chemical tests for proteins Flashcards
(+) for peptide bonds
biuret test
red coloration
nitroprusside test
reagents of conc. HNO3 and conc. NaOH
xanthoproteic test
(+) for phenolic group of tyrosine
millon’s test
red to red-orange color
sakaguchi test
reagents of NaOH and CuSO4
biuret test
(+) for the indole group of tryptophan
hopkins cole test
(+) for methionine and cysteine
fohl’s test
(+) for guanidino group of arginine
sakaguchi test
reagent is 1,2,3-indanetrione monohydrate / triketohydrindene with EtOH
ninhydrin test
(+) for cysteine
nitroprusside test
(+) for histidine and tyrosine
pauly’s test
reagent is lead acetate
fohl’s test
blue to blue-purple or yellow-orange product
ninhydrin test
(+) for proline in orsnge residue
ninhydrin test
pink to violet to blue coloration
biuret test
principle is complexation thru mercuration & nitration or nitrosation/ complexation of nitrohydroxyphenyl derivatives with Hg2+
millons test
(+) for F, Y, W aromatic AAs
xanthoproteic test
(+) for free alpha amino acids and amines
ninhydrin test
principle is complexation of copper with a peptide bond
biuret test
reagents are alpha naphthol, NaOH, NaOBr, urea
sakaguchi test
principle is diazotized sulfanilic acid with amino phenol to form a red azor in cold conditions
pauly’s test
reagent is Na2Fe(CN)5NO in dilute NH3
nitroprusside test
old rose/ flesh/ purple-red ppt.
millons test
yellow solution with heating that has orange excess NaOH
xanthoproteic test
pink to violet interface
hopkins cole test
nitration of aromatic rings
xanthoproteic test
reagents are glyoxylic acid and conc. H2SO4
hopkins cole test
brown to black ppt.
fohl’s test
principle is complexation
nitroprusside test
detects 1,2,3 amines
amide testr
base-catalyzed condensation of alpha naphthol with guanidino group of arginine
sakaguchi test
oxalate to glyoxylate and condensation of 2 tryptophans with glyoxylic acid
hopkins cole
oxidative decarboxylation and deamination followed by condensation
ninhydrin test
degradation and substitution to form PbS
fohl’s test
reagent is NaOH
amide test
turns red litmus to blue
amide test
base-catalyzed hydrolysis
amide test
