A variety of coupling agents and additives can be used during the coupling reaction, but the protecting groups for the terminal amino group is usually either an Fmoc (de-protected under basic conditions) or a Boc group (de-protected under acidic conditions). This process generally requires coupling agents and protecting groups. Peptides are synthesized by coupling the carboxyl group or C-terminus of one amino acid to the amino group or N-terminus of another, lengthening the peptide from the C-terminus to the N-terminus. SPPS is generally preferred because it does not require column purification after each coupling and deprotection step. There are two major strategies for peptide synthesis: solution-phase peptide synthesis and solid-phase peptide synthesis (SPPS). About 140 peptide drugs are in clinical trials and over 500 are in pre-clinical development. There are currently sixty FDA approved peptide drugs in the market, and pharmaceutical companies are increasingly interested in adding to that number. It was initially isolated from bovine or porcine pancreases, but now human insulin is manufactured using genetically engineered E. Insulin was the first therapeutic protein to be introduced to treat insulin-dependent diabetes in the 1920s. The development of peptide therapeutics has made many advances over the years. The first polypeptide (oxytocin - nine amino acid sequence) was synthesized by Vincent du Vigneaud in 1953. The first synthetic peptide glycyl-glycine (see picture) was discovered by Emil Fischer in collaboration with Ernest Fourneau in 1901. Synthetic peptides have been studied for over a century. They can be monitored for diagnostic purposes, such as in the case of C-peptide, which is used to monitor insulin production and to help determine the cause of low blood sugar (hypoglycemia). There is also an increasing number of examples of orally active peptides, which make them more desirable for drug development.Įndogenous peptides have also been utilized for research and medical interventions. Peptides, on the other hand, can often be accessed chemically, and their purification and analysis is much simpler. Further, biologics almost invariable must be injected. Their purification and structural analysis is often complex and expensive. ![]() While biologics are often highly safe and effective, they must be produced in bioreactors, which use whole cells. Biological therapeutics, which are generally proteins, have earned an increasing share of the pharmaceutical marketplace over the past few years. Therapeutic peptides also have some advantages compared to their protein counterparts. Peptides' activity can be lengthened by incorporating modifications, such as non-natural and D-amino acids, cyclization and modifications at the N or C-terminus. Not only can peptides be made very selelctive, decreasing the risk of side effects, but they rapidly metabolize by proteases and allow short time activity in the body. More recently, peptides have been considered as the desirable candidates for therapeutics. Researchers' interest in developing peptide ligands and probes for studying target receptors' structures and functions has increased dramatically lately. Peptides' large size and surface area allow for more specific docking to the target molecules. Modern medicinal and biochemical research is unthinkable without peptides application because of their selectivity, specificity and potency interaction with the target proteins. Other organisms have produced peptides as a means for defense, such as fungal production of cyclosporin A used clinically as an immunosuppressant, and cone snail secretion of Ziconotide which is used to treat a pain. They also play a role in endocrine signaling and can act as a growth factor. Peptides are functioning in human body on many ways, such as regulating metabolism (insulin) and mediating pain signals (dynorphin). Peptides often contain up to fifty amino acid residues, protein are molecules with more than fifty amino acid residues. ![]() Polymer molecules with ten or fewer amino acid residues are called oligopeptides. Peptides differ from proteins by amount of amino acid residues the molecule contains.
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