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Abstract: In this article, we reported here an effective and selective sensing of hemoglobin (Hb) with a stilbazolium dye, HNEP+. The nature of the HNEP+/Hb interaction was examined using a combination of various spectroscopic techniques. Complexation induced selective fluorescence quenching with a large Stern–Volmer constant, K sv, the origin of which is attributed to the neutral isoelectric point (pI) of the proteins. The stoichiometry of the DNEP+:Hb was determined to be 1:2 by a Job's plot analysis, and the induced circular dichroism measurements revealed a loss of the α-helix and the unfolding of the proteins in the complex. The addition of cyclodextrin extended fluorescence lifetime, which ensured the accuracy and repeatability of the measurements. Finally, by taking advantage of a subtle change in pI and subsequently K sv of the glycated Hb, HbA1c, we suggested the possibility of a new sensing concept for HbA1c. The current investigation demonstrates that a selective optical response of a stilbazolium dye can find significant usefulness in bio-sensing applications. [Copyright &y& Elsevier]

Abstract: We describe the properties of a series of oligomeric polyfluorophores assembled on the DNA backbone. The 11 oligomers (oligodeoxyfluorosides, ODFs), 4–7 monomers in length, were composed of only two fluorescent monomers and a spacer in varied sequences, and were designed to test how fluorescent nucleobases can interact electronically to yield complexity in fluorescence emission. The monomer fluorophores were deoxyribosides of pyrene and perylene, which emit light in violet and blue wavelengths, respectively. The experiments show that simple variation in sequence and spacing can dramatically change fluorescence, yielding emission maxima ranging from 380 to 557nm and visible colors from violet to orange-red. Fluorescence lifetime data, excitation spectra, and absorption data point to a number of multi-fluorophore electronic interactions, including pyrene–pyrene and perylene–perylene excimers, pyrene–perylene exciplexes, as well as monomer dye emissions, contributing to the final spectral outcomes. Thus, two simple fluorophores can be readily combined to give emissions over much of the visible spectrum, all requiring only a single excitation. The results demonstrate that fluorescent nucleobases in oligomeric form can act cooperatively as electronic units, and that fluorophore sequence in such oligomers is as important as fluorophore composition in determining fluorescence properties. [Copyright &y& Elsevier]

The photophysics of dialkylamino- and/or pyridine-containing functional chromophores, 1,4-distyryl-2,5-bis(ethynylaryl)benzenes (cruciforms) was investigated; their fluorescence quantum yields and emissive lifetimes were determined. Depending upon their substituents, the frontier molecular orbitals (FMOs) of these cruciforms are either congruent, i.e., HOMO and LUMO occupy the same real space, or disjoint, i.e., the HOMO is located on one branch of the cruciform while the LUMO is located on the second one. Donor-acceptor substitution leads to a disjoint FMO pattern, while the parent 1,4-distyryl-2,5-bis(phenylethynyl)-benzene shows congruent FMOs. The photophysics of the cruciforms was investigated upon addition of either an excess of trifluoroacetic acid or an excess of selected metal (Mg2+, Ca2+, Mn2+, Zn2+) trifluoromethanesulfonate salts. Addition of either metal ions or protons led to analogous but not identical changes in the spectroscopic properties of the investigated cruciforms. The collected data suggest that the metals bind preferentially at the aniline nitrogen and not at the electron-rich arene. The spatially separated FMOs permit the independent manipulation of the HOMO and the LUMO of such cruciforms. If the branches contain metal-complexing moieties, metal binding leads to either a hypsochromic or a bathochromic shift in emission via interaction of the metal cations with either the HOMO or the LUMO. [ABSTRACT FROM AUTHOR]

Four 1,2-distyryl-4,5-bis(phenylethynyl)benzenes are described. A two step synthesis, a combination of Horner and Sonogashira methods is utilized. The targets and their para isomers were examined by UV–vis and fluorescence spectroscopies as well as by cyclic voltammetry. They show solvatochromic behavior and are easily oxidized if the styryl units carry dialkylamino substitutents. Single crystal structures of three derivatives have been obtained. [Copyright &y& Elsevier]

The article focuses on the study which explores the quenching properties of fluorophores assembled on a DNA backbone. According to the study, the DNA-like fluorophores as a new class of reporters and sensors which display highly diverse and tunable properties. A simple oligomer series has been constructed containing pyrene nucleoside monomers to explore the chain length on the optical properties. Information about the details of the procedure and its results is discussed.

The article presents an abstract "Reduced Fluorescence Quenching of Cyclodextrin—Acetylene Dye Rotaxanes," by Jong S. Park, James N. Wilson, Kenneth I. Hardcastle, Uwe H. F. Bunz, and Mohan Srinivasarao.

The article analyzes switching of intramolecular charge transfer in cruciforms with respect to metal ion sensing. In most, but not all, chromophores, HOMO and LUMO are spatially superimposed. However, adding donor and/or acceptor substituents to cross-shaped chromophores at suitable positions can lead to independent electronic shifts in HOMO and LUMO into opposite directions. In the cruciforms 2-4, the HOMO is located on the distyrylbenzene branch, while the LUMO is situated on the bisarylethynyl axis of the molecule. As a consequence, the intramolecular charge-transfer emission and absorption of such cruciforms is dependent upon solvent polarity. It demonstrates dramatic blue and/or red shifts of emission and absorption upon coordination of metal cations to cruciforms.

This article reports that gold nanorods, surface-functionalized with biotin, can be assembled preferentially in an end-to-end fashion upon the addition of a streptavidin linker. Commercially available biotin disulfide, EZ-Link Biotin HPDP is also applied. Other groups have used biotin-streptavidin linkers to assemble inorganic nanospheres into three-dimensional (3D) structures, and Mann's group has shown that gold nanorods coated with DNA can be similarly assembled into 3D aggregates by the addition of a complementary linker DNA. Results of the article suggest that chemical linkages can organize nanorods in a nonrandom fashion, which may be exploited for the assembly of higher-order arrays of nanomaterials.

Investigates the chiroptical properties of p-phenyleneethynylene copolymers in thin films. Decline of circularly polarized photoluminescence signal; Presentation of the dark-field micrograph of thin polymer; Increase of dimethyloctyl side chains in copolymers.

A fluorescent probe targeting the ERBB2 receptor tyrosine was designed, synthesized and evaluated as reporter of ERBB2 dynamics in overexpressing BT474, i.e. Her2(+), cells. Two cyanoquinazoline ( CQ ) probes modeled after type-I ( CQ1 ) or active state and type-II ( CQ2 ) or inactive state inhibitors were designed and synthesized with extended π systems that impart binding-induced, turn-on fluorescence. Solution spectroscopy revealed that CQ1 exhibited attractive photophysical properties and displayed turn-on emission in the presence of purified, soluble ERBB2 kinase domain, while CQ2 was found to be non-emissive, likely due to quenching via a photoinduced electron transfer mechanism. Live cell imaging with CQ1 revealed that this probe targeted an intracellular population of ERBB2, which increased following treatment with type-I inhibitors, gefinitib and canertinib, but showed no response to type-II inhibitors. CQ1 thus provides a novel means of imaging the dynamic response of ERBB2(+) cells to kinase inhibitors. [ABSTRACT FROM AUTHOR]

Three new fluorescent molecular rotors were synthesized with the aim of using them as sensors to dose thymidine phosphorylase, one of the target enzymes of 5-fluorouracil, a potent chemotherapic drug largely used in the treatment of many solid tumors, that acts by hindering the metabolism of pyrimidines. 5-Fluorouracil has a very narrow therapeutic window, in fact, its optimal dosage is strictly related to the level of its target enzymes that vary significantly among patients, and it would be of the utmost importance to have an easy and fast method to detect and quantify them. The three molecular rotors developed as TP sensors differ in the length of the alkylic spacer joining the ligand unit, a thymine moiety, and the fluorescent molecular rotor, a [4-(1-dimethylamino)phenyl]-pyridinium bromide. Their ability to trigger an optical signal upon the interaction with thymidine phosphorylase was investigated by fluorescent measurements. [ABSTRACT FROM AUTHOR]

Nine combinations of π-electron donors and acceptors were examined by UV-vis, fluorescence and 1H-NMR spectroscopy to identify π-stacked charge transfer complexes in macromolecular and supramolecular constructs. The high association constant of pyrene and naphthalene diimide suggests a preferentially π-stacking pair rationalized by frontier orbital congruence. [ABSTRACT FROM AUTHOR]

Fluorescent probes based on a 6-hydroxycarbostyril core accumulate inside neurons and astroglia in the absence of a serotonin uptake inhibitor. [ABSTRACT FROM AUTHOR]

The photoresponse of polymer field-effect transistors (PFETs) based on the 2,5-bis(dibutylaminostyryl)-1,4-phenylene-b-alkyne-b-1,4-bis(2-ethylhexyl)benzene terpolymer (BAS-PPE) is investigated. BAS-PPE is a photoluminescent conducting polymer with a band gap of 2.25 eV. The BAS-PPE PFETs were fabricated using an open coplanar configuration and light is illuminated onto the top side of the PFETs with no shadowing present. A sweep of VDS demonstrates that IDS saturation is suppressed during illumination, which suggests that pinch-off cannot be reached since the injected photogenerated carriers continue unabated. Also, with incident light, the channel cannot be turned off, even at high positive gate biases, due to the accumulation of photogenerated carriers. A sweep of VDS shows that BAS-PPE can act as a p-type polymer and favors hole injection and transport. A sweep of VGS shows an increase in IDS with different light intensities. The Ilight/Idark ratio reaches as high as about 6000 at an incident light intensity of 4 μW and a photoresponsivity of 5 mA/W is calculated. [ABSTRACT FROM AUTHOR]

In this study, a new biodegradable cross-linker agent based on fructose was reported for fabrication of brain targeted molecularly imprinted polymer (MIP). The applied strategy for targeting drug delivery was based on two mechanisms. Firstly, the magnetic structure of prepared MIP which facilitates the aggregation of carrier near target tissue under magnetic field. Second, the tendency of brain cell to use the produced fructose during degradation of MIP as fuel. In synthesis procedure magnetic fluorescent multi core shell structure MIP was prepared via co-precipitation polymerization in the presence of olanzapine as template and fructose with double acts, as monomer and cross-linker. Various kinds of in vitro and in vivo experiments were carried out to indicate the considered properties of carrier. The obtained data confirmed the designed carrier olanzapine satisfactorily meet the requirement in brain drug delivery application. [ABSTRACT FROM AUTHOR]

Perivascular adipose tissue (PVAT) reduces vasoconstriction to norepinephrine (NE). A mechanism by which PVAT could function to reduce vascular contraction is by decreasing the amount of NE to which the vessel is exposed. PVATs from male Sprague-Dawley rats were used to test the hypothesis that PVAT has a NE uptake mechanism. NE was detected by HPLC in mesenteric PVAT and isolated adipocytes. Uptake of NE (10 μM) in mesenteric PVAT was reduced by the NE transporter (NET) inhibitor nisoxetine (1 μM, 73.68 ± 7.62%, all values reported as percentages of vehicle), the 5-hydroxytryptamine transporter (SERT) inhibitor citalopram (100 nM) with the organic cation transporter 3 (OCT3) inhibitor corticosterone (100 μM, 56.18 ± 5.21%), and the NET inhibitor desipramine (10 μM) with corticosterone (100 μM, 61.18 ± 6.82%). Aortic PVAT NE uptake was reduced by corticosterone (100 μM, 53.01 ± 10.96%). Confocal imaging of mesenteric PVAT stained with 4-[4-(dimethylamino)-styrl]-N-methylpyridinium iodide (ASP+), a fluorescent substrate of cationic transporters, detected ASP+ uptake into adipocytes. ASP+ (2 μM) uptake was reduced by citalopram (100 nM, 66.68 ± 6.43%), corticosterone (100 μM, 43.49 ± 10.17%), nisoxetine (100 nM, 84.12 ± 4.24%), citalopram with corticosterone (100 nM and 100 μM, respectively, 35.75 ± 4.21%), and desipramine with corticosterone (10 and 100 μM, respectively, 50.47 ± 5.78%). NET protein was not detected in mesenteric PVAT adipocytes. Expression of Slc22a3 (OCT3 gene) mRNA and protein in PVAT adipocytes was detected by RT-PCR and immunocytochemistry, respectively. These end points support the presence of a transporter-mediated NE uptake system within PVAT with a potential mediator being OCT3. [ABSTRACT FROM AUTHOR]

The article describes arrays of self-assembled picoliter holes fabricated from poly(para-phenyleneethynylene). These holes are formed by heating self-assembled bubble arrays to 300 degree Celsius. Picoliter beakers allow isolating very small volumes of liquid or single cells and interrogating them by either electrochemical or enzymatic methods. However, the fabrication of picoliter beakers or picoliter vials is not trivial and often involves tedious photolithographic methods that are expensive and not commonly available to chemists. It was therefore of fundamental and practical interest to develop a simple nonphotolithographic access to picoliter vials.

A new optical strategy to determine the binding modes (intercalation vs groove binding) of small fluorescent organic molecules with calf thymus DNA was developed using two-photon absorption (TPA) spectroscopy. Two-photon excited emission was utilized to investigate a series of fluorescent nuclear dyes. The results show that TPA cross-sections are able to differentiate the fine details between the DNA binding modes. Groove binding molecules exhibit an enhanced TPA cross-section due to the DNA electric field induced enhancement of the transition dipole moment, while intercalative binding molecules exhibit a decrease in the TPA cross-section. Remarkably, the TPA cross-section of 4,6-bis(4-(4-methylpiperazin-1-yl)phenyl) pyrimidine is significantly enhanced (13.6-fold) upon binding with DNA. The sensitivity of our TPA methodology is compared to circular dichroism spectroscopy. TPA demonstrates superior sensitivity by more than an order of magnitude at low DNA concentrations. This methodology can be utilized to probe DNA interactions with other external molecules such as proteins, enzymes, and drugs. [ABSTRACT FROM AUTHOR]

In this study, we report the efficient identification of proteins using (6-hydroxy-2-naphthyl)ethenyl pyridinium dyes ( HNEPs). These dyes exhibited characteristic fluorescence responses, showing enhanced fluorescence with a red shift in the case of bovine serum albumin. The nature of the interaction between the dye and the protein was examined using a combination of various spectroscopic techniques. A time-dependent density functional theory analysis supported the strong environment-dependent fluorescence emission properties of the dyes. The current investigation clearly demonstrates that a selective optical response HNEPs can find potential usefulness as bio-sensing probes. [ABSTRACT FROM AUTHOR]

Fluorescent N-phenyl-4-aminoquinazoline probes targeting the ATP-binding pocket of the ERBB family of receptor tyrosine kinases are reported. Extension of the aromatic quinazoline core with fluorophore "arms" through substitution at the 6-position of the quinazoline core with phenyl, styryl, and phenylbutadienyl moieties was predicted by means of TD-DFT calculations to produce probes with tunable photoexcitation energies and excited states possessing charge-transfer character. Optical spectroscopy identified several synthesized probes that are nonemissive in aqueous solutions and exhibit emission enhancements in solvents of low polarity, suggesting good performance as turn-on fluorophores. Ligand-induced ERBB2 phosphorylation assays demonstrate that despite chemical modification to the quinazoline core these probes still function as ERBB2 inhibitors in MCF7 cells. Two probes were found to exhibit ERBB2-induced fluorescence, demonstrating the utility of these probes as turn-on, fluoroescent kinase inhibitors. [ABSTRACT FROM AUTHOR]

The photophysical properties of 4-[2-(6-hydroxy-2-naphthalenyl)-ethenyl]-1-methyl-pyridinium(HNEP+) and its deprotonatedform (NEP), a benzofused derivative of Brooker’smerocyanine (BM), were investigated through a combinedspectroscopic and computational approach. Despite their structuralsimilarities and similar pKavalues, HNEP+/NEPand BMH+/BMdiffer in the extent ofcharge delocalization in the ground and excited states. NEPexhibits the spectral characteristics of a charge transfer speciesin solvents in which BMexists in a charge-delocalizedquinoid; however, quantum chemical calculations show that the CT absorptionof NEPis not necessarily a consequence of the zwitterioniccharacter. HNEP+displays largerStokes shifts than BMH+, and NEPdemonstrates enhanced solvatochromism relative to BMas a consequence of benzofusion. [ABSTRACT FROM AUTHOR]

Abstract: ERBB receptor kinases play a crucial role in normal development and cancer malignancies. A broad range of modifications creates receptor subpopulations with distinct functional properties in live cells. Their apparent activation state, typically assayed by tyrosine phosphorylation of substrates, reflects a complex equilibrium of competing reactions. With the aim of developing optical tools to investigate ERBB populations and their state of activation, we have synthesized a fluorescent ‘turn-on’ probe, DMAQ, targeting the ERBB ATP binding pocket. Upon binding, probe emission increases due to the hydrophobic environment and restricted geometry of the ERBB2 kinase domain, facilitating the analysis of receptor states at low occupancy and without the removal of unbound probes. Cellular ERBB2 autophosphorylation is inhibited with saturation kinetics that correlate with the increase in probe fluorescence. Thus, DMAQ is an example of a new generation of ‘turn-on’ probes with potential applications in querying receptor kinase populations both in vitro and in live cells. [Copyright &y& Elsevier]

The photophysics of 1-ethyl-4,6-bis(4-methoxyphenyl)-2(1H)-pyrimidone (1) and 1-ethyl-4,6-bis(4-(dimethylamino)phenyl)-2(1H)-pyrimidone (2) were investigated to determinethe mechanisms of emission switching in response to protonation. UV–visand steady state emission spectroscopy of the protonated and unprotonatedforms across a range of solvents reveal the polarity dependence ofthe vertical excitation energies. Emission lifetimes and quantum yieldsshow the solvent dependency of the excited states. Emission enhancementswere observed in polyethylene glycol solutions and in the solid state(both thin film and single crystal), demonstrating the role of intramolecularrotation in thermal relaxation of the excited states. TD-DFT calculationsprovide insights into the excited state geometries and the role ofintramolecular charge transfer. The collected data show that emissionof diphenylpyrimidones can be modulated by four factors, includingthe identity of the electron-donating auxochrome, protonation state,solvent polarity, and viscosity. [ABSTRACT FROM AUTHOR]

On the basis of the highly stable G2H (2 : 1) ternary complex formed by two methyl viologen cation radicals inside the cavity of cucurbit[8]uril, we prepared three monocationic 4-phenylpyridinium derivatives: 1-(hydroxyethyl)-4-phenyl-pyridinium ( 1+) bromide, 1-(octaethyleneglycol)-4-phenyl-pyridinium ( 2+) chloride, and 4-[4-(methoxymethoxy)phenyl]pyridinium ( 3+) iodide, as possible guests for 2 : 1 complexation inside cucurbit[8]uril. We also investigated a fourth monocationic guest ( 4+), in which a central vinylidene group is inserted to elongate the 4-phenyl-pyridinium residue. Using 1H NMR and UV-Vis spectroscopic data and mass spectrometric data, we obtained unequivocal evidence for the formation of G2H (2 : 1) ternary complexes in all cases. The stoichiometry of the complexes was further verified by continuous variation (Job) plots, and in some cases, high resolution ESI-MS spectrometric data. Diffusion coefficient measurements, using 1H NMR pulse gradient spin echo techniques, yielded values consistent with the formation and expected structures of the ternary complexes. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

DNA-binding, green and yellow fluorescent probes with excellent brightness and high on/off ratios are reported. The probes are membrane permeable, live-cell compatible, and optimally matched to 405 nm and 514 nm laser lines, making them attractive alternatives to UV-excited and blue emissive Hoechst 33342 and DAPI nuclear stains. Their electronic structure was investigated by optical spectroscopy supported by TD-DFT calculations. DNA binding is accompanied by 27- to 75-fold emission enhancements, and linear dichroism demonstrates that one dye is a groove binder while the other intercalates into DNA. [ABSTRACT FROM AUTHOR]

Abstract: Serotonin is a monoamine serving as a chemical messenger in diverse brain regions, as well as in blood and various other organs. We synthesized six ethylamine functionalized fluorophores as fluorescent probes for serotonin. The one with best spectral properties and aqueous solubility, 6-amino-2-(2-aminoethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione, was studied in detail both in vivo and in vitro. It was shown to act as a ligand for serotonin transporter (SERT) without acute cerebral or cardiovascular toxicity or adverse effects. Fluorescent serotonin analogs can be used for direct visualization of SERT distribution and activity in live tissue. [Copyright &y& Elsevier]