliphatic carbons, the chemical shift spectra of MGIM76 at various temperatures are shown in Fig. 153, as well as the NMR spectrum obtained for MGIM76 in solution. As for C = O(MGI) groups, spectrum shape changes only occur between 115 and 160 °C. Two spectrum regions are concerned ... 

Variable temperature (-150° to +350°) chemical shift spectra have been obtained for melt-recrystallized samples of PTFE. The NMR spectra were acquired using the REV-8 sequence which consists of a long train of closely spaced, high power rf pulses of fixed width, and varying in phase in a cyclical fashion. The cycle consists of eight ir/2 pulses. The total cycle time used was 43.2 psec with a shortest spacing between pulses of 3.6 usee. The nominal resonance frequency was 84.6... 

Chemical shift spectra of PTFE obtained at 259° are shown in Figure 1. These lineshapes, for three different samples of varying crystallinity, may be seen to be a linear combination of two lineshapes one is characteristic of an axially symmetric powder pattern and the other of an isotropic chemical shift tensor. At this temperature these two lineshapes differ greatly and may be numerically decomposed. 

Figure 1. F-19 REVS chemical shift spectra of PTFE samples of varying...

It is clear from the chemical shift spectra that the only process observable in the crystalline regions from -128° to +320° (near the melting point) is reorientation about the chain axis. Translational displacements along the chain axis in well-ordered crystalline regions (which have been previously observed—-—) would not give rise to any observable change in the chemical shift spectra. However, the chemical shift spectra of the... 

The numerical method used to decompose the chemical shift spectra are detailed in a paper submitted to Macromolecules. 

Chemical shift spectra may be obtained as a third dimension of a two-dimensional imaging technique, by selective reception of a region of interest using a surface rf coil, or by selecting a spectroscopic voxel using field gradients. 

In fact, the l3/2> — l5/2) ST, satellite (or its equivalent ST 2) transition of a spin-9/2 yields sidebands that are narrower with respect to the CT by about a factor of 18, and provides almost complete high-resolution chemical shift spectra. 

The high-resolution and the high scaling factor of 2D PISEMA, for the first time, enabled the use of the dipolar dimension to resolve resonances from non-selectively or uniformly labeled proteins. Three-Dimensional experiments were used to enhance the resolution of resonances from uniformly N-labeled peptides and proteins embedded in lipid bilayers. This was successfully demonstrated on aligned samples containing uniformly N-labeled membrane-associated peptides and proteins. Two-dimensional PISEMA spectra of some of these systems showed limited resolution due to a small frequency dispersion of resonances from a-helices oriented on the surface of the bilayer in both N chemical shift and H- N dipolar coupling dimensions. However, when an additional H chemical shift dimension was invoked, the 3D H chemical shift/ H- N dipolar coupling/ N chemical shift spectra of these systems considerably increased the resolution of peaks. ... 

Fig. 10.3.1 [Hepl] F chemical-shift spectra of PTFE. The dipole-dipole interaction has been removed by M V8 multi-pulse excitation, (a) Isotropic molecular orientation, (b) Uniaxially drawn sample. The drawing direction is parallel to the magnetic field.

The N- H dipolar/chemical shift spectra were observed for polycrystalline samples of [15N]acetylvaline, -[15N]glycyl-[15N]glycine, [15N]glycyl-[15N]glycine HC1- H20, [15N]acetyl-glycine, [7r-15N]-l-histidine HC1 H20, and [e-15N]tryptophan21 (Fig. 5). 

Some chemical-shift spectra as a function of WAHUHA irradiation for poly(o-chlorostyrene) are shown in Figure 2. 

NMR ( N-HSQC) Observation of change in two-dimensional H- or N-heteronuclear single quantum correlation (HSQC) backbone chemical shift spectra upon ligand binding described as A5( h/ N) = [L]/([L]+Kd) FKBP [9]... 

Some chemical-shift spectra as a function of WAHUHA irradiation for poly(q-chlorostyrene) are shown in Figure 2. Protonated carbon magnetizations rapidly dephase under as little as two cycles of WAHUHA irradiation, but are refocused after sixteen cycles (one rotor period). Magic-angle spinning should refocus dipolar coupling just as it does chemical shift aniso-... 

Figure 3 Chemical shift spectra of 4-androsten-3,17-dione obtained from (a) the reflected J spectrum (b) the purged J spectrum (the additional response near 61.7 is from the residual water signal) and (c) the z-filtered J spectrum. The conventional spectrum is shown in (d). Reprinted with permission from Simova S, Sengstschmid H and Freeman R (1997) Proton chemical-shift spectra. Journal of Magnetic Resonance 124 104-121.

Simova S, Sengstschmid H and Freeman R (1997) Proton chemical-shift spectra. Journal of Magnetic Resonance 124 104-121. 

Figure 3 2. Magic angle spinning carbon-13 chemical shift spectra of TBC-9 (top) and TBC-12 (bottom) at different phases and temperature. Reprinted from reference 14, with permission from the Journal of Physical Chemistry...

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