Peak folding

Retarders were originally arenecarboxylic acids. These acidic materials not only delay the onset of cross-linking but also slow the cross-linking reaction itself. The acidic retarders do not function weU in black-fiUed compounds because of the high pH of furnace blacks. Another type of retarder, A/-nitroso diphenylamine [86-30-6] was used for many years in black-fiUed compounds. This product disappeared when it was recognized that it trans-nitrosated volatile amines to give a several-fold increase in airborne nitrosamines. U.S. production peaked in 1974 at about 1.6 million kg. 

When a photoprotein solution (1.3 ml) was shaken with ethanol (0.7 ml) containing one drop of concentrated HC1 and then the mixture was extracted twice with 2 ml each of ethyl acetate, about 75% of the chromophore was extracted into the ethyl acetate extract. The chromophore isolated showed an absorption peak at 398 nm in neutral methanol (Fig. 10.2.5). The isolated chromophore was practically non-fluorescent, like the native photoprotein. However, the acidification of a methanolic solution with HC1 resulted in a sharpening and two-fold increase of the 398 nm absorption peak, accompanied by the appearance of fluorescence. In aqueous 0.1 M HC1, two fluorescence emission peaks (595 nm and 650 nm) were found, together with a corresponding excitation peak (400 nm). Treatment of the 398 nm absorbing chromophore with 0.1 M NaOH resulted in a rapid loss of the 398 nm absorption peak. Dithionite did not affect the 398 peak, suggesting that the chromophore does not contain Fe3+. 

The enhancement of the fold in structure-forming solvents leads to a strong increase of the values near 223 cm-1 to a positive peak (see Fig. 18). 

In this section we will discuss in some detail the application of X-ray diffraction and IR dichroism for the structure determination and identification of diverse LC phases. The general feature, revealed by X-ray diffraction (XRD), of all smectic phases is the set of sharp (OOn) Bragg peaks due to the periodicity of the layers [43]. The in-plane order is determined from the half-width of the inplane (hkO) peaks and varies from 2 to 3 intermolecular distances in smectics A and C to 6-30 intermolecular distances in the hexatic phase, which is characterized by six-fold symmetry in location of the in-plane diffuse maxima. The lamellar crystalline phases (smectics B, E, G, I) possess sharp in-plane diffraction peaks, indicating long-range periodicity within the layers. 

If the spectral width is inadequate to cover every peak in the spectrum, then some peaks in the downfield or upfield region may fold over and appear superimposed on the spectrum. How can you identify these folded signals ... 

Figure 1.30 (a) Normal NMR spectrum resulting from the correct selection of spectral width, (b) When the spectral width is too small, the peaks lying outside the spectral width can fold over. Thus a and b represent artifact peaks caused by the fold-over of the a and b signals. 

The folded peaks are easy to identify, since they show different phases than the normal signals. On shifting the spectral window to one side, all the normal signals will shift in the same direction, and by the same value, as the spectral window. In contrast, the folded signals will move either in the opposite direction or by a different value in the same direction, so their relative disposition to other signals in the spectrum will change. 

The enz3rme activity was adsorbed to the cation exchange chromatography. Three peaks of activities were found (fraction no. 78-81, 83-85 and 86-89). The major peak (no.83-85) was coUected (Figure 2. The enz3rme was purified to approx. 100 fold with the higher specific activity, 534.7 unit/mg protein (Table 1). 

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