ILO 1-Explain the chemical structure,classification, and properties of amino acids and how peptides are formed. 2-Describe the order of protein organization. 3-Relate the structures of amino acids and proteins to their properties. 4-Describe the physical and chemical changes due to protein denaturation 5-state different classifications of proteins giving examples. 6-Explain protein folding and pathophysiological consequences of protein misfolding. 1-Explain the chemical structure,classification, and properties of amino acids and how peptides are formed. 2-Describe the order of protein organization. 3-Relate the structures of amino acids and proteins to their properties. 4-Describe the physical and chemical changes due to protein denaturation 5-state different classifications of proteins giving examples. 6-Explain protein folding and pathophysiological consequences of protein misfolding.

Amino acid structure Amino acid properties Protein structure Forces that stabilize protein structure Levels of protein organization Protein Classification Protein folding Protein misfolding Denaturation Outlines

Forces that determine protein structureCovalent PeptideDisulfide Non covalent ElectrostatichydrophobicVander Waalhydrogen

Forces that determine protein structure CovalentPeptideDisulfide

when electrons are shared but shared unequally POLAR COVALENT BONDS

Polar Covalent Bonds: Unevenly matched, but willing to share.

Disulfide bond

Disulfide bond ( Sulfur bridge): Occurs between 2 SH groups of 2 cysteine AA The product is cystine

OXIDATION 2H Inter chain disulfide bond REDUCTION Cystine

Disulfide bond ( Sulfur bridge): intrachain disulfide bond form between two residues in the same polypeptide chain interchain disulfide bond form between two residues to link two polypeptide chains

13 The sequence of amino acids, such as for insulin.

Forces that determine protein structure CovalentNon covalent ElectrostatichydrophobicVander Waalhydrogen

Non-covalent Bonds in Proteins

Forces that determine protein structureNon covalent ElectrostatichydrophobicVander Waalhydrogen

 Hydrogen bond occur when H atom covalently bound to electronegative atom(O,N,…) is attracted to another electronegative atom.

Hydrogen bond Hydrogen bond occur when H atom covalently bound to electronegative atom(O,N,…) is attracted to another electronegative atom

Hydrogen Bonds in Proteins H-bonds form between 1) two amino acids; 2) two polypeptides 3) between amino acids and water

H-bonding, occurs between Two amino acids Two polypeptide chains amino acid and water in the surrounding environment.

Their large number in protein contribute to thermodynamic stability of folded protein. Hydrogen bond are weak in comparison to covalent bond

Repulsion between similarly charged group Attraction between oppositely charged group

Electrostatic Interactions in Proteins Figure 6.1 An electrostatic interaction between a positively charged lysine amino group and a negatively charged glutamate carboxyl group.

Interaction of charged side chain with the opposide charged side chain(acidic and basic group).

Non-covalent Bonds 3- Hydrophobic forces: Association of hydrophobic R groups to minimize contact with polar solvent(water)

Non-covalent Bonds 3- Hydrophobic forces: Hydrophobic AA Non-polar AA avoid contact with H2O Hydrophilic AA Polar AA can interact with H2O

Hydrophobic forces The most important non covalent bond that drives the process of protein folding. Hide the hydrophobic amino acids in the interior of cytosolic protein to minimize the contact with polar solvent,H2O

Hydrophobic forces

peptide bonds Hydrophilic amino acidHydrophobic amino acid H2O

Non covalent interaction 4-Van Der Waals Interaction

A A  apart B Non-specific attractive or repulsive forces between atoms when two clouds of electrons begin to overlap.