In order to verify the effectiveness of the binding optimization process and peptide design, synthesized peptides were tested for antiviral activity against DENV-2 strain NG-C in a focus forming unit (FFU) reduction assay. DENV-2 strains S1 (GenBank accession number M19197.1) and NG-C (GenBank accession number AF038403.1) share 98% amino acid sequence identity in the E protein and the majority of differences are conservative. Dose response curves generated for the optimized peptides DN57opt, DN80opt, and DN81opt are shown in Figure 2A . The domain II region peptides, DN57opt and DN81opt displayed IC 50 values of 861 mM and 3666 mM (mean 6 sem) respectively, while no inhibition of infection was observed with the fusion region peptide, DN80opt. Correspondingly, maximum inhibition of 97% and 57% was achieved at 20 mM and 50 mM for DN57opt and Names and sequences for previously tested wild type peptides are denoted with an asterisk [9] , computationally designed peptides, wild type sequence peptides, and scrambled control peptides are shown. 50% inhibitory concentrations (IC 50 values 6 sem) determined from sigmoidal curve fits to the dose response curves in Figure 2 are given for DN57opt, DN81opt, and 1OAN1. Tested peptides that did not achieve 50% inhibition are noted with a dashed line. Peptides that were not tested for antiviral activity are noted ND (no data DN81opt. Both DN57opt and DN81opt showed improved inhibition of DENV-2 compared to their non-optimized counterparts, with DN57opt and DN81opt showing a nearly 14 fold and a 2 fold increase, respectively, in inhibition of DENV-2 at equivalent concentrations [9] . The most active inhibitor, DN57opt was chosen for further study. A scrambled version of DN57opt (DN57optscr) did not display inhibition at any concentration tested ( Figure 2B ). Four de novo designed peptides, 1OAN1, 1OAN2, 1OAN3, and 1OAN4 were also tested for inhibitory activity using the same FFU reduction assay ( Figure 2C ). 1OAN1 was found to be an effective inhibitor of DENV-2 infection with an IC 50 of 764 mM and a maximum inhibition of 99% at 50 mM. A scrambled version of 1OAN1 (1OAN1scr) did not inhibit infection by DENV-2 at any concentration tested ( Figure 2D ). In addition to these full dose response inhibition experiments using approximately 100 infectious units of virus, both the DN57opt and 1OAN1 peptides were also capable of inhibiting 4,000 infectious units of virus (data not shown).