Albumin, precipitation

Because the polymer used in this experiment is a protein (albumin), precipitation denatures the polymer causing permanent changes in its secondary, tertiary, and quaternary structure. Therefore the precipitated polymer cannot redissolve. The denaturing/precipitation occurs because the three-dimensional shape of albumin is sensitive to temperature and to the nature of its environment (stable in water but not in other solvents). 

While erythrocytes have been shown not to absorb albumin from plasma (B28), washed blood platelets absorb and firmly bind radioactive albumin (S5). Although human blood platelets absorb albumin and fibrinogen, specifically from among the plasma proteins, the amount of albumin precipitated on centrifuging platelet-rich plasma is extremely small (B15). 

The solution is then diluted to 18% alcohol content and adjusted to pH 5.2 fraction IV-1 containing lipoproteins is precipitated and collected. The remaining solution is adjusted to pH 5.8, and 40% alcohol concentration this removes the remaining globulins from solution. At pH 4.8 and the same alcohol content, the albumins precipitate as the largest uniform fraction of plasma proteins. The entire procedure must be performed between —2 and —5 , otherwise denaturation sets in and the proteins become insoluble. 

Trichloroethanoic acid, CCI3COOH. A crystalline solid which rapidly absorbs water vapour m.p. 58°C, b.p. 196-5" C. Manufactured by the action of chlorine on ethanoic acid at 160°C in the presence of red phosphorus, sulphur or iodine. It is decomposed into chloroform and carbon dioxide by boiling water. It is a much stronger acid than either the mono- or the dichloro-acids and has been used to extract alkaloids and ascorbic acid from plant and animal tissues. It is a precipitant for proteins and may be used to test for the presence of albumin in urine. The sodium salt is used as a selective weedkiller. 

Factor VIII, immunoglobulin, and albumin are all held as protein precipitates, the first as cryoprecipitate and the others as the Cohn fractions FI + II + III (or FII + III) and FIV + V (or FV), respectively (Table 7, Fig. 2). Similarly, Fractions FIVj + FIV can provide an intermediate product for the preparation of antithrombin III and a-1-proteinase inhibitor. This abiUty to reduce plasma to a number of compact, stable, intermediate products, together with the bacteriacidal properties of cold-ethanol, are the principal reasons these methods are stiU used industrially. 

In addition it should be added that microdisperse forms of CP can precipitate proteins from solutions. Figs. 21-23 show that CP microdispersions with particle size of 1-2 pm precipitate serum albumin from solutions [81] in complete agreement with general flocculation laws for polyelectrolytes. The figs, show an extreme... 

Fig. 23. Influence of ionic strength of solution (p) on precipitation of serum albumin by /)FAV-17and2)FAV-16microdispersions.CSA = 10-4 mol/l,CCp = 0.09mg/ml,pH = 6.2...

The introduced THEOS did not bring about precipitation in protein solutions. This behavior differs from that observed with common silica precursors. For example, TEOS added in such small amounts caused precipitation. By using THEOS, we could prepare homogeneous mixtures. When its amount introduced into the albumin solution was less than 5 wt.%, there was no transition to a gel state (Table 3.1). A gradual increase in THEOS concentration resulted in a rise in the solution viscosity. The transition to a gel state took place as soon as a critical concentration was reached. Its value, as demonstrated in Ref. 

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