Sakaguchi Test for the Detection of Arginine
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Questions and Answers

The xanthoproteic test is used to detect the presence of ______ amino acids.

aromatic

Ninhydrin test is used to detect the presence of ______ in a compound.

amino acids

The Ninhydrin test results in a deep purple color indicating the presence of ______, primary/secondary amines, and amino acids.

ammonia

The Ninhydrin solution acts as an ______ agent in the Ninhydrin test.

<p>oxidizing</p> Signup and view all the answers

Decarboxylation and deamination are processes that can occur during the Ninhydrin test to detect the presence of ______.

<p>aldehydes</p> Signup and view all the answers

A negative result in the Ninhydrin test indicates the absence of ______, primary/secondary amine, or amino acid.

<p>ammonia</p> Signup and view all the answers

The Xanthoproteic test detects amino acids containing an __________ nucleus.

<p>aromatic</p> Signup and view all the answers

The Xanthoproteic test is used to detect amino acids containing ________ groups.

<p>phenolic</p> Signup and view all the answers

The Ninhydrin test can yield a yellow to yellow-orange color result for amino acids like ________ and hydroxyproline.

<p>proline</p> Signup and view all the answers

In the Xanthoproteic test, the appearance of a dark yellow or orange-colored solution indicates the presence of ________ groups.

<p>aromatic</p> Signup and view all the answers

The addition of the Ninhydrin reagent produces an iminium salt, resulting in a distinct yellow-orange color for amino acids like ________.

<p>proline</p> Signup and view all the answers

Ninhydrin solution is used for protein suspension in intact protein to detect ammonia, primary or secondary amine, or free alpha-amino group present in a compound. The product produced is called Ruhemann’s complex. What is the principle of Ninhydrin test? - Decarboxylation and ______

<p>deamination</p> Signup and view all the answers

The Xanthoproteic test facilitates the nitration of amino acids with the help of ________.

<p>HNO3</p> Signup and view all the answers

Which amino acid gives a positive result in Xanthoproteic test? - Only the ______ and tryptophan

<p>tyrosine</p> Signup and view all the answers

What is the principle of Xanthoproteic test? - ______ - In nitration, the nitro group should substitute to the carbon and aromatic ring

<p>Nitration</p> Signup and view all the answers

Which gives the positive result in the Xanthoproteic test? - It is the intact protein and the ______ hydrolyzate

<p>base</p> Signup and view all the answers

What is the visible result for Xanthoproteic test? - Yellow ______

<p>precipitate</p> Signup and view all the answers

What are the reagents of Hopkins Cole Test? - Conc. ______

<p>aldehydes</p> Signup and view all the answers

Study Notes

Sakaguchi Test

  • Purpose: Detect and quantify the presence of guanidinium groups, specifically arginine
  • Function of reagents:
    • NaOH: Allows the reaction to occur by making the solution alkaline
    • NaOCl: Oxidizing agent that reacts with napthol to produce a red complex product
    • Napthol Solution: Condensation agent that forms a strong base with the hydroxide ion (OH-)
  • Principle: Guanidin group (side chain of arginine) reacts with napthol to produce a red-colored complex product
  • Result:
    • Positive: Red-colored result indicates the presence of arginine or guanidine group
    • Negative: Absence of red color indicates no arginine or guanidine group present

Ninhydrin Test

  • Purpose: Detects ammonia, primary or secondary amines, or free-alpha amino group present in a compound
  • Function of reagents:
    • Water: Facilitates the connection of the amine group of the amino acid with Ninhydrin
    • Ninhydrin solution: Acts as an oxidizing agent
  • Principle: Decarboxylation and deamination lead to the liberation of aldehyde, CO2, NH3, and hydrindination (reduced form of ninhydrin)
  • Result:
    • Positive: Deep purple color indicates the presence of ammonia, primary/secondary amines, or amino acids
    • Negative: No color change indicates the absence of ammonia, primary/secondary amines, or amino acids

Xanthoproteic Test

  • Purpose: Detects amino acids containing phenolic or indolic groups (phenylalanine, tyrosine, and tryptophan)
  • Function of reagents:
    • Conc. HNO: Denatures protein, breaks peptide bonds, and initiates nitration reaction with aromatic rings
    • NaOH: Neutralizes excess acid and facilitates color change in the solution
  • Principle: Nitration of aromatic rings leads to the formation of nitro derivatives, producing a yellow-colored product
  • Result:
    • Positive: Yellow or orange-colored solution indicates the presence of aromatic groups in proteins and amino acids
    • Negative: Absence of yellow or orange color indicates the absence of aromatic groups

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Description

Learn about the Sakaguchi test, a method used to detect the presence of the amino acid arginine by quantifying guanidinium groups. Understand the purpose of NaOH in making the solution alkaline for the reaction to occur.

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