Quantitative Tests For Amino Acids And Proteins Biology

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The intent is, finding whether aminic acids or proteins are present in solution and amino acids are transporting a free aminoalkane group by utilizing biuret trial, ninhydrin trial, xanthoproteic trial and heavy metal precipitation trial.


Proteins are organic compounds made of amino acids.The amino acids joined together by the peptide bonds.Proteins have three dimensional constructions. Primary construction is the amino acerb sequence.Secondary construction, alpha spiral, beta sheet. Secondary constructions are local, many parts of different secondary construction can be present in the same protein molecule.

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It on a regular basis repeats local constructions stabilized by H bonds. Third construction, is by and large stabilized by nonlocal interactions, most normally the formation of a hydrophobic nucleus, but besides through salt Bridgess, H bonds, disulfide bonds, and even post-translational modifications.Quaternary construction, formed by several protein Molecules normally called protein fractional monetary units.

There are several quantitative trials for finding whether aminic acids or proteins are present in solution.These trials are specific for the presence of peptide bonds, certain types of side ironss and the type of secondary construction present.Biuret trial determines if there is 2 or more peptide or not.The biuret reagent is made of Na hydrated oxide and Cu sulphate. The bluish reagent turns violet in the presence of proteins, and alterations to tap when combined with short-chain polypeptides.

Ninhydrin detects if there is ammonium hydroxide or primary, secondary aminoalkanes or not.In ninhydrin trial, if reacts with these free aminoalkanes, a deep blue or violet colour will detect.

Xanthoproteic trial, determines benzine and benzine derived functions such as tyrosine, tyrptophane which are contains activated benzene rings and readily undergo nitration and phenyl alanine which is besides contains benzene pealing but non activated and non readily undergo nitration.Also the merchandise will be xanthous colored.

Heavy metal trial, makes ions to denaturate proteins.There are similar reagent with biuret trial and it uses AgNO3 and Fe ( III ) .



  • Test tubing ( 15 mL falcon ) * 16
  • Droppers
  • Test tubing rack
  • Beaker 250 milliliter
  • Hot topographic point
  • Weighing dish
  • Weight


  • 2 % glycine solution
  • 2 % gelatin solution
  • 2 % albumin solution
  • 2 % tyrosine solution
  • Casein
  • Banana Milk
  • 2.5 M NaOH solution
  • Ninhydrin reagent
  • Nitric acid
  • 5 % Cu sulphate
  • 5 % Ag nitrate
  • 5 % Fe ( III ) nitrate
  • Sodium nitrate


For biuret trial:

  • Glycine
  • Blue ( visible radiation )
  • Gelatin
  • Purple ( dark )
  • Albumin
  • Purple ( igniter )
  • Casein
  • Purple ( bluish & A ; purple )
  • Tryptophan
  • Blue ( igniter )

For ninhydrin trial:

  • Glycine immediately it becomes violet and now dark purple
  • Gelatin
  • Before the bath it was fuzzed and now dark purple ( alterations color easy )
  • Albumin
  • Dark purple and like solid ( alterations color more easy )
  • Casein
  • Grey & A ; purple ( non disassociate in H2O )
  • Tryptophan
  • Change colour to the purple easy than glycine

For xanthoproeic trial:

  • Glycine
  • Transparent
  • Gelatin
  • Fuzzy yellow
  • Albumin
  • First fuzzy xanthous so dark orange ( orange & A ; red )
  • Casein
  • Fuzzy white so fuzzy yellow
  • Tryptophan
  • First light yellow, after orange, so dark orange & A ; Brown


The purpose was, finding whether aminic acids or proteins are present in solution and amino acids are transporting a free aminoalkane group by utilizing biuret trial, ninhydrin trial, xanthoproteic trial and heavy metal precipitation trial.

At foremost, the biuret trial was showed that if there was 2 or more peptide or not.Cupper ( II ) ion was complexed with amine group ( positive ) gave the violet colour. As a consequence of biuret trial, it was identified that Casein amino acids contain dual or more bond in their construction because they gave violet colour and it shows that the trial was positive.The ninhydrin trial was showed if there was aldehyde, ammonium hydroxide and free primary amine.The name of the composite was hydrindatin and the colour was violet. The aminic acids except casein has free aminoalkane group in their construction. The colourss were by and large dark purple

The xanthoproteic trial showed if there was benzine or derived functions such as phenyl alanine, tyrosine, tryptophane, The colour was xanthous and tyrosine, tyrptophan, casein have yellow coloring material. So, it was understood that they have phenyl ring in their construction. The heavy metal trial showed that if ions denaturates proteins similar with biuret and used Fe ( III ) and AgNO3.

First Na nitrate, Ag nitrate and Fe ( III ) nitrate have same colour yellow but the colour of Silver nitrate was changed to light pink and the otheraa‚¬as colour were same ( xanthous ) .

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Quantitative Tests For Amino Acids And Proteins Biology. (2016, Dec 09). Retrieved from


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