Protein isoforms are variants of a protein that are produced from the same gene but have different amino acid sequences. These variations can arise due to alternative splicing, post-translational modifications, or genetic mutations. Protein isoforms can have different functions, localization, or stability within cells, and are therefore important for regulating various biological processes. Studying protein isoforms is crucial for understanding the complexity of cellular pathways and their dysregulation in diseases. Techniques such as mass spectrometry and bioinformatics are commonly used to identify and characterize protein isoforms.