5-15 % increase in viscosity
||Theillet FX et al., Physicochemical properties of cells and their effects on intrinsically disordered proteins (IDPs). Chem Rev. 2014 Jul 9 114(13):6661-714. doi: 10.1021/cr400695p p.6665 right column 2nd paragraphPubMed ID24901537
|| Jenkins, H. Donald B. Marcus, Yizhak. Viscosity B-Coefficients of Ions in Solution. Chemical Reviews (Washington, D. C.) (1995), 95 (8), 2695-2724  Banipal, Tarlok S. Kaur, Damanjit Banipal, Parampaul K. Apparent Molar Volumes and Viscosities of Some Amino Acids in Aqueous Sodium Acetate Solutions at 298.15 K. Journal of Chemical and Engineering Data (2004), 49 (5), 1236-1246
||P.6665 right column 2nd paragraph: "Therefore, and despite the astonishingly large intracellular concentrations of small solutes (see above), these molecules contribute little to intracellular viscosity. This observation is consistent with the measured effects of ions and metabolites, such as amino acids on water viscosity in vitro. With the exception of K+, other ions and amino acids generally increase viscosity by 5–15% at concentrations typical of intracellular conditions (primary sources)."