Figure 3. TEM, CD, and fluorescence measurements confirmed the rapid co-assembly of βTail polypeptides into Q11 nanofibers.

a) Immunogold staining identified gold beads co-localized with nanofibers assembled in the presence of βTail- GFP and then stained with an anti-GFP 1° and a gold-labeled 2° antibody, whereas few gold beads were observed near Q11 nanofibers assembled in the presence of a βTail peptide and then stained similarly (scale bar = 100 nm). b) Gold beads conjugated to streptavidin bound to Q11 nanofibers assembled in the presence of biotinylated βTail, whereas few gold beads were co-localized with Q11 nanofibers (scale bar = 200 nm). c) Tryptophan-terminated βTail (W-βTail, W-βT) integrated into Q11 nanofibers over the range of 25-100 μM in a βTail-dependent manner, as measured by loss of fluorescence from the supernatant. d) W-βTail and βTail-GFP integrated into Q11 nanofibers within minutes, as measured by loss of fluorescence from the supernatant. βTail secondary structure changed from α-helical to β-sheet following overnight co-assembly with Q11 (e), individual peptides shown left and center, after overnight co-assembly shown right, where red=spectrum of mixed peptides and black=this mixed sample with the Q11 spectrum subtracted, revealing structure of βTail. In contrast, βTmutant secondary structure remained predominantly random coil (f, same coloring scheme as e). N = 3, mean ± s.d. for c, d.