Viscosity of a Crowding Medium Obtained Through Optical Trapping

The dynamic viscoelasticity a cellular medium is mainly due to the crowding of a large number of interacting and non-interacting proteins. Our research presents how the viscosity of a medium is altered in the presence of globular proteins. Using an optical trap paired with a 980 nm infrared laser and Nikon inverted microscope we have developed a synthetic approach to calculate the viscosity of a medium. The method involves comparison of Equipartition theorem and Passive power-spectrum technique to determine viscosity. This approach has enabled us to calculate the viscosity of several water and glycerol concentrations. The method has been extended to investigate the viscoelasticity of the medium with various concentrations of globular Polyethylene glycol proteins.