Water-soluble fluorescent boronic acid compounds for saccharide sensing: substituent effects on their fluorescence properties

Four new naphthalene-based boronic acid compounds (1-4) were synthesized. The effect of various carbohydrates on their fluorescence properties has been studied in aqueous phosphate buffer at pH 7.4. Different substitutions on the aniline group of the naphthalene ring resulted in significant differences in fluorescence properties for these four compounds. Compound 1 shows ratiometric fluorescence changes upon addition of a sugar. Compounds 2 and 3 do not show ratiometric fluorescence changes but show very large fluorescence intensity changes (about 70-fold fluorescence intensity increase). In addition to the quantifiable fluorescence property changes upon sugar addition, the fluorescence color changes of 1-3 are also visible to the naked eye. However, amidation of the aniline nitrogen atom significantly diminishes the fluorescence intensity of compound 4. The crystal structure of one boronic acid provided some insight into the structural features that are important for the fluorescence properties of these compounds.     

双光子荧光探针研究及其应用

双光子荧光显微成像兼具诸如近红外激发、暗场成像、避免荧光漂白和光致毒、定靶激发、高横向分辨率与纵向分辨率、降低生物组织吸光系数及降低组织自发荧光干扰等特点而显著地优于单光子荧光显微成像,为生命科学研究提供了更为锐利的工具。而用于像离子的含量及其对生理的影响、离子参与的生理活动机制、离子与分子的作用、特定分子的分布及其相互作用等方面研究的双光子荧光探针,是实现成像的关键。双光子荧光探针的研究旨在促进双光子荧光显微镜应用的发展,促进生命科学、医学科学的快速发展,同时也带动双光子荧光探针所隶属的化学这一学科的发展。因此对双光子荧光探针的研究具有重要的理论和实践意义。该文综述了双光子荧光显微成像的优点、双光子荧光探针设计的原理及双光子荧光探针在离子分析方面的应用,并展望了这类荧光探针的发展趋势与应用前景。     

Fluorescence and photodissociation of rhodamine 575 cations in a quadrupole ion trap

The fluorescence and photodissociation of rhodamine 575 cations confined to a quadrupole ion trap are observed during laser irradiation at 488 nm. The kinetics of photodissociation is measured by time-dependent mass spectra and time-dependent fluorescence. The rhodamine ion signal and fluorescence decay are studied as functions of buffer gas pressure, laser fluence, and irradiation time. The decay rates of the ions in the mass spectra agree with decay rates of the fluorescence. Some of the fragment ions also fluoresce and further dissociate. The photodissociation rate is found to depend on the incident laser fluence and buffer gas pressure. The implications of rapid absorption/fluorescence cycling for photodissociation of dye-labeled biomolecular ions under continuous irradiation are discussed.     

Synchronous Fluorescence Spectra of Hemoglobin: A Study of Aggregation States in Aqueous Solutions

The synchronous fluorescence spectra of hemoglobin solutions are reported for the first time. The main fluorescence peaks observed in the spectra are assigned. The effect of the concentration of hemoglobin solution on the spectra is studied. Characteristic fluorescence peaks due to the dimer and tetramer of hemoglobin molecules are recognized.     

FLUORESCENCE DECAY KINETICS and CHARACTERISTICS OF BIMOLECULAR EXCITON ANNIHILATION IN CHLOROPLASTS

Abstract— The decay profiles of the fluorescence of dark-adapted spinach chloroplasts (0^A°C) excited with single 30 ps 532 nm laser pulses of varying intensities were measured with a low-jitter streak camera system. By comparing the decay profiles of the fluorescence at low and high laser fluences, i.e. in the absence and presence, respectively, of dynamic bimolecular exciton-exciton annihilation effects, the duration of such dynamic annihilation events can be estimated. A simple model suggests that the influence of bimolecular annihilation events on the fluorescence decay kinetics should disappear within a time interval corresponding to the low intensity, unimolecular lifetime of the exciton population which is subject to exciton-exciton annihilation. The low intensity fluorescence decay profiles are characterized by three to four lifetimes (Reviewed by A. R. Holzwarth, Photochem. Photobiol. 43,707–725, 1986); it is shown here that only the shortest fluorescence components are subject to exciton annihilation, since the kinetics of the fluorescence decay are influenced by annihilations only within the initial 150–200 ps time interval after the excitation pulse. The amplitudes (but not the decay kinetics) of the longer-lived fluorescence components are decreased at high levels of laser pulse excitations, suggesting that these components are derived from the shorter-lived fluorescence decay components. The implications of these results are*discussed within the contexts of current models of the fluorescence in chloroplasts.     

Calculation of the contribution of scattering effects to X-ray fluorescence intensity for coating samples

Theoretical equations to calculate fluorescence intensity enhanced by scattering effects for coating samples were developed based on fundamental parameter models. The secondary enhancement by scattering radiation from the same layer or between layer and substrate and the primary fluorescence that was scattered into the direction of detector by atoms in layer and substrate were included in calculations. The contributions of different scattering effects to fluorescence intensity were calculated for a hypothetical Zn coating on infinite Fe substrate sample. The results show that the contributions of scattering effects to fluorescence intensity are related to the thickness of coating and are up to several percents of primary fluorescence intensity.     

对几种氨基甲酸酯类农药的荧光特性研究

研究了有机物分子结构与荧光产生之间的关系。利用这一理论分析了西维因、克百威、残杀威等几种常用的氨基甲酸酯类农药的分子结构并揭示了它们的荧光光学特性,从而确定了氨基甲酸酯类农药产生荧光的特性,为进一步利用荧光分析法对氨基甲酸酯类农药进行检测提供理论依据。并且利用稳态荧光光谱仪对西维因和克百威标准溶液进行了荧光光谱实验,结果表明,氨基甲酸酯类农药在一定的溶剂条件下是能够受激发荧光的,是可以利用荧光光谱分析法来对它们进行检测．     

Coupling of narrow-bore liquid chromatography to thin-layer chromatography : Part 2. Application of fluorescence-based spectroscopic techniques for off-line detection

The effluent from a narrow-bore liquid chromatographic (l.c.) separation can be immobilized on thin-layer chromatographic (t.l.c.) plates with little loss of resolution. The deposited compounds are then available for further inspection. For off-line detection, direct fluorescence emission, fluorescence excitation emission spectra, and fluorescence line-narrowing spectroscopy are investigated with tetracene and benz[k] fluoranthene as model compounds. Detection based on direct emission measurements and on measurements for which complete spectra are obtained for the separated compounds, is suitable for identification and determination. Detection limits are of the same order of magnitude as those for on-line detection in narrow-bore l.c. The fluorescence spectra of immobilized compounds can be obtained with a conventional fluorescence spectrometer equipped with a solid-sample accessory. No other special apparatus is needed. The immobilized chromatogram is also suitable for techniques incompatible with flow systems, e.g., fluorescence line-narrowing spectroscopy, which yields fluorescence spectra via laser excitation of low-temperature solid samples. Very selective narrow-line fluorescence spectra were obtained for tetracene deposited on t.l.c. plates in amounts down to the low picogram level.     

两种不同光谱类型的R-藻红蛋白的荧光性质研究

红藻中的R-藻红蛋白(R-PE)依照其吸收光谱可分为两种不同的光谱类型,即“双峰型”和“三峰型”。本文通过对不同pH条件下的R-PE的荧光光谱及荧光寿命的研究,发现“三峰型”R-PE的pH稳定范围较“双峰型”R-PE大。在R-PE浓度对荧光光谱的影响实验中,随着蛋白浓度的增加,荧光峰位置逐渐红移。荧光寿命逐渐增大,荧光强度先行增加而后减弱。用碘离子对其荧光进行猝灭,随着碘离子浓度的增大,荧光强度逐渐降低,荧光寿命逐渐缩短,并服从Stem-Volmer规则。     

Fluorescence of the DNA double helix (dA)20 x (dT)20 studied by femtosecond spectroscopy--effect of the duplex size on the properties of the excited states

The fluorescence of the DNA double-stranded oligomer (dA)20 x (dT)20 is studied at room temperature by fluorescence up-conversion at times shorter than 10 ps. The profile of the up-conversion spectra is similar to that of the steady-state fluorescence spectrum, showing that the majority of the photons are emitted within the probed time scale. At all the probed wavelengths, the fluorescence decays are slower than those of the monomeric chromophores dAMP and TMP. The fluorescence anisotropy decays show strong wavelength dependence. These data allow us to conclude that energy transfer takes place in this double helix and that this process involves exciton states. The spectral and dynamical properties of the oligomer are compared to those of the polymer poly(dA) x poly(dT), composed of about 2000 base pairs, reported previously. The oligomer absorption spectrum is characterized by a smaller hypsochromic shift and weaker hypochromism compared to the polymer. Moreover, the fluorescence decays of (dA)20 x (dT)20 are twice as fast as those of poly(dA) x poly(dT), and its fluorescence anisotropy decays more slowly. These differences are the fingerprints of a larger delocalization of the excited states induced by an increase in the size of the duplex.     

Photophysics of Indocarbocyanine Dyes in Organic Solvents

The absorption and fluorescence properties of a series of 18 indocarbocyanine dyes in organic solvents have been determined. The wavelengths of the absorption and fluorescence maxima, the fluorescence lifetimes and the fluorescence quantum yields relative to the benzo-15-crown-5-substituted phthalocyanine have been measured. The results are discussed in relation to the molecular structures or the dye studied.     

Stimulated fluorescence and fluorescence quenching in chlorophyll a and bacteriochlorophyll a

This communication deals with the photophysical processes that take place in chlorophyll solutions under intense nitrogen laser irradiation. The effect of the pump photon density on the fluorescence yield depends strongly on the geometry of the irradiation and the sampling set-up. If the fluorescence cell and sampling probe are placed close to the transverse arrangement used for obtaining laser output, line narrowing and gain, which are processes associated with high population inversions and stimulated fluorescence, are observed. A normal fluorescence spectrum and a decrease in fluorescence quantum yield with increasing pump power are observed in the fluorescence cells in oriented at an angle of 20–40° with respect to the transverse axis of the exciting beam. The decrease in quantum yield appears to result from absorption of the pump photons by the excited singlet of the chlorophylls, and it is suggested that an analogous mechanism may be responsible for the anomalous fluorescence quantum yield reported for in in vivo Chlorella vulgaris algae.     

Fluorescence study of fullerene in organic solvents at room temperature

At room temperature, fluorescence spectra for C60 in organic solvents of four typical kinds have been reported, which indicate that intensity of fluorescence and fine structure of fluorescence peaks are dependent on the interaction between C60 and solvent. It is shown that the solvents of effective electron donors could make a comparatively strong interaction with fullerenes due to formation of the charge transfer adduct, which could greatly distort the molecular symmetry, leading to the strong and well-resolved fluorescence. The strong fluorescence spectra for C70 in room temperature solutions are also observed.     

Localisation and accumulation of a new carotenoporphyrin in two primary tumour models

We have investigated the tumour-localising properties and in vivo fluorescence kinetics of a hexamethoxylated carotenqporphyrin (CP6) in two primary tumour models: UV-B-induced early skin cancer in hairless mice and chemically induced mucosal dysplasia in the rat palate. CP6 fluorescence kinetics are investigated by measuring in vivo fluorescence spectra and images of the mouse skin and the rat palate at different time points after injection. For the tumour-localising properties, microscopic phase-contrast and fluorescence images are recorded. The in vivo fluorescence kinetics in the mouse skin show localization of CP6 in the tumours. However, fluorescence microscopy images show that CP6 localises in the dermis and structures that are not related to the malignant transformation of the mouse skin. The fluorescence kinetics in the rat palate show a significant correlation between the degree of malignancy and the CP6 fluorescence build-up time in the palate. The microscopic images show that CP6 fluorescence localises in the connective tissue and not in the dysplastic epithelium. In conclusion, CP6 does not localise preferentially in (pre-) cancerous tissue in the two primary tumour models studied here, in contrast to reports about localisation of carotenoporphyrins in transplanted tumours. However, the CP6 build-up time in rat palates correlates with the degree of malignancy and this might possibly be a useful parameter in tumour detection.     

New asymmetric monomethine cyanine dyes for nucleic-acid labelling: absorption and fluorescence spectral characteristics

Absorption spectra and fluorescence properties of a series of newly synthesized asymmetric monomethine cyanine dyes are studied. The dyes carry one or two positive charges. They are devoid of their own fluorescence in solution and become fluorescent upon binding to nucleic acids only. The fluorescence maxima of the new dyes are localized between 530 and 650 nm. The wavelength and intensity of fluorescence are dependent on molecular structure of the dye, type of nucleic acid and the concentration of both nucleic acid and salts. Some of the dyes are capable of distinguishing between single-stranded and double-stranded (ds) polynucleotides giving fluorescence maxima localized at different wavelengths. Detection threshold for dsDNA for most of the dyes is comparable to that of ethidium bromide. The sensitivity of the dye-dsDNA complexes to NaCl concentrations show that the new dyes interact with dsDNA by both intercalation and electrostatically.     

FLUORESCENCE AND ELECTROGENERATED CHEMILUMINESCENCE STUDIES OF SEVERAL DIMETHYL-SUBSTITUTED BENZO[a]PYRENES

Abstract— Absorption spectra, molar absorptivities, fluorescence spectra and fluorescence quantum yields of five dimethylbenzo[a]pyrenes (DMBP) in benzene solutions at room temperature are reported. Electrogenerated chemiluminescence (ecl) spectra and the relative eel intensities of these compounds to that of 9,10-diphenylanthracene in the 1:1 acetonitrile-benzene mixed solvent with tetra- n -butyl-ammonium perchlorate as a supporting electrolyte are also reported. Both fluorescence quantum yield and ecl intensity studies show that the vicinal dimethyl substitution lowers the fluorescence and eel efficiency, and this effect is more pronounced in a compound whose K-region is blocked. The compounds in which the L-region is blocked showed much higher fluorescence and eel efficiency. The fluorescence of DMBP molecules is quenched by the donor molecule, tri- p -tolylamine with a diffusion controlled rate to form an emitting exciplex. The cation radical of TPTA and the radical anion of the DMBPs are shown to form an exciplex efficiently by the eel experiments. Both quenching and eel results indicate that all DMBPs studied here are good acceptors.     

Complex formation between tryptophan-containing peptides and nucleic acids: Fluorescence decay studies using synchrotron radiation

Synchrotron radiation has been used to determine the fluorescence decay parameters of a tryptophan-containing oligopeptide, Lys-Trp-Lys, bound to nucleic acids. All fluorescence decay curves can be fitted by a sum of two exponentials. The two lifetimes very likely correspond to two conformational states of the oligopeptide. The mean fluorescence lifetime of the peptide is not markedly affected upon binding to nucleic acids even though the fluorescence quantum yield is strongly reduced. A model is presented that accounts for the existing fluorescence data: two consecutive complexes are formed both involving electrostatic interactions. In one of the complexes the tryptophyl ring is stacked with the nucleic acid bases and its fluorescence is completely quenched. The other complex emits a fluorescence having characteristics which are similar to those of the free peptide.     

疏水作用对光化学和光物理过程的影响 Ⅶ.芘基烷基酮的荧光光谱及其在不良溶剂中的簇集

溶剂的极性对芘基烷基酮的单体荧光和激基缔合物荧光有很大影响,在非极性溶剂中单体荧光很弱,随着溶剂极性增大,单体荧光增强,单体荧光和激基缔合物荧光明显红移。利用芘基烷基酮荧光的这些性质研究了长链分子在二甲基亚砜-水(DMSO-H₂O)中的簇集现象。在浓度非常低的情况下,长链芘基烷基酮发射激基缔合物荧光,单体荧光也明显蓝移,表明芘基烷基酮形成了簇集体。长链饱和烷烃和芘基烷基酮发生共簇集,簇集体内的极性比环己烷的极性稍大。     

Monitoring dynamic systems with multiparameter fluorescence imaging

A new general strategy based on the use of multiparameter fluorescence detection (MFD) to register and quantitatively analyse fluorescence images is introduced. Multiparameter fluorescence imaging (MFDi) uses pulsed excitation, time-correlated single-photon counting and a special pixel clock to simultaneously monitor the changes in the eight-dimensional fluorescence information (fundamental anisotropy, fluorescence lifetime, fluorescence intensity, time, excitation spectrum, fluorescence spectrum, fluorescence quantum yield, distance between fluorophores) in real time. The three spatial coordinates are also stored. The most statistically efficient techniques known from single-molecule spectroscopy are used to estimate fluorescence parameters of interest for all pixels, not just for the regions of interest. Their statistical significance is judged from a stack of two-dimensional histograms. In this way, specific pixels can be selected for subsequent pixel-based subensemble analysis in order to improve the statistical accuracy of the parameters estimated. MFDi avoids the need for sequential measurements, because the registered data allow one to perform many analysis techniques, such as fluorescence-intensity distribution analysis (FIDA) and fluorescence correlation spectroscopy (FCS), in an off-line mode. The limitations of FCS for counting molecules and monitoring dynamics are discussed. To demonstrate the ability of our technique, we analysed two systems: (i) interactions of the fluorescent dye Rhodamine 110 inside and outside of a glutathione sepharose bead, and (ii) microtubule dynamics in live yeast cells of Schizosaccharomyces pombe using a fusion protein of Green Fluorescent Protein (GFP) with Minichromosome Altered Loss Protein 3 (Mal3), which is involved in the dynamic cycle of polymerising and depolymerising microtubules.