We synthesized a water-soluble, long-wavelength K(+) sensor, TAC-Red, consisting of triazacryptand coupled to 3,6-bis(dimethylamino)xanthylium, whose fluorescence increased 14-fold at 0-50 mM K(+) with K(+)-to-Na(+) selectivity >30. We visualized K(+) waves in TAC-Red-stained brain cortex in mice during spreading depression, with velocity 4.4 +/- 0.5 mm/min, and K(+) release and reuptake half-times (t(1/2)) of 12 +/- 2 and 32 +/- 4 s, respectively. Aquaporin-4 (AQP4) deletion slowed K(+) reuptake about twofold, suggesting AQP4-dependent K(+) uptake by astroglia.
Sterically hindered fullerenyl chromophore dyad and triads, C 60 (>DPAF-C 9 ) x (x ) 1 and 2, respectively), in an acceptor-donor (A-D) molecular linkage of C 60 -(keto-fluorene) x were synthesized and fully characterized. Attachment of two 3,5,5-trimethylhexyl groups on C 9 of the fluorene ring moiety greatly improves their solubility and makes direct intermolecular aromatic stacking contacts more difficult. They are the first series of fullerene derivatives showing high three-photon absorptivity (3PA). Accordingly, C 60 (>DPAF-C 9 ) 2 exhibits 2PA and 3PA cross sections in the values of 0.824 × 10 -48 cm 4 s (or 82.4 GM) and 6.30 × 10 -25 cm 6 /GW 2 , respectively, in femtosecond region among the highest ones reported for many diphenylaminofluorene-derived AFX chromophores. Utilization of a keto linker located immediately between C 60 cage and fluorene chromophore moieties facilitates molecular polarization of the DPAF ring toward the C 60 cage. That may serve as the fundamental cause for correlation of enhanced A-D electron interactions to, ultimately, observed multiphoton absorption cross sections. By using nanosecond laser flash photolysis results taken at 355 nm as the reference, transient absorption data obtained from femtosecond pump-probe experiments at 800 nm unambiguously verified the occurrence of two-photon excitation processes of C 60 (>DPAF-C 9 ) in air-saturated benzene and subsequent efficient energy transfer from the two-photon pumped DPAF-C 9 moiety to the C 60 cage moiety.
Intramolecular photoinduced charge-separation and charge-recombination processes of a covalently bonded buckminsterfullerene−diphenylaminofluorene (C60−DPAF) dyad, in which the diphenylaminofluorene moiety is connected to C60 via a ketone group, have been investigated. Quenching of the fluorescence intensities and the observed short fluorescence lifetimes of the C60 moiety of the dyad in benzonitrile (PhCN) and DMF indicated that charge separation takes place via the singlet excited state of the C60 moiety at a fast rate with high efficiency. On the basis of the nanosecond transient absorption spectra, formation of the radical ion pair C60 •--DPAF•+ was confirmed in DMF; the radical ion pair decays with a lifetime of 150 ns. From the temperature dependence of the charge-recombination rate constants, the reorganization energy was evaluated to be 0.81 eV in DMF, which is reasonably small, characteristic of fullerene derivatives. On the other hand, a mixture of DPAF and C60 showed intermolecular electron transfer via the triplet state of C60 in polar solvents such as PhCN.
A class of acceptor-keto-donor structures as hindered 9,9-di(3,5,5-trimethylhexyl)-2diphenylaminofluoreno-methano [60]fullerene C 60 (>DPAF-C 9 ) and the related bisadducts C 60 (>DPAF-C 9 ) 2 and C 60 (>DPAF-C 2 ) 2 were synthesized. They are derivatives of multiphoton absorptive C 60 (>DPAF-C 2 ) showing enhanced cross-sections of simultaneous two-photon absorption under laser excitation at 800 nm in nanosecond region. Molecular synthesis of these C 60 -DPAF conjugates involved the covalent attachment of a diphenylaminofluorene moiety to methano[60]fullerene via a keto linkage for increasing molecular acceptor-donor polarization of the chromophore in conjunction with the fullerene cage. Preparation of 7-(1,2-dihydro-1,2methanofullerene[60]-61-carbonyl)-9,9-dialkyl-2-diphenylaminofluorene C 60 (>DPAF-C n ) involved cyclopropanation of C 60 with a key synthon 7-a-bromoacetyl-9,9-dialkyl-2diphenylaminofluorene. Synthesis of this synthon was achieved by a three-steps procedure starting from 2-bromofluorene via dialkylation at C 9 of the fluorene ring, attachment of a diphenylamino group at C 2 of dialkylfluorene, and Friedel-Craft acylation of the a-bromoacetyl group at C 7 of diphenylaminofluorene. All C 60 -DPAF derivatives were fully characterized with the chemical structures confirmed by various spectroscopic analyses and validated by the single-crystal structural analysis data of C 60 (>DPAF-C 2 ). Strong solvent-sensitive fluorescence quenching phenomena of C 60 (>DPAF-C 2 ), C 60 (>DPAF-C 9 ), and C 60 (>DPAF-C 9 ) 2 were noticed, showing no fluorescence band above 700 nm in more polar solvents, such as DMF, PhCN, and THF, while in less polar solvents (toluene, CHCl 3 , and CS 2 ) a fullerenyl fluorescence band at 700-710 nm was observed. It was attributed to the occurrence of electron transfer via the singlet excited state of the fullerene moiety 1 C 60 *(>DPAF-C n ) in the former group of the solvents. On the contrary, energy transfer processes from DPAF-C n moiety to the fullerene cage are favored in the latter group of the solvents.
We report the synthesis of a water-soluble, dextran-conjugated fluorescent K + sensor, TACLime dex , whose green fluorescence strongly increases with [K + ], and demonstrate its utility for assay of cellular K + transport. K + channels and K + -coupled ion transporters represent an important group of targets for drug discovery. 1-3 K + channels are involved in cardiac and neuronal excitability, epithelial fluid transport, extracellular and intracellular ionic homeostasis, and cell proliferation. 2 K + -coupled ion transporters are involved in transepithelial fluid secretion and absorption, and in cell volume regulation and ionic homeostasis. Patchclamp is the gold standard for assay of K + channel function, though technically tedious for high-throughput measurements. Radioactive Rb + uptake is generally used to assay electrically silent K + -coupled transporters such as the K + /Cl − symporter. Membrane voltage-sensing probes have also been used to assess K + channels. There is need for a robust fluorescence assay of K + transport for screening applications as an alternative to patch-clamp and radioactive Rb + .We previously introduced the long-wavelength, K + -sensitive fluorescent indicator, TAC-Red, consisting of a K + -binding triazacryptand ionophore (TAC) coupled to a red fluorescing xanthylium chromophore. 4 The K + sensing mechanism of TAC-Red, and that of a newer K + indicator TAC-Crimson, 5 involves charge-transfer quenching in which K + -triazacryptand binding prevents electron-transfer-type chromophore quenching. These dyes have bright fluorescence, excellent K + -selectivity, and millisecond response kinetics to changes in [K + ]. 4,5 However, they partition significantly into many cell types, limiting their utility as an extracellular K + sensor.After testing many chromophores and conjugation strategies, we devised a synthetic route to generate the K + sensor, TAC-Lime dex . TAC-Lime dex consists of a triazacryptand K + ionophore in direct conjugation with a green fluorescent chromophore, connected through an amide linkage to amino dextran via succinimidyl ester chemistry ( Figure 1a). The synthesis involved conversion of TACCHO 1 to the TAC-Lime (Bodipy dye) methyl ester 2 by reaction of aldehyde 1 with methyl 3-(2,4-dimethyl-1H-pyrrol-3-yl) propanoate. Oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) followed by treatment with boron trifluoride (BF 3 ) yielded the triazacryptand bodipy dye, TAC-Lime ester 2. Hydrolysis of the methyl ester and conversion of the free acids to the disuccinimidyl ester gave TAC-Lime-DiSE 3, which was reacted with amino dextran to give TAC-Lime dex . The principle of the method to assay cellular K + transport is diagrammed in Figure 2a. Control validation studies are shown in Figure 2c, with K + efflux data summarized in Figure 2d. K + efflux in HT-29 cells was relatively slow under control conditions and greatly increased by incubation with the K + /H + ionophore nigericin, which provides a rapid pathway for electroneutral K + efflux. Preincubation with a K...
Synthesis of emerald green fullerenes (EF) C60[C(CH3)(CO2Et)2]6 and C60[C(CH3)(CO2-t-Bu)2]6 was performed by using hexaanionic C60 intermediate (C60-6) as a reagent in one-pot reaction for attaching six alkyl ester addends on one C60 cage. These EF compounds exhibit intense optical absorption over 600-940 nm, the longest optical absorption of the C60 cage among many [60]fullerene derivatives synthesized.
Water-soluble oligo(ethylene glycolated) derivatives of two-photon absorptive diphenylaminofluorenocarbonyl-methano[60]fullerene, denoted as C60(>DPAF-EG6), were synthesized with their molecular self-assembly characteristics in H2O studied. The formation of nano- to submicron-sized spherical hollow vesicles with a shell width of 15-20 nm was observed by transmission electron microscopy (TEM) micrographs. This shell width fits approximately with the length of a disordered bilayer-like molecular packing of C60(>DPAF-EG6), arising from strong intermolecular hydrophobic interactions of fullerene cages. Photoinduced intramolecular charge separation followed by charge recombination on the nanosecond time scale, from the DPAF moiety to the C60 cage in the vesicle structure, was detected via transient spectroscopic measurements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.