small solute ~0.5: globular protein mCherry ∼1.4: 10 kDa dextran ~2.3: 40 kDa dextran ~4.5 nm
||Ming-Tzo Wei et al., Phase behaviour of disordered proteins underlying low density and high permeability of liquid organelles. Nature Chemistry 9, 1118–1125 (2017). doi:10.1038/nchem.2803 p.1121 right column bottom paragraphPubMed ID29064502
||Abstract: "Here, [investigators] utilize a novel technique, ultrafast-scanning fluorescence correlation spectroscopy [FCS], to measure the molecular interactions and full coexistence curves (binodals), which quantify the protein concentration within LAF-1 droplets."
||P.1121 right column bottom paragraph: "Small solutes (Rh ∼ 0.5 nm) and the globular protein mCherry (Rh ∼ 1.4 nm) exhibit values in the range of 0.07–0.2 Pa s. These values are roughly two orders of magnitude lower than the bulk viscosity, consistent with their motion primarily reflecting diffusion through the aqueous solvent that permeates the droplet mesh. To interrogate larger length scales, [investigators] used dextran molecules of differing molecular weights. In dilute aqueous buffers, the 10 kDa dextran has a hydrodynamic radius (Rh) of ∼2.3 nm. By plugging this value of Rh and the measured diffusion coefficient into the Stokes–Einstein equation, [they] obtain an apparent viscosity value that is comparable to those of the other small probes. However, a similar analysis applied to the measured diffusion coefficients of 40 kDa (Rh ∼ 4.5 nm) and larger molecular weight dextran molecules suggests significantly hindered motion, implying that the bulk properties of the droplet become increasingly dominant."