Fig. 1: Using mass photometry to examine the equilibrium size distribution of JB6.
From: Effects of solution conditions on the self-assembly of the chaperone protein DNAJB6b
a Schematic illustration of the equilibrium size distribution of JB6, where CN is the concentration of an N-mer. The structure of a JB6 monomer is given as an AlphaFold2 prediction with the NTD in dark green, the CTD in light green, and the linker in gold. b Mass photometry data of the size distributions of five different proteins, normalized to either area or peak height (inset). BSA (66 kDa), IgG (150 kDa), and thyroglobulin (669 kDa) were used as standard proteins with known masses (see Supplementary Note 1, Fig. S1). αB-crystallin (20.2 kDa) self-assembles with a narrow size distribution, in contrast to the very broad distribution of JB6 (55 μM). c The concentration dependence of JB6 size distribution. The inset shows how the average N of the micelles, at concentrations above 1 μM, changes with JB6 concentration. Not all of the measured concentrations are shown as distributions, to avoid cluttering of the graph. d Refractive index measurements of JB6 and BSA. To trust the masses given by mass photometry, the refractive index dependence of protein concentration, dn/dc, should be similar, which they are (0.17 ml/g for both JB6 and BSA at 546 nm, and 0.18 ml/g and 0.17 ml/g, respectively, at 579 nm).
