title: Photophysics of a Live-Cell-Marker, Red Silicon-Substituted Xanthene Dye.
abstract: Dyes with near-red emission are of great interest because of their undoubted advantages for use as probes in living cells. In-depth knowledge of their photophysics is essential for employment of such dyes. In this article, the photophysical behavior of a new silicon-substituted xanthene, 7-hydroxy-5,5-dimethyl-10-(o-tolyl)dibenzo[b,e]silin-3(5H)-one (2-Me TM), was explored by means absorption, steady-state, and time-resolved fluorescence. First, the near-neutral pH, ground-state acidity constant of the dye, pKN-A, was determined by absorbance and steady-state fluorescence at very low buffer concentrations. Next, we determined whether the addition of phosphate buffer promoted the excited-state proton-transfer (ESPT) reaction among the neutral and anion form of 2-Me TM in aqueous solutions at near-neutral pH. For this analysis, both the steady-state fluorescence method and time-resolved emission spectroscopy (TRES) were employed. The TRES experiments demonstrated a remarkably favored conversion of the neutral form to the anion form. Then, the values of the excited-state rate constants were determined by global analysis of the fluorescence decay traces recorded as a function of pH, and buffer concentration. The revealed kinetic parameters were consistent with the TRES results, exhibiting a higher rate constant for deprotonation than for protonation, which implies an unusual low value of the excited-state acidity constant pK*N-A and therefore an enhanced photoacid behavior of the neutral form. Finally, we determined whether 2-Me TM could be used as a sensor inside live cells by measuring the intensity profile of the probe in different cellular compartments of HeLa 229 cells.
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Crovetto
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Angel
authors.initials: A
authors.lastname: Orte
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Paredes
authors.affiliation: Department of Organic Chemistry, Faculty of Sciences, University of Granada , C. U. Fuentenueva s/n, 18071 Granada, Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: Resa
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Valverde
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Fabio
authors.initials: F
authors.lastname: Castello
authors.affiliation: Department of Organic Chemistry, Faculty of Sciences, University of Granada , C. U. Fuentenueva s/n, 18071 Granada, Spain.
authors.forename: Delia
authors.initials: D
authors.lastname: Miguel
authors.affiliation: Department of Organic Chemistry, Faculty of Sciences, University of Granada , C. U. Fuentenueva s/n, 18071 Granada, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Cuerva
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Talavera
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Granada , Cartuja Campus, 18071 Granada, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Alvarez-Pez
mesh_terms: D002463:Cell Membrane Permeability; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000378:metabolism*; D006367:HeLa Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D008027:Light; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000737:chemistry* / Q000378:metabolism; D055585:Physical Phenomena; D011522:Protons; D012825:Silicon / Q000737:chemistry*; D014966:Xanthenes / Q000737:chemistry / Q000378:metabolism
chemical_list: C000609889:7-hydroxy-5,5-dimethyl-10-(o-tolyl)dibenzo(b,e)silin-3(5H)-one; D005456:Fluorescent Dyes; D017646:Organosilicon Compounds; D011522:Protons; D014966:Xanthenes; D012825:Silicon