Average charge state

Example The cleavage of disulfide bonds by reduction with 1,4-dithiothreitol causes the unfolding of the protein. This exposes additional basic sites to protonation, and therefore results in higher average charge states in the corresponding ESI spectrum (Fig. 11.14). [88]... 

Fig. 2.12 Average charge state in field evaporation of Mo as a function of the applied field, obtained by Kellogg.68 The field evaporation rate is kept nearly constant by adjusting the temperature of the pulsed-laser heating. Curves are theoretical results A from the image-hump model, B from the same calculation with post field ionization correction. Calculations are based on those of...

Fig. 7. Different estimation of the mean charge state of ions in carbon foils. The lines indicated ND and SG show the empirical fitting expressions for the average charge state of ions crossing solid foils given by Nikolaev-Dmitriev [55] and Schiwietz-Grande [56], respectively. The line BK is the Brandt-Kitagawa model [15] for the equilibrium charge of ions moving inside solids. The line ZBL is the equilibrium ionization value proposed by Ziegler et al. [9].

Therefore, the cubic phase is metallic below as well as above T, and the room-temperature Mossbauer spectra can be treated as an averaged charge state. At 4.2 K, in the AFM phase below Tn, Mossbauer parameters can distinguish Fe(III) from Fe(IV) ions, but the isomer shifts at the Fe(III) remain anomalously low [240]. The ferromagnetic-spiral spin configuration with q [111] found [48, 49] below Tn = 134 K in SrFeOs is probably retained throughout the cubic phase. 

Zav is the observed average charge state and M is the molecular mass of the ion while a and b are constants. The value = 0.53 led to the best fit. Standing and co-workers observed an identical relationship for a large number of non denatured proteins, where the value of b was between 0.52 and 0.55. (The term average charge state for proteins" was first introduced and defined by Wang and Cole. )... 

Figure 1.11. Correlation between average charge state of protein ions generated by ESI under near-native conditions (10 mM ammonium acetate, pH adjusted to 7) and their surface areas in solution whose calculation was based on their crystal structures. The data are plotted in In (natural logarithmic) versus In scale (a graph using linear scales is shown in the inset). A gray-shaded dot represents a data point for pepsin, and the open circle underneath represents the maximum charge expected for pepsin if the extent of multiple charging was limited by the number of basic residues within the pepsin molecule. (Figure and text reprinted from Kaltashov and Mohimen," with permission from the American Chemical Society.)...

In a later study employing dendiimers with multiple peripheral amino groups, lavorone and Williams found that addition of /w-nitrobenzyl alcohol to methanol solutions increased the average charge state, and they attributed this shift to the resulting increase... 

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