A guanine nucleotide containing two phosphate groups esterified to the sugar moiety.

Synonyms: Guanosine 5' Trihydrogen Diphosphate, Guanosine 5'-Trihydrogen Diphosphate, GDP, 146-91-8, Guanosine 5' Diphosphate, Guanosine 5'-(trihydrogen diphosphate), 5'-Trihydrogen Diphosphate, Guanosine, Diphosphate, Guanosine, Diphosphate, Guanosine 5'-Trihydrogen, Guanosine Diphosphate, 5'-Diphosphate, Guanosine, Guanosine 5'-Diphosphate