Peptide, biologically active

The second application of the CFTI approach described here involves calculations of the free energy differences between conformers of the linear form of the opioid pentapeptide DPDPE in aqueous solution [9, 10]. DPDPE (Tyr-D-Pen-Gly-Phe-D-Pen, where D-Pen is the D isomer of /3,/3-dimethylcysteine) and other opioids are an interesting class of biologically active peptides which exhibit a strong correlation between conformation and affinity and selectivity for different receptors. The cyclic form of DPDPE contains a disulfide bond constraint, and is a highly specific S opioid [llj. Our simulations provide information on the cost of pre-organizing the linear peptide from its stable solution structure to a cyclic-like precursor for disulfide bond formation. Such... 

D. H. Schlesinger, ed.. Neurohypophyseal Peptide Hormones and Other Biologically Active Peptides, Developments in Endocrinology, Vol. 13, Elsevier Science, New York, 1981. 

Amino acid separations represent another specific application of the technology. Amino acids are important synthesis precursors - in particular for pharmaceuticals -such as, for example, D-phenylglycine or D-parahydroxyphenylglycine in the preparation of semisynthetic penicillins. They are also used for other chiral fine chemicals and for incorporation into modified biologically active peptides. Since the unnatural amino acids cannot be obtained by fermentation or from natural sources, they must be prepared by conventional synthesis followed by racemate resolution, by asymmetric synthesis, or by biotransformation of chiral or prochiral precursors. Thus, amino acids represent an important class of compounds that can benefit from more efficient separations technology. 

Yau-Yong, A., Chow, J., and Law, M. (1986). Liposome delivery of a biologically active peptide, 133rd Ann. Meeting Am. Pharm Assoc.. 16, 105. 

Important products derived from amino acids include heme, purines, pyrimidines, hormones, neurotransmitters, and biologically active peptides. In addition, many proteins contain amino acids that have been modified for a specific function such as binding calcium or as intermediates that serve to stabilize proteins—generally structural proteins—by subsequent covalent cross-hnk-ing. The amino acid residues in those proteins serve as precursors for these modified residues. Small peptides or peptide-like molecules not synthesized on ribosomes fulfill specific functions in cells. Histamine plays a central role in many allergic reactions. Neurotransmitters derived from amino acids include y-aminobutyrate, 5-hydroxytryptamine (serotonin), dopamine, norepinephrine, and epinephrine. Many drugs used to treat neurologic and psychiatric conditions affect the metabolism of these neurotransmitters. 

These include nicotinic acetylcholine receptors, neuronal calcium channels, muscle sodium channels, vasopressin receptors, and iV-methyl-D-aspartate (NMDA) receptors. Some general features of the structure, function, and evolution of biologically active peptides isolated from Conus venom are presented. 

The a -, /z-, and a-conotoxins are the best characterized of the peptides isolated from Conus venoms so far. However, a large number of other peptides are found in these venoms. These comprise both paralytic toxins to immobilize the prey of the cone snail, and other biologically active peptides which are not themselves directly paralytic. Only the briefest overview of these peptide components will be presented here. 

A large number of other non-paralytic but biologically active peptides have been purified and sequenced. In most cases however, the detailed mechanism of action has not yet been elucidated. Clearly, Conus venoms will be a rich source of such peptides that can be used to probe various receptor targets, particularly in the central nervous system. 

Schmidt, G. Recent Developments in the Field of Biologically Active Peptides. 136,109-159 (1986). 

Henderson, D. E. and Mello, J. A., Physicochemical studies of biologically active peptides by low-temperature reversed-phase high-performance liquid chromatography, /. Chromatogr., 499, 79, 1990. 

The regulation of mast-cell activity by biologically active peptides is an area of research, the rapid growth of which has been sparked in part by this intense interest in the interactions between neural, endocrine and immune systems [4, 26, 41] and in part by the recognition that activation of mast-cell secretion as a purely allergic IgE-dependent event is undoubtedly too restrictive. The involvement of the mast cell in the inflammatory response, for example, has for years been suspected to involve a number of non-immunologic, IgE-inde-pendent factors [24,42], Direct evidence for peptide involvement, however, has... 

Other collaborative work from our laboratories has recently shown a second biologically active peptide to be generated by cathepsin D (as well as pepsin)... 

Peptides are short chains of amino acids linked by peptide bonds. Most biologically active peptides contain two to ten amino acids. Peptide bonds are formed between the carboxyl carbon of one amino acid and the amino nitrogen of another. Since water is released, this is an example of dehydration synthesis. The bond forms as illustrated in Figure 16.7. 

W Bauer, J Pless. The use of boron tristrifluoroacetate (BTFA) in the synthesis of biologically active peptides, in R Walter, J Meienhofer, eds. Peptides Chemistry, Structure, Biology. Proceedings of the 4th American Peptide Symposium. Ann Arbor Science, Ann Arbor, MI, 1975, pp 341-345. 

L. D. Possani R. C. Rodriguez de la Vega, Scorpion Venom Peptides. In Handbook of Biologically Active Peptides] J. Kastin, Ed. Elsevier Burlington, MA, 2006 p 339. 

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