peptide bonds and primary structure

How are proteins formed

Amino acids link together via peptide bonds (amide bond)

What parts of the amino acid form the peptide bond

a-COOH of one amino acid reacts with the a-NH2 of another

Peptide backbone

NH-CH-CO

Everything but the side chain

Nomenclature of peptides

Written from N terminus to C terminus

Ex) alanylglutamylserylglycine

Characteristics of a peptide bond

Delocalized pi binding making the bond planar (not the peptide)

Rotation around the C-N bond is restricted due to its double bond character

Length of peptide bond

Shorter than its surrounding bonds at 1.32 A

Rotation around the peptide bond

At psi and phi

What configuration is the peptide if the R groups are on the same side

Cis

How much do amino acids weigh

One residue is 110 g/mol

Dalton

1 g/mol

How much does a protein with 64 amino acids weigh?

64 aa x 110 g/mol= 7040 g/mol

= 7040 Da x 1kDa/1000 Da

= 7.04 kDa

Polypeptide

Polymer of amino acids

10 or fewer amino acids is called

Oligopeptide

More than 10 amino acids is called

Polypeptide

Chain length of 50 or more amino acids is called

Protein

Why is Cysteine special

Can create disulfide bonds (covalent) to force a certain type of folding of the protein

What kind of links can cysteine make

Interchain and intrachain

Sangers results of insulin

Sequenced 2 chains of insulin and found that all molecules of a given protein have the same sequence

Primary structure of proteins

Amino acid sequence that forms the polypeptide (backbone)

What is the directionality of the primary structure

N terminus towards C terminus

Influences of the primary structure

Interactions between the aa side chain and water and the polypeptide

3D structure of the protein