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Fluorescence Emission (fluorescence + emission)
Terms modified by Fluorescence Emission Selected AbstractsMetal-Directed Self-Assembly: Two New Metal-Binicotinate Grid Polymeric Networks and Their Fluorescence Emission Tuned by Ligand ConfigurationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2004Benlai Wu Abstract Two new 2-D metal-binicotinate coordination polymers, namely, [CdII(bpdc)]n (1) and {[ZnII8(bpdc)8(H2O)8](H2O)8}n (2) (H2bpdc = binicotinic acid) have been synthesized using hydrothermal and three-layer diffusion methods, respectively. Single-crystal X-ray analyses revealed that both are extended grid networks of the (4,4) topology. Their structures alter with the configuration and function of bpdc. The achiral, free H2bpdc has axial chirality induced by metal coordination in 1, and bpdc connects to four metal centers forming a 2-D (4,4) net with three kinds of apertures generated through self-assembly. In 2, however, bpdc connects to three metal centers, fabricating a microporous framework containing hydrophilic channels. Studies on the solid emission spectra of the free ligand, 1, and 2 confirmed, that the configuration of bpdc resulting from metal-directed coordination has a profound effect on the fluorescence emissions of 1 and 2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Reversible Three-State Switching of Multicolor Fluorescence Emission by Multiple Stimuli Modulated FRET Processes within Thermoresponsive Polymeric Micelles,ANGEWANDTE CHEMIE, Issue 30 2010Changhua Li Micellare Verkehrsampeln: Das im Titel bezeichnete System mit resonantem Fluoreszenzenergietransfer (FRET) nutzt eine Art Donorfarbstoff und zwei Arten Akzeptorfarbstoffe. Das An- und Ausschalten der Fluoreszenz der beiden Akzeptorfarbstoffe kann über den pH-Wert bzw. Licht gesteuert werden. Dieses neuartige vielfarbige lumineszierende Polymersystem kann als ratiometrische Sonde mit einstellbarer Empfindlichkeit für pH-Wert und Temperatur fungieren. [source] Dry film microchips for miniaturised separationsELECTROPHORESIS, Issue 24 2009Rosanne M. Guijt Abstract In this work microfluidic devices were made from the dry film photoresist Ordyl SY330, characterised by optical and electron microscopy and used for electrophoretic separations. A simple and fast microfabrication process was developed for the fabrication of channels that are 50,,m wide and 30,,m in height, requiring only the use of an office laminator, a hot plate, an exposure source and mask and an electric drill to make four microdevices in less than 1,h. The optical properties of the photoresist were studied and the resist showed significant absorbance below 370,nm and 570,630,nm, and had an optical transmission of 80% between 400 and 550,nm. Fluorescence emission over the region of maximum transmission was low allowing these devices to be used for fluorescence detection at 488/512,nm. Electrophoretic separation of APTS and three derivatised sugars was performed in 20,mM phosphate buffer, pH 2.5 with efficiencies of the three sugars of 40,000 plates (2,100,000,plates/m) within 30,s at a field strength of 500,V/cm. The simple fabrication process also allowed microchannels to be easily filled with chromatography particles before sealing, avoiding the challenging task of slurry packing, and the potential of these devices for liquid chromatography was demonstrated by the extraction of fluorescein onto anion exchange particles. [source] Synthesis and Characterization of CuII Complexes with Amino Acid Substituted Di(2-pyridyl)amine LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2007ko I. Kirin Abstract The two-step syntheses of the substituted di(2-pyridyl)amine ligands (dpa), dpa-CH2CO2H (1) and dpa-PhCO2H (2), are described. Ligands 1 and 2 are successfully coupled to the amino acid phenylalanine, yielding the derivatives 4 and 6, respectively. Four CuII(dpa)2 complexes, [Cu(dpa-CH2CO2tBu)2(NO3)2] (3Cu), [Cu(dpa-CH2CO-PheOMe)2(H2O)2](NO3)2·2MeOH (4Cu), [Cu(dpa-PhCO2Me)2 (MeOH)2](ClO4)2 (5Cu) and [Cu(dpa-PhCO-PheOMe)2(ClO4)2] (6Cu) have been prepared and characterized, including their single crystal X-ray structures. Fluorescence emission at UV (for 3 and 4) or blue (for 5 and 6) wavelengths of the free ligands is preserved in the corresponding Cu complexes, although with lower intensity. X-band EPR spectra of 4Cu and 6Cu both revealed one axial CuII signal with hyperfine and superhyperfine splittings. Complexes 4Cu and 6Cu are chiral inorganic complexes with amino acid bioconjugates that may serve as nucleoside analogs in modified peptide nucleic acids (PNA). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Design, synthesis and properties of novel iron(III)-specific fluorescent probesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2004Wei Luo ABSTRACT Bidentate chelators such as hydroxypyridinones and hydroxypyranones are highly iron selective. The synthesis of two novel fluorescent probes N -[2-(3-hydroxy-2-methyl-4-oxopyridin-1(4H)-yl)ethyl]-2-(7-methoxy-2-oxo-2H -chromen-4-yl)acetamide (CP600) and N -[(3-hydroxy-6-methyl-4-oxo-4H -pyran-2-yl)methyl]-2-(7-methoxy-2-oxo-2H -chromen-4-yl)acetamide (CP610) is reported. The method involves coupling the bidentate ligands, 3-hydroxypyridin-4-one and 3-hydroxypyran-4-one, with the well-characterised fluorescent probe methoxycoumarin. Fluorescence emission of both probes at 380 nm is readily quenched by Fe3+. The fluorescence was quenched to a greater extent by Fe3+ than by Mn2+, Co2+, Zn2+, Ca2+, Mg2+, Na+ and K+ and to approximately the same extent as Cu2+. Comparison of the fluorescence-quenching ability by a range of metal ions on CP600 and CP610 and the hexadentate chelator, calcein, under in-vitro conditions, demonstrated advantages of the two novel fluorescent probes with respect to both iron(III) sensitivity and selectivity. Chelation of iron(III) by CP600 and CP610 leads to the formation of a complex with a metal-to-ligand ratio of 1:3. Fluorescence is quenched on formation of such complexes. These probes possess a molecular weight less than 400 and thus they are predicted to permeate biological membranes by passive diffusion, and have potential for reporting intracellular organelle labile iron levels. [source] Phototoxicity in Human Retinal Pigment Epithelial Cells Promoted by Hypericin, a Component of St. John's Wort,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2007Albert R. Wielgus ABSTRACT St. John's wort (SJW), an over-the-counter antidepressant, contains hypericin, which absorbs light in the UV and visible ranges. In vivo studies have determined that hypericin is phototoxic to skin and our previous in vitro studies with lens tissues have determined that it is potentially phototoxic to the human lens. To determine if hypericin might also be phototoxic to the human retina, we exposed human retinal pigment epithelial (hRPE) cells to 10,7 to 10,5 M hypericin. Fluorescence emission detected from the cells (,ex = 488 nm; ,em = 505 nm) confirmed hypericin uptake by human RPE. Neither hypericin exposure alone nor visible light exposure alone reduced cell viability. However when irradiated with 0.7 J cm,2 of visible light (, > 400 nm) there was loss of cell viability as measured by MTS and lactate dehydrogenase assays. The presence of hypericin in irradiated hRPE cells significantly changed the redox equilibrium of glutathione and a decrease in the activity of glutathione reductase. Increased lipid peroxidation as measured by the thiobarbituric acid reactive substances assay correlated to hypericin concentration in hRPE cells and visible light radiation. Thus, ingested SJW is potentially phototoxic to the retina and could contribute to retinal or early macular degeneration. [source] Facial skin fluorescence as a marker of the skin's response to chronic environmental insults and its dependence on ageBRITISH JOURNAL OF DERMATOLOGY, Issue 1 2006G.N. Stamatas Summary Background, Throughout life facial skin is exposed to a variety of adverse environmental conditions and is constantly required to repair itself. The rate of epidermal cell proliferation is indicative of the skin's repair rate and can be monitored noninvasively in vivo using skin intrinsic fluorescence markers. Objectives, The goal of the present study was to assess the effects of ageing, geographical region, ethnic origin and season on the ability of facial skin to repair itself in the presence of chronic environmental insults using in vivo fluorescence spectroscopy. Methods, Skin fluorescence emission was measured on the cheeks of 522 individuals in winter and repeated in summer in five different geographical locations in the Asia-Pacific region. Fluorescence emission was also measured from 80 caucasians of fair complexion in the United States (New Jersey area) on the face and on a relatively protected area (upper inner arm). The age range of the participants was 14,75 years. Results, We found that epidermal proliferation rates decrease monotonically with age, while the fluorescence of collagen and elastin cross-links increases with age indicating accumulation of advanced glycation end-products. These trends were independent of geographical region, ethnic origin and season of measurement. Epidermal proliferation rates of facial skin were higher than those of unexposed sites; they may be 10 times higher in younger (second decade) than in older (seventh decade) individuals, and they decrease with age at rates 10 times faster compared with those of unexposed sites. Conclusions, This is the first time that epidermal proliferation and its dependence on ageing have been measured noninvasively on the human face. The higher tryptophan fluorescence values on the face vs. the protected site are indicative of accelerated rates of epidermal proliferation in the presence of chronic environmental insults. The repair potential of facial skin, i.e. its ability to maintain high proliferation rates, is maximal in younger populations and gradually decreases with age. [source] Community heterogeneity and single-cell digestive activity of estuarine heterotrophic nanoflagellates assessed using lysotracker and flow cytometryENVIRONMENTAL MICROBIOLOGY, Issue 7 2010Eva Sintes Summary Heterotrophic nanoflagellates (HNFs) are an essential component of all aquatic microbial food webs, and yet the exploration of the numerical and single-cell responses of these organisms in mixed assemblages still represents a major technical challenge. LysoTracker Green staining combined with flow cytometry was recently proposed for the enumeration of aquatic HNFs. Here we show that LysoTracker Green not only allows the enumeration of HNFs in estuarine samples with a wide range of HNF abundances, but also allows the discrimination of distinct HNF populations in mixed assemblages. In addition, the resulting cytometric parameters can be used to characterize cell size and the level of activity of the cells in the different populations that are detected. LysoTracker Green accumulates preferentially in lysosomes, and we demonstrate that the green fluorescence emission from HNF cells stained with LysoTracker strongly correlates with cell-specific ,-glucosaminidase (,-Gam) activity, a key digestive enzyme of lysosomal origin in eukaryotic cells. Our results further show that different populations that develop in estuarine regrowth cultures are characterized by different intrinsic ranges of size and of feeding activity, and that there is a wide range of single-cell responses within these HNF populations. We found a large degree of uncoupling between cell size and feeding activity, both between and within HNF populations, and there appears to be no clear allometric scaling of feeding activity. We were able to reconstruct the succession of distinct HNF populations that developed during the regrowth experiments, and explore the complex interactions that occurred between numerical (change in abundance of the cytometric populations) and single-cell HNF responses. [source] (Benzimidazolylmethyl)cyclen: A Potential Sensitive Fluorescent PET Chemosensor for ZincEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2007Abir El Majzoub Abstract A new fluorescent probe for Zn2+, methylbenzimidazole-pendant cyclen [LH: 1-(benzimidazol-2-ylmethyl)-1,4,7,10-tetraazacyclododecane] was designed and synthesized. The protonation constants of (benzimidazolylmethyl)cyclen and the stability constants of the corresponding zinc complex were determined by potentiometric titrations. The single-crystal X-ray diffraction analysis showed that LH and Zn2+ form a 1:1 complex [ZnLH]2+. The results of potentiometric, 1H NMR and UV titrations indicated that above pH 8, [ZnLH]2+ mainly deprotonates into [ZnL]+. On addition of successive amounts of Zn2+ at pH 10.4 (2,×,10,2 mol,L,1 CAPS, 25 °C), the fluorescence emission of cyclen(methylbenzimidazole) increases linearly by a factor of 3.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Novel Metallosupramolecular Networks Constructed from CuII, NiII, and CdII with Mixed Ligands: Crystal Structures, Fluorescence, and MagnetismEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2006Miao Du Abstract Reactions of mixed ligands succinic acid (H2suc) and bent dipyridines, such as 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and its 4- N -donor analog (4-bpo), with inorganic CuII, NiII, and CdII salts yield three new metal-organic coordination frameworks {[Cu(suc)(3-bpo)(H2O)2]·(H2O)1.75}n (1), {[Ni(suc)(4-bpo)(H2O)2]·(H2O)5}n (3), and {[Cd2(suc)2(3-bpo)2(H2O)2]·(H2O)6.75}n (4), in which the metal centers are linked by bridging ligands 3-bpo/4-bpo and suc2, along two directions to form 2D infinite networks. The corrugated 2D nets of 1 and 4, obtained under hydrothermal conditions, align in an interdigitated manner with the presence of significant aromatic-stacking interactions to result in similar 3D architectures. The 2D sheets in 3 are extended by interlayer hydrogen bonds to afford a 3D structure. However, when succinic acid is replaced by fumaric acid (H2fum) in the reaction with 3-bpo and CuII salt, a metallacyclophane [Cu(Hfum)2(3-bpo)(H2O)]2·(3-bpo)2·(H2O)6 (2) is generated. The binuclear coordinated motifs are hydrogen-bonded to the lattice water chains to furnish a unique 3D channel-like framework, in which the guest 3-bpo molecules are accommodated. The thermal stabilities of these new materials were investigated by thermogravimetric analysis (TGA) of mass loss. The magnetic coupling in complexes 1,3 is antiferromagnetic and very small, which is as expected considering the long organic bridges between the paramagnetic centers. The solid-state luminescence properties of 4 reveal an intense fluorescence emission at 378 nm. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Non-Covalent Aggregation of Discrete Metallo-Supramolecular Helicates into Higher Assemblies by Aromatic Pathways: Structural and Chemical Studies of New Aniline-Based Neutral Metal(II) DihelicatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2005Miguel Vázquez Abstract Neutral manganese(II), iron(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) complexes with an N -tosyl-substituted N4 -donor Schiff base containing a 4,4'-methylenedianiline residue as spacer [H2La: N,N' -bis(2-tosylaminobenzylidene)-4,4'-methylenedianiline], and the zinc(II) complex with an analogous ligand [H2Lb: N,N' -bis(2-tosylaminobenzylidene)-4,4'-oxodianiline] have been prepared by an electrochemical procedure. FAB and ESI mass spectra of the complexes show peaks due to species corresponding to a general formula [M2(La,b)2 + H]+, thereby suggesting their dinuclear nature. A detailed study of the crystal packing in the unit cell of the zinc(II) complex with H2La shows that the helicates aggregate to form discrete prismatic moieties containing three molecules held together by ,,, and ,,, interactions. Moreover, the ZnII neutral dihelicate with H2Lb forms a 3D network in the solid state due to intermolecular ,-stacking interactions. 1H NMR studies of the diamagnetic compounds reported herein have been performed. Finally, the ligand H2La and its ZnII and CdII complexes have been studied by spectrophotometric and spectrofluorimetric techniques in order to get a better understanding of the formation mechanisms of the complexes and of the nature of their fluorescence emission. Emission studies show that the ZnII and CdII dihelicates with H2La display a green fluorescence in acetonitrile solution (, = 473 nm, , = 0.03 and , = 476 nm, , = 0.01, respectively). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Pressure-exploration of the 33-kDa protein from the spinach photosystem II particleFEBS JOURNAL, Issue 9 2001Kangcheng Ruan The 33-kDa protein isolated from the spinach photosystem II particle is an ideal model to explore high-pressure protein-unfolding. The protein has a very low free energy as previously reported by chemical unfolding studies, suggesting that it must be easy to modulate its unfolding transition by rather mild pressure. Moreover, the protein molecule consists of only one tryptophan residue (Trp241) and eight tyrosine residues, which can be conveniently used to probe the protein conformation and structural changes under pressure using either fluorescence spectroscopy or fourth derivative UV absorbance spectroscopy. The different experimental methods used in the present study indicate that at 20 °C and pH 6, the 33-kDa protein shows a reversible two-state unfolding transition from atmospheric pressure to about 180 MPa. This value is much lower than those found for the unfolding of most proteins studied so far. The unfolding transition induces a large red shift of the maximum fluorescence emission of 34 nm (from 316 nm to 350 nm). The change in standard free energy (,Go) and in volume (,V) for the transition at pH 6.0 and 20 °C are ,14.6 kJ·mol,1 and ,120 mL·mol,1, respectively, in which the ,Go value is consistent with that obtained by chemical denaturation. We found that pressure-induced protein unfolding is promoted by elevated temperatures, which seem largely attributed to the decrease in the absolute value of ,Go (only a minor variation was observed for the ,V value). However, the promotion of the unfolding by alkaline pH seems mainly related to the increase in ,V without any significant changes in ,Go. It was also found that NaCl significantly protects the protein from pressure-induced unfolding. In the presence of 1 m NaCl, the pressure needed to induce the half-unfold of the protein is shifted to a higher value (shift of 75 MPa) in comparison with that observed without NaCl. Interestingly, in the presence of NaCl, the value of ,V is significantly reduced whilst that of ,Go remains as before. The unfolding-refolding kinetics of the protein has also been studied by pressure-jump, in which it was revealed that both reactions are a two-state transition process with a relatively slow relaxation time of about 102 s. [source] Time-resolved fluorescence analysis of the recombinant photosystem II antenna complex CP29FEBS JOURNAL, Issue 2 2001Effects of zeaxanthin, phosphorylation Nonradiative dissipation of excitation energy is the major photoprotective mechanism in plants. The formation of zeaxanthin in the antenna of photosystem II has been shown to correlate with the onset of nonphotochemical quenching in vivo. We have used recombinant CP29 protein, over-expressed in Escherichia coli and refolded in vitro with purified pigments, to obtain a protein indistinguishable from the native complex extracted from thylakoids, binding either violaxanthin or zeaxanthin together with lutein. These recombinant proteins and the native CP29 were used to measure steady-state chlorophyll fluorescence emission and fluorescence decay kinetics. We found that the presence of zeaxanthin bound to CP29 induces a ,,35% decrease in fluorescence yield with respect to the control proteins (the native and zeaxanthin-free reconstituted proteins). Fluorescence decay kinetics showed that four components are always present but lifetimes (,) as well as relative fluorescence quantum yields (rfqy) of the two long-lived components (,3 and ,4) are modified by the presence of zeaxanthin. The most relevant changes are observed in the rfqy of ,3 and in the average lifetime (, 2.4 ns with zeaxanthin and 3.2,3.4 ns in the control proteins). When studied in vitro, no significant effect of acidic pH (5.2,5.3) is observed on chlorophyll a fluorescence yield or kinetics. The data presented show that recombinant CP29 is able to bind zeaxanthin and this protein-bound zeaxanthin induces a significant quenching effect. [source] Thermally induced conformational changes in horseradish peroxidaseFEBS JOURNAL, Issue 1 2001David G. Pina Detailed differential scanning calorimetry (DSC), steady-state tryptophan fluorescence and far-UV and visible CD studies, together with enzymatic assays, were carried out to monitor the thermal denaturation of horseradish peroxidase isoenzyme c (HRPc) at pH 3.0. The spectral parameters were complementary to the highly sensitive but integral method of DSC. Thus, changes in far-UV CD corresponded to changes in the overall secondary structure of the enzyme, while that in the Soret region, as well as changes in intrinsic tryptophan fluorescence emission, corresponded to changes in the tertiary structure of the enzyme. The results, supported by data about changes in enzymatic activity with temperature, show that thermally induced transitions for peroxidase are irreversible and strongly dependent upon the scan rate, suggesting that denaturation is under kinetic control. It is shown that the process of HRPc denaturation can be interpreted with sufficient accuracy in terms of the simple kinetic scheme where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation; N is the native state, and D is the denatured state. On the basis of this model, the parameters of the Arrhenius equation were calculated. [source] A New Series of Quadrupolar Type Two-Photon Absorption Chromophores Bearing 11, 12-Dibutoxydibenzo[a,c]-phenazine Bridged Amines; Their Applications in Two-Photon Fluorescence Imaging and Two-Photon Photodynamic TherapyADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Marappan Velusamy Abstract A new series of quadrupolar type two-photon absorption (2PA) chromophores 3,9 bearing a core arylamine-[a,c]phenazine-arylamine motif are synthesized in high yields. Palladium-catalyzed Stille coupling and CN coupling reactions are utilized to prepare target chromophores. Detailed characterization and systematic studies of these molecules, including absorption and fluorescence emission, are conducted. These compounds are found to exhibit very large 2PA cross section values, for example, ,7000 GM at 800,nm for 8 in toluene. Two-photon-induced fluorescence imaging is successfully demonstrated in vitro using compound- 8 -encapsulated silica nanoparticles with excellent bio-compatibility. In combination with the capability of both one- and two-photon singlet-oxygen sensitizations, this nanocomposite demonstrates its promising potential in dual functionality toward two-photon fluorescence imaging and two-photon photodynamic therapy. [source] Synthesis, Photophysical, and Electroluminescent Device Properties of Zn(II)-Chelated Complexes Based on Functionalized Benzothiazole DerivativesADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Soo-Gyun Roh Abstract New Zn(II)-chelated complexes based on benzothiazole derivatives, including substituted functional groups such as methyl (MeZn), methoxy (MeOZn), or fluorenyl unit (FuZn), are investigated to produce white-light emission. 2-(2-Hydroxyphenyl)benzothiazole derivatives in toluene and DMSO exhibit excited-state intramolecular proton transfer (ESIPT), leading to a large Stokes shift of the fluorescence emission. However, in methanol they exhibit no ESIPT due to the intermolecular hydrogen bonding between the 2-(2-hydroxyphenyl)benzothiazole derivative and methanol. Their Zn(II)-chelated complexes exhibit the absorption band red-shifted at 500,nm in nonpolar solvent and the absorption band blue-shifted at about 420,nm in protic solvent. In multilayer electroluminescent devices, methyl-substituted Zn(II)-chelated complex (MeZn) exhibits excellent power efficiency and fluorene-substituted Zn(II)-chelated complex (FuZn) has a high luminance efficiency (1,cd,m,2 at 3.5,V, 10,400,cd,m,2 at 14,V). The EL spectra of Zn(II)-chelated complexes based on benzothiazole derivatives exhibit broad emission bands. In addition, their electron-transport property for red,green,blue (RGB) organic light-emitting diodes (OLEDs) is systematically studied, in comparison with that of Alq3. The results demonstrate the promising potential of MeZn as an electron-transporting layer (ETL) material in preference to Alq3, which is widely used as an ETL material. [source] Fluorescence of Dissolved Organic Matter as a Natural Tracer of Ground WaterGROUND WATER, Issue 5 2001Andy Baker The fluorescence properties of dissolved organic matter (DOM) in ground water in the Permian limestone of northeast England is determined from six monitoring boreholes, a private water supply well and from a natural resurgence in a flooded collapse doline in the environs of Darlington, County Durham, northeast England. Measurements of both protein and "fulvic-like" fluorescence was undertaken from January to December 1999. The wavelengths of fulvic-like fluorescence excitation and emission and of protein fluorescence emission were all determined to be sensitive fingerprints of organic matter fluxes through the ground water, with water within the till and within both gypsum and limestone strata deep inside the Magnesian Limestone being differentiated by these parameters. Previous research has suggested that proteins in waters are "young" in age, hence our seasonal variations suggest that we are sampling recently formed DOM. The rapid response of all deep borehole samples suggests relatively rapid ground water flow, probably through karstic cave systems developed in the gypsum and solution widened features in the dolomitic limestone. Our results suggest that use of both protein and fulvic-like fluorescence wavelength variations provides a DOM signature that can be used as a natural tracer. [source] Photophysical and Photochemical Studies of PyridoxamineHELVETICA CHIMICA ACTA, Issue 10 2003Claudio Bueno The absorption and fluorescence emission of pyridoxamine were studied as function of pH and solvent properties. In the ground state, pyridoxamine exhibits different protonated forms in the range of pH,1.5,12. Fluorescence studies showed that the same species exist at the lowest singlet excited state but at different pH ranges. The phenol group is by ca. 8,units more acidic in the excited state than in the ground state. On the other hand, the pyridine N-atom is slightly more basic in the lowest excited state than in the ground state. Excitation spectra and emission decays in the pH range of 8,10 indicate the protonation of the pyridine N-atom by proton transfer from the amine group, in the ground and singlet excited states. Spectroscopic studies in different solvents showed that pyridoxamine in the ground or excited states exhibits intramolecular proton transfer from the pyridine N-atom to the phenol group, which is more favorable in solvents of low hydrogen-bonding capacity. The cationic form with the protonated phenolic group, which emits at shorter wavelength, is the dominant species in nonprotic solvents, but, in strong proton-donor solvents, both forms exist. The fluorescence spectra of these species exhibit blue shift in protic solvents. These shifts are well-correlated with the polarity and the H-donor ability of the solvent. [source] Mercury Biosensors: Polydiacetylene,Liposome Microarrays for Selective and Sensitive Mercury(II) Detection (Adv. Mater.ADVANCED MATERIALS, Issue 36 200936/2009) Polydiacetylene (PDA) liposome microarrays have been developed for selective and sensitive mercury detection. The sensors, reported on p. 3674 by Jinsang Kim and co-workers, are designed to produce red fluorescence emission upon binding with Hg2+; when the single-stranded DNA aptamers on the microarray selectively wrap around the mercury ions, the resulting complexes repulse each other. The epoxy-based PDA liposome design is an excellent universal platform that can be readily extended to other sensor designs. [source] Polydiacetylene,Liposome Microarrays for Selective and Sensitive Mercury(II) DetectionADVANCED MATERIALS, Issue 36 2009Jiseok Lee Polydiacetylene (PDA) liposome microarrays are developed for selective and sensitive mercury (Hg2+) detection. The PDA mercury sensors are designed to produce red fluorescence emission upon binding with Hg2+, when the ssDNA aptamers on the PDA surface recognize and wrap around mercury ions and the resulting bulky T-Hg-T complexes repulse each other. [source] A Novel NADH Model: Design, Synthesis, and its Chiral Reduction and Fluorescent EmissionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Nai-Xing Wang Abstract A novel chiral nicotinamide adenine dinucleotide hydrogen (NADH) model with C3 symmetry was designed and synthesized. Hydrogens at the C-4 position of all dihydropyridine rings in the inner part of the bowl could transfer to the substrate with powerful enantioselectivity. This novel C3 symmetrical NADH model is capable of fluorescence emission at 455,nm when excited at 390,nm. [source] Contents of Total Phenolics and Ferulic Acid, and PAL Activity during Water Potential Changes in Leaves of Maize Single-Cross Hybrids of Different Drought ToleranceJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2008T. Hura Abstract The aim of this study was to determine whether the resistance and/or sensitivity to drought stress, can be attributed to the level of phenolic compounds in the leaves of maize genotypes. The experiments were carried out on seedlings of three maize genotypes characterized by different levels of drought resistance. Experiments with three periods of drought were conducted (8, 11 and 14 days), to obtain plants with different levels of water potential in leaves, which induced changes in the total phenolic content and ferulic acid, and l -phenylalanine ammonia-lyase (PAL) activity. Only for the drought-resistant genotype Tina, was the low water potential found to be correlated with the high level of the total phenolic content and ferulic acid, which is the main source of blue fluorescence emissions. Moreover, only for Tina were the highest intensities of blue fluorescence emission correlated with the low water potential in leaves. The phenolic compounds present in leaf tissues can protect the deeper situated mesophyll, by absorbing light reaching the leaf and transforming it into a blue fluorescence. Phenolic compounds can, in this way, function as photoprotectors limiting the excitation of chlorophyll during conditions of water deficit in leaves. [source] Unexpected fluorescence emission of poly(,,,- L -malic acid) in aqueous mediumJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Yaofeng Fan Abstract Unexpected fluorescence of poly(,,,- L -malic acid) (,,,-PMA) without traditional fluorophore was observed firstly. This fluorescent polymer was synthesized via melt polycondensation of L -malic acid. The polymer was characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared spectroscopy (IR), Fourier transform Raman spectroscopy (Raman), and X-ray powder diffractometry (XRD). The high molecular weight ,,,-PMA was synthesized by the optimum polycondensation at 130°C for 15 h, followed by fractional precipitation with diethyl ether and petroleum ether. The degree of branching of ,,,-PMA was from 10% to 20% according to the reaction condition. Terminal group of ,,,-PMA was mainly hydroxycarboxylic group companied with a few CHCHCOOH groups owing to dehydration of a normal terminal during the melt polycondensation. A fluorescence emission maximum of ,,,-PMA in water appeared at 420 nm when it was excited at 340 nm. Further study indicated that the fluorescence intensity was concentration-dependent, pH-dependent, and molecular-weight-dependent. The fluorescence formation may result from multichain aggregations, which was formed readily in aqueous solution due to intermolecular hydrogen bonds between branched ,,,-PMA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] A convenient route to synthesize 1,2,4-triazolo[1,5- a]pyrimidine derivatives and their one and two-photon absorption spectral propertiesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2007Hongli Wang A convenient method for synthesizing ,-(1,2,4-triazolo[1,5- a]pyrimidine-2-sulfonyl)methane derivatives, 3 and 4, by the well known Knoevenagel reaction, in one step, is described. The two chromophores are stilbene-type chromophores containing the same D-,-A structures and end-capped with aromatic group as their donors. Measured with femtosecond multipass Ti:sapphire amplifier as irradiation source (pumped by the laser at 800 nm), the two chromophores show efficient two-photon induced orange red fluorescence emission. The experimental results indicate that the numbers of branches of the two chromophores affect their one-photon properties and two-photon up-conversion emission behaviors, and with the increasing numbers of branches, their wavelengths of ,absmax, ,spfmax and ,tpfmax exhibit bathochromic shifts. [source] The effect of temperature on the stability of compounds used as UV-MALDI-MS matrix: 2,5-dihydroxybenzoic acid, 2,4,6-trihydroxyacetophenone, ,-cyano-4-hydroxycinnamic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, nor-harmane and harmaneJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2009Olga I. Tarzi Abstract The thermal stability of several commonly used crystalline matrix-assisted ultraviolet laser desorption/ionization mass spectrometry (UV-MALDI-MS) matrices, 2,5-dihydroxybenzoic acid (gentisic acid; GA), 2,4,6-trihydroxyacetophenone (THA), ,-cyano-4-hydroxycinnamic acid (CHC), 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid; SA), 9H-pirido[3,4-b]indole (nor-harmane; nor-Ho), 1-methyl-9H-pirido[3,4-b]indole (harmane; Ho), perchlorate of nor-harmanonium ([nor-Ho + H]+) and perchlorate of harmanonium ([Ho + H]+) was studied by heating them at their melting point and characterizing the remaining material by using different MS techniques [electron ionization mass spectrometry (EI-MS), ultraviolet laserdesorption/ionization-time-of-flight-mass spectrometry (UV-LDI-TOF-MS) and electrospray ionization-time-of-flight-mass spectrometry (ESI-TOF-MS)] as well as by thin layer chromatography analysis (TLC), electronic spectroscopy (UV-absorption, fluorescence emission and excitation spectrosco y) and 1H nuclear magnetic resonance spectroscopy (1H-NMR). In general, all compounds, except for CHC and SA, remained unchanged after fusion. CHC showed loss of CO2, yielding the trans-/cis -4-hydroxyphenylacrilonitrile mixture. This mixture was unambiguously characterized by MS and 1H-NMR spectroscopy, and its sublimation capability was demonstrated. These results explain the well-known cluster formation, fading (vanishing) and further recovering of CHC when used as a matrix in UV-MALDI-MS. Commercial SA (SA 98%; trans -SA/cis -SA 5 : 1) showed mainly cis- to- trans thermal isomerization and, with very poor yield, loss of CO2, yielding (3,,5,-dimethoxy-4,-hydroxyphenyl)-1-ethene as the decarboxilated product. These thermal conversions would not drastically affect its behavior as a UV-MALDI matrix as happens in the case of CHC. Complementary studies of the photochemical stability of these matrices in solid state were also conducted. Copyright © 2008 John Wiley & Sons, Ltd. [source] Upconversion fluorescence imaging of erbium-doped fluoride glass particles by apertureless SNOMJOURNAL OF MICROSCOPY, Issue 3 2003A. Fragola Abstract We have imaged fluorescent erbium-doped fluoride glass particles by apertureless scanning near-field optical microscopy. The optical excitation has been performed at , = 780 nm whereas fluorescence emission has been collected around , = 550 nm. This process, called upconversion by energy transfer, involves two erbium ions and is not linear. Besides an improvement of the lateral resolution, we have observed on some particles that the fluorescence is not homogeneously distributed, but is rather localized in some zones brighter than others. By making tip approach curves, we have also observed that the amount of fluorescence intensity scattered by the tip is increasing when the tip is approaching the sample surface. [source] Matrix dependence of blue light emission from a novel NH2 -functionalized dicyanoquinodimethane derivativeJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2006Marek Szablewski Abstract The reactions of primary and secondary amines with (cyclohexa-2,5-diene-1,4-diylidene)-dimalononitrile (TCNQ) lead to mono- and disubstituted dicyanoquinodimethane derivatives and fluorescence emission has been observed for several of these compounds. We report the luminescence properties, synthesis and crystal structure of the novel dicyanoquinodimethane derivative 2-{4-[amino-(2,6-dimethyl-morpholin-4-yl)-methylene]-cyclohexa-2,5- dienylidene}-malononitrile (Ammor), a unique example of an asymmetric dicyanoquinodimethane derivative in which one of the nitrile groups has been replaced with an NH2 moiety, which provides a reactive centre for potential further substitution or tethering to larger molecules or polymers. The luminescence properties of the title compound were investigated in a variety of environments, including alcohol solutions at room temperature and a glass-forming solvent at low temperature. The fluorescence quantum yields and Stokes' shifts of the blue emission were found to be very sensitive to the matrix. The crystal structure of the subject compound was determined, revealing that the molecules are non-planar in the ground state. The environmentally sensitive emission is discussed in terms of the conformational change during photoexcitation and the constraint imposed on this by the matrix. This behaviour is also compared with that of other related amino-functionalized dicyanoquinodimethane derivatives. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis of azobenzene-containing polymers via RAFT polymerization and investigation on intense fluorescence from aggregates of azobenzene-containing amphiphilic diblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Jie Xu Abstract The well-defined azobenzene-containing homopolymers, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via reversible addition fragmentation chain transfer polymerization (RAFT) in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2,-azobisisobutyronitrile (AIBN) as the initiator. The first-order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs , 1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)}- b -poly{2-(dimethylamino)ethyl methacrylate (DMAEMA)} (PAHMA- b -PDMAEMA), was prepared with the obtained PAHMA as the macro-RAFT agent. The structures and properties of the polymers were characterized by 1H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl3) solution (PAHMA23 - b -PDMAEMA97 (4 × 10,5 M, Mn(GPC) = 18,400 g/mol, PDI = 1.48) and PAHMA28 - b -PDMAEMA117 (6 × 10,5 M, Mn(GPC) = 19,300 g/mol, PDI = 1.51) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA- b -PDMAEMA in CHCl3 was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min and later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self-assembled micelles composed of azobenzene-containing amphiphilic diblock copolymers, (PAHMA- b -QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N -dimethyl formamide (DMF)/H2O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5652,5662, 2008 [source] Hybrid Rayleigh, Raman and two-photon excited fluorescence spectral confocal microscopy of living cellsJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2010Vishnu Vardhan Pully Abstract A hybrid fluorescence,Raman confocal microscopy platform is presented, which integrates low-wavenumber-resolution Raman imaging, Rayleigh scatter imaging and two-photon fluorescence (TPE) spectral imaging, fast ,amplitude-only' TPE-fluorescence imaging and high-spectral-resolution Raman imaging. This multi-dimensional fluorescence,Raman microscopy platform enables rapid imaging along the fluorescence emission and/or Rayleigh scatter dimensions. It is shown that optical contrast in these images can be used to select an area of interest prior to subsequent investigation with high spatially and spectrally resolved Raman imaging. This new microscopy platform combines the strengths of Raman ,chemical' imaging with light scattering microscopy and fluorescence microscopy and provides new modes of correlative light microscopy. Simultaneous acquisition of TPE hyperspectral fluorescence imaging and Raman imaging illustrates spatial relationships of fluorophores, water, lipid and protein in cells. The fluorescence,Raman microscope is demonstrated in an application to living human bone marrow stromal stem cells. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fluorescence background suppression in Raman spectroscopy using combined Kerr gated and shifted excitation Raman difference techniquesJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2002P. Matousek An exceptionally high level of fluorescence rejection from resonance Raman spectra was achieved using a combination of two techniques, namely Kerr gated temporal rejection with shifted excitation Raman difference spectroscopy. The method was able to recover the resonance Raman spectrum from the intense fluorescence background with a signal-to-noise ratio at least 10 times higher than that achievable with either of the two approaches used individually. To demonstrate the effectiveness of the technique we obtained the resonance Raman spectrum of the laser dye rhodamine 6G (1 × 10,3 mol dm,3) in methanol by excitation at 532 nm and measuring under the maximum of fluorescence emission at 560,590 nm. The method reached the photon shot noise limit of the residual fluorescence providing a detection limit for Raman spectra 106 times lower than the original fluorescence intensity in an accumulation time of 800 s. A unique feature of the experiment was the way in which the optical parametric amplifier light source was configured to alternate automatically between the two excitation wavelengths using an optogalvanic mirror arrangement. The ultra-high sensitivity of the combined approach holds great promise for selective probing of complex biological systems using resonance Raman spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||