Valine isoelectric point

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.

The compounds investigated were the amino acids L-isoleucine, L-leucine, L-valine, and L-a-amino butyric acid. These compounds have similar molecular structures, as shown in Figure 2, and will be referred to throughout the present work as L-Ile, L-Leu, L-Val, and L-a-ABA. Where there is little likelihood of confusion, the designation L- will be omitted. Operations examined included crystallization of He through the addition of hydrochloric acid and through cooling. Under acidic conditions He crystallizes as a hydrochloride salt while in the vicinity of the isoelectric point (pH 5.2) it crystallizes as the neutral zwitterionic... 

You will obtain a titration curve of an amino acid with a neutral side chain such as glycine, alanine, phenylalanine, leucine, or valine. If pH meters are available, you read the pH directly from the instrument after each addition of the base. If a pH meter is not available, you can obtain the pH with the aid of indicator papers. From the titration curve obtained, you can determine the pK values and the isoelectric point. 

Hemoglobin A (the major, normal form in humans) has an isoelectric point of pH 6.9. The variant hemoglobin M has a glutamate residue in place of the normal valine at position 67 of the a chain. What effect will this substitution have on the electrophoretic behavior of the protein at pH 7.5 ... 

Since pH 7.5 is above the isoelectric point of hemoglobin A, the protein carries a negative charge and will migrate to the anode. At pH 7.5 the glutamate side chain has a negative charge, while valine... 

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

Table 5 presents the amino acid compositions of a number of apoferritins together with their isoelectric point (taken from the literature) where available. There are a number of features whihc are of quite considerable interest. In the first place, although there are clear cut differences between the proteins of different species, a number of very considerable similarities exist. Thus, for all of the apoferritins for which data is available the content of non-polar amino acids (proline, glycine, alanine, valine, methionine, leucine, isoleucine, phenylalanine and tryptophan) remains constant at about 45%. What is even more remarkable is that the content... 

Amphomycin is a highly siurface active acidic polypeptide with an isoelectric point of 3-5 to 3 6 . One free amino group and three to four acidic gproups have been determined . It crystallized as the calcium salt. Total acid hydrolysis and separation of the components by combined electrophoresis and paper-chromatography showed glycine, proline, valine, aspartic acid, an unknown monoaminomonocarboxylic acid, CgHnNO, and an unknown diaminomonocarboxylic acid, to be present . ... 

During investigation of the electrochemical removal of salts from numerous amino acids (glycine, alanine, valine, lysine, arginine, glutamic acid, and aspartic acid) with varying isoelectric points, considerable losses were found from the central compartment of the cell, shown in Fig. 9 [41]. It was found that not only the pH of the amino acid solution in the central compartment but also the... 

Amino acid-like compound when amino acids are present in aqueous solution and at a pH close to the isoelectric point (pi), they are present in the form of a zwitterion, a form bearing both a positive and a negative charge. Figure 2.6 clarifies the case of valine, as well as the domains of existence of each form depending on the pH. The vahne pKa are equal to 2.3 and 9.7, and the pi is equal to 6.0. 

---