AMINO ACIDS CLASSIFICATION AND PROPERTIES
AMINO ACIDSCLASSIFICATIONANDPROPERTIES
WHAT ARE AMINO ACIDS. Amino acids are organic compounds containingamine [- NH 2 ]carboxyl [-COOH]side chain [R group] The major key elements if amino acids are carbon,hydrogen, nitrogen, oxygen. About 500 amino acids are known (though only 20appear in the genetic code) and can be classified inmany ways
BASIC STRUCTURE[SKELETON]
NEED FOR CLASSIFICATION Classification of amino acids gives the groupingbetween 20 acids and a basic outline for grouping. It makes a clear idea to pick the amino acid type This is much useful for biochemists for the easyunderstanding between each amino acids.
Classification:Based on R group Polarity and R group Distribution in protein Nutritional requirements Number of amino and carboxylic groups
Based on R-Group Simple amino acids:these have no functional group in their sidechain.Example: glycine, valine, alanine, leucine,isoleucine Hydroxy amino acids:these have a hydroxyl group in their sidechainEg: serine, threonine
Sulfur containing amino acids:have sulfur in their side chainEg: cysteine, methionine Aromatic amino acids:have benzene ring in their side chainEg: phenylalanine, tyrosine Heterocyclic amino acids:having a side chain ring which possess atleast on atom other than carbonEg: Tryptophan, histidine, proline
Amine group containing amino acids:derivatives of amino acids in whichone of carboxyl group has been transformedinto an amide groupEg: Asparagine, glutamine Branched chain amino acids:A branched-chain amino acid (BCAA) isan amino acid having aliphatic side-chains witha branchEg: leucine, isoleucine, valine
Acidic amino acids:have carboxyl group in their side chainEg: Aspartic and Glutamic acid Basic amino acids:contain amino group in their side chainEg: Lysine, Arginine Imino acid:Amino acids containing a secondary aminegroupEg: Proline
Polarity and R Group Amino acids with non polar R group:these are hydrocarbons in nature,hydrophobic, have aliphatic and aromatic groups[aliphatic R groups]Eg: Alanine, Valine, Leucine, Isoleucine, Proline.[Aromatic groups]Eg: Phenylalanine, Tryptophan,Methionine(sulfur)
Amino acids with polar but uncharged RGroup:these amino acids are polar and possessneutral pH value.Eg: Glycine, Serine, Threonine, Cysteine,Tyrosine, Glutamine, Asparagine.
Negatively charged amino acids:their side chain [R Group] contain extracarboxyl group with a dissociable proton.And renders electrochemical behaviour toproteinsEg: Aspartic acid and Glutamic acidAspartic acid
Positively charged amino acid:their side chain have extra amino groupRendering basic nature to protein,Eg: Lysine, Arginine, Histidine.Lysine
Distribution in protein: Standard protein amino acids:the amino acids that are used to formproteins,recognized by ribozyme autoaminoacylationsystemsEg:Histidine, isoleucine, leucine, lysine, methionine,phenylalanine, threonine, tryptophan,and valine
Non standard protein amino acids:these amino acids are not required to buildproteins.have a vital role as metabolic intermediates.Eg. Hydroxyproline, Hydroxylysine,Carboxyglutamate, Diaminopimelate.
Non standard non protein amino acid:These are the derivative of amino acids andhave role in metabolism.Eg: Alpha amino butyrate, Citruline, Ornithine,beta-alanine.
Based on nutritional requirements: Essential amino acids:Essential amino acids cannot be made by thebody.As a result, they must come from food.The essential amino acids are: Arginine,histidine, isoleucine, leucine, lysine, methionine,phenylalanine, threonine, tryptophan, andvaline.
Non essential amino acids:An amino acid that can be made by humans andso is essential to the human diet.The nonessential amino acids: Alanine,asparagine, aspartic acid, cysteine,glutamic acid, glutamine, glycine, proline,serine, and tyrosine.
On basis of number of amino and carboxylicgroups:Monoamino- monocarboxylic aminoacids glycine, alanineprolinephenylalaninemethionineserine, threonine
Monoamino-dicarboxyli amino acid:Aspartic and glutamic acid
Diamino-monocarboxylic amino acids:Lysine, arginine, histidine.
Properties : Physical ColourlessCrystalline in natureTasteless[tyrosine], sweet[glycine, alanine]Melting point above 200 C Soluble in polar solvent and Insoluble in nonpolar solvent Have absorbance at 280nm
Mol wt: 100 – 50,000Dt All amino acids possess optical isomers due tothe presence of asymmetric α-carbon atoms. Some are structurally stable and stericallyhindered [Glycine] Amino acids [proteins]posses enzymaticactivities Amino acids exhibit colloidal nature anddenaturing property
Chemical properties Decarboxylation:The amino acids will undergo decarboxylationto form the corresponding “amines”. Thusamines are produced Histidine Histamine CO2 Tyrosine Tyramine CO2 Lysine Cadaverine CO2
Reaction with Ninhydrin:
Reaction with Alkalies (Salt formation): The carboxyl group of amino acids can release aH ion with the formation of Carboxylate (COO–) ions. Reaction with Alcohols (Esterification) : the amino acids is reacted with alcohol to form,“Ester”. The esters are volatile in contrast to the formamino acids.
Reaction with DANSYl Chloride:DANSYl chloride means “Dimethyl Amino NapthaSulphonyl Chloride”.When the amino acid reacts with DANSYl chloridereagent, it gives a “Flourescent DANSYl derivative Reaction with acylating agents (Acylation):When the amino acids react with “Acid chloride” andacid anhydride in alkaline medium it gives “pthaloylamino acid
Reaction with Sanger’s reagent: “1-flouro-2,4-dinitrobenzene” is calledSanger’s reagent (FDNB).sanger’s reagentreacts with α-amino acid to produce Yellowcoloured derivative, DNB-amino acid.
Reaction with Edmann’s reagent:Edmann’s reagent is “phenylisothiocyanate”. When aminoacids react with Edmann’s reagentit gives “phenyl thiohydantoic acid” finally it turns intocyclized form “Phenyl thiohydantoin” (Edmann’s derivative).
Reference : Dr. J.L. Jain – Fundamentals of Biochemistry byChand publications, New Delhi.
Non essential amino acids: An amino acid that can be made by humans and so is essential to the human diet. The nonessential amino acids: Alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serin
1. Given the following chain of amino acids: Val-Cys-Asp-Leu-Ala-Arg-Phe-Glu-Trp a. identify the largest and smallest amino acids, b. identify the amino acids with ionizable side chains, c. identify the amino acids whose side chains are non-polar. 2. Draw glycine, lysine, and glutamic acid below.
3.2 Amino Acid Profile Amino acids are vital and have to be presented in catfish fingerlings diet for maximal growth. Table 3 shows the amino acids profile for each feed ingredients used in fish feed formulation. The amino acids profile shows 16 types of amino acids present among 22 amino acids in nature which has been analyzed through HPLC.
Terminology There are a variety of different types of amino acids, however the MCAT only focuses on the 20 alpha-amino acids that are encoded by the human genetic code. o Called the proteinogenic amino acids Stereochemistry of Amino Acids Alpha carbon is usually a chiral center since it has four different groups attached to it.
20 standard amino acids classification based on properties Non-Polar/ Hydrophobic Aromatic Polar/Hydrophilic Acidic . Titration of amino acids with ionizableside chains Acidic amino acids Basic amino acids Histidine NPTEL. NPTEL. Lysine titration NPTEL. Histidine Titration 3 2 1 0 0 2 4 6 8 10 1214 pK a 1.8 pK a
Properties of Acids and Bases Return to the Table of contents Slide 5 / 208 What is an Acid? Acids release hydrogen ions into solutions Acids neutralize bases in a neutralization reaction. Acids corrode active metals. Acids turn blue litmus to red. Acids taste sour. Properties of Acids Slide 6 / 208 Properties
The amino acid degradation The first step in degradation of many standard amino acids is the removal of the α-amino group, i.e. deamination or transamination. The product is mostly the corresponding 2-oxoacid (α-ketoacid) and α-amino group is released as ammonia or ammonium ion. Direct deamination of amino acids
Introduction to amino acid metabolism Overview The body has a small pool of free amino acids. The pool is dynamic, and is . require dietary sources of these amino acids. In general, the synthesis pathways for the essential amino acids are complex, and involve a large number of reactions.
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