Proteins (Lab) Flashcards
QUALITATIVE ANALYSIS TESTS OF PROTEINS (9)
Biuret Test
Millon’s Test
Hopkins-Cole Test
Reduces Sulfur Test
Ninhydrin Test
Xanthoproteic Test
Sakaguchi Test
Fohl’s Test
Pauly Test
Test for amines or α-amino acids/free
amino acids
NINHYDRIN TEST
NINHYDRIN TEST
When exposed to ninhydrin (C9H6O4), the amino acid undergoes oxidative deamination then releases?
CO2 and an aldehyde (while simultaneously transferring the amino group to ninhydrin)
NINHYDRIN TEST
The amino-containing ninhydrin then
forms a complex with another
ninhydrin molecule to form?
diketohydrin/Ruhemann’s complex (dark purple color)
Test for peptide bonds
BIURET TEST
Biuret test requires a peptide with at least how many peptide bonds?
2
All proteins should test ___ in the Biuret test
positive
Free amino acids yield ___ result in Biuret test.
negative
form a violet-colored chelate complex with peptide bonds in alkaline conditions (still biuret test)
Cu2+ ions
BIURET TEST
T/F - the greater the peptide
bonds, the greater the color (violet) intensity
T
This test is specific for sulfur-containing
amino acids
REDUCES SULFUR TEST
sulfur-containing amino acids (3)
cysteine
cystine
methionine
REDUCES SULFUR TEST
On boiling the sulfur-containing amino
acids, the sulfur is split off from these
amino acids as?
metallic sulfides.
REDUCES SULFUR TEST
By the addition of ____, they are oxidized to black-colored lead sulfides (PbS
lead acetate (Pb(C2H3O2)2)
Test for phenol groups/derivatives
MILLON’S TEST
phenol groups/derivatives in Millon’s test
tyrosine
(T/F) - Million’s test is not specific to proteins and will test positive for other phenol derivatives.
T
MILLON’S TEST
___ form a red colored complex with mercury
Hydroxybenzene radicals
The only amino acid with a
hydroxybenzene (phenol) group is
tyrosine (the phenol group is nitrated)
MILLON’S TEST
Upon the application of ___ the nitrated tyrosine form as a complex with mercury
heat
Test for aromatic amino acids
XANTHOPROTEIC TEST
aromatic amino acids (2)
tyrosine
tryptophan
XANTHOPROTEIC TEST
Phenylalanine yields a negative result
due to the ____ of its side chain
stability (Phenylalanine doesn’t react with nitric acid in the conditions of this test)
XANTHOPROTEIC TEST
Aromatic compounds react with ____ in a
nitration reaction which results to a yellow
color
HNO3 (Nitric acid)
XANTHOPROTEIC TEST
Upon the addition of a ___, the color
further ____ and turns almost orange-yellow.
base, intensifies
Test for indole groups
HOPKINS-COLE TEST
Indole group (1)
tryptophan
‘glyoxylic acid reaction’
HOPKINS-COLE TEST
HOPKINS-COLE TEST
In the presence of indole-containing
compounds like tryptophan, glyoxylic acid
undergoes a ____ reaction,
forming a purple-colored product.
condensation