Chemical functionalization alkali treatment

The action of alkali on SXVIII is dependent on the concentration of alkali and the temperature and time of exposure, and products are obtained whose activity with Type XVIII antibody also varies. Treatment at pH 10 and 22° for one to three days causes no serological or chemical changes, whereas treatment at pH 12 and 28° for 3 or 10 days liberates all the 0-acetyl functions without appreciable loss of phosphate. The products (5% Alk.-SXVIII and 6% Alk.-SXVIII) from which 5% and 6% of the phosphate, respectively, have been released, precipitate only one-fifth and one-twelfth of the Type XVIII horse antibody in two different homologous antisera. 

This selective review, which deals primarily with the chemical modification of soy proteins, is further limited to nondestructive chemical reactions which alter physical and biochemical properties of importance in food systems. Soy protein products have been modified by various chemical reactions including (a) treatment with alkalies and adds, (b) acylation, (c) alkylation and esterification, and (d) oxidation and reduction. In most instances these reactions have been applied to heterogeneous protein mixtures containing nonprotein impurities, and often to proteins of unknown prior history. Nonetheless, these reactions indicate that protein functional properties of value in food fabrication can be altered significantly through reaction with chemical reagents. It is recognized that chemically modified proteins must be critically evaluated for food safety. 

The mode of action of sulfonamides was greatly clarified by Woods in 1940. It had been shown that tissue extracts, pus, bacteria, and particularly yeast extract contained a heat-stable substance of low molecular weight which would inhibit the action of sulfonamides on bacteria (Stamp, 1939). Woods, recalling that enzymes are inhibited by substances which chemically and sterically resemble their substrates (see Section 9.3.1), adopted this hypothesis that the inhibitory substance in yeast is the substrate of an enzyme widely distributed in nature, and that it resembles sulfanilamide chemically. He found activity was concentrated in an alkali-soluble fraction of yeast, and that it ran parallel to a colour test for an aromatic amino-group. Activity was lost on esterification or acetylation, recovered on hydrolysis, and lost again on treatment with nitrous acid (Woods, 1940). Thus he made it clear that the active substance was an aromatic amino-acid. Because -aminobenzoic acid (/ AB) 2,12, p. 31) is the aromatic amino acid that most resembles sulfanilamide 2.13) he tried it as an inhibitor of bacteriostasis, and found that one molecule could prevent 5000 to 25 000 molecules of sulfanilamide from functioning. 

The variations in Co chemical shifts for salts of the type Co(CN), 3M" " are shown as a function of salt concentration in Figure 1. Whereas, in the presence of H" " or of alkali metal counterions (Li" ", Na" ", K, Rb" ", Cs ), the concentration dependence is nil or slight, use of Q" " counter-ions leads to considerable vatiations, increasing as expected with the number of carbon atoms in the alkyl chains. An approximate treatment of the data, neglecting further equilibria and the change of ion activity with the ionic strength, yields an equilibrium constant - 35 M for the ion padring ... 

---