Reactant concentrations from fluorescence correlation spectroscopy with tailored fluorescent probes. An example of local calibration-free pH measurement

Publication Type:

Journal Article

Source:

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Volume 127, Number 44, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, p.15491-15505 (2005)

DOI:

10.1021/ja053909w

Keywords:

2-PHOTON EXCITATION; CELLS; DIFFUSION; DYNAMICS; EQUILIBRIUM-CONSTANTS; FLUCTUATIONS; KINETICS; TIME

Abstract:

The present account is concerned with the measurement of local reactant concentrations by observing specific fluorescent probes in fluorescence correlation spectroscopy (FCS). The Theoretical Analysis section revisits the photophysical, thermodynamic, and kinetic information that is contained in the corresponding FCS correlation curves. In particular, we examine the conditions under which FCS is revealed as a superior tool to measure concentrations of reactive species. Careful molecular engineering of the specific fluorescent probes that simultaneously integrates photophysical, thermodynamic, and kinetic constraints will be required to benefit most from FCS. We illustrate the FCS titration approach with a series of fluorescent probes that we tailored to measure pH at around 4-6 by FCS after two-photon excitation. We show that an optimal design allows one to access pH without any preliminary calibrations such as the determination of the protonation constant or the photophysical properties of the fluorescent probe.