T.C.

ÇÜKUROVA ÜNİVERSİTESİ.
FEN EDEBİYAT FAKULTESI
KIMYA BOLUMU
BİYOKİMYA LAB.I

General Reaction of amino acids

 Daniel Alejandro MALAVER RANGEL

 2019144315.

Introduction and theoretical Basis.

Understading how proteins work is

understading how life itself works in
its magical and egnimatic way.
During this experiment the basic
behaviour of this biomolecules will
be analyzed and studied in order to
have a better undersdtanding of how
this biomolecules work.
Amino acids can undergo
condensation reactions, losing -H
from the amino group and -OH from
the carboxylic acid group to form
water. As a result a peptide bond (-
CONH-) is formed between each
amino acid residue. The union of
two aminoacids will give a peptide.
proteins can be organized by their basic structure. And their
biological activity. Due to the fact that during this experiment the
chemistry of proteins will be studied the most important is to
know their chemical clasification and the way it can be devided.
During this experiment, the logic behind every reaction will be
tested and explain for each protein used.

Calculation of the solutions

 General reactions and their experimental observations
 Biuret reagent
is a chemical solution used to test for the presence of proteins in a sample. It is named
after the organic compound biuret, which is formed when urea is heated. The reagent
contains copper sulfate (CuSO₄) and alkaline sodium or potassium hydroxide (NaOH or
KOH). When the biuret reagent reacts with proteins, a violet or purple color is produced.

Tüp Örnekler Biüret Gözlenen Renk

No ayıracı

1 1mL %1’lik üre çözelitisi 4 mL Mor rengi

2 1 mL süt 4 mL Mor rengi

3 1 mL serum 4 mL Mor rengi

4 1mL%1’likyumurta akı çöz. 4 mL Mor rengi

5 1 mL %1’likalanin çözeltisi 4 mL NO CHANGE

6 1 mL %1’likglutamik asit çöz. 4 mL NO CHANGE

7 1 mL su 4 mL NO CHANGE

8 Biüre kristalleri 4 mL NO CHANGE

 Structural Stability:
o Folding: Proteins undergo a process called folding, where they adopt a specific
three-dimensional structure. This folding is essential for their proper function.
o Denaturation: Proteins can lose their structure and function when exposed to
extreme conditions such as high temperatures or extreme pH levels. This process
is called denaturation
o During this experiment nittric acid will be added, afterwards, the solution will be
neutralized with sodum hidroxide
Protein strcuture HNO3 NaOH
Milk The solution became No change
white
Eggs white The solution became No change
white

 Proteins and their reacitons with Anionic complexes

o Metalloproteins:
Some proteins contain metal ions as cofactors, and these ions can be anionic.
Examples include iron-sulfur clusters, where sulfur contributes negative charge, or
proteins with metallocofactors involving anionic ligands.
o Anionic Ligands in Protein Binding:
Proteins can interact with anionic ligands or molecules. For example, proteins
involved in DNA binding may interact with the negatively charged phosphate
groups of the DNA backbone.
TCA Precipitate that disolves in basic a basic
solution
fosfo tungustik asit Precipitate that disolves in basic a basic
solution

 Heavy Metal Precipitation:

Some heavy metal cations can form insoluble complexes with proteins, leading to
precipitation. For example, trichloroacetic acid (TCA) is often used for this purpose,
during this experiment serum will be exposed to three cations; Hg(II) Cu(II) Ba(II)
o Hg(II): yellowish solution
o Cu(II): purple solution
o Ba(II): No change.
  Dialysis
common technique used for the purification and buffer exchange of proteins. It involves
the separation of small and large molecules based on their size and molecular weight.
sample
BaCl2 No change.
Biuret reagent No change
AgNO3 Brown colloid

Conclusion and Discussion.

During the experiment most of the expected results were obtained and most of its part were
concluded successfully, this experiment were mostly divided into their respective reactions and
organized with its respective reaction. In the first part of this process the biuret reagent was used
in order to create a complex that chelated the copper in the reagent solution. Copper needs in total
four pair of electrons (that amines groups possess) in other to create a four dentate complex. This
is easily provided by the proteins remembering that the main structure of proteins are basically
large chains of aminoacids that extend themselves in an specific order.
Having explained this, it is logical that the blood serum, milk, and white eggs give the
characteristic purple color that this complex shows. At the same time, urea has two amino
substituents in its structure facilitating the creation of this complex. This is a basic explanation of
the four changes observed in the experience. Likewise, aminoacids do not react with copper due
to the lack of amine groups that their structure have, explaining also the negative results.
When realizing a denaturalization of the aminoacids is important to remember that their helix or
plate structure would not be recovered due to the acid distroying all connections and interactions
inside of the protein chain. Logically, after neutralization, the aminoacid would not return into its
original structure and this is a clear explanation of why the protein show no change when it is
neutralized back after being wreaked with nitric acid.
After studying the basic structure of proteins the next point of interest was the capacity of
proteins to precipitate with anionic complexes and heavy metals. When analyzing how they
precipitate with anionic complexes the most notorious fact was how the precipitate reacted with
the pH, the protein will not precipitate unless a acidic medium is provided otherwise it would
dissolve again.
The main explanation of this might be based in the fact that aminoacids (the squeleton of
proteins) and their zwitterion shape. The aminoacid needs to gain a proton in its amin group in
order to be able to stand a positive charge and thus neutralize itself with the anionic complex.
When analyzed the protein behaviour with the heavy metals we can see that the only metal that
the aminoacid did not show any behaviour was barium, barium can cause a denaturalization of
the protein, however, any changes were not registered. In this cases the pH of the solution should
be adjusted for being able to see any changes. Another experiment that was not accomplished as
expected was the dialisis, being retired before expected.
As a conclusion, the qualitative analysis of these biomolecules are merely in a educational
purpose and this purpose was achieved just by observing and connecting the theorical predictions
with the experimental correspondence. All of the main purposes were easily explained due to the
easiness of these reactions. Easy but not basic, these reactions were able to expose the
fundamentals of what a protein is.

Articles and References.

Antioxidant Activity of Proteins and Peptides

Ryan J. Elias,Sarah S. Kellerby &Eric A. Decker
Pages 430-441 | Published online: 02 May 2008
Cite this article https://doi.org/10.1080/10408390701425615

The measurement of amino groups in proteins and peptides

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Author and article information
Biochem J (1971) 124 (3): 581–590.
https://doi.org/10.1042/bj1240581
Molecular Interaction of Proteins and Peptides with Nanoparticles
Anton A. Shemetov†, Igor Nabiev†‡*, and Alyona Sukhanova†‡*
View Author Information
Cite this: ACS Nano 2012, 6, 6, 4585–4602
Publication Date:May 23, 2012
https://doi.org/10.1021/nn300415x
Copyright © 2012 American Chemical Society

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