2physical properties of aa and biologically important peptide
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1. The document discusses the physical and chemical properties of amino acids, including their solubility, taste, melting points, ability to absorb ultraviolet light, and chirality. 2. It also describes how amino acids can act as acids or bases depending on the pH, existing as zwitterions at physiological pH with both positive and negative charges. 3. Several biologically active oligopeptides are discussed, including hormones like oxytocin, vasopressin, angiotensin, and neuropeptides like methionine enkephalins. Other peptides mentioned include glutathione, bradykinin, carnosine, antibiotics, and the artificial sweetener aspartame.
2physical properties of aa and biologically important peptide
- 2.  SOLUBLE  polar solvents  Water  alcohol  INSOLUBLE  (non-polar solvents)  benzene 2Dr GayathriG Nair
- 3. ï‚¡ Sweet:- ï‚¡ Bitter:- ï‚¡ Tasteless:-Leucine 3 Glycine, Alanine,Valine, Serine tryptophan, histidine and proline Isoleucine and arginine Dr GayathriG Nair
- 4. ï‚¡ Melting point: ï‚¡ all amino acids have high melting points more than 2000 c ï‚¡ ABSORBS ULTRAVIOLET LIGHT:The aromatic amino acids viz tryptophan, tyrosine ,phenylalanine and histidine. 4Dr GayathriG Nair
- 5. ï‚¡ Amino acids having asymmetric carbon atom exhibit optical activity ï‚¡ Asymmetry arises when 4 different groups are attached to the same carbon atom Glycine is the simplest amino acids with no asymmetric carbon atom and optically inactive 5Dr GayathriG Nair
- 6. ï‚¡ The mirror image forms produced with reference to alpha carbon atom are called D & L isomers ï‚¡ L-AA occur in nature therefore are called natural amino acids ï‚¡ D-AA seen in small amounts in micro organisms and as constituents of certain antibiotics . 6Dr GayathriG Nair
- 7.  All amino acids have acidic(carboxyl ) and basic (amino) group  Acid –base behaviour : the carboxyl group of an amino acid can donate one proton (H+ ) and behave as an acid forming an negatively charged anion  Similiarly amino group can accept a proton and behave as base forming positively charged cation  Substances having two way property are called ampholytes or amphoteric  Amino acids have both acidic and basic groups and are amphoteric in nature 7Dr GayathriG Nair
- 8. ï‚¡ Zwitter in german means hybrid ï‚¡ At physiological pH; ï‚¡ The carboxyl group exists as carboxylate ion coo- ï‚¡ And amino group is in the protonated form NH3+ ï‚¡ Mono amino mono carboxylic acids exist in aqueous solution as dipolar or zwitter ion ï‚¡ which means that they have both positive and negative charges on the same amino acids ï‚¡ The overall molecule is electrically neutral 8Dr GayathriG Nair
- 9. ï‚¡ Definition:Thus the molecular species which contain equal number of ionizable group of opposite charge and as a result bear no net charge are zwitter ion ï‚¡ As amino acids are both a proton donor and a proton acceptor it is an ampholyte 9Dr GayathriG Nair
- 10. ï‚¡ The pH at which the molecules carry no net charge is known as isoelectric point or isoelectric pH ï‚¡ The amino acids at its isoelectric pH does not move in electric field as it carries no net charge 10Dr GayathriG Nair
- 11.  Amino acids exerts chemical properties because of their  Carboxyl group  Amino group  Side chain ‘R’  All amino acids contain first two groups and hence undergo chemical reaction characteristic for these group 11Dr GayathriG Nair
- 12. Reactions Answered by group Biuret reaction Nitrogen in Peptide bonds Ninhydrin Alpha amino group Xanthoproteic test Benzene ring(phe,tyr,trp) Millons test phenol(tyrosine) Aldehyde test Indole (tryptophan) Sakaguchi test Guanidinium (arginine) Sulphur test Sulfhydryl (cysteine) Pauly’s test Imidazole (histidine) 12Dr GayathriG Nair
- 13. Physical properties ï‚¡ Soluble ,taste,melting ï‚¡ Optical property ï‚¡ Ionising property ï‚¡ Isoelectric pH Chemical properties ï‚¡ Colour reaction 13Dr GayathriG Nair
- 15.  Some of the biologically active oligopeptides are: 1. THYROTROPIN RELEASING HORMONE (TRH) is a tripeptide  Hormone secreted from hypothalamus  stimulate pituitary gland to releaseTSH 15Dr GayathriG Nair
- 16. 2. GLUTATHIONE:Tripeptide,found in all mammalian cell except neurons with the sequence of glu-cys-gly  Found in all mammalian cells except neurons  Maintains RBC membrane integrity  Involved in detoxification mechanism  Transport of aa across the cell membrane. 16Dr GayathriG Nair
- 17. 3. Oxytocin: It’s a nano peptide (9 AA), a hormone of posterior pituitary gland  Function: contraction of uterus 17Dr GayathriG Nair
- 18. 4. Vasopressin/antidiuretic hormone:  Nanopeptide  It is secreted from posterior pituitary gland  Function: retention of water from renal tubules. Increases BP 18Dr GayathriG Nair
- 19. 5. Angiotensin:  Angiotensin I is a decapeptide  Angiotensin II is a octapeptide, vasoconstrictor  Functions: 1) Raises blood pressure by stimulation of adrenal gland 2) Release of aldosterone that promote sodium retention 19Dr GayathriG Nair
- 20. 6. Bradykinin :Nanopeptide,  Powerful vasodilator and causes contraction of smooth muscle  Responsible for producing peripheral and visceral pain by stimulating pain receptors  Mediates production of Pg’n E2 from arterial walls 7. Kallidin: Decapeptide, vasodilator 20Dr GayathriG Nair
- 21. 8. Methionine encephalins:  Pentapeptide found in brain  Binds to receptors in certain cells of brain and induce analgesia (decreases pain sensations) 9. Aspartame:  Commercially synthesized ,  Dipeptide (aspartic acid + phenylalaninie)  Its an artificial sweetner  Unsuitable for phenyl ketonurics 21Dr GayathriG Nair
- 22. 10. Antibiotics:Gramicidin S  An antibiotic produced by bacillus brevis  Decapeptide  It contains D-phenylalanine, 11.CARNOSINEAND ANSERINE: Dipeptide with sequence beta-Alaninie+ Histidine  Carnosine stimulates muscle contraction and it is methylated to form anserine  both are present in skeletal muscle 22Dr GayathriG Nair
- 23. ï‚¡ Hormones:TRH,OXYTOCIN,VASOPRESSIN ANGIOTENSIN I / II ï‚¡ GLUTATHIONE ï‚¡ BRADYKININ ï‚¡ KALLIDIN ï‚¡ CARNOSINE/ANSERINE ï‚¡ ANTIBIOTICS ï‚¡ ASPARTAME 23Dr GayathriG Nair