Spatial variability of and effect of light on the cœlenteron pH of a reef coral.

Coral reefs, the largest bioconstruction on Earth, are formed by calcium carbonate skeletons of corals. Coral skeleton formation commonly referred to as calcification occurs in a specific compartment, the extracellular calcifying medium (ECM), located between the aboral ectoderm and the skeleton. Calcification models often assume a direct link between the surrounding seawater and the ECM.

Photosensitizing properties and subcellular localisation of 3,4-dihydro-β-carbolines harmaline and harmalol.

Harmaline (1) and harmalol (2) represent two 3,4-dihydro-β-carboline (DHβCs) most frequently reported in a vast number of living systems. Fundamental aspects including the photosensitizing properties, cellular uptake, as well as the cyto- and phototoxicity of 1 and 2 were investigated herein. The molecular basis underlying the investigated processes are elucidated.

Self-Assembled Lanthanide Antenna Glutathione Sensor for the Study of Immune Cells.

The small molecule 8-methoxy-2-oxo-1,2,4,5-tetrahydrocyclopenta[de]quinoline-3-carboxylic acid () behaves as a reactive non-fluorescent Michael acceptor, which after reaction with thiols becomes fluorescent, and an efficient Eu antenna, after self-assembling with this cation in water. This behavior makes a highly selective GSH biosensor, which has demonstrated high potential for studies in murine and human cells of the immune system (CD4 T, CD8 T, and B cells) using flow cytometry. GSH can be monitored by the fluorescence of the product of addition to (445 nm) or by the luminescence of Eu (592 nm).

Studying the reactivity of alkyl substituted BODIPYs: first enantioselective addition of BODIPY to MBH carbonates.

The first enantioselective addition of alkyl BODIPYs to Morita-Baylis-Hillman (MBH) carbonates is reported. This is the first reported enantioselective methodology using the methylene position of BODIPYs as a nucleophile. The reaction is efficiently catalyzed by cinchona alkaloids, achieving high enantioselectivities and total diastereoselectivity.

-Methyl-β-carboline alkaloids: structure-dependent photosensitizing properties and localization in subcellular domains.

N-Methyl-β-carboline (βC) alkaloids, including normelinonine F (1b) and melinonine F (2b), have been found in a vast range of living species playing different biological, biomedical and/or pharmacological roles. Despite this, molecular bases of the mechanisms through which these alkaloids would exert their effect still remain unknown. Fundamental aspects including the photosensitizing properties and intracellular internalization of a selected group of N-methyl-βC alkaloids were investigated herein.

Synthesis, Photophysics, and Solvatochromic Studies of an Aggregated-Induced-Emission Luminogen Useful in Bioimaging.

Biological samples are a complex and heterogeneous matrix where different macromolecules with different physicochemical parameters cohabit in reduced spaces. The introduction of fluorophores into these samples, such as in the interior of cells, can produce changes in the fluorescence emission properties of these dyes, caused by the specific physicochemical properties of cells. This effect can be especially intense with solvatofluorochromic dyes, where changes in the polarity environment surrounding the dye can drastically change the fluorescence emission.

New Thiol-Sensitive Dye Application for Measuring Oxidative Stress in Cell Cultures.

A xanthene derivative, Granada Green dinitrobenzene sulfonate (GGDNBS), has been synthesized to assay cellular oxidative stress based on changes in the concentration of biothiols. The dye is able to react with biological thiols by a thiolysis reaction that promotes a change in fluorescence intensity. To demonstrate the usefulness of GGDNBS for in vivo oxidative stress measurements, 661 W photoreceptor-derived cells were exposed to light to induce ROS generation, and changes in GGDNBS fluorescence were measured.

O-H and (CO)N-H bond weakening by coordination to Fe(ii).

New N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-ethane-1,2-diamine derivatives bearing covalently linked OH and (CO)NH groups have been synthesized. The coordination of those pendant hydroxyl/amide groups to a Fe(ii) metal center is demonstrated both in solution, even in the presence of chloride as the counterion, and in solid state, by means of X-ray diffraction crystal structures. As a result of this coordination, the experimental bond dissociation free energies (BDFE) of O-H and (CO)N-H bonds are remarkably diminished down to 76.

Sulfoxide-Induced Homochiral Folding of ortho-Phenylene Ethynylenes (o-OPEs) by Silver(I) Templating: Structure and Chiroptical Properties.

A new family of homochiral silver complexes based on carbophilic interactions with ortho-phenylene ethynylene (o-OPE) scaffolds containing up to two silver atoms are described. These compounds represent a unique class of complexes with chirality at the metal. Chiral induction is based on the inclusion of chiral sulfoxides, which allow efficient transfer of chirality to the helically folded o-OPE, leading to circularly polarized luminescence (CPL)- and vibrational circular dichroism (VCD)-active compounds.

Versatile synthesis and enlargement of functionalized distorted heptagon-containing nanographenes.

Highly distorted polycyclic aromatic hydrocarbons (PAHs) are predicted to be attractive goals in nanoscience owing to the new properties they can exhibit. We have shown that a variety of functionalized distorted heptagon-containing nanographenes can be easily prepared from simple building blocks by a sequence of Co-catalyzed cyclotrimerization and cyclodehydrogenation reactions. The versatility of this strategy allows easy subsequent enlargement of these nanostructures by Ni-catalyzed cross-coupling and final cyclodehydrogenation reactions.

Stapled helical -OPE foldamers as new circularly polarized luminescence emitters based on carbophilic interactions with Ag(i)-sensitivity.

-Oligo(phenylene)ethynylenes (-OPEs) stapled with enantiopure 2,3-dihydroxybutane diethers have highly intense circular dichroism (CD) spectra and excellent circular polarized luminescence (CPL) responses ( values up to 1.1 × 10), which are consistent with homochiral helically folded structures. In the presence of Ag(i), a change in the CPL emission is observed, representing the first example of CPL active small organic molecular emitters, which can be modulated by carbophilic interactions in a reversible manner.

Photophysics of a Live-Cell-Marker, Red Silicon-Substituted Xanthene Dye.

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.

New Dual Fluorescent Probe for Simultaneous Biothiol and Phosphate Bioimaging.

The simultaneous detection of relevant metabolites in living organisms by using one molecule introduces an approach to understanding the relationships between these metabolites in healthy and deregulated cells. Fluorescent probes of low toxicity are remarkable tools for this type of analysis of biological systems in vivo. As a proof of concept, different naturally occurring compounds, such as biothiols and phosphate anions, were the focus for this work.

Rational design of a new fluorescent 'ON/OFF' xanthene dye for phosphate detection in live cells.

A new fluorescein derivative with ON/OFF features, 9-[1-(4-tert-butyl-2-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (Granada Green, GG), was designed and synthesised. The new dye has spectral characteristics similar to those of other xanthenic derivatives but shows a higher pK(a) value for the equilibrium between its neutral and anionic forms. In addition, GG undergoes the same phosphate-mediated excited state proton transfer (ESPT) reaction as other xanthenic derivatives, giving rise to fluorescence decay traces that are dependent on both the phosphate concentration and pH of the medium.

Fluorescence enhancement of a fluorescein derivative upon adsorption on cellulose.

9-[1-(2-Methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (2-Me-4-OMe TG) is a fluorescein derivative dye whose photophysical properties show a remarkable pH dependence. In aqueous solution the fluorescence quantum yield (Φf) of its anionic species is nearly a hundred times higher than that of its neutral species. Such a large difference in Φf makes 2-Me-4-OMe TG useful as an "on-off" pH indicator.

8-HaloBODIPYs and their 8-(C, N, O, S) substituted analogues: solvent dependent UV-vis spectroscopy, variable temperature NMR, crystal structure determination, and quantum chemical calculations.

The UV-vis electronic absorption and fluorescence emission properties of 8-halogenated (Cl, Br, I) difluoroboron dipyrrin (or 8-haloBODIPY) dyes and their 8-(C, N, O, S) substituted analogues are reported. The nature of the meso-substituent has a significant influence on the spectral band positions, the fluorescence quantum yields, and lifetimes. As a function of the solvent, the spectral maxima of all the investigated dyes are located within a limited wavelength range.

Synthesis and photophysics of a new family of fluorescent 9-alkyl-substituted xanthenones.

9-Alkyl xanthenones with different aliphatic pendant groups have been easily prepared by means of nucleophilic addition of the corresponding Grignard derivative to a tert-butyldimethylsilyl ether (TBDMS)-protected 3,6-dihydroxy-xanthenone. The photophysical behavior of the new dyes has been explored by using absorption, steady-state-, and time-resolved fluorescence measurements. We determined the equilibrium constants, visible spectral characteristics, fluorescence quantum yield, and decay times.

Real-time phosphate sensing in living cells using fluorescence lifetime imaging microscopy (FLIM).

Phosphate ions play important roles in signal transduction and energy storage in biological systems. However, robust chemical sensors capable of real-time quantification of phosphate anions in live cells have not been developed. The fluorescein derivative dye 9-[1-(2-methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (2-Me-4-OMe TG) exhibits the characteristic excited-state proton-transfer (ESPT) reaction of xanthenic derivatives at approximately physiological pH resulting in the dependence of the dye's nanosecond fluorescence decay time on the phosphate buffer concentration.

Visible absorption and fluorescence spectroscopy of conformationally constrained, annulated BODIPY dyes.

Six conformationally restricted BODIPY dyes with fused carbocycles were synthesized to study the effect of conformational mobility on their visible electronic absorption and fluorescence properties. The symmetrically disubstituted compounds (2, 6) have bathochromically shifted absorption and fluorescence spectral maxima compared to those of the respective asymmetrically monosubstituted dyes (1, 5). Fusion of conjugation extending rings to the α,β-positions of the BODIPY core is an especially effective method for the construction of boron dipyrromethene dyes absorbing and emitting at longer wavelengths.

Effects of the anion salt nature on the rate constants of the aqueous proton exchange reactions.

The proton-transfer ground-state rate constants of the xanthenic dye 9-[1-(2-methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II), recovered by Fluorescence Lifetime Correlation Spectroscopy (FLCS), have proven to be useful to quantitatively reflect specific cation effects in aqueous solutions (J. M. Paredes, L.

Photophysics of the interaction between a fluorescein derivative and Ficoll.

Ficoll has been widely used as a crowding agent to mimic intracellular media because it is believed to be noninteracting and is composed of mixed sizes such that smaller and larger diffusing solutes can be studied. Due to the interest that the fluorescent dye 9-[1-(2-methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II) as a fluorometric probe of phosphate ions in intracellular media could generate, we describe the spectral characteristics of the system TG-II-Ficoll in aqueous solution by means of absorption spectroscopy, steady-state fluorescence, time-resolved fluorescence, time-resolved emission spectroscopy, and fluorescence lifetime correlation spectroscopy. The spectral characteristics found are consistent with the formation of an adsorption complex on the surface of Ficoll, probably due to hydrogen bonding between TG-II and Ficoll.

Rational design, synthesis, and spectroscopic and photophysical properties of a visible-light-excitable, ratiometric, fluorescent near-neutral pH indicator based on BODIPY.

A visible-light-excitable, ratiometric, brightly fluorescent pH indicator for measurements in the pH range 5-7 has been designed and synthesized by conjugatively linking the BODIPY fluorophore at the 3-position to the pH-sensitive ligand imidazole through an ethenyl bridge. The probe is available as cell membrane permeable methyl ester 8-(4-carbomethoxyphenyl)-4,4-difluoro-3-[2-(1H-imidazol-4-yl)ethenyl]-1,5,7-trimethyl-3a,4a-diaza-4-bora-s-indacene (I) and corresponding water-soluble sodium carboxylate, sodium 8-(4-carboxylatophenyl)-4,4-difluoro-3-[2-(1H-imidazol-4-yl)ethenyl]-1,5,7-trimethyl-3a,4a-diaza-4-bora-s-indacene (II). The fluorescence quantum yield Φ(f) of ester I is very high (0.

Dynamics of water-in-oil nanoemulsions revealed by fluorescence lifetime correlation spectroscopy.

The size, diffusional properties, and dynamics of reverse water-in-oil nanoemulsions, or reverse micelles (RMs), have been widely investigated because of interest in this system as a model for biological compartmentalization. Here, we have employed fluorescence lifetime correlation spectroscopy (FLCS) to reveal the dynamics and sizes of aerosol-OT (AOT)/isooctane RMs using a fluorescent xanthene derivative called Tokyo Green II (TG-II). The dye undergoes a partition and a shift in its tautomeric equilibrium such that the TG-II anion remains in the inner micellar aqueous core, and the neutral quinoid form lies in the interfacial region.