protein / colour reaction of amino acids

Question 1

bieuret reaction

Answer 1

to 1ml of protein solution add 3 drops of 5% naoh followed by addition of 3-4 drops of 1% cuso4
purple of pink
presence of protein

Question 2

xanthoprotein test

Answer 2

to 3ml of protein solution add 2ml of conc hno3 and boil for half a minute. cool and add 90% naoh until the reaction is alkaline.
deeping of the yellow to orange
aromatic amino acids

Question 3

Modified millton’s test

Answer 3

to 1ml of protein add an equal volume of 10% mercuric sulphate in 10% h2so4 boil it gently and add 2 or 3 drops of 1% sodium nitrate.
a red color precipitate
tyrosin

Question 4

aldehyde test of tryptophan

Answer 4

to 1ml of the protein add a drop of 1 in 500 formalin an 10% mercuric sulphate in 10% h2so4
violet ring
tryptophan

Question 5

sakaguchi

Answer 5

to 3ml of the protein solution add 5 drop of 5% naoh and 4 drop of molish reagent. then add 10 drops of bromide water
a blood red colour is obtained
arginine

Question 6

sulphur test

Answer 6

to 2ml of protein solition add equal volume of 40% naoh and boil it for 3 minutes. add 1 ml of lead acetate solutionm
a black ppt
cystein and cystine

Question 7

ninhydrin

Answer 7

to 1ml of prteion sol add 2 drops of ninhydrin reagent and boil
a bluish purple color is obtained
presence of AA