(3S,4S)3-[2-(2,3-Dihydro-4-methoxy-7-nitro-1H-indol-1-yl)-2-oxoethyl]-4-(1-methylethenyl)-L-proline is a photolabelled D-aspartate which is transported efficiently by high-affinity Na+/K+ glurtamate transporters, and effective ligand for NMDA receptors.