Discrimination angle

Fig. 12A, has a 10° libration. This gives a channel size which would be optimal for an ionic radius between that of Rb+ and Cs+. Therefore enhanced discrimination is not expected between Rb+ and Cs+, but the energy required to librate further inward to make contact with smaller ions in the series can be expected to enhance selectivity between these ions. Work is currently in progress to calculate the change in channel energy as a function of libration angle or of the equivalent, the effective channel radius S6). The implications of a peptide libration mechanism for enhancing ion selectivity can also be pursued experimentally as outlined below. 

Scattered radiation. In a transmission experiment, the Mossbauer sample emits a substantial amount of scattered radiation, originating from XRF and Compton scattering, but also y-radiation emitted by the Mossbauer nuclei upon de-excitation of the excited state after resonant absorption. Since scattering occurs in 4ti solid angle, the y-detector should not be positioned too close to the absorber so as not to collect too much of this unwanted scattered radiation. The corresponding pulses may not only uimecessarily overload the detector and increase the counting dead time, but they may also affect the y-discrimination in the SCA and increase the nonresonant background noise. 

The largest change in K for a given AM2 occurs when 0=180°, and so large scattering angles maximise the mass discrimination of the technique. 

Figure 5.6. Diagram of a low-energy, high-angle electron-impact spectrometer. (A) Electron gun (B) monochromator (180° spherical electrostatic energy selector) (C) electron optics (D) scattering chamber (E) analyzer (180° spherical electrostatic energy selector) (F) electron multiplier (G) amplifier and pulse discriminator (H) count-rate meter (I) multichannel scaler (J) X Y recorder (K) digital recorder. (After Kupperman et a/.<42))...

According to X-ray and neutron diffraction structures [3, 4] the binding of CO to the heme leads to a bent FeCO unit. The Fe-C-O angle is, however, found to be linear in synthetic models of the protein (hiomimetic molecules). Because of this, it was originally thought that the FeCO distortion was responsible for the well known discrimination of the protein against CO - the affinity ratio C0/02 is lower in the protein than in biomimetic systems [1]. In... 

An interesting property that can be extracted from the simulation is the allowed distortion of the Fe-C-O fragment. We quantified this distortion by using the tilt (S) and bend (0) angles, which have been often related to the protein discrimination... 

Lyotropic polymeric LC, formed by dissolving two aromatic polyamides in concentrated sulphuric acid, have been studied using variable-director 13C NMR experiments.324 The experimental line shapes at different angles w.r.t the external field were used to extract macromolecular order and dynamic in these ordered fluids. An interesting application of lyotropic LC is for the chiral discrimination of R- and S-enantiomers, and has recently been demonstrated by Courtieu and co-workers.325 The idea was to include a chiral compound 1-deutero-l-phenylethanol in a chiral cage (e.g., /1-cyclodextrin) which was dissolved and oriented by the nematic mean field in a cromolyn-water system. Proton-decoupled 2H NMR spectrum clearly showed the quad-rupolar splittings of the R- and S-enantiomers. The technique is applicable to water-soluble solutes. 

From the CCR rate one can easily discriminate between an a-helical conformation (y/ -60°) and a yS-sheet (y/ 120°) conformation, as indicated in Fig. 16.6. The curves in the figure are scaled by arc. A more precise determination of the torsion angle is also possible in the case that both CCR rates are measured. By combining the two rates, the term arc as well as the angle i/r can be determined ... 

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