The genome tells you what proteins could be made. Proteomics tells you what proteins are actually present. It is the large-scale study of proteins, including their expression, modification, interaction, and function. Proteins are the workhorses of the cell, and their levels change in response to disease, drugs, and environment. Proteomics captures that dynamic state.

The field relies on mass spectrometry and separation techniques. A sample is digested into peptides, separated by liquid chromatography, and analyzed by mass spectrometry. The resulting spectra are matched to protein databases to identify and quantify the proteins. Thousands of proteins can be detected in a single experiment. Post-translational modifications, like phosphorylation and glycosylation, can also be mapped.

Proteomics is used to find biomarkers for disease, understand drug mechanisms, and study protein interactions. It is used in cancer research to identify proteins that drive tumor growth. It is used in microbiology to study how pathogens respond to antibiotics. It is used in agriculture to improve crop stress tolerance.

The challenges are technical. Proteins vary widely in abundance, from millions of copies per cell to a few. Low-abundance proteins are hard to detect. The data is complex, and interpretation requires bioinformatics. But proteomics is maturing, and it is complementing genomics and transcriptomics to give a fuller picture of biology.