Band distortion

To minimize band distortion, sample concentration must be much less than the background electrolyte concentration. Otherwise it is necessary to choose a buffer co-ion that has the same mobility as the analyte ion. (The co-ion is the buffer ion with the same charge as analyte. The counterion has the opposite charge.)... 

Leave sufficient space between wicks to avoid cross-contamination of samples caused by diffusion of the homogenate. Allow at least 0.5 cm on either end of the line of wicks to eliminate band distortion arising from edge effects. The tops of the wicks should be barely visible above the gel surface. 

For a configuration, the ground state in octahedral symmetry is a Eg term and the excited state is a "T2g term. On distortion to >4/, geometry, these terms split, as shown in Figure 11-10. In an octahedral complex, we would expect excitation from the Eg state to the state and a single absorption band. Distortion of the complex to >4 , geometry splits the "Tig level into two levels, the Eg and the B2g. Excitation can now occur from the ground state (now the Big state) to the Ajg, the Eg, or the B2g (the... 

Figure 7.3 Schematic of the situation at the electrode/SAM interface The use of palladium nanoparticles for the deposition of gold electrodes results in hetero-metallic interfaces at which band distortion in the organic material might build up due to field gradients.

Schematically, one can get a variety of band profiles from column design and bed structure parameters. On the top left of Figure 4 is one profile from a high linear velocity flow of the column. The center profile shows the effect of wall effect and point source distribution of sample and solvent at high linear velocities. If one eliminates the wall effect by utilizing very wide diameter columns and smaller particle packing, but still has a point source distribution of sample and solvent, one will get band distortion in the center of the band at higher fluid velocities.

It should be noted that protein loading tolerances are also dependent upon the pH range and the particular manufacturer of the synthetic carrier ampholytes. For example, more than twice the protein that can be applied to a pH 5-7 ampholyte (LKB) gel can be applied to a pH 4 5-5.5 Servalyte gel without any protein band distortion. While a gel containing pH 4.5-5.4 Pharmalytes can only handle 70% of the protein of the Servalyte gel (unpublished data). 

As described in Section 3.1, Baier et al. (1974) have used a machined germanium prism to sample surface organic monolayers in the manner developed earlier by Blodgett (1934,1935) for fatty acid films. The basis of their analytical method, infrared spectroscopy by the technique of internal reflections inside the machined prisms, is only qualitative but serves very well to examine the chemical nature of the surface organics. It is well known that when an internal reflection prism made of a material with a sufficiently high index of refiraction such as germanium is used, the internal reflection IR spectrum obtained suffers no band distortion or band shift when compared to conventional transmission spectra of the same substance (Barr and Flournoy, 1969). 

D. S. Lee and J. G. Fossum, Energy band distortion in highly doped silicon, IEEE Trans. Electron Devices ED-30 (1983) 626-634. 

Band distortion This is often due to high ion concentrations in the sample applied on the gel. Precipitate the sample following Wessel and Fliigge (see Section 1.5.1), dry the pellet, and dissolve it in a test buffer. 

Distorted bands are the result of bad sample appbcation, adsorption of protein to the column material, or a balance of protein between different polymerization states. A prebminary run with BSA and/or adding TRITON-X-100 or salt to the column buffer helps against the adsorption to the column material. Ideally, you apply colored markers (e.g., a mixture of cytochrome c, dextran blue, potassium dichromate) to the column before the run to check for run properties and band distortion. 

Contact between the pipet tip and the sample well should be avoided as this can damage the well and lead to band distortion. An unsteady hand can result in the sample missing the well altogether, a particular problem when loading very small sample wells. 

The absorption spectrum containing many bands with partially overlapped contours is typical for the majority of materials [4], The magnitudes of damping of the corresponding IR-active modes can be determined by nonlinear energy transfer processes from the given vibration to other vibrations. The formulas for the dielectric functions in the case of coupled modes were obtained by Barker and Hopfield [85]. The interaction of a (discrete) phonon with a continuous electronic excitation can result in specific band distortions [86] named the Fano resonances. 

The use of a buffer (interference) layer between a film and the metallic substrate (the BML-IRRAS technique) allows one to measure the 5-polarized spectra and to avoid the band distortions in the p-polarized spectra. At... 

The band distortions are explained by the redistribution of contributions of the vertical and lateral components of the mode in the p-polarized spectrum as either the real or imaginary part of the refractive index of the substrate is changed. In spite of this, however, the SSR for dielectrics (Sections 3.3.2 and 3.11.4) is independent of the optical properties of the substrate. The phenomenon outlined above can also be considered from the viewpoint of geometric optics, rather than invoking the complex origin of the absorption bands in the p-polarized spectra (Section 3.2). The intensity of the radiation reflected from the film-substrate system can be represented as the sum of the intensities of the radiation reflected from the front fihn-snbstrate interface, 7i, and the radiation multiply reflected in and emerging from the film, I (see Fig. 1.12). Clearly, in IRRAS, the... 

The band distortion has been interpreted in terms of a non-uniform distribution of the external load in the regions of different state of order resulting in a non-symmetrical displacement of the individual atomic absorption frequencies about the maximum of the band Thus, Vettegren postulated that overstressed segments are predominantly located in the amorphous regions of the polymer. In a recent publication Wool has derived that for Lorentzian absorption bands... 

High-performance fibres have historically been difficult to analyse by transmission FT-IR spectroscopy. Until a few years ago, the analysis of samples smaller than 25 pm was virtually impossible even with an IR microscope because the visible light portion did not have sufficient depth of field to focus the sample, and diffraction effects would result in a sloping baseline and stray light. Filament physical geometry, especially for highly orientated samples, causes optical aberrations resulting in band distortions that can lead to poor spectral quality. 

---