do peptides have isoelectric points?
316952
Calculating approximate isoelectric points for amino acids and peptides: Amino acids: If the side chain does not have an ionizable group, then the pI is simply the average of the α- NH3 and α-COOH pKa values. If the side chain has an ionizable group then all three pKa values must be considered.
104934
Both the amino group and the carboxyl group of each amino acid are ionizable. The carboxyl group (with a pKa of about 3) is deprotonated at physiological pH. The amino group is protonated at physiological pH. ... In addition, the side chains of some of the amino acids contain ionizable groups.
420952
Ionizable Amino Acids. Seven out of the twenty amino acids contain readily ionizable side chain groups. That means that at specific pH values, each side chain can participate in an acid-base reaction in which it can exchange a hydrogen atom with some other biomolecule.
233572
Acidic and Basic Amino Acids. There are three amino acids that have basic side chains at neutral pH. These are arginine (Arg), lysine (Lys), and histidine (His). ... Their side chains have carboxylic acid groups whose pKa's are low enough to lose protons, becoming negatively charged in the process.
205849
When an amino acid contains both a plus and a minus charge in the "backbone", it is called a zwitterion and has an overall neutral charge. The zwitterion of an amino acid exists at a pH equal to the isoelectric point. Each amino acid has its own pI value based on the properties of the amino acid.
910096
Properties of amino acids are grouped based on the functional side chains (R), and one such property is hydrophobicity. If the R group is repelled by water, then it is hydrophobic (nonpolar), eg, valine; whereas hydrophilic (polar) amino acids are attracted to water, eg, arginine.
1233581
There are three amino acids that have basic side chains at neutral pH. These are arginine (Arg), lysine (Lys), and histidine (His). Their side chains contain nitrogen and resemble ammonia, which is a base. Their pKa's are high enough that they tend to bind protons, gaining a positive charge in the process.
304401
Proteins are built from a set of only twenty amino acids, each of which has a unique side chain. The side chains of amino acids have different chemistries. The largest group of amino acids have nonpolar side chains.
1450270
Peptide hormones are water-soluble and, unlike steroid hormones, do not readily cross hydrophobic cell membranes. Most peptide hormones exert their actions by binding to specific receptors located on the surface of target cells.
272877
All amino acids except for glycine are stereoisomers. This means that there are mirror images of their structure. It is just like how we have left hands and right hands. These are labeled L (left-handed) and D (right-handed) to distinguish the mirror images.
845723
The isoelectric point is the average of the 2 pKa values that have a neutral molecule as one of its equilibrium species.
536691
The simplest member of this group is glycine, where the saturated carbon atom is unsubstituted, rendering it optically inactive. The rest of the 20 most common amino acids are optically active existing as both D and L stereoisomers. ... Amino acid side chains can be polar, non-polar, or practically neutral.
803989
The pH at which the net charge of an amino acid is 0 is called the isoelectric point. ... Figure 5 animates the separation of a mixture of glycine, lysine, and aspartic acid at a pH of 6. At this pH the net charge on the aspartic acid is -1, while that on the lysine is +1. There is no net charge on the glycine.
798472
Polar amino acids. ... The polar group consist of 10 amino acids, two are negatively charged - aspartic acid and glutamic acid, 3 have a positive charge - arginine, lysine and histidine, and 5 are uncharged - asparagine, glutamine, serine, threonine and tyrosine.
659701
Lysine and arginine are basic amino acids because their side chain group contains a full positive charge at the physiological pH. Histidine is also considered basic but it can have a positive or a neutral charge on its side chain group at the physiological pH.
56188
The charge of zwitterions increases solubility in polar solvents such as water. Since amino acids and some other compounds form zwitterions, it seems solubility is important. In addition, the folding of long chain molecules is seriously affected by electrical charge. An area of current research is zwitterion transport.
552920
Amino acids are generally soluble in water and insoluble in non-polar organic solvents such as hydrocarbons. This again reflects the presence of the zwitterions. In water, the ionic attractions between the ions in the solid amino acid are replaced by strong attractions between polar water molecules and the zwitterions.