AFM images of EAK 16-II-modified HOPG surface at different concentrations and time periods: (a) 2 µM, 25 min; (b) 2 µM, 2 h; (c) 6.2 µM, 10 min; (d) 6.2 µM, 2 h after different incubation periods.

<p>(e) schematic diagram of EAK16-II in a β-strand conformation on HOPG. Each AFM image corresponds to a scan area of 1000 nm×1000 nm.</p

Schematic diagram of EAK16-II structure.

<p>The red portion shows the hydrophilic side of the peptide and the green portion shows the hydrophobic side of the peptide.</p

Photographs of water drops on the various surfaces used in the determination of the water contact angles: (a) mica; (b) EAK16-II-modified mica; (c) HOPG; (d) EAK16-II-modified HOPG.

<p>Photographs of water drops on the various surfaces used in the determination of the water contact angles: (a) mica; (b) EAK16-II-modified mica; (c) HOPG; (d) EAK16-II-modified HOPG.</p

Effect of EAK16-II concentration on the surface coverage of peptide assemblies on mica.

<p>AFM images of EAK16-II-modified mica surfaces at 10 min incubation in solutions with various peptide concentrations: (a) 1 µM; (b) 2 µM; (c) 4 µM; (d) 8 µM; (e) 12 µM. Surface coverage of EAK16-II nanofibers on mica as a function of peptide concentration is plotted in panel (f). Proposed molecular arrangement of EAK16-II assembly on mica is plotted in panel (g). Each image corresponds to a scan area of 2000 nm×2000 nm.</p

Proposed model of EAK16-II assembly on HOPG.

<p>(a) Schematic representation showing the orientation of assembled EAK16-II strands; (b) AFM image of EAK16-II on HOPG surface over a scan area of 1000 nm×1000 nm; the inset shows the 2-dimensional Fourier transform of the AFM image and characteristic 6-fold symmetry.</p

Time evolution of 4 µM EAK16-II assembly on the mica surface.

<p>AFM images collected at various incubation times: (a) 1 min; (b) 2 min; (c) 5 min; (d) 10 min; (e) 20 min; (f) 40 min; (g) 80 min; (h) 120 min; (i) 160 min. Surface coverage of EAK16-II on mica as a function of incubation time is plotted in panel (j). Each image corresponds to a scan area of 2000 nm×2000 nm.</p

The preferred location of EAK16-II assembled nanofibers on the HOPG surface.

<p>(a) A representative AFM image of nanofibers on HOPG surface over a scan area of 800 nm×800 nm; (b) cross-sectional heights of nanofiber on one terrace (green line in a) and a step edge of HOPG (red line in a); (c) schematic diagram of nanofibers on HOPG surface.</p

AFM images of EAK16-II modified mica and HOPG surfaces after immersion in pure water, 10 mM HCl and 10 mM NaOH solutions for 10 h.

<p>(a) mica, water; (b) mica, 10 mM HCl; (c) mica, 10 mM NaOH; (d) HOPG, water; (e) HOPG, 10 mM HCl; (f) HOPG, 10 mM NaOH. Scan areas are 2000 nm×2000 nm for mica and 1000 nm×1000 nm for HOPG.</p

Contact angles measured on mica, HOPG and their EAK16-II-modified surfaces.

<p>Contact angles measured on mica, HOPG and their EAK16-II-modified surfaces.</p

Peptide coverage on EAK16-II-modified mica and HOPG surfaces after 10 h incubation under acidic and basic environments.

<p>Note: The peptide coverage on the mica and HOPG surfaces in pure water corresponds to the initial coverage before the surfaces were immersed into an acidic or basic solution. It served as a control for comparison with that of peptide-modified surfaces in acidic and basic environments.</p