Download CHMI 2227E Biochemistry I

CHMI 2227E
Biochemistry I
Amino acids:
-Structure
-General
chemical properties
CHMI 2227 - E.R. Gauthier, Ph.D.
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Proteins: Building blocks of life!
CHMI 2227 - E.R. Gauthier, Ph.D.
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Amino acids
Ca
COOH
H C NH2
R
CHMI 2227 - E.R. Gauthier, Ph.D.
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General properties of amino acids.
CHMI 2227 - E.R. Gauthier, Ph.D.
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General properties of amino acids.
Net charge: +1
Acidic pH
Net charge: 0
pKa 1
(pH 2-2.5)
pKa 2
(pH 9-10.5)
Zwitterion
CHMI 2227 - E.R. Gauthier, Ph.D.
Net charge: -1
Basic pH
5
Amino acid titration
1. simplest scenario
Buffer!
Buffer!
CHMI 2227 - E.R. Gauthier, Ph.D.
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The twenty amino acids:
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
1. Hydrophobic amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
1. Hydrophobic amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
2. Aromatic amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
2. Aromatic amino acids
Absorbance
max
(nm)
Molar
Absorbance
(M-1 cm-1)
Phenylalanine
257.4
197
Tyrosine
274.6
1420
Tryptophan
279.8
5690
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
3. polar, uncharged amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
Cysteine and cystine
In biochem:
-oxidation: lose H
-Reduction: gain H
Disulfide bond
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
Tyr, Ser, Thr
Ser
PO4-3
ATP
Protein
kinase
Protein
phosphatase
ADP
H2O
OP=O
Phospho-Ser O
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
4. Negatively charged amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
4. Negatively charged amino acids
100% D
pH
9.5
pKa2
100% C
pKa1
A
pKaR
B
4.1
pKa2
C
pKaR
D
2.1
What is the pI of glutamate?
pKa1
100% B
100% A
NaOH
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
5. Positively charged amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
5. Positively charged amino acids: His
pKa2
pKaR
CHMI 2227 - E.R. Gauthier, Ph.D.
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Structure of the 20 amino acids
pKa values of amino acids
CHMI 2227 - E.R. Gauthier, Ph.D.
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Analysis of amino acids
1. Ion exchange chromatography
pH << pI
pH >> pI
+
+
Elution
CHMI 2227 - E.R. Gauthier, Ph.D.
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Analysis of amino acids
2. Detection of amino acids: ninhydrin reagent
O
COOH
OH
OH
C
NH3+
R-HC=O
CO2
O
O
R
N
O
Ninhydrin
2
Amino acid
O
O
Purple!!
CHMI 2227 - E.R. Gauthier, Ph.D.
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