Disclosed herein are methods and compounds for profiling a lysine reactive protein. Also described herein are methods, compounds, and compositions for identifying a small molecule fragment ligand that interacts with a reactive lysine residue.

Disclosed herein are methods, compositions, probes, polypeptides, assays, and kits for identifying a cysteine containing protein as a binding target for a small molecule fragment. Also disclosed herein are methods, compositions, and probes for mapping a biologically active cysteine site on a protein and screening a small molecule fragment for interaction with a cysteine containing protein.

Disclosed herein are methods and compounds for profiling a lysine reactive protein. Also described herein are methods, compounds, and compositions for identifying a small molecule fragment ligand that interacts with a reactive lysine residue.

Disclosed herein are methods, compositions, probes, polypeptides, assays, and kits for identifying a cysteine containing protein as a binding target for a small molecule fragment. Also disclosed herein are methods, compositions, and probes for mapping a biologically active cysteine site on a protein and screening a small molecule fragment for interaction with a cysteine containing protein.