Haemoglobin is a helix of globin chains composed of amino acids. A haemoglobin variant refers to an alteration in the amino acid composition of the globin chain that can occur through genetic mutation and may result in changes not only to the net charge on the molecule but also changes in polarity due to alterations in the helical structure. These changes in physical characteristics may, in some cases, produce clinically significant effects and have been used to fractionate haemoglobin species.