Posttranslational modification (PTM) is the chemical modification of a protein after its translation from mRNA. This process involves adding functional groups, such as phosphate, lipid, or carbohydrate, to modulate the protein's structure and function. PTMs can affect protein stability, activity, localization, and interaction with other proteins. Understanding PTMs is crucial for biomedical research, as many diseases are caused by PTM dysregulation. Expertise in PTM analysis is a specialized skill that requires knowledge of protein chemistry, mass spectrometry, and bioinformatics.