||Budding yeast Saccharomyces cerevisiae
||Plášek J et al., A novel method for assessment of local pH in periplasmic space and of cell surface potential in yeast. J Bioenerg Biomembr. 2017 Jun49(3):273-279. doi: 10.1007/s10863-017-9710-3 abstract & p.276 right column 4th paragraphPubMed ID28405872
||Abstract: "Here [investigators] present a novel method enabling the assessment of local pH at the periplasmic membrane surface which can be directly related to the underlying cell surface potential. In this proof of concept study using Saccharomyces cerevisiae cells with episomally expressed pH reporter, pHluorin, intracellular acidification induced by the addition of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) was measured using synchronously scanned fluorescence spectroscopy (SSF)."
||Abstract: "The cell surface potential was estimated to amount to -130 mV." P.276 right column 3rd paragraph: "The cell surface potential in yeast is negative due to the presence of anionic groups on the plasma membrane surface. Hence, cations including H+ tend to accumulate in the vicinity of the cell surface. The ratio between the surface cs and bulk concentration c∞ is related to the surface potential ψs through an exponential Boltzmann factor (Ehrenberg 1986, Itoh 1979, Tsui et al. 1986) as follows: cS=c∞e^−[FψS/(RT)] (eq.3) After converting the bulk and periplasmic pH values to corresponding H+ concentrations, the ratio cs/c∞ can be inserted into Eq. 3. [Investigators] obtained ψs = − 131 and − 89 mV in a plain 25 mM MES-TEA buffer and in a buffer of high ionic strength (25 mM MES-TEA with 145 mM choline chloride and 5 mM KCl), respectively. In the other series of measurements using PCP [pentachlorophenol, a protonophore] instead of CCCP [carbonyl cyanide m-chlorophenylhydrazone, another protonophore] the estimated cell surface potential was ψs = − 113 mV."