Solvent peak residual

The authors expressed PKA consisting of 353 amino acids, of which eight are prolines. Resonances of 274 backbone amide peaks were visible in the spectrum, of which 191 were assigned. It was possible to assign resonances for the N- and C-terminal sequences, the majority of the N-lobe, including the glycine-rich loop, and most of the solvent-exposed residues of the C-lobe. This enabled a determination of the structure for the more flexible parts of the structure. However, many correlations were missing for the... 

Extraction or dissolution almost invariably will cause low-MW material in a polymer to be present to some extent in the solution to be chromatographed. Solvent peaks interfere especially in trace analysis solvent impurities also may interfere. For identification or determination of residual solvents in polymers it is mandatory to use solventless methods of analysis so as not to confuse solvents in which the sample is dissolved for analysis with residual solvents in the sample. Gas chromatographic methods for the analysis of some low-boiling substances in the manufacture of polyester polymers have been reviewed [129]. The contents of residual solvents (CH2C12, CgHsCI) and monomers (bisphenol A, dichlorodiphenyl sulfone) in commercial polycarbonates and polysulfones were determined. Also residual monomers in PVAc latices were analysed by GC methods [130]. GC was also... 

As mentioned in Chapter 3, we standardise our reporting of chemical shifts with reference to TMS or the residual solvent peak. Your spectrometer software should do this for you automatically. If it gets it wrong (which is possible if you have a mixed solvent or a spurious peak near TMS), then you can set it manually using your software. 

By a method similar to that described in the last section phenylazide in cyclohexene was irradiated with ultraviolet radiation and unreacted cyclohexene was distilled off with evaporation. The residue was extracted with n-hexane. The extract was separated into several products by gas and liquid chromatography. The gas chromatogram and the liquid chromatogram are shown in Figures 7 and 8, which give five peaks from A to E, and four peaks from A to D, respectively in addition to the peak due to the solvent. Peaks A and A were determined to be aniline by their retention times. Peaks B and C are due to 3,3 -bicyclohexenyl. Peaks C and D are those of aziridine[9] and the product which was formed by the insertion of phenylnitrene to C-H bond of cyclohexene. ... 

Fig. 13. Stereo drawing of one contour level in the electron density map at 2 A resolution for the residue 54-68 helix in staphylococcal nuclease. Carbonyl groups point up, in the C-terminal direction of the chain the asterisk denotes a solvent peak bound to a carbonyl oxygen in the last turn. Side chains on the left (including a phenylalanine and a methionine) are in the hydrophobic interior, while those on the right (including an ordered lysine) are exposed to solvent.

Fig. 46. — Structural-reporter-group Regions of the Resolution-enhanced, 500-MHz, H-N.m.r. Spectrum of Compound 63. [The bold numbers and letters in the spectrum refer to the corresponding residues in the structure. The relative-intensity scale of the IV-acetyl-proton region (see insertion) differs from that of the other parts of the spectrum, as indicated. For solvent-peak suppression, a w.e.F.t. pulse-sequence was used.]...

Figure 9.153 Detection of chloramphenicol acyltransferase (CAT) reaction products by HPLC. Triplicate reaction mixtures containing 10 units of CAT were incubated at 37°C. At the times indicated 200 /xL aliquots were removed and immediately mixed with 300 piL of ethyl acetate. Samples were extracted twice with ethyl acetate, and the solvent was then allowed to evaporate in a vacuum chamber. The residues were then redissolved in 20 /nL of ethyl acetate and injected on top of the HPLC column. Peaks C, chloramphenicol D, 1,3-diacetoxy chloramphenicol E, solvent peak, ethyl acetate M, 1- and 3-monoacetoxy chloramphenicol. Traces from 0-, 5-, 10-, 30-, and 60-minute time points are superimposed on the figure. (From Davis et al., 1992.)...

Figure 6-42 (a) Water suppression with excitation sculpting on 2-mM sucrose in 9 1 H2O/D2O. (b) The residual solvent peak has been eliminated by further processing. (Reproduced from T. D. W. Claridge, High-Resolution NMR Techniques in Organic Chemistry, Pergamon Press, Amsterdam, 1999, p. 365.)... 

Residual Solvent Peaks in Nuclear Magnetic Resonance... 

There are usually no problems when the sample concentration is decreased to get a large residual solvent peak within the standard range. If the sample concentration is increased, then one needs to make sure there are no issues with solubility. When adjusting the standard range, one needs to confirm that the new standard levels are within the linear range of the method. 

NMR measurements were made on a Nicolet 360 MHz spectrometer. Both and 13c chemical shifts were referenced to TMS by correcting the shifts relative to residual deuterated solvent peaks. Paramagnetic materials were referenced (in Hz) to the highest field solvent peak (+ = down field). Samples for NMR... 

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