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عدد الرسائل : 1800 العمر : 35 الموقع : every where المزاج : Happy كليتك : علوم جنسيتك : مصرى هل تحب منتدانا : جدا كيف تعرفت على منتدانا : جوجل السٌّمعَة : 4 نقاط : 11432 تاريخ التسجيل : 07/03/2009
| موضوع: Peptide classification الإثنين أبريل 13, 2009 9:23 pm | |
| presented to Dr Hamed Abd Elbary Peptide classification by function of peptidesPeptides are involved intomany processes in the living organisms and it is possible to classify them onthe basis of their function. As usually this classification is not perfectbecause some of the peptides can belongs to different groups simultaneously,for example, oxytocin can be considered as a hormone (transmitting signalbetween cells) and also oxytocin can be classified as neuropeptide because therfunction as neurotransmitter in the brain.
- Hormones. Hormones
are involved into carrying signals between cells. Classical examples of hormones are: bradykinins, gastrins, oxytocins etc.
- Neuropeptides.
Neuropeptides found in neural tissues. usually these peptides are produced in the brain and involved into regulatory and signalling processes. Classical examples of neuropeptides are: endorphins, vasopressin, atrial-natriuretic peptide etc.
- Alkaloids. Alkaloids
are peptides, usually from plants, fungi and some animals like shellfish. Alkaloids involved into defend of one organism from consuming by other organisms. Classical examples of peptide alkaloid are: ergotamine, pandamine, dynorphin A-(1--octapeptide, N beta-(D-Leu-D-Arg-D-Arg-D-Leu-D-Phe)-naltrexamine, etc.
- Antibiotics. Antibiotics
are inhibits the grows of micro organisms, usually bacterial cells and locationally fungi and protozoa. Classical examples of peptide antibiotics are: tyrothricinm bacitracin, gramicidin, valinomicin etc.
- Toxins. Toxin is
the poison substance. Peptide toxins are the most poison substances. Examples of peptide toxins are: palutoxins, agatoxins, curtatoxins etc.
- Regulation
peptides. The group of regulation peptides is not well defined because almost any peptides can regulate some processes in organisms, but this group is used to classify peptides which are not clearly belongs to other groups. examples of regulatory peptides are: anserine, carnosine, etc.
Peptide classification by synthesisSometimes peptides can beclassified by their synthesis type.
- Ribosomal
peptides. Ribosomal peptides (almost all known peptides) are synthesized by translation of mRNA on ribosomes. Usually they subjected to further postranslational modification, wich can involve even recemization of L-amino acids to D-amino acids.
- Nonribosomal
peptides. Nonribosomal peptides (glutathione cyclopeptides etc.), are synthesized during enzymatic catalysis
- Peptones. Peptones
are peptides derived from digestion processes.
Peptide synthesisPeptide synthesis is achemical process of coupling of the carboxyl group of one amino acid to theamino group of another amino acid. Usually chemical techniques are used tosynthesize peptides of up to 30-40 amino acids length. The fist peptidesynthesis was carries out by T. Curtius 1882 via reaction between benzylcloride and silver salt of glycine. During this process Curtius producecrystals of N-benzyl-glycile-glycine. The first pure di-peptide (Gly-Gly) wassynthesized by E. Fischer in 1901. In 1932, Bergmann from Fisher's lab discover carbobenzoxy group C6H5CH2OCO whichis very convenient as a protective group for peptide synthesis. In 1950-1960the first biological peptides, like oxytocin, vasopressin, insulin and otherswere synthesized. Types of peptide synthesisPeptide synthesis processcan be classified on the basis of used techniques and type of the finalproduct.
- Liquid-phase
peptide synthesis. Liquid-phase, or classical peptide synthesis can be devided into two classes - step-by-step peptide synthesis with subsequent adding of one amino acid at ones from C-terminal to N-terminal and block-synthesis with coupling of polypeptide fragments. Liquid-phase peptide synthesis is used in large-scale peptide production for industry.
- Solid-phase
peptide synthesis. Solid-phase peptide synthesis is a process during which the polypeptide chain is covalently bound via linker to the porous insoluble beds particles. Each cycle of this solid-phase peptide synthesis can be described in few steps - deprotection of N-terminal group, coupling with N-protected amino acid. The standard repetitious steps allows to use robotic equipment for this type of synthesis. Solid-phase peptide synthesis is perfect for researche laboratories and small quantities of production.
- Homo-polymerisation.
Homo-polymerisation is used to synthesize homo-polymeric chains of amino acids.
- Enzymatic peptide
synthesis. Enzymatic peptide synthesis is based on enzymes which are able to formate peptide bond. Unfortunately this technique is very complicated and there is no remarkable results was achieved yet.
- Partial
peptide synthesis. In partial peptide synthesis technique the natural peptides and proteins are used as a source of peptide fragments.
- Cyclopeptide
synthesis. Cyclopeptide synthesis is the cyclization of linear peptides.
- Non-standard
peptide synthesis. Non-standard peptide synthesis is used to produce peptides with non-standard peptide bonds, for example ester-bonds etc.
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عدد الرسائل : 420 العمر : 35 الموقع : المزاج : كليتك : هل تحب منتدانا : نعم السٌّمعَة : 1 نقاط : 5854 تاريخ التسجيل : 24/02/2009
| موضوع: رد: Peptide classification الإثنين أبريل 13, 2009 10:06 pm | |
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sima_s مشرفة مؤسسة
عدد الرسائل : 1800 العمر : 35 الموقع : every where المزاج : Happy كليتك : علوم جنسيتك : مصرى هل تحب منتدانا : جدا كيف تعرفت على منتدانا : جوجل السٌّمعَة : 4 نقاط : 11432 تاريخ التسجيل : 07/03/2009
| موضوع: رد: Peptide classification الثلاثاء أبريل 14, 2009 4:22 pm | |
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