Download Chapter 26 Biomolecules: Amino Acids, Peptides, and Proteins

Chapter 26 Biomolecules: Amino
Acids, Peptides, and Proteins
Amino Acid
Peptide 2~50
Protein 50
26.1 Structures of Amino Acids
O
O
H3C
H3C
OH
H2N
H
uncharged
O
+
H3N
H
zwitterion
Internal salts
amphoteric
Large dipolar moments
Soluble in water but insoluble in hydrocarbons
High melting points
Amphoteric
O
O
H3C
O
+
H3N
+
+ H3O
H3C
OH
+
H
H3N
+ H2O
H
In acid solution
O
O
H3C
O
+
H3N
-
+ OH
H
H3C
O
H2N
In base solution
H
+ H2O
chirality
CO2-
CO2H3+N
H
CH3
L-Alanine
(S)-Alanine
丙氨酸
Neutral
Acidic
basic
H3+N
CO2H
CH2OH
L-Serine
(S)-Serine
丝氨酸
H3+N
CHO
H
CH2SH
L-Cysteine
(R)-Cysteine
HO
H
CH2OH
L-Glyceraldehyde
Aspartic acid 天冬氨酸
Glutamic acid 谷氨酸
Lysine 赖氨酸
Arginine 精氨酸
Histidine组氨酸
Cysteine 半胱氨酸
Serine 丝氨酸
Tyrosine 酪氨酸
天冬氨酸
赖氨酸
26.3 Synthesis of Amino Acids
1. Hell-Volhard-Zelinskii reaction
Br
OH
1. Br2, PBr3
OH
2. H2O
O
O
4-Methylpentanoic acid
2-Bromo-4-methylpentanoic acid
NH2
NH3
OH
excess
O
(R,S)-Leucine (45%)
亮氨酸
The Amidomalonate Synthesis
CH2(CO2C2H5)2 + HNO2
1. H2/ Pd
Et2O
O=N-CH(CO2C2H5)2
AcNHCH(CO2C2H5)2
2. Ac2O
1. NaOEt/EtOH
2. (CH3)2CHCH2Br
HO-N=C(CO2C2H5)2
AcNHC(CO2C2H5)2
H3O+

CH2CH(CH3)2
NH2
(CH3)2CHCH2CHCO2H
Serine (丝氨酸）
O
N-K+
CH2(CO2C2H5)2 + Br2
O
BrCH(CO2C2H5)2
1. NaOEt/EtOH
NCH(CO2C2H5)2
O
CCl4
or NH2NH2
DMF
O CH2C6H5
N-CH(CO2C2H5)2
2. C6H5CH2Cl
NH2
KOH/H2O
O
C6H5CH2CHCO2H
Phenylalanine
O
Gabriel amine Synthesis
蛋氨酸
谷氨酸
Strecker Synthesis
Reductive Amination of a-Keto Acids: Biosynthesis
O
CH3CCO2H
NH3
NaBH4
Pyruvic Acid
NH2
CH3CHCO2H
Alanine 丙氨酸 Serine 苏氨酸
26.6 Covalent Bonding in Peptides
Mild oxidation
26.7 Structure Determination of
Peptides: Amino Acid Analysis
What amino acids are present?
How much of each is present?
In what sequence do the amino acids occur in the peptide chain?
The answers to the first two questions are provided by
an instrument called an amino acid analyzer
Chromatography column
O
O
OH
+
OH
茚三酮水合物
H2N
H
C
R
HO-
C
H2O
OH
O
-
O
O
O
+
N
O
O
Ninhydrin 茚三酮水合物 Purple color
R
CH
+ CO2
26.9 Peptide Sequencing:
C-Terminal Residue Determination
O
Peptide
NHCHC
O
H2O
NHCHCOH
Carboxypeptidase
R
R'
O
O
Peptide
NHCHCOH
R
+
H2NCHCOH
R'
26.10 Peptide Synthesis
氨基的保护
氯代甲酸苯甲酯
Cbz or Z
CH3
H3C
O
O
O
O
CH3
O
CH3
CH3
CH3
di-tert-butyl dicarbonate
(BOC)2O
O
H2NCHCOH
CH3
O
+ (BOC)2O
Et3N
BOC
NHCHCOH
CH3
羧基的保护
酯
甲酯/乙酯/苄酯
亮氨酸
26.11 Automated Peptide Synthesis: The
Merrifield Solid-Phase Technique
26.12 Protein Classification
Simple proteins: such as blood serum albumin, amino acids
Conjugated proteins: amino acids, carbohydrates, fats, nucleic acids
Fibrous proteins: collagen (胶原质）, keratin （角蛋白）
tendons, hooves, horn, muscles
Globular
The primary structure of a protein is simply the amino acid sequence
The secondary structure of a protein describes how segments of
the peptide backbone orient into a regular pattern.
The tertiary structure describes how the entire protein molecule
coils into an overall three-dimensional shape.
The quaternary structure describes how different protein molecules
Come together to yield large aggregate structures.
Fibroin （蚕丝蛋白）
The b-pleated-sheet structure in silk fibroin
Myoglobin (肌血球素）
胆固醇
27.3 Phospholipids
27.5 Terpenoids
单萜
倍半萜
二萜
三萜
10C
15C
20C
30C
2 个异戊二烯
3
4
5
27.6 Biosynthesis of Terpenoids
27.7 Steroids
27.8 Stereochemistry of Steroids