This lecture series will cover:

1. The structure of amino acids

2. Ionisations of free amino acids

3. Structure and properties of peptide bond

4. Purification and sequencing of proteins

5. Steady state kinetics of enzyme-catalysed reactions.
    

Proteins are linear polymers of amino acids which fold up to form a functional 3D shape which is determined by the sequence of amino acids (the primary structure). 

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The central carbon in the amino acid is called the alpha carbon and, due to its four different groups, displays chirality. 

 

Amino acids are joined by peptide bonds which are covalent. A dipeptide is formed by joining two amino acids together with a peptide bond. This is a condensation reaction, via the removal of water. 

 

Secondary structure:

• Regions of localised organisation

• Alpha helix - Areas of coiling in a spiral to form a helix, meaning the structure can move lineally like a spring

• Beta sheets - This can be a parallel sheet or an antiparallel sheet. The sheet is very flexible laterally but longitudinally it is very strong due to covalent bonds

 

The tertiary structure is the 3D folding of the whole structure and the packing together of different secondary structures to form the whole shape. 

 

Purification is the separation of the desired protein for all other proteins present in the preparation/sample. Proteins are separated based on their different properties. 

 

Methods of filtration:

• Separation by solubility

• Precipitation by ammonium sulphate (referred to as salting out)

• Size exclusion chromatography

• Ion exchange chromatography

• Affinity chromatography