(A) AFM image of the affinity-purified mucins highlighting examples of two polymer types, labeled I and III. 1200 × 1200 nm scan size, z-range 3 nm. Reprinted with permission from Round AN, McMaster TJ, Miles MJ, Corfield AP, Berry M. The isolated MUC5AC gene product from human ocular mucin displays intramolecular conformational heterogeneity. Glycobiology. 2007;17:578–585. The Society for Glycobiology. (B) Examples of force-distance retract curves for mucin-mica interactions. Force curves in I and III were taken without added cations, with dwell times of 0 s and 5 seconds, respectively. Force curves II and IV were taken with the addition of Ni(II) cations and with dwell times of 0 seconds and 5 seconds, respectively. Both detachment (short jumps) and single molecule stretching (arrows) were observed in the force curves. The number of detachment events and the prevalence of the stretching events increased with the addition of the cations. Reprinted with permission from Berry M, McMaster TJ, Corfield AP, Miles MJ. Exploring the molecular adhesion of ocular mucins. Biomacromolecules. 2001;2:498–503. Copyright 2001 American Chemical Society.