Amino acid aqueous solution

Ion Chromatography (IC) is a subset of one of the modes of HPLC - ion-exchange chromatography. It uses ion-exchange resins to separate ions based on their interaction with the fixed groups on the resin. Its greatest use is for the analysis of anions for which there are no other rapid analytical methods. It is also commonly used for cations and simple biochemical species such as amino acids. Aqueous solutions are normally required for analysis. 

Derivatization of an amino acid with FDAA produces a diastereomer referred to as 2,4-dinitrophenyl-5-L-alanine amide amino acid or simply DNPA-amino acid. Aqueous solutions (50 vaM) of amino acids (D- and L-isomers) are used as starting materials for synthesis. Solution of each of the amino acid (50 lA, 2.5 /tmol) is placed in separate 2 ml plastic tubes. To each is added 100 ii of 1% acetone solution of FDAA (1 mg, 3.6 /zmol), the molar ratio of FDAA to amino acid is 1.4 1, followed by NaHCOs (1 M, 20 ii, 20 umol). The contents are mixed and heated over a hot plate at 30-40°C for 1 h with frequent mixing. After cooling to room temperature, HCl (2 Af, 10 /u-1, 20 /umol) is added to each reaction mixture. After mixing, the contents are dried in a vacuum desiccator over NaOH pallets. Each residue is then dissolved in DMSO (0.5 ml). A1 1 dilution of these is made (2.5 mM) and 5 /ul sample of each is pooled and analyzed, for example, injected for HPLC. 

Salt Formation and Metal Chelation, Most a-ainiao acids form salts in alkaline and acidic aqueous solutions (88). For example, a-amino acids form inner complex salts with copper. 

Crown ethers may also be used to functionalize salicylideneimine complexes.1179 The crown ether-functionalized tetra-t-butyl-salicylideneimines are useful in studies on the selective com-plexation and transport of cations (e.g., Na+ and K+). 4,5-Bis(3,5-di-/-butylsalicylideneimino) benzo-18-crown-6 coordinates Ni11 via the Schiff base N202 donor system and K+ or Cs+ at the crown site.1180 These Ni-alkali metal complexes are able to transport amino acids from acidic aqueous solution to pure water. 

The mechanism of interaction of amino acids at solid/ aqueous solution interfaces has been investigated through adsorption and electrokinetic measurements. Isotherms for the adsorption of glutamic acid, proline and lysine from aqueous solutions at the surface of rutile are quite different from those on hydroxyapatite. To delineate the role of the electrical double layer in adsorption behavior, electrophoretic mobilities were measured as a function of pH and amino acid concentrations. Mechanisms for interaction of these surfactants with rutile and hydroxyapatite are proposed, taking into consideration the structure of the amino acid ions, solution chemistry and the electrical aspects of adsorption. 

Some authors based their approach to selective binding of the more lipophilic a-amino acids in water on hydrophobic effects using water-soluble, cavity-containing cyclophanes for the inclusion of only the apolar tail under renouncement of any attractive interaction of the hosts with the zwitterionic head . Kaifer and coworkers made use of the strong affinity of Stoddart s cyclobis(paraquat-p-phenylene) tetracation 33 for electron-rich aromatic substrates to achieve exclusive binding of some aromatic a-amino acids (Trp, Tyr) in acidic aqueous solution [48]. Aoyama et al. reported on selectivities of the calix[4]pyrogallolarene 34 with respect to chain length and t-basicity of aliphatic and aromatic amino acids, respectively [49]. Cyclodextrins are likewise water-soluble and provide a lipophilic interior. Tabushi modified )S-cyclodextrin with a 1-pyrrolidinyl and a carboxyphenyl substituent to counterbalance the... 

Procedure for BOC-amino acids. A solution of the amino acid (10 mol) in a mixture of dioxane (20 ml), water (10 ml) and 1 m sodium hydroxide (10 ml) is stirred and cooled in an ice-water bath. Di-t-butyl pyrocarbonate (1) (2.4 g, 11 mmol) is added and stirring is continued at room temperature for 30 minutes. The solution is concentrated in vacuo to about 10-15 ml, cooled in an ice-water bath, covered with a layer of ethyl acetate (30 ml) and acidified with dilute aqueous potassium hydrogen sulphate solution to pH 2-3 (Congo red). The aqueous phase is extracted with ethyl acetate (2 x 15 ml). The ethyl acetate extracts are pooled, washed with water (2 x 30 ml), dried over anhydrous sodium sulphate and evaporated in vacuo. The residue is recrystallised with a suitable solvent (e.g. ethyl acetate-hexane). 

The term acid dye derives from the dyeing process, which is carried out in an acidic aqueous solution (pH 2-6). Protein fibers contain amino and carboxyl groups, which in the isoelectric range (ca. pH 5) are ionized mostly to NH3+ and COO. In the acid dyebath the carboxylate ions are converted to undissociated carboxyl groups owing to the addition of acid HX (sulfuric or formic acid), which causes the positively charged wool (H3N+-W-COOH) to take up an equivalent amount of acid anions X (hydrogensulfate, formate Scheme 3.7) [5] ... 

Exploiting the structure-based strategy, the quinuclidinyl and the piperidinyl side chains of quinine (QN) and mefloquine (MF) were, respectively, substituted with a ferrocene moiety while maintaining a basic amino group (Fig. 16). In vitro, lower activities than the parent compounds were reported [106], In acidic aqueous solution, these ferrocenyl analogs seemed to be unstable, leading to the formation of the presumably inactive carbeniums. 

From the CD spectra of PLL-A-67 (poly-L-lysine having 67% adenine units) in acidic aqueous solution, the residual elliptidty at 222 nm ([ J222)is plotted against the pH of the system (Fig. 21). The value [0)222 is known to be related to the helix content of poly-(a-amino acid)73. ... 

The monomeric building blocks of the biopolymers, called proteins, are the a-amino acids. The simplest amino acid is glycine, which has the molecular structure shown in Figure 23.18. An amino acid, as indicated by the name, must contain an amine group (—NH2) and a carboxylic acid group ( —COOH). In a-amino acids, the two groups are bonded to the same carbon atom. In acidic aqueous solution, the amine group is protonated to form —NHj in basic solution, the... 

Properties White, crystalline powder. Bulk d 70 lb/ cu ft, decomposes to monohydrate at 100C. Soluble in water slightly soluble in alcohol insoluble in hydrocarbons. Aqueous solutions are strongly acidic, will precipitate potassium ions and amino acids from solution, are decomposed by bases and heat. 

Applications of the BOHLM systems (Chapter 5) in separation of (1) metals in the cationic and anionic forms in the weak and strong acidic aqueous solutions, (2) carboxylic and amino acid mixtures in aqueous solutions, (3) valuable drug species from the biochemical mixtures, and (4) potential application in catalysis and separation of valuable compounds (bioreactors) are reviewed. 

Klussmann et al. (2006) found an alternative mechanism based on the equilibrium solid-liquid phase behavior of amino acids in solution that resulted in asymmetric amplification of one enantiomer. The reaction operates in aqueous media that can... 

Irradiation of acidic aqueous solutions of Fe(III) tetrakis(2-N-methylpyridyl)-porphyrin in the presence of mono- or dibasic amino acids or the corresponding... 

Figure 4 shows the C NMR spectrum of the liquid silk from S.c. ricini mature larva.-" The spectrum of S.c. ricini liquid silk is sharp, indicating very rapid segmental motion of the main chain characterized by a very small correlation time on the order of 10 " s at room temperature (as in the case of B. mori silk fibroin). Assignment was performed by reference to chemical shift data of the pentapeptides, Gly-Gly-X-Gly-Gly, where X equals the specified residue.- "- and the amino acid composition. Solution - C and N NMR studies of S.c. ricini silk fibroin in aqueous solution indicate that about 70% of Ala residues form a-helices while, the conformation of the other Ala residues is random coil." - - ... 

Amino acids may be bound in water by molecules with hydrophobic cavities. Cyclodextrin derivatives were studied extensively. Enantioselectivities are usually modest, with some exceptions. For example, a diphenoxyphos-phoryl-substituted p-cyclodextrin bound serine with 3.6 1 enantioselectivity " and an a-cyclodextrin with a pyr-idinium substituent showed 10 1 enantioselectivity toward the same substrate.Synthetic cyclophanes were also used. The bipyridinium-based macrocycle 36 bound DOPA 37 with 13 R S selectivity in acidic aqueous solution. 

Liu. Y. Han, B.H. Qi, A.D. Chen, R.T. Molecular recognition study of a supramolecular system. 11. Chiial recognition of aliphatic amino acids by natural and modified a-cyclodextrins in acidic aqueous solution. Bioorg. Chem. 1997. 25 (3), 155-162. 

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