Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Amino acid buffering capacity

However, similar problems can also occur with the alkylammonium extractants, especially as the pH of the solution must be sufficiently high to produce an adequate concentration of the amino acid anions, i.e., more than two units above the pK of the amino acid. Thus, coextraction of hydroxyl ions competes with the amino acid anions and in addition lowers the pH of the aqueous phase and reduces the concentration of amino acid anions. To avoid such problems, a large buffer capacity is required in the aqueous phase with the buffer chosen to minimize coextraction of anions. [Pg.441]

Due to their high concentration, plasma proteins—and hemoglobin in the erythrocytes in particular—provide about one-quarter of the blood s buffering capacity. The buffering effect of proteins involves contributions from all of the ionizable side chains. At the pH value of blood, the acidic amino acids (Asp, Glu) and histidine are particularly effective. [Pg.288]

Note - Some products such as amino acid solutions and multiple electrolyte solutions containing dextrose will not be brought to near physiologic pH by the addition of sodium bicarbonate neutralizing additive solution. This is due to the relatively high buffer capacity of these fluids. [Pg.41]

Separates aqueous phase without altering the ionic composition. Principally applied in studies on calcium and phosphate in cheese, buffering capacity, lysis of starter cultures Commonly used to extract short peptides and amino acids. Suitable for bacterially ripened cheeses... [Pg.183]

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. [Pg.23]

Fig. 4. Temperature dependence of the specific enthalpy of denaturation of myoglobin and ribonuclease A (per mole of amino acid residues) in solutions with pH and buffer providing maximal stability of these proteins and compensation of heat effects of ionization (see Privalov and Khechinashvili, 1974). The broken extension of the solid lines represents a region that is less certain due to uncertainty in the A°CP function (see Fig. 2). The dot-and-dash lines represent the functions calculated with the assumption that the denaturation heat capacity increment is temperature independent. Fig. 4. Temperature dependence of the specific enthalpy of denaturation of myoglobin and ribonuclease A (per mole of amino acid residues) in solutions with pH and buffer providing maximal stability of these proteins and compensation of heat effects of ionization (see Privalov and Khechinashvili, 1974). The broken extension of the solid lines represents a region that is less certain due to uncertainty in the A°CP function (see Fig. 2). The dot-and-dash lines represent the functions calculated with the assumption that the denaturation heat capacity increment is temperature independent.
Other common species that have an effect on the pH and buffering capacity of natural systems include phosphates, borates, amino acids, and some organic compounds (generally weak acids). Phosphoric acid is a polyprotic acid that liberates one proton in each of its three dissociation steps, leaving a weaker acid... [Pg.118]

ProTherm (16) is a large collection of thermodynamic data on protein stability, which has information on 1) protein sequence and stmcture (2) mutation details (wild-type and mutant amino acid hydrophobic to polar, charged to hydrophobic, aliphatic to aromatic, etc.), 3) thermodynamic data obtained from thermal and chemical denaturation experiments (free energy change, transition temperature, enthalpy change, heat capacity change, etc.), 4) experimental methods and conditions (pH, temperature, buffer and ions, measurement and method, etc.), 5) functionality (enzyme activity, binding constants, etc.), and 6) literature. [Pg.1627]

The solubilizing capacity of the choline residue is so pronounced that even substrates combining two hydrophobic amino acids are homogeneously soluble in aqueous buffer without any additional cosolvent. These favorable physical properties were also used in the enzymatic formation of peptide bonds. The amino acid choline ester 38 acts as the carboxyl component in kinetically controlled peptide syntheses with the amino acid amides 39 and 40 [52] (Fig. 11). The fully protected peptides 41 and 42 were built up by means of chymotrypsin in good yields. Other proteases like papain accept choline esters as substrates also, and even butyrylcholine esterase itself is able to generate peptides from these electrophiles. [Pg.78]

Determination of total nitrogen content of the gastric juice, introduced by Wolff and Junghans (W22) and used later by others (D4), is inadequate for quantitation of gastric juice mucosubstances because proteins, peptides, and amino acids contribute to this measurement. Other authors precipitated gastric juice with methyl alcohol or acetone and determined the amount of alkali bound by the precipitate (M4-M6). These methods determined only the buffer capacity of the precipitate,... [Pg.283]

The common amino acids are simply weak polyprotic acids. Calculations of pH, buffer preparation, and capacity, and so on, are done exacdy as shown in the preceding sections. Neutral amino acids (e.g., glycine, alanine, threonine) are treated as diprotic acids (Table l-l). Acidic amino acids (e.g., aspanic. acid, glutamic acid) and basic amino acids (e.g., lysine, histidine, arginine) are treated as triprotic acids, exactly as shown earlier for phosphoric acid. [Pg.69]

B. The side chains of the amino acid residues in proteins contain functional groups with different pKs. Therefore, they can donate and accept protons at various pH values and act as buffers over a broad pH spectrum. There is only one N-terminal amino group (pK=9) and one C-terminal carboxyl group (pK= 3) per polypeptide chain. Peptide bonds are not readily hydrolyzed, and such hydrolysis would not provide buffering action. Hydrogen bonds have no buffering capacity. [Pg.44]

The first studies of carrier ampholytes were conducted using amino acids and dipeptides, but these species did not work well because their pK values for the amino and carboxylate groups are too far removed from their pi values. After they were prefocused, these species had very low buffering capacity. Good... [Pg.215]

The eluents suitable for the separation of amino acids on latex cation exchangers do not comprise the classical citrate/borate buffers but mixtures of nitric acid and potassium oxalate. In comparison to buffers composed of sodium citrate and borate, these components may be obtained at much higher purity. The retention of the amino acids to be analyzed, however, is possibly affected by the sample pH due to the limited buffer capacity of the eluents that are based on nitric acid and potassium oxalate. Fig. 4-21 shows the separation of a calibration standard for collagen hydrolysates on an Amino Pac PA-1 latex cation exchanger at ambient temperature. The advantage is the short... [Pg.231]

Various types of media have been used to cultivate different cell lines. The choice is mostly empirical, but formulations can be optimized for different cell lines and purposes. Most media, however, have the following essential components balanced salt solutions (BSS), essential amino acids, glucose, vitamins, buffers, and antibiotics. The BSS provides a concoction of inorganic salts required by the cells and usually has an osmolality between 260 and 320mOsm/kg, which is similar in range to that experienced by cells in vivo. Balanced salt solution often contains sodium bicarbonate and phosphates, which apart from nutrient value, also act in a buffering capacity. [Pg.71]


See other pages where Amino acid buffering capacity is mentioned: [Pg.61]    [Pg.61]    [Pg.61]    [Pg.61]    [Pg.63]    [Pg.63]    [Pg.229]    [Pg.165]    [Pg.129]    [Pg.1074]    [Pg.370]    [Pg.30]    [Pg.235]    [Pg.60]    [Pg.67]    [Pg.102]    [Pg.334]    [Pg.404]    [Pg.10]    [Pg.185]    [Pg.165]    [Pg.41]    [Pg.125]    [Pg.131]    [Pg.102]    [Pg.108]    [Pg.368]    [Pg.417]    [Pg.34]    [Pg.165]    [Pg.150]    [Pg.1086]    [Pg.642]    [Pg.134]    [Pg.175]    [Pg.327]    [Pg.16]    [Pg.122]   
See also in sourсe #XX -- [ Pg.241 ]




SEARCH



Acid capacity

Acid) buffer

Acidic buffering

Acidic buffers

Acids buffering

Buffer amino acids

Buffer buffering capacity

Buffered acids

Buffers buffer capacity

© 2024 chempedia.info