Hypoallergenic Fel d 1 derivatives. (a) Representation of the recombinant Fel d 1 allergen and its mosaic derivatives. Peptides (P1–P8) used for construction of hypoallergenic Fel d 1 derivatives (Fel d 1 M1, M, MA, MB, MC, ME, MF) are indicated in rFel d 1 consisting of an N-terminal chain 2 and a C-terminal chain 1 in different colours. Cysteines (C), serines (S), N- and C-termini of proteins as well as C-terminal hexa-histidine tags (6XHis) are indicated. (b) Coomassie-stained SDS–PAGE of purified rFel d 1 and rFel d 1 derivatives. M, molecular weight marker (kDa).