Fig. 3

SpyTagged noro-VLPs show high stability and storability. In these stability experiments, the noro-VLPs were stored in PBS (137 mM NaCl, 2.7 mM KCl, 8 mM Na2HPO4, 2 mM KH2PO4, pH 7.4. a Dynamic light scattering analyses executed monthly during a 5-month storage period at + 4 °C. Graphical data shown in Additional file 1: Figure S4. b–d The melting temperatures (Tm) of native noro-VLP (b), SpyTag-noro-VLP (b, c), M2e- and HA2-conjugated SpyTag-noro-VLP (c), SpyCatcher-M2e (d) and SpyCatcher-HA2 (d) were measured with differential scanning fluorimetry (DSF). The fluorophore, SYPRO Orange, binds hydrophobic areas that emerge from the particles and proteins as they unfold upon heating from 25 to 105 °C. Water quenches the fluorescence of SYPRO Orange, so fluorescence increases as more protein becomes unfolded and thus available for binding. T_m was calculated from the midpoint of each transition peak. Plotted here are the arithmetic means of normalized fluorescence from three independent measurements. e SpyTag-noro-VLP aliquots were stored at + 4 °C and conjugated with SpyCatcher-M2e monthly. The SpyCatcher-M2e aliquots used for this were stored at − 20 °C until conjugation. After overnight conjugation, the reaction was stopped by boiling in SDS