Figure 4. Minimum length for TLR3 activation.

a, 21-nucleotide or 23-nucleotide Luc siRNA but not truncated versions suppressed CNV in wild-type mice. n = 8–11; asterisk, P < 0.05 compared to vehicle (buffer); mean ± s.e.m. Equimolar amounts to 1 μg of 21-nucleotide Luc siRNA. nt, nucleotide. b, c, Orthogonal views of a model of TLR3 ectodomain dimer (green and cyan subunits shown as backbone ribbons) with computer-docked 21-nucleotide dsRNA. Protein modules interact via C-terminal domains to form a highly symmetrical dimer. The model incorporated potential interactions involving a larger set of TLR3 residues considered important in RNA binding (displayed as purple and red side chains on ectodomain subunits); these residues were within 4.5 Å of RNA. d, TLR3 dimer with docked 19-nucleotide dsRNA shows proximity to fewer putative RNA-binding residues. Binding of 19-nucleotide dsRNA was less favourable than 21-nucleotide dsRNA (ΔE = &minus308 kcal mol⁻¹; 95% confidence interval: 261–355; n = 5; P = 0.008).