title: 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.
authors.affiliation: Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
authors.forename: Supratik
authors.initials: S
authors.lastname: Sen Mojumdar
authors.forename: Rajdeep
authors.initials: R
authors.lastname: Chowdhury
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Mandal
authors.forename: Kankan
authors.initials: K
authors.lastname: Bhattacharyya
mesh_terms: D000818:Animals; D001190:Arylsulfonates / Q000737:chemistry*; D016466:CHO Cells; D003412:Cricetulus; D018613:Microscopy, Confocal; D015394:Molecular Structure; D011522:Protons
chemical_list: D001190:Arylsulfonates; D011522:Protons; C005047:pyranine