Proteins are complex and dynamic three dimensional molecules that work in groups and can change each other. Proteins interact with themselves and other proteins via different forms of intra (within the same protein) and inter (between proteins) molecular forces that can either be covalent or non-covalent in nature. The main covalent interaction is disulphide bonds and the main non-covalent interactions are hydrophobic, electrostatic, polar and hydrogen bonding. These forces make proteins fold up and interact with other molecules collectively termed the protein structure and this can be described in 4 levels. Primary structure is the amino acid sequence of the protein, secondary structure describes how sections of primary structure can arrange to make defined folds such as alpha helices and beta sheets, tertiary structure describes how these folds can then arrange into higher level structures and quaternary structure is how these folded proteins can interact with each other.

For more information on non-covalent interactions click here (NB hydrophobic interactions don’t strictly exist but reflect the power of hydrogen bonding in water and the drive to maximise the interactions with electrostatic and polar groups with the water surrounding the protein)

For Wikipedia links click on the keyword: Non-covalent interactions, disulphide bonding, protein structure