AMINO ACIDS AND PROTEINS Flashcards
Classic method (determine nitrogen)
Kjeldahl Method
The procedure is way too tedious for it to be a
part of routine activity
Kjeldahl Method
Requires many reagents
Kjeldahl Method
Time-consuming
Kjeldahl Method
Average of ______ nitrogen as in proteins
Kjeldahl Method - 16%
No proteins of significant concentration in the unknown
specimen are lost in the precipitation step which is the
first step of the method
Kjeldahl Method
Start with the precipitation of proteins
● Proteins will be precipitated with the presence of tungstic
acid
● Pag naa na si tungstic acid, the non-protein nitrogens
will also be removed with the supernatant
● Proceed with digestion
Kjeldahl Method
_____________ is a rapid, simple method, but is not commonly used for total protein analysis.
Refractometry
Digestion of protein; measurement of
nitrogen content
kjeldahl method
Reference method; assume average nitrogen
content of 16%
Kjeldahl method
Formation of violet-colored chelate between
Cu2+ ions and peptide bonds
Biuret
Routine method; requires at least two peptide
bonds and an alkaline medium
Biuret method
Protein binds to dye and causes a spectral
shift in the absorbance maximum of the dye
Dye binding
Research use
Dye binding
Research use
Dye binding
Will occur if you mix the sample with sulfuric acid and
heat between 340°C - 360°C
Digestion
In neutralization, your ammonium bisulfite was highly
exposed to an acid which is sulfuric acid which needs to
be neutralized before proceeding to distillation
Neutralization and Distillation
Sulfuric acid will oxidize the __________
in the protein to become CO2, CO, H2O, SO2
Carbon, hydrogen, sulfur
Nitrogen in the protein will be converted to become your
___________ which is then utilized for
neutralization and distillation
ammonium bisulfite
The neutralizing agent is by the addition of an _________
alkaline,
sodium hydroxide - Neutralization and distillation
Once it is neutralized, proceed with distillation into a
___________
standard boric acid solution
From ammonium bisulfite, because of the presence of
your boric acid, it now becomes your ________
Ammonium borate - neutralization and distillation
Ammonium borate will be titrated with standard HCl so
we can be able to determine the number of proteins that
is present on the patient sample
titration
Most widely used method
Biuret Method
Recommended by IFCC for determination of Total Protein
Biuret method
There will be a violet-colored soln if there are at
least two peptide bonds detected in the sample
Biuret method
Provides an alkali medium so the rxn
can take place
Potassium hydroxide
Complex cupric ions to prevent their
precipitation in the alkaline soln
Sodium potassium tartrate