1. Amino acids: Structure General chemical properties
CHMI 2227E Biochemistry I
Amino acids:
Structure
General chemical properties
CHMI E.R. Gauthier, Ph.D.

2. Proteins: Building blocks of life!
CHMI E.R. Gauthier, Ph.D.

3. Amino acids C H R
COOH
NH2 Ca
CHMI E.R. Gauthier, Ph.D.

4. General properties of amino acids.
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5. General properties of amino acids.
Zwitterion
Net charge: +1
Net charge: 0
Net charge: -1
Acidic pH
Basic pH
pKa 1
(pH 2-2.5)
pKa 2
(pH )
CHMI E.R. Gauthier, Ph.D.

6. Amino acid titration 1. simplest scenario
Buffer!
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7. The twenty amino acids:
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8. Structure of the 20 amino acids 1. Hydrophobic amino acids
CHMI E.R. Gauthier, Ph.D.

9. Structure of the 20 amino acids 1. Hydrophobic amino acids
CHMI E.R. Gauthier, Ph.D.

10. Structure of the 20 amino acids 2. Aromatic amino acids
CHMI E.R. Gauthier, Ph.D.

11. Structure of the 20 amino acids 2. Aromatic amino acids
Absorbance
max
(nm)
Molar
(M-1 cm-1)
Phenylalanine
257.4
197
Tyrosine
274.6
1420
Tryptophan
279.8
5690
CHMI E.R. Gauthier, Ph.D.

12. Structure of the 20 amino acids 3. polar, uncharged amino acids
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13. Structure of the 20 amino acids Cysteine and cystine
Disulfide bond
In biochem:
oxidation: lose H
Reduction: gain H
CHMI E.R. Gauthier, Ph.D.

14. Structure of the 20 amino acids Tyr, Ser, Thr
P=O O-
Ser
Phospho-Ser
Protein
kinase
phosphatase
ATP
ADP
H2O
PO4-3
CHMI E.R. Gauthier, Ph.D.

15. Structure of the 20 amino acids 4. Negatively charged amino acids
CHMI E.R. Gauthier, Ph.D.

16. Structure of the 20 amino acids 4. Negatively charged amino acids
pKa1
pKa2
pKaR
What is the pI of glutamate?
NaOH pH
9.5
4.1
2.1
100% A
100% B
100% C
100% D A B C D
CHMI E.R. Gauthier, Ph.D.

17. Structure of the 20 amino acids 5. Positively charged amino acids
CHMI E.R. Gauthier, Ph.D.

18. Structure of the 20 amino acids 5. Positively charged amino acids: His
pKaR
pKa2
CHMI E.R. Gauthier, Ph.D.

19. Structure of the 20 amino acids pKa values of amino acids
CHMI E.R. Gauthier, Ph.D.

20. Analysis of amino acids 1. Ion exchange chromatography
Elution +
pH >> pI
pH << pI
CHMI E.R. Gauthier, Ph.D.

21. Analysis of amino acids 2. Detection of amino acids: ninhydrin reagentOH
Ninhydrin
Amino acid 2 N C H R
COO-
NH3+
CO2
Purple!!
R-HC=O
CHMI E.R. Gauthier, Ph.D.