Fig. 3.

Sequences of in situ AFM images showing transformation from short to tall domains. Δt indicates time elapsed since collection of images i and i*. S-layer crystals were initially grown in 5 mL solution at 25 °C and further development of the domains was monitored in the same solution. Series in A shows evolution in distribution of domains in protein solution with C_P = 41 μg/mL (10 mM Tris pH 7.2, 50 mM CaCl₂, 100 mM NaCl) following an incubation time of 4.5 h. (i) Initial ratio of tall to short domains by area was 1.3. (ii) By Δt ∼ 2.3 h, about 25% of the short domains in i had transformed into tall domains without any dissolution of S-layer proteins from the domains. (iii) and (iv) At Δt ∼ 3.2 and 19.2 h, most of the short domains had transformed into tall domains. However, a few short domains still remained, indicating that the transformation does not go to 100% completion until much later times. Series in B shows transformation of a single domain in protein solution with C_P = 70 μg/mL (10 mM Tris pH 7.2, 50 mM CaCl₂, 100 mM NaCl) following an incubation time of 2.5 h. The transition began at the free edge of the short domain. In between (iii*) and (iv*), the short domain continued to grow by adding new tetramers at the bottom edge. Times of image collection were (i*) 2.5, (ii*) 2.7, (iii*) 2.8, and (iv*) 2.9 h.