Yeast nucleate

If the conclusion drawn is correct, a similar behaviour of other negative hydrophilic sols as to the influence of indifferent salts on the relative viscosity was to be expected. Indeed the electroviscous effect has been found to exist in all cases investigated, viz.t gtim arabic soluble starch mucilage of semen lini and of carrageen, sodium thymus nucleate and sodium yeast nucleate. Pecularities shown by some of these examples will be discussed later p. 223 10 and p. 227 11. 

Curve forms as in Fig. 23, or at least the left descending branch of it, have been found in all sols that were investigated agar, gum arabic, soluble starch, sodium thymus nucleatesodium yeast nucleate and gelatin. ... 

Thus it is interesting to compare the viscous behaviour of yeast nucleate and thymus nucleate. 

Now turning to Na-yeast nucleate, we meet with a colloid which only slightly increases the viscosity of the solvent. Compare Fig. 36, where we see that the 0.83% sol has only a relative viscosity of 1.052 (The 0.1% thymus nucleate however gives i]sMo = 1.45). 

The yeast nucleate molecule is however relatively so small that its four mononucleotide residues possibly do not suffice to form a chain element. Thus a skein proper will not be present in solution. Nevertheless in principle the decrease... 

Fig. 36. Neutralisation of the electroviscous effect for a 0.83% sol of Na yeast nucleate (42° C). Beyond 13.3 m. eq. per 1. Luteo—s (= Co(NH3)oCl3) flocculation occurs. This figure should be compared with Fig. 34 from which it appears that, notwithstanding the fact that yeast nucleate belongs to the low viscous, thymus nucleate to the very high viscous type of macromolecular colloids, the character of the bundle of curves is the same and also CoCNHaloClg causes flocculation with both (and this occurs with both with CaClg also at higher concentrations, see p. 270).

It is interesting that yeast nucleate also gives flocculation with Co(NH3)bC13. Later (see p. 395) we shall see that as regards transgression of solubility by adding different cations the low polymeric yeast nucleate and the high polymeric thymus nucleate behave very similarly. 

The low viscous character could further be connected (as above in the case of Na-yeast nucleate) with the macromolecules being very short, consisting only of a few monomeric residues. This once more does not strictly apply for clupein, the latter though a protein of relative low molecular weight (a few thousands) still consists of more than 30 amino acid residues linked together by peptide groups. 

On the upper curve are situated egg lecithin, both soya bean phosphatides thymus and yeast nucleates all having ester phosphate groups. They may be called phosphate colloids. 

For this investigation a sulphate colloid (Na agar), a carboxyl colloid (Na pectinate) and three phosphate colloids (Na yeast nucleate, purified egg lecithin, and a soya bean phosphatide fraction soluble in alcohol) were used. 

Fig. 41. Flocculation of Na yeast nucleate with some salts. ...

Krishnan, R., and Lindquist, S. L. (2005). Structural insights into a yeast prion illuminate nucleation and strain diversity. Nature 435, 765-772. 

An interesting development in this field is the recent report by Dameron et al. (88) of the biosynthesis of quantum-sized CdS crystals in the yeast cells Candida glabrata and Schizo saccharomyces pombe. Exposed to Cd ions these cells synthesize certain peptides with an enhanced sulfide production. Small CdS crystals are formed inside the cells. These crystallize in the rock salt structure (and not in the thermodynamically stable hexagonal configuration). The organism controls particle nucleation and growth, so that uniformly sized CdS particles of about 20 A are formed. They show pronounced quantum-size effects. This is the first example of the biosynthesis of quantum-sized semiconductor crystallites. It constitutes a metabolic route for the detoxification of Cd " -infected living cells (see also 89). 

F. Franks, T. Wakabayashi and S.F. Mathias, Nucleation kinetics in undercooled yeast cells long-term stability against freezing, J. Gen. Microbiol, 1987, 133, 2807-2815. 

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