(Bio Mathematical Lab of Sikander Aqeel)
CHAPTER 3 PROTEINS
Proteins
(2/25/2016)
Amino Acid Sequence of Polypeptide Chain:
The sequence of amino acids in the covalent backbone of a protein is known as its primary structure, the first step in establishing the amino aicd sequence of a polypeptide chain is complete hydrolysis of all peptide bonds to yield all the amino acids in free form, the polypeptide chain is heated with excess 6 N HCl at 100 centigrade to 120 centigrade for 24 hours in a sealed glass tube,
However this acid treatment has side effects on three specific amino acids, it hydrolyzes the amide groups of Glutamine and Asparagine to yield Glutamic acid and Aspartic acid,
Respecvely, plus ammonia, from the amount of ammonia in the hydrolyzed
For example
= a2 + b2 = c2
= a2 = CHl and b2 = 24 hours = c2
= a2 = 1.25 (H) + 35 (Cl) and b2 = 24 = c2
= a2 = 36.25 + b2 = 24 = c2
= a36.25 + b24 = c2
= 1314.0625 + 576 = c2
= a + b = 1890.0625 = c2
= a + b = 1890.0625 / 43.5 = 43.5
= 43.5 * 120 centigrade = 5220
Treatment side effects = 5220 / 148.5, m/g Glutamine = 35.15
Treatment side effects = 5220 / 134, m/g Asparagine = 38.95
total = 74.1
To yield = 74.1 * 2.01 hydrolyzes = 148.941 or 149.25, m/g Glutamic acid
To yield = 74.1 * 1.81 hydrolyzes = 134.121 or 134.75, m/g Aspartic acid
Respecvely, plus ammonia, from the amount of ammonia in the hydrolyzed
Two hydrolyzes = 3.82 = H3 hydrogen atom
149.25 - 134.75 = 14.5 = N nitrogen atom
Total = NH3 = ammonia in the hydrolyzed
The sum of the Glutamine and Asparagine can be determined, the acids hydrolysis also destroys tryptophan, In order to determine the tryptophan content of a polypeptide a separate sample is hydrolyzed by boiling with sodium hydroxide, although this treatment destroy several amino acids, it leaves tryptophan intact by this matematics,
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