title: Porosity of the yeast cell wall and membrane.
abstract: The limiting sizes of molecules that can permeate the intact cell wall and protoplast membrane of Saccharomyces cerevisiae were determined from the inflection points in a triphasic pattern of passive equilibrium uptake values obtained with a series of inert probing molecules varying in molecular size. In the phase identified with the yeast protoplast, the uptake-exclusion threshold corresponded to a monodisperse ethylene glycol of molecular weight = 110 and Einstein-Stokes hydrodynamic radius (r(ES)) = 0.42 nm. In the cell wall phase, the threshold corresponded to a polydisperse polyethylene glycol of number-average molecular weight ( M(n)) = 620 and average radius (r(ES)) = 0.81 nm. The third phase corresponded to complete exclusion of larger molecules. The assessment of cell wall porosity was confirmed by use of a second method involving analytical gel chromatographic analyses of the molecular weight distribution for a single polydisperse polyglycol before and after uptake by the cells, which indicated a quasi-monodisperse threshold for the cell wall of M(n) = 760 and r(ES) = 0.89 nm. The results were reconciled with two situations in which much larger protein molecules previously have been reported able to penetrate the yeast cell wall.
mesh_terms: D001692:Biological Transport; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism*; D002463:Cell Membrane Permeability; D002473:Cell Wall / Q000378:metabolism*; D002845:Chromatography; D003911:Dextrans / Q000378:metabolism; D004058:Diffusion; D006018:Glycols / Q000378:metabolism; D007444:Inulin / Q000378:metabolism; D008722:Methods; D008970:Molecular Weight; D011523:Protoplasts / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D003911:Dextrans; D006018:Glycols; D007444:Inulin