Structural parameters, calculation from branching theory

Recently Tanford and his collaborators have made use of the electrostatic term w to analyze the titration curves of a number of proteins. By combining graphical methods and trial-and-error selection they obtained values of p(Kint) and w from experimental titration curves. In each case the value for the apparent average net charge was corrected for the binding of anions and cations as determined by independent experimental methods. Differences between their experimental values of w and those calculated from theory were interpreted by these workers in terms of alterations in molecular parameters or structure. For example, observed values which were low, especially when they became low only at pH s far removed from neutrality, were attributed to alteration in the size or shape of the molecule brought about by electrostatic repulsion. Thus, with human serum albumin Tanford (1950) found that although the basic branch of the titration curve could be computed from theory, the acid branch was much too steep... 

As can be seen from the above, the shape of the resolved rotational structure is well described when the parameters of the fitting law were chosen from the best fit to experiment. The values of estimated from the rotational width of the collapsed Q-branch qZE. Therefore the models giving the same high-density limits. One may hope to discriminate between them only in the intermediate range of densities where the spectrum is unresolved but has not yet collapsed. The spectral shape in this range may be calculated only numerically from Eq. (4.86) with impact operator Tj, linear in n. Of course, it implies that binary theory is still valid and that vibrational dephasing is not yet... 

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