Color Reaction of Proteins Flashcards
essential constituents of the living cells, are hgih molecular weight compounds which, upon hydrolysis, produce amino acids
proteins
proteins, constituents of the living cells, are hgih molecular weight compounds which, upon hydrolysis, produce
amino acids
in a protein, amino acids are linked by
peptide bonds
GENERAL TESTS FOR COLOR REACTIONS OF AMINO ACIDS
- Biuret Test
- Ninhydrin Test
- Folin’s Test
a general test for proteins comparable to Molisch’s Test for carbohydrates
Biuret Test
what color appears when Biuret’s reagent is added to any compound which contains 2 or more of the following groups which all contain the -CO - NH2 groups
a violet color
if the biuret test is negative, the color is
blue
if the biuret test is positive, the color is
violet/deep purple
(Ninhydrin Test) in the presence of strong alkalies and of amino acid ___________________________________________ develops a striking, deep red color
beta-naphthoquinone
(Ninhydrin Test) __________________________________________________________________________ do not yield colors
urea, uric acid, creatinine and hippuric acid
ninhydrin test show positive test for:
alpha amino acids and proteins that contain free amino acid groups
a positive ninhydrin test is indicated by:
the formation of red, blue, or purpple color
folin’s reagent or sodium 1, 2-napththoquinone-4-sulfonate is a chemical reagent used as a derivatizing agent to measure levels of amines and amino acids
folin’s reagent
folin’s reagent or
sodium 1, 2-napththoquinone-4-sulfonate
SPECIFIC TESTS FOR COLOR REACTIONS OF AMINO ACIDS
- Millon’s test
- Xanthoproteic Test
- Hopkins-Cole Test/Trytophan Reaction
- Reduced Sulfur Test
- Sullivan Cystine Reaction
- Diacetyl Test
- Nitroprusside Reaction
- Bromine-Water Reaction
a test for the presence of a phenolic ring, as in tyrosine which gives a red color with reagent made by dissolving mercury in nitric acid
Millon’s test
is made by dissolving metallic mercury in nitrous acid and diluting with water
Millon’s Reagent
Millon’s test was developed by the French chemist
Auguste Nicolas Eugene Millon
is not only speficic for proteins; it also gives a positive test for other compounds containing the phenol functional group
Millon’s Test
it directs the presence of benzene rings on which there are amino groups or hydroxyl groups which are easily nitrated to give yellow-colored aromatic nitro compounds
Xanthoproteic test
is used to detect amino acids containing an aromatic nucleus in a protein solution which gives yellow colored nitro derivative on heating with conc. HNO3.
Xanthoproteic Test
amino acids containing an aromatic nucleus
tyrosine, tryptophan, and phenylalanine
When tryptophan or containing tryptophan is heated with strong sulphuric or hydrochloric acid in the presence of aldehyde,
a blue or violet color is produced
Many proteins give the test without the addition of an aldehyde, owing either to contaminations or to the presence of carbohydrate units in the protein
molecule
Leibermann Reaction
