BPS - 125L: COLOR REACTION OF AMINO ACIDS

Amino acids

_______ are the building blocks of proteins.

Peptide bond

In order for the amino acids to link together to form numerous proteins necessary to keep a human functioning, they form a special bond with each other called the __________.

dipeptide

The protein bond is formed between the carboxyl group of the first amino acid and the amino group of the second amino acid to form a ________.

proteins

Long chains of amino acids connected by peptide bonds are called ______.

Ninhydrin (triketohydrindene hydrate) test

___________________ is an oxidizing agent which leads to the oxidative deamination of α-amino groups. It is very important for the detection and the quantitative analysis of amino acids. _______ also reacts with primary amines however the formation of carbon dioxide is quite diagnostic for amino acids.

Free amino acids and proteins

Ninhydrin is a test for _______________

purple yellow

Ninhydrin test have the positive result of _______ if it’s alpha amino acid and _______ if its alpha imino acid

Free amino group

oxidative deamination

The structure that is responsible for ninhydrin test is ___________ with the reaction that involves oxidative deamination

Alpha-amino acids

In ninhydrin tests, _______ yield a purple solution reaction.

Alpha imino acid (proline)

In ninhydrin tests, _______ yield a yellow solution reaction.

Biuret test

A test wherein the color is caused by the formation of a complex of copper (II) ion with four nitrogen atoms, two from each of the peptide chains.

copper sulfate

In Biuret test, polypeptides and proteins with two or more peptide bonds give a characteristic purple color when treated with dilute _______ at alkaline pH values.

purple solution

The biuret test have the positive result of ______.

Casein and Gliadin

In biuret test, the samples that will give positive are __________

two or more peptide bonds

coordination complex

In biuret test, the structure responsible is _____________. Copper ion forms a ___________ with peptide nitrogens.

Millon’s Test

Pauly’s test

Sakaguchi reaction

Ehrlich’s test

Xanthoproteic test

Hopkins-cole reaction

Lead acetate test

Specific test for amino acids

Ninhydrin and Biuret test

What are the general tests for amino acids?

Millon’s test

This test is for phenolic –OH group present in protein. ________ test is given by any compound containing a phenolic hydroxyl group.

Millon’s reagent

________ is prepared from mercuric and mercurous nitrate in nitric acid.

mercury salt of nitrated tyrosine

In millon’s test, any protein containing tyrosine will give a positive test of a pink to dark-red color. The red color is probably due to a _______________.

Phenolic group

Millon’s test is a test for _______.

White precipitate to dark red

The positive result in millon’s test is

Tyrosine

Positive sample on millon’s test is ________.

Phenolic -OH group

The structure responsible for the millon’s test is the _____________

Pauly’s test

Imidazole ring of histidine, under basic condition, undergo reaction with diazonium salt of sulfanilic acid (p-aminobenzenesulfonic acid diazonium salt), yielding orange to red colored azo dye. Tyrosine will also give a positive result.

Imidazole & phenolic rings

The Pauly’s test is the test for _______________________.

orange to red azo dye

The positive result for the pauly’s test is __________.

histidine and tyrosine

Posive samples in the Pauly’s testa are ______________.

Imidazole ring (histidine) and Phenolic aromatic ring (Tyrosine)

The structure responsible for the pauly’s test are ______ and _________

Diazonium salt

In Paulys’ test, _________ couples with aromatic rings that forms azo dye formation

Sakaguchi reaction

The __________ depends on the presence of the hydroxyl group and is positive for arginine or peptides and proteins containing arginine.

Guanidines

In sakaguchi test, ________ in alkaline solution develop an intense red color when treated with α-naphthol and sodium hypochlorite (or sodium hypobromite).

Guanidino group

The sakaguchi reaction is a test for _______.

Pink or wine red solution

The sakaguchi reaction will have the positive result of ____________.

Arginine

The sample that will test positive to the sakaguchi reaction is ______.

α-naphthol + oxidizing agent

The principle behind the sakaguchi reaction is that Guanidino group reacts with ________________ in alkaline medium

Ehrlich’s Test

p-Dimethylaminobenzaldehyde in strong acid reacts with the indole side chain of tryptophan to yield a purple product.

Indole ring

The Ehrlich test is the test for _________.

Tryptophan

The positive sample in ehrlich’s test is ________.

p-dimethylaminobenzaldehyde

The principle behind the erlich’s test is that Indole reacts with __________________ in strong acid.

Aromatic amino acis

The xanthoproteic test is the test for _________.

yellow precipitate to orange

The positive result for xanthoproteic test is ________________.

Tyrosine and Tryptophan

The positive samples in xanthoproteic test are ____________

nitration

The principle behind the xanthoproteic test is that aromatic rings undergo ________ by nitric acid.

indole ring (Trp, W)

The hopkins-cole reaction is a test for _______

Principle behind the hopkins-cole reaction is that Indole reacts with glyoxylic acid in presence of conc. H₂SO₄

Xanthoproteic test

This is a test for the presence of aromatic amino acids (e.g.., tryptophan, tyrosine). The reaction involves nitration of the aromatic ring.

xanthoproteic acids

The nitrated aromatic rings are yellow in color and are called ___________.

Hopkins-Cole Reaction

If tryptophan is present a violet ring will form at the junction of the two fluids after a few seconds, especially after gentle shaking. The indole ring reacts with glyoxylic acid to form a violet cyclic product.

Lead estate test

The presence of sulfur-containing amino acids such as cysteine can be determined by converting the sulfur to an inorganic sulfide through cleavage by base. If cysteine is present the solution darkens, the color deepening into black if sufficient sulfur is present due to the formation of PbS.

free sulfur-containing

The lead acetate test is the test for __________ amino acid.

Black precipitate

The positive result for the lead acetate test is ___________.

cysteine

In lead acetate test, the positive sample is _____.

Lead sulfide

The principle behind the lead acetate test is that sulfur reacts with lead and have the product ________.

Free sulfhydryl group

The nitroprusside reaction is a test for ___________.

Purple

The nitroprusside test have a positive result of color _______.

free thiol groups

The principle behind nitroprusside is that nitroprusside reacts only with _____________.

Nitroprusside reaction

____________ with sulfhydryl group –SH in amino acids, i.e., cysteine. A purple color will develop if free sulfhydryl groups are present. Cystine will not give the same result.