Neurogranin is a postsynaptic protein that binds calmodulin and participates in calcium-dependent synaptic signalling. Its interest outside basic neuroscience comes from its behaviour in disease: intact neurogranin is reduced in brain tissue from patients with both familial and sporadic Alzheimer's disease, while fragments of it accumulate in cerebrospinal fluid, making CSF neurogranin one of the more promising fluid markers of synaptic loss. The fragments are not arbitrary. Work on the molecular forms of neurogranin in cerebrospinal fluid established that the C-terminal region dominates the species detected there, and that Alzheimer-associated fragments are generated by calpain-1 and prolyl endopeptidase. Assays therefore depend on which region an antibody recognises, since a reagent raised against a part of the protein not present in the circulating fragments will not measure the analyte of clinical interest. This product supplies residues 48 to 76 with an N-terminal biotin, suited to streptavidin capture in immunoassay development, antibody characterisation and epitope work. The supplied sequence is notably rich in glycine and proline, which is worth anticipating in practice: such regions are flexible and poorly structured, can behave unusually on reversed-phase chromatography, and may give weaker antibody binding than a structured epitope would. | 