Glutamine solubility

Theanine and Other Amino Acids. Amino acids (qv) make up 4—8% of the soluble soHds found in brewed tea. There is an amino acid unique to tea, y-A/-ethyl glutamine, called theanine [3081-61-6] (7) (23). 

Scheme 16 Synthesis of water-soluble polyfhydroxyalkyl glutamines)...

The biosynthesis of sulfate esters with the help of phosphoadenosine phosphosulfate (PAPS), the active sulfate , (see p. 110) and amide formation with glycine and glutamine also play a role in conjugation. For example, benzoic acid is conjugated with glycine to form the more soluble and less toxic hippuric acid (N-benzoylglycine see p. 324). 

Only proteins that contain proline bind polyphenols. Asano et al. (1982) demonstrated that the haze-forming activity of a protein is roughly proportional to the mole percentage of proline it contains (see Fig. 2.3). DNA has codes for exactly 20 amino acids. If each of these were equally present in a protein, there would be 5 mol% of each one. In fact, most proteins have much less proline than this. There are a few exceptions. Casein has about 8 mol% proline and the grain prolamins (proline-rich, alcohol-soluble proteins) are even higher. Hordein, the barley prolamin, contains about 20 mol% proline. As a result, it readily forms haze with polyphenols and is the main beer haze-active (HA) protein. Hordein contains even more glutamine (Q) than proline (P), and often these amino acids are adjacent in the protein (see Fig. 2.4). In fact, the sequence P-Q-Q-P occurs... 

Figure 4. Influence of urea and pH on the solubilities of synthetic polypeptide copolymers of glutamine and glutamic acid (17)...

Water-soluble random copolymers containing L-serine and A/5-(4-hydroxybutyl)-L-glutamine are prepared, and the thermally induced helix-coil transition of these copolymers in water is studied. The Z/mm-Bragg parameters cr and s for the (hypothetical) helix-coil transition in poly(l-serine) in water are deduced. The values of s, computed from both the Lifson and Allegra theories are (.Llfson, o-1 x 10-4 / Allegra, o = 7.5 x 10 5 s - 0.667/0.726 (273 K), 0.757/0.784 (293 K), 0.777/0.792 (313 K), 0.731/0.744 (333 K),... 

The synthesis and characterization of water-soluble "random" copolymers containing t-valine with either A -O-hydroxypropyD-L-glutamine or / -(A-hydroxybutyD-L-glutamine are described, and the thermally induced helix-coil transitions of these copolymers in water are studied. The incorporation of /.-valine is found to decrease the helix content of the polymer at low temperatures and increase it at high temperatures. The Zimm-Bragg parameters o and s for the helix-coil transition in poly(t-valine) in water are deduced from an analysis of the melting curves of the copolymers. The values of s, computed for o = 1 x 1CI-4, are s 0.85 (273 K), 0.93 (293 K), 1.00 (313 K), 1.06 (333 Kl. 

MIP membranes were prepared for the recognition of water soluble L-glutamine [218], tetracycline [221], uric acid [223], theophylline [216, 222] and naringin... 

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