Figure 2: QCM-D immobilization assays for CD44 on His-tag-capturing sensors.

QCM-D responses in (a) indicate formation of a stable and HA-binding CD44 monolayer, and demonstrate that CD44 is specifically immobilized through its polyhistidine tag (i.e., it can be fully eluted in imidazole). Data in (b) demonstrate that HA binds through the authentic HA-binding site on CD44 (largely blocked with anti-CD44 Ab). The magnitude of the final shifts upon binding of HA polymer to CD44-coated surfaces were ∆f = −7.4 ± 1.0 Hz and ∆D = 1.7 ± 0.2 × 10−6.