Basic buffers

Bates and Bower have reported values of dpHIdT for several important basic buffers. 

Fig. 7.4.3 Relationships between the total light emission of polynoidin and the concentrations of the photoprotein (A), H2O2 (B), Fe2+ (C), and EGTA (D). The basic buffer solution used was 50 mM phosphate buffer, pH 6.6, containing 3 mM H2O2, 0.1 mM FeSC>4 and 10 mM EGTA the concentrations of H2O2, FeSC>4 and EGTA were varied in B, C and D, respectively. FeSC>4 was added last to initiate light emission. From Nicolas et al., 1982, with permission from the American Society for Photobiology.

Step 1. Gel filtration on Sephadex G-100, in 10 mM sodium phosphate buffer, pH 6.5, containing 5mM EGTA and 0.2 M NaCl, which was the basic buffer used throughout the purification process. 

Step 2. Hydrophobic interaction chromatography on a column of Phenyl-Sepharose CL-4B. The sample was adsorbed on the column in the basic buffer containing 0.5 M (NH SC. The photoprotein adsorbed was first washed with the same buffer, then eluted with the basic buffer. 

Step 3. Gel filtration on Ultrogel AcA 44, using the basic buffer. 

Step 4. Anion-exchange chromatography on a column of DEAE-Sephadex A-50. The column had been equilibrated with the basic buffer containing 0.12 M NaCl. The NaCl in the photoprotein solution was removed by gel filtration, and then the solution was added onto the column. The photoprotein adsorbed on the column was eluted with the equilibration buffer. 

The same expression can be used for a basic buffer, with pKa that of the conjugate acid of the base (for example, in the case of an ammonia buffer, we would use the pKa of NH4+). If only pKb is available, calculate pKa by using Eq. 1 lb of Chapter 10 (pKa + pKb = pfCw). For example, for an ammonia/ammonium buffer we would write... 

Solutions which resist changes in their pH values on the addition of small amounts of acids or bases are called buffer solutions or simply buffers. The resistance to a change in the H+ ion concentration on the addition of an acid or an alkali is known as buffer action. Just as the buffer of railway carriages resists shocks, similarly buffer solutions resist the action of various substances which can affect the pH value. There are two types of buffers (i) acidic buffer and (ii) basic buffer. 

Fig. 1.9 Dependence of pH on the buffer composition according to the Henderson-Hasselbalch equation (1) acidic buffer (Eq. 1.4.26) (2) basic buffer. Calculation for K A = K B = 10-4, s = 0.1 mol dm-3...

Other types of ester have been studied (Fendler and Fendler, 1975 Bender and Komiyama, 1978 Szejtli, 1982), though in much less detail. Brass and Bender (1973) studied the cleavage of two diaryl carbonates and three diaryl methylphosphonates in basic buffers (Table A5.ll). For the carbonates, reacting with /1-CD, introduction of p-nitro groups increases the acceleration ratio and worsens substrate binding, so that KTs barely alters. More interesting are the results for the phosphonates in that the effects of nitro groups depend on their position and on the CD. 

A basic buffer consists of a solution of a weak base and one of its salts, such as a solution of ammonia and ammonium chloride. The weak base, ammonia, removes any added hydrogen ions. The conjugate acid, the ammonium ions from the ammonium chloride salt, replaces any hydrogen ions removed when the alkali was added. 

If the HPLC mobile phase is operated close to the pA of any solute or if an acidic or basic buffer is used in the mobile phase, the effects of temperature on retention can be dramatic and unpredicted. This can often be exploited to achieve dramatic changes in the separation factor for specific solutes. Likewise, the most predictable behavior with temperature occurs when one operates with mobile phase pH values far from the pA s of the analytes [10], Retention of bases sometimes increase as temperature is increased, presumable due to a shift from the protonated to the unprotonated form as the temperature increases. As noted by Tran et al. [26], temperature had the greatest effect on the separation of acidic compounds in low-pH mobile phases and on basic compounds in high-pH mobile phases. McCalley [27] noted anomalous changes in retention for bases due to variations in their pA s with temperature and also noted that lower flow rates were needed for optimal efficiency. 

Ionic liquids are generally regarded as highly stable, and the widely used dial-kylimidazolium ionic liquids are indeed thermostable up to 300 °C [4]. The propensity of the [BF4] and [PF6] anions to hydrolyze with liberation of HF [37], which deactivates many enzymes, has already been mentioned. The [TfO] and [ Tf2N] anions, in contrast, are hydrolytically stable. Dialkylimidazolium cations have a tendency to deprotonate at C-2, with ylide (heterocarbene) formation. Such ylides are strong nucleophiles and have been used as transesterification catalysts, for example [38]. These could cause enzyme deactivation as well as background transesterification when formed in small amounts from anhydrous ionic liquids and basic buffer salts, for example. 

This mode of electrophoresis, in which the electrolyte migrates through the capillary, is the most widely used. The electrolyte can be an acidic buffer (phosphate, citrate, etc.) or basic buffer (borate) or an amphoteric substance (a molecule that possesses both an acidic and an alkaline function). The electro-osmotic flow increases with the pH of the liquid phase, or can be rendered non-existent. 

For faster reactions, it maybe necessary to monitor the progress of the reaction in an NMR tube in a thermostatted NMR probe. If an aliquot method is used, it should be possible to remove an aliquot rapidly and quench it by adding cold solvent - reaction rates are lower under colder, more dilute conditions. In reactions involving bases or acids, reactions may be quenched by addition of acidic or basic buffer solutions. Of course, whether or not the reaction can be quenched efficiently, the aliquots should be analysed as expeditiously as possible to reduce the possibility of further reaction or degradation. 

Acidic proteinoid potentiates the active structure of lysine-rich proteinoid participating in forming microspheres in neutral buffer. Physical surface effects and providing micro condition in the microspheres could be surmised. Activation of amino acids generally requires acidic condition. Amino acids are activated by ATP and Mg2+ at pH 4-5 32 33). Aminoacyl adenylate anhydride and ester is formed preferentially from amino acid and adenylate imidazolide at pH 6.0J7). On the other hand, polycondensation of activated amino acids undergoes at pH values higher than 7. Peptides are formed from aminoacyl adenylate in basic buffer (the optimum pH is 10 for alanyl adenylate 40) from amino acid adenylate phosphoramidate and imidazole at pH 7.0 from N-(aminoacyl)-imidazole at pH 6-9 43). In this context, acidic and basic environments may be provided inside and/or on the surface of the microspheres composed of acidic and basic proteinoids in neutral buffer. Acidic micro condition suitable for the activation of amino acids and basic micro environment favorable for peptide formation from activated amino add may be provided. 

Solutions of rhamnose and proline (150 ml.) in deionized water were prepared according to the experimental design. The pH was adjusted with blends of sodium phosphate, mono-, di- and tri-basic buffers. 

In general terms, capillary electrophoresis is the electrophoretic separation of a substance from (usually) a complex mixture within a narrow tube filled with an electrolyte solution which is normally an aqueous buffer solution. Although one example of separation performed in a totally non-aqueous solution has been reported (50), neutral and slightly basic buffer solutions are generally used. Small tubes dissipate heat efficiently and prevent disruption of separations by thermally driven convection currents. Therefore, capillary electrophoresis can use... 

To favor the release of preadsorbed oligonucleotides, various desorption conditions have been systematically investigated. The desorption has been first examined as a function of washing steps. The results obtained revealed the decrease in the residual ODN adsorbed amount until three or four washes, after which the desorbed amounts ODN are almost nil [29] (see Fig. 7). The influence of pH on the desorption process has been reported to be the key parameter leading to high desorption of ODN. Indeed, the desorption of preadsorbed ODN at acidic pH revealed high desorption yield when high basic buffer (pH 10) was used. The behavior was attributed to the reduction in attractive electrostatic... 

The separation selectivity can be significantly affected as a result of different pH shift of different buffers even at the same organic composition. For example, if two buffers are prepared at the same pH, one using an acidic buffer such as phosphate and another using a basic buffer such as ammonia, both at WpH 8, the separation of a mixture of ionizable components could be different. This could be attributed to the different mobile-phase pH after the aqueous is mixed with the organic. Espinosa et al. [64] analyzed A,A-dimethyl-... 

Different types of buffers at the same ionic strength and wpH can have a significant impact on the dissolution of silica. The dissolution of silica is usually measured by the silicomolybdate colorimetric method [41]. When determining the bonded-phase stability using different run buffers (effect of buffer counteranion or countercation), the same H must be used. The H values (pH of the mobile phase aqueous -i- organic) may be different from the aqueous portion of the mobile phase and may obscure if the dissolution of the silica is directly related to the type of anion/cation and/or the pH. Generally, with the addition of organic solvents the pH of the mobile phase decreases for basic buffers and increases for acidic buffers (see Section 4.5 for more details). 

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