1. Proteins Fibrous 1o structure amino acid sequence 2o structure
- helix
-sheet
H-bonding between
C=O and N-H of backbone - +
some proteins only have 1o and 2o structure:
fibroin (silk)
-sheet
insoluble in H2O
keratin
collagen
hair
skin
- helix
non-polar residues

2. Tertiary structure Primary structure sequence of amino acids Non-polar
Ala-Phe-Ser-Ser-Val-Glu-His-Ile-Met-Arg-Asp-Val-His-Asn-Gly
Ala-
Phe-
Ser-
Ser-
Val-
Glu-
His-
Ile-
Met-
Arg-
Asp-
Val-
His-
Asn-
Gly-
Non-polar
Polar
Acidic or Basic
Alanine
Serine
Glutamic acid
Phenylalanine
Histidine
Arginine
Valine
Aspartic acid
Isoleusine
Asperagine
Methionine
Glycine

3. Tertiary structure arrange these in an -helix polar non-polar
Ala-Phe-Ser-Ser-Val-Glu-His-Ile-Met-Arg-Asp-Val-His-Asn-Gly
arrange these in an -helix
Asp 11
Ser 4
His 7
Gly 15
polar
Ser 3
non-polar
Ile 8
interior
Val 12
Asn 14
Arg 10
Glu 6
Phe 2
His 13
Ala 1
Val 5
Met 9
exterior

4. Tertiary structure interaction of the R-groups globular proteins+
globular proteins
proteins fold around
non-polar groups
hydrophobic residues
inside
polar and charged residues
outside

5. Tertiary structure interactions of R-groups LDF
1. Hydrophobic interactions
non-polar R-groups
LDF
2. Hydrogen bonding
polar R-groups
between H-bond
donors and acceptors
3. Ionic bonds
(salt bridges)
acidic and basic R-groups
ion-ion
4. Covalent bonds
(disulfide)
cysteins

6. C-terminus N-terminus His Arg NH+ Asp -O-CH O = His Fe2+ Phe Ala CH3
Cys S
Cys
N-terminus
Pro
Pro

7. Quaternary Structure subunits hemoglobin heme groups 4 - Fe
globin chains
2 -chains
2 - chains
held in position by interaction of R-groups
polar histidine inside - holds Fe2+
pKa = 6.1

8. Denaturation form is function loss of native configuration
peptide bonds not affected
H-bonds
disulfide bonds
ionic bonds
L.D.F.
disrupted

9. Denaturation 4o structure disrupted first subunits separate
protein unfolds
2o structure disrupted
H-bonds broken
treatments are sometimes reversible
renatured
sometimes irreversible
insulin

10. Denaturing treatments
1. Heat
above 50-60oC
frying egg
sunburn
2. pH
disrupt salt bridges
approach pHI
3. detergents
unfold globular proteins
SDS - +
Na+
SO4-

11. Denaturing treatments
4. reducing agents
S-S SH HS
oxidizing agents
5. Metal salts
Hg+, Pb+, Ag+
S-Hg C = O _ O-
Hg+
6. H-bonding solvents
alcohol
acetone
7. “Chaotropes”
urea
guanidine