Narrative

Proteins are essential executors of cellular biological functions, from digesting food to transporting oxygen through the blood to building muscle. Usually, proteins are made up of 20 different kinds of amino acids linked together in very long chains called peptides. Amino acids are like tiny building blocks, represented here by the colorful smiley faces in this oil painting by Grace Cassidy at Georgia Tech. The many different personalities of the smileys shown represent the fact that each kind of amino acid is unique – they all have different chemical properties! Each amino acid interacts with other amino acids and surrounding chemicals based on its chemical properties, and this helps control the shape and structure of the protein. A technique called mass spectrometry (MS)-based proteomics is used to identify the proteins, which is the focus of Zeyu Wang’s research at Georgia Tech. Mass spectrometry breaks peptides into tiny fragments and detects the mass of each fragment. In our artwork, we have represented one peptide chain in the left half of the painting, with many resulting fragments containing just a few amino acids on the right half. See if you can spot where each fragment comes from on the main peptide! Because the molecular mass of the 20 amino acids is known, and the fragmentation pattern of peptides is regular, a computer can use this information to reconstruct the structure of the protein and the order of the amino acids. In addition, our painting abstractly demonstrates the key principle of using crosslinking-MS to study protein structure and shape. We add an active molecule to link some amino acids together from different parts of the chain if these amino acid pairs are close enough together. In our artwork, this crosslinking is represented as blue ribbons linking pairs of smileys together. After a crosslinked peptide is detected by mass spectrometry, the computer can identify which two amino acids are crosslinked on the same protein. This can provide us with helpful evidence for the shape of one protein.