Influence shoulders

The exponential nature of the fall-curve is responsible for sample interaction. Provided that the between-sample time is made long enough, or blanks are inserted between samples, the effect is negHgible, but if the sampHng rate is increased then the response to any given sample will be influenced by the tail of the response of the preceding one. The effect can be particularly severe when a concentrated sample precedes a dilute one the peak due to the latter may appear as a shoulder on the tail on the one due to the former, or, in severe cases, it may be entirely hidden. 

The shape of the asymmetric S-O bands in the Ci4AO/SDS difference spectra change with composition. The higher frequency shoulder increases in relative intensity as the SDS content decreases. This change indicates that the dilution of SDS in C14AO results in a replacement of the sulfonate-sodium ion interactions with sulfate-amine oxide interactions, since the exact frequency and shape of the complex S-O band depends on the size and location of the hydrated counterion of the sulfate group (4). A weak band due to amine oxide is known to occur near 1200 cm"1. The influence of this band on the vm S-O bandshape can only be observed at the highest amine oxide concentration (mass fraction SDS = 1%) where a low frequency shoulder near 1200 cm"1 is observed in the difference spectra. 

The LRS of similarly prepared V-loaded aluminosilicate gels (AAA-aluminas) are shown in Fig. 4 band positions are listed in Table 3. These spectra are essentially featureless for V concentrations below the 1%V level, Fig.4. For loadings in the 1.0 to 3.0% V range, relatively intense bands near 517 cm"1 and 700 cm"1, together with a broad shoulder centered near 815 cm and a very weak band near 1020 cm"1 can be seen in the Raman spectra of these samples, Figs. 4B-4D. Recently, Wokaun, et. al. (25) have shown Raman spectral characteristics for SiO, supporting low V loadings which are similar to those in Fig. 4 but did not indicate whether H20 influenced their results. 

Inomata etal31,32 observe even at relatively low vanadium contents a clear absorption at 1020 cm-1 for V2Os on Ti02. When the V205 is supported on A1203, however, this absorption is only seen as a shoulder, suggesting that the support influences the exposure of certain crystal planes as the (V= O) bond is only present in the (010) planes. 

The additional effects in the aromatic region of the difference spectrum (250-300 nm) are probably caused by aromatic transitions which are influenced by the redox state of the copper. The shoulder at 270 nm, which occurs in all three proteins, could result from an increase in tyrosine absorption. In this context, it is interesting to recall that Tyr 108 (azurin numbering), which is relatively close to the proposed copper ligands Cys 112 and Met 121, is completely invariant both in azurin and plastocyanin and may therefore be an obligatory constituent of the copper site. 

Figure 8 Low-frequency spectta of MbCO, deoxyMb, and photolyzed MbCO (Mb ). Shoulders on the recoilless absorption line are attributed to translational motion of the heme in response to global oscillations of the surrounding protein matrix, and become more prominent with increasing temperature. Filled circles overlaid on the photolyzed MbCO spectrum represent the spectrum of imphotolyzed MbCO. Subtraction of the latter two spectra reveals no measurable influence of ligand binding on these vibrations...

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