In biology, a protein isoform is a version of a protein with some small differences, usually a splice variant or the product of some posttranslational modification. The discovery of isoforms explains the apparantly small number of coding genes revealed in the human genome project: the ability to create catalytically different proteins from the same gene increases the diversity of the genome. Isoforms are readily described and discovered by microarray studies and cDNA libraries.

Glycoforms

A glycoform is an isoform where different versions of a glycoprotein have different glycans attached to them, by either posttranslational or cotranslational modifications