Fig. 2: Effect of headgroup charge on SLP oligomerization.

a Illustration of the LLPS mechanism for SLPs. Micellar arrangement of the oligomers is caused by the amphiphilic nature of SLP⁵⁹. Representative structures for monomer and micellar oligomers derived from MD simulations are shown below. b Normalized autocorrelation curves of SLP1–4 determined by fluorescence correlation spectroscopy (FCS) as performed for Cy5-labeled SLPs (black, red, blue, and green crosses). FCS data show that the assemblies of SLP1–2 are globally larger than that of SLP3–4. The measurement concentration was 4 mM of SLPs in PBS (pH 7.4) of which 1 out of 4000 peptides was labeled with Cy5. The FCS autocorrelation curves were fitted with the maximum entropy method (MEM) for higher-resolution analysis on size distribution, indicated by the solid lines. c The size distribution of SLPs obtained from MEM analysis of the FCS measurements. The dashed line at D = 150 µm²/s indicates the cut-off size between monomeric (D > 150) and oligomer (D < 150) populations. SLP1–2 with two glutamic acid residues in the headgroup formed oligomers with ~10 times slower diffusivity than SLP3–4 with three glutamates in the headgroup.