Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Practicals Latest Biochemistry Cysteine Test Practical
? Proteins or aminoacids when heated with
sodium hydroxide,sulphur splits out as sodium
sulphide ,which on reaction with lead acetate,
forms greyish brown to black precipitate of
Principle
lead sulphide (PbS).
? Pipette
? Test tube
? Test tube holder
?
App
Burner
aratus
? Original solution or protein solution
? 20% sodium hydroxide
? 2% lead acetate
Reagents
? To 1ml of O.S in a test tube add 1ml of 20%
NaOH and 0.5ml of 2% lead acetate.A white
precipitate is obtained due to denaturation of
proteins.now boil the mixture,the white ppt
tur Pr
ns ocedu
greyish br re
own or black indicating the
presence of sulphur.
? A positive reaction is due to the presence of a
sulphur containing amino acids in the protein.
? This can be Cysteine or Methionine
Interpretation
This post was last modified on 30 November 2021