Fig. 1 | Nature Communications

Fig. 1

From: Modular assembly of proteins on nanoparticles

Fig. 1

Binding of GST to GNPs. a GST binding measured using time-resolved DLS and fitted to a pseudo-first order association kinetic model (dashed lines) was used to determine the observed association rate kOBS at the GST concentrations indicated. The inset shows the values of kOBS and their 95% confidence interval (vertical bars) determined from each binding curve as described in Methods section. The dashed line in the inset represents the fit to the equation kOBS = kON [GST] + kOFF, from which the on- and off-rates of GST/GNPs binding were determined. b Equilibrium binding data showing that GST has higher affinity to GNPs than HSA. Δd values for GST were averaged over three measurements and the error bars represent standard deviations. The dashed line is the best fit of GST data to the binding model used, whereas the dotted line is a representation of an ideal binding curve of HSA binding to GNPs, based on a previously reported KD and a ΔdMAX of 14 nm. The latter was used assuming a complete corona with a thickness that equals the hydrodynamic diameter of serum albumin (~7 nm). c SDS-PAGE of GNPs incubated in human serum (HS). Lane 1: protein marker (relevant molecular weights are shown on the left); lane 2: unprotected GNPs incubated in HS showing prominent binding of HSA; lane 3: GST-protected GNPs incubated in HS showing no binding of HSA; lane 4: control GST-GNPs which were processed like lane 3 but not incubated in HS. d Zeta potential of GST-coated GNPs (solid line) measured at different pH, showing a marked increase at pH lower than pI. Naked GNPs (dashed line) are highly negative at all pH. The data are averages of three measurements and the error bars represent standard deviations. The inset shows the predicted net charge and pI of GST calculated using APBS algorithm at pH 5–9. e 95% confidence intervals of GST/GNPs KD (left), ΔdMAX (center) and tabled data (right) at different pH. The ΔdMAX estimates (also listed in the table inset) are significantly different, as indicated by the dashed horizontal line

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