Carboxylic acid group, polypeptides

Finally, a new water-soluble polyphosphazene was recently synthesized that has the structure shown in 36 (46). This polymer has two attributes as a biomedical macromolecule. First, the pendent carboxylic acid groups are potential sites for condensation reactions with amines, alcohols, phenols, or other carboxylic acid units to generate amide, ester, or anhydride links to polypeptides or bioactive small molecules. Second, polymer forms ionic crosslinks when brought into contact with di- or trivalent cations such as Ca or Ai3+. The crosslinking process converts the water-soluble polymer to a hydrogel, a process that can be reversed when the system... 

The link between adjacent units or monomers in a polypeptide is formed in a condensation reaction between the amine group of one amino acid and the carboxylic acid group of another with the elimination of H20 molecules. These links are called peptide bonds. 

Amino acid The monomers of polypeptides, each monomer consisting of an amine group and a carboxylic acid group bonded to the same carbon atom. 

Proteins are composed of many amino adds joined together with amide bonds. The amino group of one can combine with the carboxylic acid group of another to give an amide. This special amide, which results from the combining of two amino acids, is known as a peptide—two amino acids join to form a dipeptide many join to give a polypeptide. 

Linear soluble PEG (polyethylene glycol) is used as a liquid phase in the synthesis of polypeptides. In this case the esterification of the carboxylic acid group of the N-protected amino acids with the terminal - OH groups of PEG can be conducted using DCC or a water soluble carbodiimide to give 684. Reaction of 684 with a different N-protected amino acid produces 685. 

Each cimino acid has an eimine (NH2) group, a central carbon atom known as the alpha carbon, a side chain (denoted R), and a carboxylic acid (COOH) group. The amine groups and carboxylic acid groups of amino acids cem be joined in a chain to form polymers of amino acids, known as peptides. Two amino acids form a dipeptide, three form a tripeptide, and chains of four or more amino acids are commonly referred to as polypeptides. Long polypeptides fold into specific conformations, which is what makes up a protein. 

Two amino acids can react with each other in an acid-base type of reaction. The basic amino group of one amino acid reacts with the acidic carboxylic acid group of another amino acid to form a peptide, and a molecule of water is lost. This reaction, shown below, is classified as a condensation reaction, or a dehydration synthesis, and the two amino acid molecules join together. The bond formed is called a peptide bond, and the product is a dipeptide because it is made up of two amino acid units. Longer chains are called polypeptides, and chains of 50 or more amino acids are called proteins. 

Amino acids " are amine derivatives of carboxylic acids and may, in fact, contain a number of amino and carboxylic acid groups. In the simplest case, with one acid and one amino group, the amino group may occupy a or or y, etc., positions. Amino acids, polypeptides and proteins are related compounds... 

Condensation polymerisation between the amino and carboxylic acid groups in amino acids produces a polypeptide or protein. The amide links in these polymers are known as peptide links (also known as peptide bonds). 

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