Some Buffers

Trist(hydroxymethyl)amino-methane, hydrochloride (CH20H)3-C-NH3,C1 8,08 

In the case of a diacid solution and concerning its buffer index calculation, it is not possible to consider it a simple equimolecular mixture of two monoacidic buffers as long as the ratio of the two ionization constants remains lower than 5%. 

The values are given for the temperature of 25°C. After some preceding considerations, it is clear that pH buffer ranges change with temperature and the ionic strength. In the latter case, it takes place when the pK values are the apparent ones. Some particular buffers have been devised for some special applications. For example, the use of buffers that do not absorb in the wavelength range of the radiations used to perform a spectrophotometric analysis is required. This is often the case in the visible domain. Likewise, electrochemical measurements preclude the electroactive buffers use. 

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These same dependencies will, in general, apply to the heat of ionization of the buffer acid, AH. Thermodynamic quantities, namely, AH°, have been reported for some buffer substances, and it is found that A//° is temperature dependent. Bates and Hetzer studied the temperature dependence of for the important buffer tris(hydroxymethyl)aminomethane (TRIS), finding... 

The kinetics of decarboxylation of 4-aminosalicylic acid in some buffer solutions at 50 °C were studied. The first-order rate coefficients increased with increasing buffer concentration, though the pH and ionic strength were held constant (Table 217). This was not a salt effect since the rate change produced by substituting potassium chloride for the buffer salt was shown to be much smaller. It follows from the change in the first-order rate coefficients (kx) with... 

Fixation in 6-12 hours with a mixture of sodium hydroxide and trisodium orthophosphate, a metering device being necessary. This method is recommended for regenerated cellulosic fibres. This formulation contains the same total amount of alkali as method (1) with the same bath stability, but may be preferred where some buffering capacity is required and sodium silicate is undesirable. 

Dissolve the amine-containing molecule to be thiolated at a concentration of lOmg/ml in cold (4°C) 1M sodium bicarbonate (reaction buffer). For proteins, dissolve them in deionized water at a pH of 7.0-7.5, at room temperature. Note The presence of some buffer salts, like phosphate or carbonate, is incompatible with silver nitrate. 

This is a common ion effect problem similar to some buffer problems. 

While some buffer gas is beneficial in case of QITs, ICR cells are preferably operated at the lowest pressure available. The typical path from an external ion source into the ICR cell is therefore characterized by multistep differential pumping to achieve some 10 -10 Pa in the cell. 

Some buffer overlies the bed and the sample, which has a higher density made by supplementing with salt or sucrose it is added to form a lower layer. 

By addition of up to 80% (v/v) of organic solvents such as methanol, ethanol, or acetone to protein solutions, a formation of precipitates occurs. Varying the solvent concentration allows a fractionation as described for salting out. Because organic solvents tend to denature proteins at temperatures above 10 °C, precipitation and all further steps have to be performed at 0 °C or below. Some buffer salts may precipitate also at elevated concentrations of organic solvents therefore, the ionic strength of buffers should not be above 0.2. 

The change of pH at different temperature is illustrated for some buffer substances in Fig. 7.1. 

Some buffer substances interfere with enzymes. They act as competitive inhibitors, inhibit as products, or withdraw essential ligands by chelate formation. 

Since some buffers contain reactive groups as primary amino groups, they do not suit in covalent coupling of proteins. 

Some buffers have excellent characteristics with respect to biologic compatibility and/or buffering features, but they are so expensive that large-scale use is nearly impossible. 

Cells often have some buffers too. The reason for this is that, by providing a part in the input queue of the cell just before the currently processed part is finished at the particular cell, the cell is kept running at its highest efficiency level, since time is only wasted for part changing. The other important point to note is that well-designed part buffers offer a direct access pickup/load facility, making the rescheduling process in the queues short, simple, and dynamic [18,19,21-27]. 

Buffers for lyophilized formulations need additional consideration. Some buffers like sodium phosphate can crystallize out of the protein amorphous phase during freezing resulting in rather large shifts in pH. Other common buffers such as acetate and imidazole should be avoided since they may sublime or evaporate during the lyophilization process, thereby shifting the pH of formulation during lyophilization or after reconstitution. 

The rare-earth metals may have some buffering power. 

Accordingly, the quantitation of proteins by peptide bond absorption at 205 nm (A2os) is more universally applicable among proteins. Furthermore, the absorptivity for a given protein at 205 nm is several-fold greater than that at 280 nm (Scopes, 1974 Stoscheck, 1990). Thus lower concentrations of protein can be quantitated with the A205 method. The disadvantage of this method is that some buffers and other components absorb at 205 nm (Stoscheck, 1990). 

There are always preferences as to which stain to use for any given virus. An aqueous solution of uranyl acetate (UA) at 2% is a good general stain but others should be tried if this does not give the results required (2). UA is incompatible with some buffers, especially phosphate, which is the buffer of preference in this chapter. To avoid precipitation, treated grids must be washed with distilled water before UA is used (1,4). In addition UA is toxic, so users should refer to the Hazard Data Sheet produced by the manufacturer before use. 

An acid-base conjugate pair can act as a buffer, resisting changes in pH. From a titration curve of an acid the inflexion point indicates the pK value. The buffering capacity of the acid-base pair is the ptC 1 pH unit. In biological fluids the phosphate and carbonate ions act as buffers. Amino acids, proteins, nucleic acids and lipids also have some buffering capacity. In the laboratory other compounds, such as TRIS, are used to buffer solutions at the appropriate pH. 

Buffers are usually chosen on the basis of the required pH some buffers, however, are particularly useful for specific applications. Phosphate,... 

For anionic cITP, chloride is often selected as the leading ion selection of the counterion is based on the operating pH, and amino acids or zwitter-ions are generally used. For cationic cITP potassium or ammonium are the leading ions of choice. Table 5.7 lists some buffer solutions for cITP at a series of pH values. 

A buffer acts to keep the pH of the solution fairly constant. A buffered developer will maintain a constant pH whether it is diluted 1 1 or 1 3. A non-buffered developer may change its pH as it is diluted. Most alkalis used in developers have some buffering ability. 

Instead of using a separate vial with buffer for the calibration of the EVOM, it is also possible to pipette some buffer into the interjacent slots between the wells of a Transwell plate and measure the buffer resistance there. This guarantees also comparable conditions (temperature, etc.). 

These three atoms can accept electrons but not give up electrons without change in valence. 6 The rare-earth metals may have some buffering power. 

Some buffers display a large temperature coefficient. The most notorious of these is Tris. To a first approximation the pH of a Tris solution increases 0.03 pH units for every degree the temperature of the solution decreases (25 to 5°C). On the other hand, a 0.025 pH unit decrease is observed for every one degree rise from 25 to 37°C. In view of these considerations it is very hazardous to prepare Tris, or any buffer possessing a large temperature coefficient, at room temperature and then use it at 0 to 4°C. The only certain way to circumvent this problem is to measure the pH of the buffer at the temperature at which it will be used. 

Chemical structures for the most commonly occurring phospholipids in commercial soybean lecithin are shown in Figure 1 (7). PC and PE are cationic and anionic at the same time that is, they are zwitterions, and thus they can have some buffering action for both bases and acids. PI, however, is a relatively strong acid and, therefore, is anionic. The classes of compounds in commercial lecithin are as follows (31) ... 

Shells can be stuffed with some buffer like sawdust or chaff in the space to protect the content from the shock. (But chaff may be forbidden in exports due to quarantine regulations.) Shells must have an outside strength which stands the shock when fired. Sometimes we have an accident because a Poka-shell is broken at the mouth of the mortar when it is fired and the contents are projected at the same time being ignited by the flame of the propellant charge. In the case of Poka-shells or some signal shells... 

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