Hoffmeister series

A second stage occurs at 90°C when amylopectin-rich granules swell and deform (Hermansson and Svegmark, 1996). These temperatures are altered by starch type, and the presence of small solutes sugars elevate the gelatinisation temperature and ionic solutes exhibit varying effects related to their position in the Hoffmeister series. 

The effects of ionic cosolvents are less well understood. For denaturation ( melting ), trends have been related to Hoffmeister series effects, but for glass transitions no systematic data exists. 

Inert electrolytes show ion specificity, as discussed in Chapter 2 and illustrated in Figures 2.4, 2.5, 2.9, and 2.10. The anions affect the positive branches of the charging and electrokinetic curves, and the cations affect the negative branches. The affinity to particular monovalent anions and cations depends on the character of the surface, and follows the hard- soft acid-base principle that is, hard surfaces prefer to adsorb hard ions, and soft surfaces prefer to adsorb soft ions. The effects of ion specihcity on the charging and electrokinetic curves are usually minor. The affinity series observed in coagulation behavior are termed Hoffmeister series. 

For proteins, alter the hydration layer surrounding the protein by (i) electrolyte addition follow the Hoffmeister series of lyotropic ions (sulfates are preferred to phosphates because of the solubility) (ii) adding hydrophilic, non-ionic polymers, polyethylene glycol (iii) adjusting the pH to shift to zpc (but avoid low pH) (iv) lower the dielectric permeability of the continuous phase by the addition of ethanol, methanol, acetone or isopropanol (v) adding flocculant polyelectrolytes (alginate, pectate, carrogcenan, CMC). 

The dependence of T, for poly(GVGVP) on the addition of a series of salts (the Hoffmeister series) is shown in Figure 5.11A. With the exceptions of 1 and SCN", the addition of salts to poly(GVGVP) lowers the value of T,. With... 

The lyotropic or Hoffmeister series is a series of salts in which a gradation in properties including solubility is observed. This is illustrated in Table 9.3, in which the solubilities of gluten protein in 1.0 M solutions of sodium salts with different univalent anions are tabulated (Preston 1981). 

The influence of electrolytes divides into two areas, i.e. the influence on nonionic (uncharged) surfactants and that on ionic materials. For nonionic surfactants, the effects are either salting-out or salting-in , in line with observations from the Hoffmeister series of electrolyte effects on protein precipitation. While there has been much discussion over the past 50 years on the molecular mechanism involved, including many words on the structure of water, Ninham and Yaminsky have recently shown in a landmark paper that the phenomena can be explained by dispersion interactions (194). 

Table 3 The Hoffmeister series of lyotropic and chaotropic ions ...

The ability of different salts to promote binding to HlC media is ranked according to the Hoffmeister series (Table 3), and this can be understood in terms of their relative abilities to penetrate the hydration shell. Salts high in the lyotropic series (NH4, K, Na, POg , S04 ) are strongly excluded from protein and media surfaces and therefore promote binding, whereas chaotropic salts (Ba, Ca, Mg, SCN ) tend to penetrate the hydration shell, reduce local hydration, and diminish binding. The most commonly used salt is ammonium sulfete, but it requires care to control the pH and alternatives such as potassium... 

Second-order effects in these properties were seen when the chemical identity of the anion was changed for a given symmetry and valence class, and yet weaker second-order effects were seen when changing the cation in a given class, effects rationalized in terms of Hoffmeister series [49]. 

The total effect of a given salt on 7 is the sum of the effect of its constituent ions. It is independent of ionic charge. The effectiveness of the various ions closely follows the Hoffmeister series. For the anions, it corresponds to the following series CNS",, Br , NOJ, Cr, CHaCOO", SOI", COi . A similar behavior was observed for thermodenaturation of / -lactoglobulin (Dupont and Yon, 1961). Von Hippel and Wong (1964,1965), also found a linear variation of versus salt concentration for guanidinium salts and... 

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