Fig. 2. Stimulator of interferon genes (STING) binding and activation by the PSC7A polymer.

a Isothermal titration calorimetry (ITC) analysis shows the PSC7A copolymer has a much higher binding affinity to STING than PSDEA. K_d: apparent dissociation constant. The error bars are estimates of the integration error based on the noise in the baseline regions flanking each injection. b Summary of K_b values (binding affinity, K_b = 1/K_d) of PSC7A and PSDEA to STING from ITC experiments. c Interferon (IFN) induction levels of THP1-ISG cells incubated with PSC7A or PSDEA (0.5 μM for 48 h) correlate with STING binding affinity. n = 5 experimental replicates in each group. Data are presented as means ± s.e.m. and statistical significance was calculated using Student’s two-tailed t test (PSC7A vs. PSDEA: ^****P < 0.0001). Results from additional dUPS polymers are presented in Supplementary Fig. 13.