TEST FOR PROTEINS AND THEIR DERIVATIVES.

TEST FOR PROTEINS AND THEIR DERIVATIVES:-

■BIURET TEST:-

ADD ABOUT 2ml OF 10%NaOH SOLUTION TO AN EQUAL VOLUME IF TEST SOLUTION,MIX AND ADD 1 OR 2 DROPS OF 1% CuSO4 AND MIX.

ALL HIGHER PROTEINS(EG,ALBUMIN) GIVE A PURPLISH VIOLET COLOUR,GELATIN GIVES A BLUISH VIOLET COLOUR AND LOWER PROTEINS,SUCH AS PROTEOSES AND PEPTONES GIVE A ROSE-PINK COLOUR.

■MILLON'S TEST:-

ADD 2 TO 3 DROPS OF MILLON'S REAGENT TO ABOUT 2 ml OF THE TEST SOLUTION.HEAT THE MIXTURE OVERFLAME AND BRING TO THE BOILING POINT GRADUALLY AND VERY GENTLY.

IN CASE IF HIGHER PROTEINS(ALBUMIN,GLOBULIN) A WHITE PRECIPITATE,IS FIRST FORMED,WHICH TURNS RED COAGULUM UPON HEATING .PROTEOSES AND PEPTONES YIELD VERY LITTLE PRECIPITATE.WHICH DISSOLVED HEATING ,SOLUTION TURNS RED.GELATIN GIVES A NEGATIVE RESULT.

■XANTHOPROTEIC TEST:-

ADD ABOUT 1ml OF CONCENTRATED NITRIC ACID TO ABOUT 3ml OF THE TEST SOLUTION.

A WHITE PRECIPITATE FORMS IN PRESENCE  OF HIGHER PROTEINS HEAT TO BOIL.

HIGHER PROTEINS(ALBUMIN)AT FIRST FORMS  YELLOW PRECIPITATE WHICH ON BOILING IS COAGULATED.PROTEOSES AND PEPTONES GIVE A YELLOW SOLUTION WITHOUT THE FORMATION OF A PRECIPITED GELATIN FAILS TO GIVE A POSITIVE TEST.

■ESBACH'S TEST:-

ADD A FEW ml OF ESBACH'S REAGENT TO ABOUT 3ml OF TEST SOLUTION IN A TEST TUBE.HEAT THE SOLUTION AND THEN COOL.

ALBUMIN GIVES YELLOW PRECIPITATE,WHICH DOES NOT DISAPOEAR ON HEATING .GELATIN ALSO GIVES YELLOW PRECIPITATE,WHICH DISAPPEARS ON HEATING BUT REAPPEARS ON COOLING.

■HEAT COAGULATION OF PROTEINS:-

BOIL 5ml OF THE TEST(PROTEIN) SOLUTION IN A TEST TUBE.

AS OPALESCENCE OCCURS BUT USUALLY NO COAGULUM IS FORMED.

COOL ACIDIFY WITH 2 DROPS OF ACETIC ACID AND BOIL THE MIXTURE.

A FLOCCULENT COAGULUM IN CASE OF ALBUMIN.

NO COAGULUM IN CASE OF GELATIN AND PEPTONE.

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