In what time scale proton transfer takes place in a live CHO cell?

Abstract

Excited state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) in a live Chinese hamster ovary (CHO) cell is studied by time resolved confocal microscopy. The cytoplasm region of the cell is stained by a photoacid, HPTS (HA). The time constant of initial proton transfer (τ(PT)) in the cell is found to be ~10 times longer than that in bulk water, while the time constants of recombination (τ(rec)) and dissociation (τ(diss)) in the cell are ~3 times and ~2 times longer, respectively. The slower rate of proton transfer (~10 times) inside the CHO cell compared to that in bulk water is ascribed to slower solvation dynamics, lower availability of free water molecules, and disruption of hydrogen-bond network inside the cell. Translational and rotational diffusion of HPTS inside a single CHO cell have been investigated by fluorescence correlation spectroscopy (FCS) and picosecond anisotropy measurement, respectively. Both the translational and rotational diffusion slow down inside the live cell. FCS studies indicate that HPTS remains tightly bound to a macromolecule inside the cell.

Time Evolution of Local pH Around a Photo‐Acid in Water and a Polymer Hydrogel: Time Resolved Fluorescence Spectroscopy of Pyranine

“…Acid‐base reaction is one of the fundamental chemical reactions in nature and has implications in many natural and biological processes . The dissociation equilibrium of an acid HA into proton and its deprotonated species (A − ) is, …”

“…The primary prcocesses of excited state proton transfer (ESPT) of HPTS in a wide variety of media have been monitored by time evolution of the fluorescence from the anion (A − *) and the undissociated acid (HA*). This includes binary solvent mixtures, live biological cell, reverse micelles, micelle, nafione membrane and niosome . ESPT of HPTS has not been studied in polymer hydrogel.…”

“…[8][9][10][11][12] ESPT is implicated in rhodopsin (involved in the vison process) [13] and in green fluorescence protein (GFP). [14][15] The primary prcocesses of excited state proton transfer (ESPT) of HPTS in a wide variety of media [10][11][12][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] have been monitored by time evolution of the fluorescence from the anion (A À *) and the undissociated acid (HA*). This includes binary solvent mixtures, [10][11]22] live biological cell, [17,18] reverse micelles, [19,30,32] micelle, [21] nafione membrane [30] and niosome.…”

“…[29] ESPT of HPTS has not been studied in polymer hydrogel. In spite of the great deal of work on HPTS, [10][11][12][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] there has been almost no effort to understand how the local pH around a photo-acid varies with time, following excitation of the photoacd. Huppert and co-workers proposed that rise time of the A À emission scales with pK a * in the case of 2-naphthols and using this they calculated pK a * of pyranine (8-hydroxypyrene-1,3,6trisulphonic acid, HPTS, Scheme 1).…”

Switchable amplification of fluoresence from a photosynthetic microbe

“…where F (0) and F (τ ) denote the intensity of fluorescence at time 0 and at a lag time τ , respectively.The autocorrelation traces are fitted to a 3D-diffusion model [30,31] having triplet contribution as,…”