Utilization of dual-wavelength pH-sensing dyes in the characterization of pH buffers under hydrostatic pressure

POSTER

Abstract

Biologically-compatible pH-buffer solutions are routinely used in biochemical and biophysical studies at ambient pressure. When using buffers under high-pressure however, the existence of a thermodynamic volume change ($\Delta $V) for the buffer's acid-dissociation reaction leads to a pressure-dependent equilibrium constant (pK$_{\mathrm{a}})$. The result is a pressure-induced shift in pH. Here we use pH-sensing, dual-wavelength probe dyes, SNARF-1 and SNARF-5F, to characterize the pressure-response of three biologically-relevant buffers: MOPS, HEPES, and TRIS. Emission spectra from the dyes, excited at 337-nm wavelength, are used to track the pressure-induced change in pH of the buffer systems, up to 600 atm (61 MPa). From this the $\Delta $V of the buffers' acid-dissociation reaction was determined and found to be in the 0 to $+$10 ml/mol range. Results presented are important when accounting for pressure-induced pH changes during high-pressure biophysical studies because a large range of biochemical reactions involve H$^{\mathrm{+}}$ and have a $\Delta $V similar in range to the these buffers.

Authors

  • Paul Urayama

    Miami University

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis