Colloidal stability and osmotic pressure in living cells
Abstract
A living cell contains more than one hundred different protein species. There are then at least 104 potential protein-protein contacts, but only a few of these result in metabolic activity. How is chaos avoided? We argue, based on a quantitative description, that the protein-protein interaction at a range of order 0.5nm beyond contact has a generic species independent character. There is a delicate balance between electrostatic repulsion and dispersion attraction. In this way molecular contact is allowed but aggregation is prevented. The dominantly repulsive protein-protein interaction has the result that at high concentrations the protein contribution to the osmotic pressure in the cell is substantial and of the same order as that from small ions. Diffusional motion is limiting the rate of metabolic process and the higher the concentration the shorter is the diffusional paths. However, at too high concentrations obstruction effects slows the diffusional transport. There is then an optimal intracellular concentration. It is experimentally found that optimal cellular metabolic rates occur for osmotic pressures in the range 0.25 to 0.40 M valid for “simple” bacteria as well as for plants and mammals. Halophiles represent an exception to this rule and the reason is discussed in the seminar.
Papers
Colloidal stability of the living cell, HW, E Vallina Estrada, J. Danielsson, M. Oliveberg PNAS 2020, 117, p 10113-10121
On the osmotic pressure of cells, HW, M Oliveberg QRB, Discovery, 2022
Derivation of the the Derjaguin approximation for inhomogenous solvents HW, J.Stenhammar, JCP 2020,152, p234704
Participate on campus or via Zoom.
On campus: PJ lecture hall
Zoom link: https://gu-se.zoom.us/j/64681043702
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Theoretical Physics Seminar
