Probing the nanoscale viscoelasticity of intracellular fluids in living cells

We have used fluorescence correlation spectroscopy to determine the anomalous diffusion properties of. fluorescently tagged gold beads in the cytoplasm and the nucleus of living cells. From the extracted mean-square displacement v( t); t a, wehave determined the complex shear modulus G(v); v a for both compartments. Without treatment, all tested cell lines showed a strong viscoelastic behavior of the cytoplasm and the nucleoplasm, highlighting the crowdedness of these intracellular. fluids. We also found a similar viscoelastic response in frog egg extract, which tended toward a solely viscous behavior upon dilution. When cells were osmotically stressed, the diffusion became less anomalous and the viscoelastic response changed. In particular, the anomality changed from a approximate to 0.55 to a approximate to 0.66, which indicates that the Zimm model for polymer solutions under varying solvent conditions is a good empirical description of the material properties of the cytoplasm and the nucleoplasm. Since osmotic stress may eventually trigger cell death, we propose, on the basis of our observations, that intracellular. fluids are maintained in a state similar to crowded polymer solutions under good solvent conditions to keep the cell viable. We have used fluorescence correlation spectroscopy to determine the anomalous diffusion properties of fluorescently tagged gold beads in the cytoplasm and the nucleus of living cells. From the extracted mean- square displacement v(tau)similar to tau(alpha), we have determined the complex shear modulusG(omega)similar to omega(alpha) for both compartments. Without treatment, all tested cell lines showed a strong viscoelastic behavior of the cytoplasm and the nucleoplasm, highlighting the crowdedness of these intracellular. uids. We also found a similar viscoelastic response in frog egg extract, which tended toward a solely viscous behavior upon dilution. When cells were osmotically stressed, the diffusion became less anomalous and the viscoelastic response changed. In particular, the anomality changed from a approximate to 0.55 to a approximate to 0.66, which indicates that the Zimm model for polymer solutions under varying solvent conditions is a good empirical description of the material properties of the cytoplasm and the nucleoplasm. Since osmotic stress may eventually trigger cell death, we propose, on the basis of our observations, that intracellular. uids are maintained in a state similar to crowded polymer solutions under good solvent conditions to keep the cell viable.