doublet
A subunit of the axoneme in which 10 microtubule protofilaments are grafted longitudinally on to a whole microtubule, which itself consists of 13 protofilaments. Also, in magnetic resonance, a peak that has been split into two by the interaction of a resonance with a nearby perturbing centre.
[О. С. Воеводина Англо-русско-немецкий словарь биотехнологических терминов с определениями.]