19Fa NMR spectroscopy as a probe of cytoplasmic viscosity and weak protein interactions in living cells

Abstract

Protein mobility in living cells is vital for cell function. Both cytosolic viscosity and weak protein-protein interactions affect mobility, but examining viscosity and weak interaction effects is challenging. Herein, we demonstrate the use of 19Fa NMR spectroscopy to measure cytoplasmic viscosity and to characterize nonspecific protein-protein interactions in living Escherichiaa coli cells. The origins of resonance broadening in Escherichiaa coli cells were also investigated. We found that sample inhomogeneity has a negligible effect on resonance broadening, the cytoplasmic viscosity is only about 2-3 times that of water, and ubiquitous transient weak protein-protein interactions in the cytosol play a significant role in governing the detection of proteins by using in-cell NMR spectroscopy. The soft cell: Cytosolic viscosity and weak protein-protein interactions in cells affect mobility, but examining these effects is challenging. A 19Fa NMR method to quantify these effects in living Escherichia coli cells has been developed and the origins of resonance broadening in E.a coli cells have been investigated (see figure). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.