Study on the Synthesis and Spectra of a Novel Kind of Carbozole Benzothiazole Indole Styryl Cyanine Dye with a Carbazole Bridged Chain

Based on the frequently-used cyanine dye probe thiazole orange (TO) and Cy3, a novel kind of styryl cyanine dye was designed and synthesized. Carbazole was inserted into the structures of two cyanine dyes, TO and Cy3, to act as a bridge to link the benzothiazole and indole. This modification resulted in a novel kind of carbozole benzothiazole indole cyanine dye with a carbazole-bridged chain. The dyes were characterized by HNMR and MS. The spectra of the novel dyes were also studied and the results showed that the fluorescence wavelength of novel carbazole benzothiazole indole cyanine dye shifted red, the Stokes shift and Fluorescence quantum yields increased and the fluorescence intensity was enhanced compared to that of TO. These results indicated that the novel dye could be used as an excellent fluorescent probe in biological labeling.     

Fluorescence and Electronic Structure of the Laser Dye DCM in Solutions and in Polymethylmethacrylate

The photophysical properties and polarization of the fluorescence of the laser dye 4-dicyanomethylene-2-methyl-6-(p(dimethylamino)styryl)-4H-pyran (DCM) in solutions of different polarities and in polymethylmethacrylate (PMMA) at 293 and 77 K were investigated by stationary and pulsed fluorescent spectroscopy. Based on the data of polarized fluorescence, an oscillator model has been suggested, according to which the electronic absorption spectrum of DCM in the 240–500-nm range is formed by at least three electron transitions. The quantum yield of fluorescence _f increases linearly with increase in the polarity of a solvent in a toluene dimethylsulfoxide (DMSO) mixture from 0.08 (toluene) to 0.80 (DMSO). An increase of _f to 0.90 was also observed on increase in the rigidity of the medium by freezing a solution of DCM in n-propanol at 77 K or introducing of a dye to the polymeric matrix of PMMA at room temperature ( _f = 0.76). The fluorescence-decay kinetics of DCM in toluene, n-propanol, and PMMA at 293 K follows a biexponential law, whereas in n-hexane and vaseline oil at 293 K and in n-propanol at 77 K it follows a monoexponential law. The mechanisms underlying radiationless deactivation of the electron-excitation energy in solutions and in polymeric media are discussed.     

Early Detection of Breast Cancer: Synthesis and Characterization of Novel Target Specific NIR-Fluorescent Estrogen Conjugate for Molecular Optical Imaging

Estrogen induced proliferation of existing mutant cells is widely understood to be the major risk determining factor in the development of breast cancer. Hence determination of the Estrogen Receptor[ER] status is of paramount importance. We have carried out the synthesis and characterization of a novel NIR fluorescent dye conjugate aimed at measuring ER+ve status in-vivo. The conjugate was synthesized by ester formation between 17-β estradiol and a cyanine dye namely: bis-1, 1-(4-sulfobutyl) indotricarbocyanine-5-carboxylic acid, sodium salt. The replacement of the sodium ion in the ester by a larger glucosammonium ion was found to enhance the hydrophilicity and reduce the toxic effect on cell lines. The excitation and emission peaks for the dye were recorded as 750 and 788 nm respectively; ideal for non-invasive optical imaging owing to minimal tissue attenuation and auto-fluorescence at these wavelengths. The dye (NIRDC1) has a significant drop in plasma-protein binding therefore leading to marked improvement in pharmacokinetic profile such as dye evacuation in comparison to ICG. In addition the dye showed enhanced fluorescence quantum yield, molar extinction coefficient and linearity in fluorescence relative to ICG. This dye can be potentially used as a target specific exogenous contrast agent in molecular optical imaging for early detection of breast cancer.     

Fluorescence Properties of Dibenzofluorescein in Aqueous Solution

The deprotonation of dibenzofluorescein (DBFL), a long wavelength fluorescence probe, results in the simultaneous occurrence of neutral form, monoanion and dianion under physiological conditions. The fluorescence properties of the former two cannot be measured directly because they are always coexistent with some other species. By measuring the fluorescence under various pHs we computed the fluorescence parameters for each species involved in the prototropic equilibria of DBFL, including each species’ emission spectrum, excitation spectrum, emission and excitation maximum, fluorescence quantum yield and lifetime. It was found that the monoanion is the most fluorescent chromospheres (Φ _f = 0.66, compared to Φ _f = 0.25 for dianion, 0.18 for cation and 0.0 for the neutral form). Together with the computed pK _as, we are able to suggest that the monoanion plays a major role under physiological conditions when DBFL is used as a fluorescence probe, contrary to the assumption in literature.     

Synthesis and Spectra of a Kind of Novel Longer-Wavelength Benzoxazole Indole Styryl Cyanine Dye with a Carbazole-Bridged Chain

Based on cyanine dye probe oxazole yellow (YO) and Cy₃, a series of novel styryl cyanine dyes were designed and synthesized. Carbazole was inserted into the structures of YO and Cy₃ to act as a bridge to link the benzoxazole and indole group. This modification resulted in a novel kind of benzoxazole indole styryl cyanine dye with a carbazole-bridged chain. The dyes were characterized by ¹HNMR and MS. The spectra of the novel dyes were also performed and the results showed that the maximum emission wavelength of the carbazole styryl cyanine dye was shifted red, the Stokes shift increased and the fluorescence intensity enhanced compared with those of YO and Cy₃. These results indicated that the novel dye could be used as an excellent fluorescent probe in biological labeling.     

Obviously Enhanced Fluorescent Signal of Core-Shell Nanostructures through Simultaneous Regulation of Spectral Overlap and Shell Thickness for Imaging and Photothermal Therapy of Ovarian Cancer Cells

In this research, by simultaneously regulating the two major factors affecting the plasmonic enhanced fluorescence (PEF), spectral overlap and the distance between the fluororophores and the noble metal nanoparticles, a significantly enhanced fluorescent signal is achieved. Core-shell nanostructures composed of aspect ratio (AR) adjustable gold nanorods (GNRs) and various thickness of SiO₂ are prepared and the decorated fluorophores are realized optimized PEF. A typical stimuli-responsive conjugated polymer, polydiacetylene (PDA), and a near-infrared (NIR) dye Cy5.5 are selected as fluorophores and their fluorescent signal are enhanced 7.26 and 4.41 times, respectively. Based on the optimized optical properties, a multifunctional antibody modified Mab-Cy5.5-GNRs@SiO₂ is successfully demonstrated the targeting, imaging, and photothermal therapy (PTT) effects on SKOV-3 ovarian cancer cells.     

Fluorescence spectroscopy of potential electroluminescent materials: Substituent effects on DSB and segmented PPV derivatives

The absorption and fluorescence of substituted distyrylbenzene (DSB) derivatives and segmented poly(phenylene vinylene) (PPV) derivatives are characterized by long-wavelength absorption maxima and absorption coefficients of λ_a = 380–450 nm, ε = 20,000–60,000 M⁻¹ cm¹ and fluorescence maxima, quantum yields, and decay times of λ_r = 440–530 nm, Φ_f = 0.2–0.9, and Τ = 0.8–2.5 ns, respectively. Alkoxy substituents at the central phenylene ring of DSB groups increase the bathochromic shift in the spectra in comparison to DSB, without a significant decrease in the high DSB fluorescence quantum yield. Both phenyl and cyano substitutions at the vinylene bridge lead to a further bathochromic shift of the fluorescence and a decrease in the quantum yield to ca. 0.4. The DSB derivatives and the related segmented PPV derivatives show nearly the same absorption spectra, fluorescence spectra, and radiative rate constantsk _f= Φ_f/Τ, indicating the efficacy of the segmentation of the polymer chain. The radiative rate constants determined by the Φ_f and Τ values and by the Strickler/Berg formula are in reasonable agreement. This supports the possibility of interpreting the properties of the polymers in terms of their DSB units. The decrease in the emission anisotropy can be ascribed to multistep energy transfer processes between different oriented segments.     

Mechanisms of Fluorescence Quenching in Donor—Acceptor Labeled Antibody—Antigen Conjugates

The cyanine dyes Cy5 and Cy5.5 are presented as a new long wavelength-excitable donor-acceptor dye pair for homogeneous fluoroimmunoassays. The deactivation pathways responsible for the quenching of the fluorescence of the antibody-bound donor are elucidated. Upon binding of the donor dye to the antibodies at low dye/protein ratios, its fluorescence quantum yield rises to unity. Higher dye/protein ratios lead to progressive aggregation of the dyes, which results in quenching of monomer fluorescence due to resonance energy transfer (RET) from the monomers to the nonfluorescent dimers. The dependence of the quenching efficiency on the labeling ratio is described quantitatively by assuming a Poisson distribution of the dyes over the antibodies. The maximum fluorescence intensity per antibody is obtained at a labeling ratio of 4. Upon formation of the antibody-antigen complex, electron transfer and RET to the antigen-bound acceptor dye occur. Steady-state and time-resolved fluorescence measurements reveal that approximately 50% of the donor quenching is due to RET, while the residual quenching effect is caused by the static quenching process.     

Cy3B™: Improving the Performance of Cyanine Dyes

The spectral properties of a rigidified trimethine cyanine dye, Cy3B have been characterised. This probe has excellent fluorescent properties, good water solubility and can be bioconjugated. The emission properties of this fluorophore have also been investigated upon conjugation to an antibody. This study compared the conjugated emission properties of Cy3B with other commercially available fluorophores emitting at similar wavelengths.     

Electronic absorption and emission spectral data and fluorescence quantum yields of bridgedp-oligophenylenes,bi- to deciphenyls,and related furans and carbazoles

Absorption and fluorescence emission spectral data, as well as fluorescence quantum yields (_f), were determined for 41p-oligophenylene compounds containing 2–6, 8, and 10 benzene rings. Of 29 compounds containing carbon-bridged rings (fluorenes), 28 were dialkylated on each bridge for improved solubility and photostability. Absorption maxima for oligophenylenes were observed at wavelengths as long as 366 nm, emission maxima to 437 nm, and molar extinction coefficients () as large as 153,000 L/mol-cm; all three exceeded predicted maximum values for the corresponding unbridged oligophenylenes. The substitution of furan for benzene or carbazole for a fluorene (two examples each) bathochromically shifted absorption and emission maxima. Dialkylated carbon bridges bathochromically shifted absorption and emission maxima, and lowered _f in biphenyl and in one terphenyl analogue, but appeared to cause no diminution of _f in higher oligophenylenes. Bis(2-methoxyethyl) substitution on the bridges, incorporated to provide solubility in polar solvents, lowered _f in all examples. Tertiary alkyl substituents on terminal rings bathochromically shifted the absorption and emission maxima and generally increased _f. The loose bolt effect, which lowers _f in mononuclear substituted benzenes, may operate in 9,9-dialkylfluorenes, but not in 2,7-di-t-butylfluorene or in higher oligophenylenes. Cyclic ether and methoxy substituents as auxofluors on terminal rings generally bathochromically shifted absorption and emission maxima and increased and _f. Cyano substituents bathochromically shifted absorption and emission maxima, and increased , but lowered _f slightly.     

Photophysical Characterization of New 3-Amino and 3-Acetamido BODIPY Dyes with Solvent Sensitive Properties

The structural, electronic and photophysical properties of three new asymmetric, highly fluorescent difluoroborondipyrromethene (BODIPY) dyes, bearing an amino or an acetamido group at position 3 of the chromophoric core, have been studied in different apolar, polar and polar/protic solvents. The presence of the 3-amido group extents the delocalization of the π-system, leading to bathochromic shifts in the absorption and fluorescence bands, as predicted by quantum mechanic calculations. The 3-amino dye shows photophysical properties highly dependent on the solvent polarity and acidity, and is characterized by a hypsochromic shift of its absorption band, with regard to the corresponding acetylated dye, as well as a low fluorescence quantum yield in acid media with proton concentration lower than 4 × 10⁻⁴ M. In media with higher proton concentration, the BF₂ bridge group of the 3-amino dye is removed, yielding the corresponding non-fluorescent dipyrromethene precursor. These results suggest that the 3-amino dye could be used as a fluorescence probe for the study of the acidity of different environments.     

Thermal lens technique to evaluate the fluorescence quantum yield of a schiff base

The fluorescence spectrum of the schiff base obtained from salicylaldehyde and 2-aminophenol is studied using an argon-ion laser as the excitation source and its fluorescence quantum yield (Q_f) is determined using a thermal lens method. This is a nondestructive technique that gives the absolute value of Q_f without the need for a fluorescence standard. The quantum-yield values are calculated for various concentrations of the solution in chloroform and also for various excitation wavelengths. The value of Q_f is relatively high, and is concentration dependent. The maximum value of Q_f obtained is nearly 0.78. The high value of the fluorescence quantum yield will render the schiff base useful as a fluorescent marker for biological applications. Photostability and gain studies will assess its suitability as a laser dye. PACS 42.55.Mv; 42.62.Cf; 42.62.Fi; 42.70.Hj     

Nucleobase-Specific Enhancement of Cy3 Fluorescence

We report on the role of dye–nucleobase interactions on the photophysical properties of the indocarbocyanine Cy3. The fluorescence efficiency and lifetime of Cy3 increase in the presence of all four nucleoside monophosphates. This behavior correlates with an increase in the activation energy for photoisomerization and a ∼4 nm red shift in the fluorescence spectrum. Changes are more dramatic for the purines (dAMP, dGMP) than the pyrimidines (dCMP, dTMP), and for the nonsulfonated cyanine (DiIC₂(3)) than the sulfonated dye (Cy3–SE). These results are consistent with a model in which Cy3–nucleoside π–π interactions decrease the efficiency of photoisomerization, increasing the efficiency of fluorescence. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fluorescence Characteristics of Variously Charged Asymmetric Monomethine Cyanine Dyes in the Presence of Nucleic Acids

Three asymmetric monomethine cyanine dyes bearing one, two, and three positive charges have been synthesized, and their absorption and fluorescence characteristics in the presence of nucleic acids were studied. The maxima of their longest wavelength absorption band lie between 500 and 520 nm. The dyes do not show fluorescence of their own in TE buffer (pH = 7.5), but become strongly fluorescent (Q_F = 0.2–0.6) on binding to double-stranded DNA. The fluorescence maxima of the investigated dye-dsDNA complexes are in the region of 530–550 nm. The influence of the dye/DNA ratio on both the position and intensity of the fluorescence maxima of the complexes is investigated.     

Visualizing Acidophilic Microorganisms in Biofilm Communities Using Acid Stable Fluorescence Dyes

Bacteria in acidophilic biofilm communities, i.e. acid streamers and snottites, obtained from a subsurface mine in Königstein were visualized by fluorescence microscopy using four new fluorescent dyes (DY-601XL, V07-04118, V07-04146, DY-613). The pH of the bulk solution in which these bacteria thrive was pH 2.6 to 2.9. The new fluorescent dyes were all able to clearly stain and microscopically visualize in-situ the bacteria within the biofilm community without changing pH or background ion concentration. The commonly used fluorescent dyes DAPI and SYTO 59 were also applied for comparison. Both dyes, however, were not able to visualize any bacteria in-situ, since they were not stable under the very acid conditions. In addition, dye V07-04118 and dye DY-613 also possess the ability to stain larger cells which were presumably eukaryotic origin and may be attributed to yeast cells or amoeba-like cells. PCR analyses have shown that the dominant bacterial species in these acidophilic biofilm communities was a gram negative bacterium of the species Ferrovum myxofaciens. The presented four new dyes are ideal for in-situ investigations of microorganisms occurring in very acid conditions, e.g. in acidophilic biofilm communities when in parallel information on pH sensitive incorporated fluorescent heavy metals should be acquired.     

Novel,Monomeric Cyanine Dyes as Reporters for DNA Helicase Activity

The dimeric cyanine dyes, YOYO-1 and TOTO-1, are widely used as DNA probes because of their excellent fluorescent properties. They have a higher fluorescence quantum yield than ethidium homodimer, DAPI and Hoechst dyes and bind to double-stranded DNA with high affinity. However, these dyes are limited by heterogeneous staining at high dye loading, photocleavage of DNA under extended illumination, nicking of DNA, and inhibition of the activity of DNA binding enzymes. To overcome these limitations, seven novel cyanine dyes (Cyan-2, DC-21, DM, DM-1, DMB-2OH, SH-0367, SH1015-OH) were synthesized and tested for fluorescence emission, resistance to displacement by Mg²⁺, and the ability to function as reporters for DNA unwinding. Results show that Cyan-2, DM-1, SH-0367 and SH1015-OH formed highly fluorescent complexes with dsDNA. Of these, only Cyan-2 and DM-1 exhibited a large fluorescence enhancement in buffers, and were resistant to displacement by Mg²⁺. The potential of these two dyes to function as reporter molecules was evaluated using continuous fluorescence, DNA helicase assays. The rate of DNA unwinding was not significantly affected by either of these two dyes. Therefore, Cyan-2 and DM-1 form the basis for the synthesis of novel cyanine dyes with the potential to overcome the limitations of YOYO-1 and TOTO-1.     

Cooper pairing and superfluidity in the Emery model

The energy E of the system as a function of the gauge phase Φ is calculated by exact diagonalization in a two-dimensional Cu₄O₈ cluster and by the slave-boson method for large systems. It is shown that motion of carriers with charge 2e, i.e., Cooper pairs, is observed for certain values of the parameters in the Hamiltonian. This motion is identified from the onset of a characteristic maximum of E(Φ) at Φ≈Φ₀/2, where Φ₀ is the flux quantum. The phase diagram is constructed and the range of values of the model parameters where the effect is observed is determined. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 78–82 (25 January 1996)     

The optical transition in porous Si: The effects of quantum confinement,surface states and hydrogen passivation

Summary We present a theoretical study of two infinite wires of Si with a different lateral size. The analysis is based on the linear muffin tin orbitals method in the atomic sphere approximation (LMTO-ASA). We consider free, partially and totally H-covered [001] Si quantum wires with rectangular cross-section. The results of this investigation prove the quantum wire nature of porous Si and interpret many of its physical features. In particular we show thata) as expected quantum confinement originates the opening of the LDA gap;b) the gap opening effect is asymmetric: 1/3 of the widening is in the valence band, while 2/3 in the conduction band;c) the near band gap states originate from Si atoms located at the center of the wire;d) the confinement is enhanced in the case of free surfaces;e) the imaginary part of the dielectric function shows a low-energy side structure strongly anisotropic, identified as responsible of the luminescence transition;f) the presence of dangling bonds destroys the luminescence properties;g) in spite of featurec), all Si atoms are collectively involved in the luminescence transition;h) the shift detected by the Si L_{2, 3}VV Auger signal is due to H-interaction effect and is not a measure of the quantum confinement effect;i) the Si atoms probed by the Si L_{2, 3}VV Auger are bonded with H and H₂. Paper presented at the III INSEL (Incontro Nazionale sul Silicio Emettitore di Luce), Torino, 12–13 October 1995.     

Universality of Operator Ordering in Kinetic Energy Operator for Particles Moving on two Dimensional Surfaces

When the motion of a particle is constrained on the two-dimensional surface, excess terms exist in usual kinetic energy 1/(2m)∑ p _i ² with hermitian form of Cartesian momentum p _i (i = 1,2,3), and the operator ordering should be taken into account in the kinetic energy which turns out to be 1/(2m)∑ (1/f _i )p _i f _i p _i where the functions f _i are dummy factors in classical mechanics and nontrivial in quantum mechanics. The existence of non-trivial f _i shows the universality of this constraint induced operator ordering in quantum kinetic energy operator for the constraint systems.