Fig. 5. Effects of HA surface density on the recovery of the initial HA conformation. Japan HA-cells pre-incubated without (A) or with 5 mM NaBut (B) were first treated with an AP (30 s at pH 4.9, 22°C) in the absence of RBCs. Cells were then incubated at pH 7.4 for 0 or 30 min, incubated with RBCs for 15 min and treated with an FTP (2 min at pH 5.2). The time interval T between the end of the AP and the beginning of the FTP was either 15 or 45 min. In the experiment shown in the ‘control’ bar, the FTP (2 min at pH 5.2) was applied to the HA-cells, with bound RBCs untreated with an AP.