Amino add solutions

The salt ions are captured by the ion exchange membranes that are present. The applications are limited to desalting amino add solutions, eg removal of HQ from L-glutamic add solution. 

Dis derivatives are prepared by mixing equal volumes of the amino add solution in 0.1 M NaHC03 with the solution of Dis-Cl (Imgml in acetone). If the sulphonyl chloride is precipitated, acetone is added until a clear soluton is obtained (172). After being left for 3 h in a closed tube at room temperature, the solution is evaporated to dryness. The residue is dissolved in 1 ml of acetone methanol (l.T). Aliquots of this solution are used for chromatographic separation. 

In the SYMPHONY/Multiplex system, the activator solution consists of HBTU or TBTU at a concentration equimolar with the amino acid solutions in conjunction with two- to fourfold equivalents of a base such as NMM. For a specified coupling step, the system transfers a determined number of aliquots of amino add solution to the solid support, followed by the same volume of activator solution. Subsequent to completion of addition, the resin is agitated by gas bubbling for the specified coupling time. 

Crystallisation is often used as a method to recover tire amino add. Because of tire amphoteric character (contains both addic and basic groups) of amino adds, their solubility is greatly influenced by the pH of the solution and usually show minima at the isoelectric point (zero net charge). 

Copper-complexes prepared with other type of N-chelating ligands have been also prepared and evaluated as catalysts for the Diels-Alder reaction. Eng-berts et al. [103] studied enantioselective Diels-Alder reaction of 3-phenyl-l-(2-pyridyl)-2-propen-l-one with cyclopentadiene in water (Scheme 39). By using coordinating chiral, commercially available a-amino-adds and their derivatives with copper salts as catalysts, they obtained the desired product with yields generally exceeding 90%. With L-abrine (72 in Scheme 39) as chiral moiety, an enantiomeric excess of 74% could be achieved. Moreover, the catalyst solution was reused with no loss of enantioselectivity. 

Amino adds find apphcations as ingredients of infiision solutions for parenteral nutrition and individnally for treatment of specific conditions. They are obtained either by fermentation processes similar to those used for antibiotics or in cell-fiee extracts employing enzymes isolated fiom bacteria (Table 25.1). Details of the mar and varied... 

X=Br) can be efficiently recovered from aqueous solution of the work-up for reuse.1241 Utilizing this N-anthracenylmethyl technology, various amino add derivatives have been synthesized by Lygo and coworkers in 40-86 % yields with 67-94 % ee as the N-free tert-butyl esters 25 and by Corey and coworkers in 67-91% yields with 92-99.5% ee as the imines 24, respectively. Some representative results are shown in Table 2... 

To cuvette (BLANK) add 0.1 ml distilled water and note absorbance / ,. To the other cuvette (TEST) add 0.1 ml amino acid solution and again record absorbance T. ... 

Weak acids and bases are not restricted to amino adds many other compounds also behave similar in aqueous solutions. The dissociation into anion A and proton (in aqueous solution the dissociated protein is captured by a water molecule to form a hydronium ion HsO ) in the case of acids, and the addition of a proton to a base B to form the cation BH", is an equilibrium... 

Among the analytical methods presently used for the characterization of natural and synthetic peptides and proteins, the primary value of amino acid analysis is the determination of absolute peptide and protein content in solids and solutions and the quantitation of their amino acid composition and stoichiometry. It involves two steps, i.e. complete hydrolysis of peptides and proteins, followed by photometric determination of the released amino adds. The steps are laborious and time-consuming, and there is a continuous need for improvement of the techniques to increase precision and sensitivity. 

Other than water, protein is the major constituent of meat averaging nearly 21% in heef or chicken meat, with fat varying fiom 4.6 to 11.0% in beef and fiom 2.7 to 12.6% in chickoi. The principal radiolytic reactions of aqueous solutions of aliphatic amino acids are reductive deamination and decarboxylation. Alanine yields NH3, pyruvic add, acetaldehyde, propionic acid, CO2, H2, and ethylamine (6). Sulfur-containing amino adds are espedally sensitive to ionizing radiation. Cysteine can be oxidized to cystine by the hydroxyl radical or it can react with the hydrated electron and produce... 

The enantioselective binding properties of certain chiral crown ethers have been employed in the resolution of amino add racemates. The racemic amino ester is adsorbed onto silica gel as its ammonium salt and eluted by a chloroform solution of the chiral crown ether. An excellent separation of the two enantiomers is achieved by this method (74JA7100). 

Complexes of simple amino adds with chromium(lll) were first prepared by Ley.1148 The isomers possible for tris chelated complexes of this type are illustrated below (248-251). The consequences of such isomerism were first seriously considered by Gillard.1149 Red complexes of the formulae [Cr(gly)3] and [Cr(L-ala)3] were prepared by neutralizing refluxed solutions of hexaaquachromium(Ill) and the amino add in ratios between 1 5 and 1 10. These complexes were shown to be isomorphous with 0-[Co(gly)3] and D- -[Co(L-ala)3] respectively. The crystal structure of red j8-[Cr(gly)3] has also been reported.1150... 

Ninhydrin Reaction. A neutral solution of an amino acid will react with ninhydrin (triketohydrindene hydrate) by heating to cause oxidative decarboxylation. The central carbonyl of the tnketone is reduced to an alcohol. This alcohol further reacts with ammonia formed from the amino add and causes a red-purplish color. Since the reaction is quantitative, measurement of the optical density of the color produced is an indication of amino add concentration. Imino acids, such as hydroxyproline and proline, develop a yellow color in the same type of reaction. 

PK. A measurement of the complete ness of an incomplete chemical reaction. It is defined as the negative logarithm ito the base 101 of the equilibrium constant K for the reaction in question. The pA is most frequently used to express the extent of dissociation or the strength of weak acids, particularly fatty adds, amino adds, and also complex ions, or similar substances. The weaker an electrolyte, the larger its pA. Thus, at 25°C for sulfuric add (strong acid), pK is about -3,0 acetic acid (weak acid), pK = 4.76 bone acid (very weak acid), pA = 9.24. In a solution of a weak acid, if the concentration of undissociated acid is equal to the concentration of the anion of the acid, the pAr will be equal to the pH. 

NMR studies have been carried out on Schiff bases derived from pyridoxal phosphate and amino acids, since they have been proposed as intermediates in many important biological reactions such as transamination, decarboxylation, etc.90 The pK.d values of a series of Schiff bases derived from pyridoxal phosphate and a-amino adds, most of which are fluorinated (Figure 11), have been derived from H and19F titration curves.91 The imine N atom was found to be more basic and more sensitive to the electron-withdrawing effect of fluorine than the pyridine N atom. Pyridoxal and its phosphate derivative are shown in Figure 12a. The Schiff base formation by condensation of both with octopamine (Figure 12b) in water or methanol solution was studied by 13C NMR. The enolimine form is favoured in methanol, while the ketoamine form predominates in water.92... 

---