Protein Structures - Lecture Slides | CHEM 332, Study notes of Inorganic Chemistry

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Bioinorganic Chemistry

The Structures of Proteins The Structures of Proteins

CHEM-

Protein Structures

Peptide Bond Formation Peptide Bond Formation

Two amino acids can react in a

condensation reaction. The product is a

peptide which consists of the coupled

amino acids.

peptide product (^) by-product

Protein Structures

Peptide Bond Formation Peptide Bond Formation

In natural biological processes the polypeptide

chains grow in the direction from the N-terminal

residue to the C-terminal residue.

Peptide chain growth Beginning End further growth Key Concept

Protein Structures

The Peptide Bond The Peptide Bond

The resulting peptide bond does not

exhibit much rotation, the C,O,N and H

are pretty much on a single plane.

peptide product (^) by-product

Protein Structures

The Peptide Bond The Peptide Bond

Note that the backbone of the polypeptide

consists of repeating units.

N

N

N

N

C

C C

C C

C

N C C

Protein Structures

Peptides Peptides

# of amino acids Convention Another Convention 1 Amino Acid 2 Oligopeptides Peptides 3 20 20-50 Polypeptide 50-100 Proteins

100 Protein There is no clear convention on when a peptide becomes a protein. Another convention states that a peptide becomes a protein when the polypeptide starts to fold and maintain a preferred conformation.

Protein Structures

Protein Structures Protein Structures

Proteins are said to have these structures:

• Tertiary structure, which is define as the

overall shape of the protein chain. This

shape is greatly influenced by how the

secondary structures come together.

• Quaternary structure , which is exhibited

only when a protein is made of more

than one chain. This structure is how

the protein chains come together to

form their superstructure.

Protein Structures

Primary Structure Primary Structure

Primary Structure: Amino Acid Sequence

Protein Structures

Secondary Structure: alpha-helix Secondary Structure: alpha-helix

Protein Structures

Secondary Structure: alpha helix Secondary Structure: alpha helix

Protein Structures

Secondary: beta pleated sheet Secondary: beta pleated sheet

Protein Structures

Secondary: beta pleated sheet Secondary: beta pleated sheet

Protein Structures

Secondary Structure Secondary Structure

Protein Structures

Secondary Structure Secondary Structure

Question

Is this a parallel or antiparallel pleated sheet? A.parallel B.antiparallel

Question

Is this a parallel or antiparallel pleated sheet?