Fig. 3: Viscoelastic properties of BMCs.
a–d, Schematic (a) and snapshot of an MEC-2/UNC-89 protein droplet measured with a pair of optically trapped polyethylene-glycol-terminated microspheres in a dual optical trap. Scale bar, 10 µm. Pin and Pout define the light momentum before and after interacting with the trapped microsphere (Supplementary Video 1). b,c, Storage (G′(ω), filled circles) and loss (G″(ω), open circles) moduli measured in the dual optical trap at t = 0 h (b) and t = 24 h (c) after condensate formation. The solid and dashed lines are the real and imaginary parts of the G modulus, derived from a fit of the Maxwell model to the acquired data. The circles and shadows are the median and ±25% quantiles measured for N = 10 (b) and N = 9 (c) droplets. d, Variation in the fitting parameters showing the changes in dynamic viscosity η (Pa s), stiffness E (Pa), time constant τ = η/E (s) and crossover frequency ωc = 1/τ (Hz) over 24 h condensate maturation in the dual optical trap. The mean and standard deviation derived from the fits in b and c. e–h, Schematic (e) and snapshot of a TimSOM experiment on MEC-2/UNC-89 protein droplet with an embedded carboxylated microbead (Supplementary Video 2). f,g, Storage (G′(ω), filled squares) and loss (G″(ω), open squares) moduli measured with TimSOM at t = 0 h (f) and t = 24 h (g) after condensate formation. The solid and dashed lines are the real and imaginary parts of the G modulus, derived from a fit of the Maxwell model to the acquired data. The squares and shadows are the median and ±25% quantiles measured for N = 17 (f) and N = 14 (g) droplets. h, Variation in the fitting parameters (dynamic viscosity η (Pa s), stiffness E (Pa), time constant τ = η/E (s) and crossover frequency ωc = 1/τ (Hz)) over 24 h extracted from the TimSOM routine. The mean and standard deviation derived from the fits in f and g.
