1. Amino acids R-groups non-polar polar acidic basic proteins
condensation between
carboxylic acids and amines + +
H2O
carboxylic acid
amine
amide

2. Amides amides resonance structure dipeptide alanine glycine Ala-Gly
+H2O

3. Polypeptides _ “backbone” _ H _ R _ H _ R _ H _ R H N1- C1- C1- N2-OH = O = O = O
peptide bonds
C-terminal
residue
N-terminal
residue
biological activity
= structure
protein structure
4 levels

4. Primary structure sequence of amino acids hemoglobin
transports O2 and CO2
4 protein chains
300 amino acids
Sickle cell anemia
6th amino acid from
N-terminus R
Glu
Val
-CH2CH2-CO2H
-CH(CH3)2
water soluble
water insoluble

5. Primary structure study evolution -chain 146 residues
horses - humans = 26
pigs - humans = 10
gorillas - humans = 1
1 successful change /
10,000,000 years
Primary structure -
selective hydrolysis

6. Phe-Val-Asn-Gln-His
Gln-His-Leu-Cys
His-Leu-Cys-Gly-Ser
His-Leu-Val-Glu
Gly-Ser-His-Leu-Val
Leu-Val-Glu-Ala
Phe-Val-Asn-Gln-His
Gln-His-Leu-Cys
His-Leu-Cys-Gly-Ser
Leu-Val-Glu-Ala
Gly-Ser-His-Leu-Val
His-Leu-Val-Glu

7. Secondary structure hydrogen bonding backbone groups N1- C1- C1- N2-_ H = O OH R
H-bond donors
H-bond acceptors
Two main secondary structures:
-helix
-sheet

8. Alpha helix = = Every C=O bonded to N-H 4 residues away forms a helix
core is backbone
R-groups outside
3.6 amino acids per turn C = O N H
proline
no H-bonding
breaks helix = O C

9. Beta sheet Every C=O bonded to N-H far apart in 1o structure
on different chains
peptide chains extended
side-by-side
maximal H-bonding for anti-parallel chains
small R-groups
above and below the sheet
if not -helix or -sheet
random coil

10. Secondary structure some proteins 1o structure amino acid sequence
-helix
-sheet
-sheet
silk
-helix
collagen
bone, teeth
triple helices
keratin
hair, skin, wool, hooves
cross-linked with disulfide bonds

11. Disulfide bonds cysteine -CH2-SH C H N C C H N C S-H H-S reduced [O]
oxidized

12. Protein function enzymes biological catalysts immunoglobulins
antibodies
transport
hemoglobin
hormones
regulation
structural
keratin, collagen
motion
actin, myocin
function depends on
structure