He had been studying the Rh blood group antigens and had isolated the Rh molecule, but a second molecule, 28 kilodaltons in size (and therefore called 28K) kept appearing.
Ia sedang mempelajari antigen golongan darah Rh dan mengisolasi molekul Rh, tetapi molekul kedua sebesar 28 kilodalton (dan oleh sebab itu disebut 28K) tetap muncul.