Fig. 2: Sequence-dependent control over linear viscoelastic (LVE) behavior of peptide-RNA condensates.
From: Programmable viscoelasticity in protein-RNA condensates with disordered sticker-spacer polypeptides
a A scheme showing the sticker-spacer architecture of associative peptide and RNA chains. Here, sticker-RNA interactions drive the condensation. b A plot showing the average elastic modulus (G’, black) and the average viscous modulus (G”, red) of [RGRGG]5-rU40 condensates (n = 17 measurements over 3 independent samples). Green lines are fits to experimental data using a single-mode Maxwell fluid model. The crossover frequency is indicated by the black dashed line and is the inverse of terminal relaxation time\(\,{\tau }_{M}\). Shaded regions represent the dominant elastic regime (light-blue) and the dominant viscous regime (light-green), respectively. Error bars represent one standard deviation (±1 s.d.). c The relative abundance of different amino acids within the inter-RG/RGG spacers of RG/RGG motifs in human RNA-binding proteins represented as bubble charts. Sizes of individual bubbles represent the fraction of inter-RG/RGG spacers that contain the corresponding amino acid (see Methods section). Residues that occurred in more than 10% of the analyzed protein sequences (RG/RGG domains from 407 human RNA-binding protein sequences) are indicated in cyan. Residues marked with red circles are utilized for peptide design for the experimental studies reported here. d The average frequency-dependent viscoelastic moduli of [RGXGG]5-rU40 condensates where X = P/S/R/F/Y. The crossover frequencies are indicated by black dashed lines. Shaded regions represent the dominant elastic regime (light-blue) and the dominant viscous regime (light-green), respectively. Error bars represent ±1 s.d. e The terminal relaxation time \({\tau }_{M}\) of [RGXGG]5-rU40 condensates as measured by pMOT (X = P/S/R/F/Y). f The zero-shear viscosity of [RGXGG]5-rU40 condensates as measured by pMOT (X = P/S/R/F/Y). g An LVE state diagram indicating the timescales at which the elastic modulus dominates (blue) and the timescales where the viscous modulus dominates (green) in [RGXGG]5-rU40 condensates (X = P/S/R/F/Y). Error bars represent one standard deviation (±1 s.d.). For d–g, the sample size is n = (29,16,17,17,16) measurements over 3 independent samples for X = (P,S,R,F,Y), respectively.
