Proline isoelectric point

Proline (isoelectric point = 6.3) will migrate toward the cathode. Its structure is... 

Amino acids are commonly represented by three-letter abbreviations, for example Pro for proline. There is also an even more succinct one-letter abbreviation or code to represent each amino acid. These abbreviations, the structures of the amino acids, and their isoelectric points (the pH at which the amino acid has no net electrical charge,... 

The properties of the isolated peptides were quite similar in nature, whereby each peptide consisted of 12 amino acids in length and possessed a munber of residues with functional side groups that could stabilize nanoclusters. In many instances, these side chains were the hydroxyl-terminated side chains of serine, threonine, and tyrosine. In two of the peptides (AG3 and AG4), the location of the hydroxylated amino acids was conserved within two of the peptides. Similarly, one proline amino acid was conserved throughout all three of the sequences. Upon incubating each peptide in a solution of silver nitrate with no exogenous reductant, a clearly observable plasmon resonance peak arose at 440 nm for AG3 and AG4, but not with AG5. The peak was quite broad, indicative of a disperse size and shape distribution. The main difference between the active peptides and inactive AG5 was an overall basic isoelectric point for AGS The assays were performed at neutral conditions which would modulate the side-chain dynamics under acidic or basic conditions. 

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

PSA is a single-chain glycoprotein that is 7% carbohydrate. It has 237 amino acid residues and four carbohydrate side chains with linkages at amino acid 45 (asparagine), 69 (serine), 70 (threonine), and 71 (serine). The N-terminal amino acid is isoleucine, and the C-terminal residue is proline. Its MW is 28,430, and it has isoelectric points from 6.8 to 7.2 because of its various isoforms. The three-dimensional structure and the antigenic domain of PSA have been characterized. ... 

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... 

Acid-labile formylation of A-terminal proline of HIV-1 was found by proteomics. The role of formylation of human immunodeficiency virus type 1 p24 is unclear so far, but it is surmised that the acid-labile formylation of H1V-1lav-i p24 may play a critical role in the formation of the HIV-1 core for conferring HlV-1 infectivity. Furthermore, peptide-mass fingerprinting data suggest that two isoforms of cyclophilin A (CyPA), one with an isoelectric point (pi) of 6.40 and one with a pi of 6.53, are inside the viral membrane and another isoform with a pi of 6.88 is outside the viral membrane, and that the CyPA isoform with a pi of 6.53 is V-acetylated. The mechanisms that permit the redistribution of CyPA on the viral surface have not yet been clarified, but it is surmised that the CyPA isoform with a pi of 6.88 may play a critical role in the attachment of virions to the surface of target cells, and both the CyPA isoforms with pis of 6.40 and 6.53 may regulate the conformation of the HlV-1 capsid protein. 

The mechanism of the entry of fructose into the Maillard reaction (a series of sugar/amino acid processes in vivo) has been studied by DFT the order of reactivity for the isomers is predicted as a- > /3- > open-chain. Heyns rearrangement products are most favourable under basic conditions, possible under neutral conditions, but unfeasible at or below glycine s isoelectric point. Kinetic and activation parameters have been reported for the corresponding glucose/proline reaction. ... 

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 . ... 

FIGURE 5.2 Zwitterion (dipolar ion) of amino acids used as chiral selectors for CCSPs preparation, pi = isoelectric point. Asterisk represent pi of proline, an amino acid analogous to 2-azabicyclo[3.3.0]octan-3-carboxylic acid. 

---