The original studies were on the structure of sheep hemoglobin, but when this work had progressed as far as was possible using the resources then available, Kendrew embarked on the study of myoglobin, a molecule only a quarter the size of the hemoglobin molecule.
Původní studie probíhala na struktuře hemoglobinu u ovcí, ale s postupem práce a jakmile byly k dispozice dosažitelné zdroje, začal se Kendrew věnovat studiu myoglobinu, jehož molekula dosahuje jen čtvrtinu velikosti molekuly hemoglobinu.