Isoelectric point, glutamic acid

The side chains of aspartic acid and glutamic acid contain acidic carboxyl groups. These amino acids have acidic isoelectric points around pH 3. An acidic solution is needed to prevent deprotonation of the second carboxylic acid group and to keep the amino acid in its neutral isoelectric state. 

Some ammo acids have side chains that bear acidic or basic groups As Table 27 3 indicates these ammo acids are characterized by three values The third pK reflects the nature of the side chain Acidic ammo acids (aspartic and glutamic acid) have acidic side chains basic ammo acids (lysine arginine and histidine) have basic side chains The isoelectric points of the ammo acids m Table 27 3 are midway between the pK values of the zwitterion and its conjugate acid Take two examples aspartic acid and lysine Aspartic acid has an acidic side chain and a pi of 2 77 Lysine has a basic side chain and a pi of 9 74... 

The isoelectric point for glutamic acid is that pH at which the compoimd is in an electrically neutral form, and this will be the average of pA ai (the... 

Fig. 6. Effect of modifying temperature on EDA with the following modifying reagent and conditions ( ) (+)-erythro-2-methyltartaric acid, pH 5.0 5.2, 0°C (O) (S.S)-tartaric acid, pH 5.0-5.2, 0°C (A) ( + )-2-methyl glutamic acid, pH 5.0, 0°C (O) (S)-valine, isoelectric point, 0 C ( ) (S)-glutamic acid, pH 5.2, 0 C. Reaction conditions MAA (neat), 60"C, 80 100 kg/cm2.

Problem 21.43 What occurs when an electric current is passed through an aqueous solution, buffered at pH = 6.0, of alanine (6.0), glutamic acid (3.2). and arginine (10.7) The isoelectric points are shown in parentheses. ... 

By using the above arguments, we can consider the example of the isoelectric point of glutamic acid, with the aid of the pKa values given in Table 3.2. 

What form exists at the isoelectric point of each of the following amino acids (a) valine (b) leucine (c) proline (d) glutamic acid ... 

Using amphoteric, isoelectric buffers at pH close to their isoelectric points (p7), at which the electrolytes have a net charge of zero, is an efficient way to decrease the BGE conductivity and apply extremely high field strength. Thus the separation time can be reduced to the order of a few minutes, and high resolution is achieved as a result of minimal diffusion-driven peak spreading. Several acidic isoelectric buffers, such as cysteic acid (p7 1.85), iminodiacetic acid (p7 2.23), aspartic acid (p7 2.77), and glutamic acid (p7 3.22), all at 50 mM concentra-... 

Table 4 examines the amino acid composition of purified SCP2 [21] and compares it with the amino acid compositions of 3 other preparations of interest [47-49], The most abundant amino acid in purified SCP2 is lysine, which accounts for 14 mole%. Since the isoelectric point for SCPj is approximately 8.6, it follows that a substantial portion of the glutamic and aspartic acid residues are amidated. Also of interest is the finding that SCPj contains no arginine or tyrosine, and only small amounts (perhaps 1 residue each) of histidine and tryptophan. 

The pK (near 4.5) of amino acids with a carboxyl group on the side chain (aspartic and glutamic acids) gives a better threshold value between stability and unfolding domains of these two enzymes than their respective isoelectric points. 

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