Figure 3. Glycan-induced caging of the head domain. Glycans impede head rearrangement by introducing a steric cage.

(A) Snapshot from the caged ensemble illustrates the high density of glycans surrounding the head. (B) To define the duration of each caging event (${\tau }_{\mathrm{cage}}={\tau }_{\mathrm{exit}}-{\tau }_{\mathrm{enter}}$), we measured z_head and r_head (Figure 2D). Based on the 2D probability distribution (Figure 2E), the system was defined as entering the cage when z_head first drops below 6.5 nm: ${\displaystyle {\tau }_{\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}}}$. ${\displaystyle {\tau }_{\mathrm{e}\mathrm{x}\mathrm{i}\mathrm{t}}}$ is the time at which the head moves laterally, relative to the trans-membrane region ($r_{\mathrm{head}}>5$ nm). (C) Distribution of ${\tau }_{\mathrm{cage}}$ values when glycans are present. There is an extended tail at large values ($100-500\mu s$). (D) When glycans are absent, the ${\tau }_{\mathrm{cage}}$ values are narrowly distributed around short timescales.