Folks, We're holding us busy by applying CFDASE for ratiometric determination of internal pH in bacteria and yeast. Apart from strain- and pre-history - dependent difficulties in dye uptake the generation of a 'useful' calibration curve is the biggest challenge. The well-known combination valinomycin/nigericin results in a high degree of variability and curve shifts upon repetition. Also, apart from these, other agents (e.g. alcohols) or methods (e.g. electroporation) to facilitate equilibration of internal and external pH give stunning differences compared to mentioned 'standard' method. All remarks, suggestions and experiences with agents which provide reliable calibration curves for pHi in microorganisms are welcome. Providing a sufficient number of responses, I will post a summary on the list. Thanks in advance. - Joerg ------------------------------------------------ Joerg Ueckert Unilever Research Microbiology Vlaardingen, NL Email joerg.ueckert@unilever.com ------------------------------------------------
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