A Nanometric Probe of the Local Proton Concentration in Microtubule-Based Biophysical Systems

Aarat P. Kalra, Boden B. Eakins, Sergei I. Vagin, Hui Wang, Sahil D. Patel, Philip Winter, Maral Aminpour, John D. Lewis, Vahid Rezania, Karthik Shankar, Gregory D. Scholes, Jack A. Tuszynski, Bernhard Rieger, Alkiviathes Meldrum

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We show a double-functional fluorescence sensing paradigm that can retrieve nanometric pH information on biological structures. We use this method to measure the extent of protonic condensation around microtubules, which are protein polymers that play many roles crucial to cell function. While microtubules are believed to have a profound impact on the local cytoplasmic pH, this has been hard to show experimentally due to the limitations of conventional sensing techniques. We show that subtle changes in the local electrochemical surroundings cause a double-functional sensor to transform its spectrum, thus allowing a direct measurement of the protonic concentration at the microtubule surface. Microtubules concentrate protons by as much as one unit on the pH scale, indicating a charge storage role within the cell via the localized ionic condensation. These results confirm the bioelectrical significance of microtubules and reveal a sensing concept that can deliver localized biochemical information on intracellular structures.

Original languageEnglish (US)
Pages (from-to)517-523
Number of pages7
JournalNano Letters
Issue number1
StatePublished - Jan 12 2022

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Condensed Matter Physics
  • Mechanical Engineering
  • Bioengineering
  • General Materials Science


  • biochemical sensor
  • biological pH
  • double functional
  • fluorescence
  • microtubules
  • photonic sensing


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