Test for proteins and amino acids

Question 1

What are the common tests for proteins

Answer 1

1. Biuret test
2. Hopkins-cole test
3. Millon’s Test
4. Xanthoproteic test
5. Reduced sulfur test
6. Nitroprusside test
7. Sakaguchi test

Question 2

The compounds having two or more peptide bonds and copper salts in alkaline solution create a purple color complex

Answer 2

Biuret test

Question 3

This test is a confirmatory test the presence of amino acid tryptophan (indole group).

Answer 3

Hopkins-cole test

Question 4

what is the result of a Hopkin-cole reagents result?

Answer 4

the formation of purple or violet color ring at the interface.

Question 5

This test is used to detect the presence of phenolic group-containing amino acids like tyrosine.

Answer 5

Millon’s test

Question 6

This test is identification test for the presence of aromatic amino acids.

Answer 6

Xanthoproteic test

Question 7

what is the result of Xanthoproteic test>

Answer 7

Orange color

Question 8

This is a test for sulfur containing amino acids cysteine and cystine (except for methionine where its sulfur is not reactive).

Answer 8

Reduced sulfur test

Question 9

What does reduced suflur test result to?

Answer 9

black lead sulfide

Question 10

is a biochemical test used for the detection of the free –SH groups in amino acids or the cysteine amino acid in a protein.

Answer 10

Nitroprusside test

Question 11

What color does nitroprusside test results to?

Answer 11

Red-colored compound

Question 12

This test is given by guanidine compounds for example arginine

Answer 12

Sakaguchi test

Question 13

What color does sakaguchi test result to?

Answer 13

Red color

Question 14

Procedure of Biuret test

Answer 14

• Mix 2 ml of test solution and 2 ml 10% NaOH
• Add 1 drop of 0.1% CuSO4 solution
• Mix thoroughly and note if a pink or violet color develop

Question 15

Hopkins-cole test procedure

Answer 15

• take 1 ml of the reagent
• add concentrated H2SO4 along the side of the test tube

Question 16

Millons test procedure

Answer 16

• Take 2 mL of test sample, add 4 drops of Millon’s reagent.
• Mix well and observe if a white precipitate forms
• Then boil it for 2-5 minutes in a water bath to develop a red color precipitate

Question 17

Xanthoproteic test

Answer 17

• Add 1ml of test sample and add same amount of conc. HNO3
• Mix well
• Allow it to cool for some time
• Add 1-2 mL of 40% NaOH.
  -Orange color is observed if the test is positive

Question 18

Reduced sulfur test procedure

Answer 18

• Add equala mount of 2ml test sample and 10% NaOH and heat carefully for 15-30- seconds
• Add 5 drops of lead (II) acetate
• If black precipitate of lead sulfide does not form, boil it again.

Question 19

Nitroprusside test procedure

Answer 19

• Take 2 ml of test sample
• then add 0.5 freshly prepared nitroprusside by shaking the test tube thoroughly
• add sodium hydroxide dropwise
• Watch for red color to indicate positive

Question 20

Chemicals in Biuret test

Answer 20

10% (w/v) NaOH
0.1% CuSO4 solution

Question 21

Chemicals in Hopkins-cole test

Answer 21

-Hopkins-cole reagent
-Conc. Sulfuric acid (H2SO4)

Question 22

Chemicals in Millon’s test

Answer 22

Millon’s reagent

Question 23

Chemicals in Xanthoproteic test

Answer 23

Concentrated Nitric Acid (HNO3)
10% (w/v) NaOH

Question 24

Chemicals in Reduced sulfur test

Answer 24

• 10% (w/v) NaOH (same as in Biuret Test)
• 1% Lead acetate

Question 25

Chemicals in nitroprusside test

Answer 25

• 2% sodium nitroprusside
• 10% (w/v) NaOH (same as in Biuret Test)

Question 26

Chemicals in sakaguchi test

Answer 26

• 40% (w/v) NaOH
• α-naphthol solution (1% w/v in ethanol)
• 10% sodium hypochlorite