A micro-spectrophotometric study on the spectral properties of phenol red injected into cytoplasm for pHi determination

H. Sun, F. Jacquey, J. C. Bernengo

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The spectral properties of phenol red, used to determine intracellular pH (pHi), have been studied in the myoplasm of cultured rat skeletal muscle cells, by means of a micro-spectrophotometric technique. Two sets of intracellular calibration spectra at different dye concentrations were established in the presence of nigericin. Intracellular spectra of phenol red differ from the absorption spectra obtained in buffered solutions in the following ways: (1) Considerably greater absorbance in the violet region, owing to scattering of light by intracellular particles, which can be corrected by applying an energy transfer model derived from the work of Kubelka and Munk (Z Tech. Phys. 12 (1931) 593). (2) Slight spectral red-shift and an increase in the dye pKd, assumed to be due to interaction of the dye with intracellular constituents, especially soluble proteins, since the same spectral modifications are observed in buffered solutions containing bovine serum albumin. The potential advantages of using phenol red to determine pHi are the simple dye-H+ interaction, both in buffered solutions and in myoplasm, and the absence of dye selfassociations at the high dye concentrations required to perform intracellular measurements. Finally, our results show that absolute pHi can be measured to an accuracy of ±0.02 pH units using phenol red, if complete absorption spectra and intracellular spectral calibrations are available.

Original languageEnglish (US)
Pages (from-to)91-100
Number of pages10
JournalBiophysical Chemistry
Issue number1
StatePublished - Nov 1993
Externally publishedYes


  • Intracellular pH (pH)
  • Light scattering
  • Micro-spectrophotometry
  • Myoball
  • Nigericin
  • Phenol red

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Organic Chemistry


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