Adsorbates amino acids

Ion-exchange Separations. Because amino acids are amphoteric, they behave as adds or bases, depending upon the pH of die solution. This makes it possible to adsorb amino acids dissolved in water on either a strong-acid cation exchange resin or a strong-base anion exchange resin. The affinity varies with the amino acid and the solution pH. Ion-exchange resins are widely used in amino acid separations. 

Fig. 46. EELS spectra of adsorbed amino acids and related compounds at Pt(lll). (a) L-Dopa (b) L-Tyrosine (c) L-Cysteine (d) L-Phenylalamine (e) L-Alanine (f) Dopamine (g) Catechol. Experimental conditions adsorbate concentrations (mM) were LD (5.0), TYR (1.0), CYS (0.5), PHE (1.0), ALA (1.0), DA (1.0), CT (1.0) other conditions were as in Fig. 20. Reprinted from ref. 84.

A number of years ago Seno and Yamabe [25] derived equations that examined the amounts of adsorbed amino acid on an ion exchanger in the presence of competing ions. More recently HelfEerich [26] derived equations describing the effective distribution coefficients of amino acids on a strong-acid (cation) and strong-base (anion) exchanger as a function of pH, amino acid concentration and added electrolyte. 

Figure 4.20. XPS spectra in the Cls region of MAA, adsorbed at room temperature on nickel surface (a), and in the Nls region of adsorbed amino acids (b).

Isoda, T., Ichikawa, A, Shimamoto, T. (1958) Asymmetric reduction by means of catalytic complex Tyrosine-Palladium and Raney Nickel with adsorbed amino acid, II., Rikagaku Kenkyusho Hokoku, Inst Rhys. Chem. Res. (Tokyo) 34, 134-142 and 143-151, Chem. Abstr. 1960,287d. 

The human venous plasma and whole blood contain amino acids and the successful identification and quantification of those amino have been previously reported [28, 29]. Conconi et al. [30] reported that the amino adds (lysine, threonine, methionine, tryptophan, arginine, which are all present in the DMEM solutions) increased both the osteoblast proliferation and alkaline phosphatase activity of rat osteoblasts cultured in vitro. Imamura et al. [31] and Tentorio and Canova [32] separately showed that the amino acid lysine adsorbs itself on pure metallic Ti and on amorphous Ti hydrous oxide surfaces, respectively, at neutral pH values. While the inoiganic SBF solutions cannot provide any practical means of producing synthetic biomaterials with some amino acids adsorbed on their surfaces, DMEM solutions can provide unique biomaterial surfaces already containing adsorbed amino acids. 

FIGURE 24.2 A section of a cation-exchange resin with adsorbed amino acids. 

The adsorption behavior of 25 amino acids at the mercury surface was studied by the Lippman electrocapillary method. The amount of surface excess of adsorbed amino acid, as evidenced by lowering of interfacial... 

Ion exchangers which adsorb amino acids are also suitable for deproteinisation. Proteins are only weakly adsorbed for steric reasons and consequently largely pass... 

From cyclovoltammetric data it is known that the sensitivity for the adsorbing amino acids can be enhanced by an appropriate potential 1 (usually negative) as part of the detection waveform. Because the sensitivity for non-adsorbing amino acids is not enhanced, the result can be a divergence of response factors. Moreover, an enhanced adsorption comes at the cost of limiting the linear range for basic amino acids, so that the duration for the adsorption potential must be limited to 40 ms. Cyclovoltammetric data also demonstrated a dependence of amino acid adsorption on the electrode potential. As 1 decreases from -r0.05 V to — 0.2 V, the response increases for all amino acids except arginine, lysine, and methionine. When 1 is smaller than - 0.2 V, the response for all amino acids... 

Tissue-protein Synthesis.—Since the tissue proteins are highly specific compounds, it is believed that the process of their elaboration from amino acids takes place within the cell on a catalytic surface (endo-enzyme) that in some way resembles the required protein pattern, and acts as a mould or pattem-die for the arrangement of the adsorbed amino acids. The protein assembled in a particular tissue may become part of the tissue structure or may be used for other purposes. Thus, the serum proteins are built up in the liver, the zymo-proteins are manufactured in the secreting glands, and caseinogen is manufactured in the mammary gland. 

Amberlite IRC-50 3.5 1.25 Methacrylic acid-DVB. Selectivity adsorbs organic gases such as antibiotics, alkaloids, peptides, and amino acids. Use pH >5. 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

Differences in the materials employed for the layers can also become evident when chemical reactions are performed on them. Thus, Macherey-Nagel report that the detection of amino acids and peptides by reaction with ninhydrin is less sensitive on layers containing luminescent or phosphorescent indicators compared to adsorbents which do not contain any indicator [7]. 

This step is almost always performed to get rid of the coloured impurities in the fermentation broth. The method is based on the fact that amino adds (esperially the non-aromatic amino acids) do not adsorb onto activated charcoal. Although the treatment is very effective, some of the amino acid is lost during this step. 

A pair of amino acids is separated in a column in which the stationary phase is saturated with water and the carrier solvent is methanol, CH,OH. The more polar the acid, the more strongly it is adsorbed by the stationary phase. The amino acids that were separated in this column are (a) HOOCCHNH2CH,COOH and (b) HOOCCHNH2CH(CH,)2. Which amino acid would you expect to be eluted first Explain your reasoning. Refer to Major Technique 4 on chromatography, which follows these exercises. 

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