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Chromophore
Kinds of Chromophore Terms modified by Chromophore Selected AbstractsSelective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Krishanu Sarkar Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source] Blue Emission of a Soluble Poly(p -phenylene) with a Cross-Conjugated Bisimidazole-Based ChromophoreMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2007Frank Dierschke Abstract A novel poly(p -phenylene) (6) has been synthesized by a cruciform combination of a polyphenylene backbone with 2,2,-(p -phenylene)-bis(4,5-diphenylimidazole) (5) as an additional, orthogonal chromophore. Polymer 6 showed in solution and in the solid state, a blue-green emission, which is obviously arising from the second bisimidazole-based chromophore. UV-Vis spectroscopy, and cyclic voltammetry revealed that the optical and electronic properties of 6 were fully determined by the incorporated 2,2,-(1,4-phenylene)bisimidazole structure. The bisimidazole unit led to high solubility and, despite the steric demand of the substituents, at the same time to the blue-green emission of the poly(p -phenylene) (6). In addition, the oxidation of 6 with potassium ferricyanide yielded a low bandgap polymer with a quinoid-type structure and a bandgap of 1.6 eV. [source] Hybrid Nonlinear Optical Materials Containing Imidazole Chromophore through the Sol-Gel ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2007Yuanjing Cui Abstract A new sol-gel hybrid film based on heterocyclic chromophore, namely 2-[4,-(N -ethyl- N -hydroxyethyl)amino phenyl azo]-4,5-dicyanoimidazole (IZ), has been synthesized and characterized. The hybrid system possesses a high chromophore loading density up to 65 wt.-% without observing a phase separation. The initial decomposition temperatures of the chromophore and hybrid material were determined to be 260 and 272,°C, respectively. Poled films show a fairly high and stable nonlinear optical (NLO) response, even at an elevated temperature. [source] Homogeneous Photocatalytic Oxidation of Alcohols by a Chromophore,Catalyst Dyad of Ruthenium Complexes,ANGEWANDTE CHEMIE, Issue 51 2009Weizhong Chen Dr. Eine Chromophor-Katalysator-Dyade aus Rutheniumpolypyridylkomplexen wurde synthetisiert und sowohl strukturell als auch elektronisch charakterisiert. Ihre Eignung für die protonengekoppelte Mehrelektronenphotooxidation wurde anhand der photokatalytischen Oxidation aliphatischer und benzylischer Alkohole unter Bestrahlung mit sichtbarem Licht gezeigt, die in Wasser unter Umgebungsbedingungen hohe Selektivitäten und Umsatzzyklen über 100 liefert. [source] Trimeric Cyclic Assemblies of Calix[4]arene-Tethered Bismerocyanines,ANGEWANDTE CHEMIE, Issue 33 2009Andreas Lohr Dr. Ein cyclischer Komplex aus drei Calixaren-Bismerocyanin-Konjugaten entsteht durch Paarung der Chromophore (siehe Bild). Die Bildung der Trimere wird mit einem einfachen mathematischen Modell beschrieben, und das Potenzial der Aggregation von dipolaren Merocyanin-Farbstoffen als gerichtetes und spezifisches supramolekulares Bindungsmotiv wird aufgezeigt. (Calixarene: grün; Merocyanine: C,hellblau, N,dunkelblau, O,rot). [source] ChemInform Abstract: Synthesis of the Pyoverdin Chromophore (Va) by a Biomimetic Oxidative Cyclization.CHEMINFORM, Issue 33 2009Raymond C. F. Jones Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Novel Molecular Building Blocks Based on the Boradiazaindacene Chromophore: Applications in Fluorescent Metallosupramolecular Coordination PolymersCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2009Ö. Altan Bozdemir Dr. Abstract Bright polymers: Fluorescent coordination polymers made up of versatile functionalized bodipy (boron-dipyrrin) chromophore building blocks, such as that depicted, are described. Polymerization is signaled by changes in fluorescence emission intensity and shifts in peak emission wavelengths. We designed and synthesized novel boradiazaindacene (Bodipy) derivatives that are appropriately functionalized for metal-ion-mediated supramolecular polymerization. Thus, ligands for 2-terpyridyl-, 2,6-terpyridyl-, and bipyridyl-functionalized Bodipy dyes were synthesized through Sonogashira couplings. These fluorescent building blocks are responsive to metal ions in a stoichiometry-dependent manner. Octahedral coordinating metal ions such as ZnII result in polymerization at a stoichiometry corresponding to two terpyridyl ligands to one ZnII ion. However, at increased metal ion concentrations, the dynamic equilibria are re-established in such a way that the monomeric metal complex dominates. The position of equilibria can easily be monitored by 1H,NMR and fluorescence spectroscopies. As expected, although open-shell FeII ions form similar complex structures, these cations quench the fluorescence emission of all four functionalized Bodipy ligands. Bu çal,,mada, metal iyonlar, arac,l,,,yla supramoleküler polimerizasyon için uygun ,ekilde fonksiyonland,r,lm,, yeni boradiazaindasen (Bodipy) türevleri tasarlanm,, ve sentezlenmi,tir. Bu amaçla, ligand olarak Sonogashira reaksiyonu ile 2- ve 2,6-terpiridil ve bipiridil gruplar,n, içeren Bodipy boyarmaddeleri sentezlenmi,tir. Bu floresan yap, bloklar, stokiyometriye ba,l, bir biçimde metal iyonlar,na duyarl,l,k gösterirler. ZnIIgibi oktahedral koordinasyon e,ilimi olan metal iyonlar,, iki terpiridil ligand,na bir ZnIIiyonu tekabül edecek bir stokiyometride polimerizasyona yol açmaktad,rlar. Bununla beraber, yüksek metal iyonu deri,imlerinde monomerik metal kompleksinin bask,n olaca,, bir biçimde, dinamik dengeler yeniden kurulmaktad,r. Bu dengelerin pozisyonu1H,NMR ve fluoresans spektroskopileriyle kolayl,kla izlenebilmektedir. Beklenildi,i gibi, benzer kompleks yap,lar olu,turmas,na ra,men FeIIiyonu, sentezlenen tüm fonksiyonalize Bodipy ligandlar,n,n emisyonlar,n, sönümlendirmektedir. [source] Organoplatinum(II) Complexes with Chromophore,Acceptor Dyad Studied by Ultrafast Time-Resolved Absorption SpectroscopyCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2010Siu-Wai Lai Dr. Femtosecond time-resolved absorption revealed the formation of charged-separated [ClPtIII{C,N,N(PhMV+,)}] species (left) with a forward rate constant of about 1012,s,1, which is more rapid than that of the back electron-transfer process (k,1=1.6×109,s,1). Similar slower back ET reaction than forward light-induced ET reaction of [Pt(MV-bpy)(CCPh)2](PF6)2 (right) has been observed. MV=methyl viologen. [source] Polymer Matrix Effects on the Nonlinear Optical Response of Incorporated Chromophore: New Analytical ModelsCHEMPHYSCHEM, Issue 10 2006Marina Yu. Abstract A new approach aimed at the modeling of the nonlinear optical (NLO) response of a dipole chromophore incorporated into a locally anisotropic, deformable, polarizable polymer matrix is suggested. The general continuum methodology is used with a specific cavity ansatz being employed; the cavity is chosen to be conformal to the characteristic ellipsoid of the generalized permittivity tensor of the polymer medium. The suggested ansatz allows the electrostatic boundary value problem to be solved analytically, and the local field experienced by the chromophore in the polymer electret to be found. Four analytically solvable models, which correspond to two singular and two nonsingular models, are considered; in two of them the chromophore is characterized by singular dipole and quadrupole moments; the other two use the approximation of the electric moment of the chromophore with that of the polarized ellipsoid. The relation between the macroscopic polymer properties and the microscopic characteristics of the NLO chromophore is established. The compliance of the obtained formulas for the local field with those of the classical Onsager approach is analyzed, and their specific features are considered. [source] Solvent and Protein Effects on the Structure and Dynamics of the Rhodopsin ChromophoreCHEMPHYSCHEM, Issue 9 2005Ute F. Röhrig Dr. Abstract The structure and dynamics of the retinal chromophore of rhodopsin are investigated systematically in different environments (vacuum, methanol solution, and protein binding pocket) and with different computational approaches (classical, quantum, and hybrid quantum mechanics/molecular mechanics (QM/MM) descriptions). Finite temperature effects are taken into account by molecular dynamics simulations. The different components that determine the structure and dynamics of the chromophore in the protein are dissected, both in the dark state and in the early photointermediates. In vacuum and in solution the chromophore displays a very high flexibility, which is significantly reduced by the protein environment. In the 11- cis chromophore, the bond-length alternation, which is correlated with the dipole moment, is found to be similar in solution and in the protein, while it differs greatly with respect to minimum-energy vacuum structures. In the model of the earliest protein photointermediate, the highly twisted chromophore shows a very reduced bond-length alternation. [source] Torsional Barriers in Aromatic Molecular Clusters as Probe of the Electronic Properties of the ChromophoreCHEMPHYSCHEM, Issue 11 2004Christoph Jacoby Dr. Abstract We present a computer program that is capable of fitting n -fold torsional barriers Vn(n=2,6) and torsional constants F simultaneously to high- and low-resolution spectroscopic data of different isotopomeric internal rotors. The program has been utilized to fit independently barriers and torsional constants for both electronic states of several aromatic clusters. The constant F of the ammonia moiety in the phenol,ammonia cluster is shown to decrease upon electronic excitation, thus imaging the formation of a hydrogen-bonded complex between the phenoxy radical and the NH4 radical in the excited state. In contrast, for the naphthol,ammonia 1:1 clusters no change of F of ammonia could be found. For phenol,methanol cluster we found a decrease of F upon excitation which points to a stronger hydrogen bond between phenol and methanol in the excited state. A strong reduction of the torsional barrier upon excitation points to the formation of a methoxonium radical in a similar photoreaction as in phenol,ammonia cluster. For the phenol,water system we postulate the same mechanism, a photoreaction, which leads to a translocated hydrogen atom in the S1 state what can be deduced from the change of the torsional constant upon electronic excitation. [source] Crystal structure of a ternary mononuclear copper (II) complex: 4-chloro-3-methyl-6[(N-2-picolyl)-1,-iminomethyl]phenolato copper(II)perchlorateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2006S. M. Malathy Sony Abstract The complex crystallizes in monoclinic space group P21/n with unit cell parameters a = 7.295(4), b = 19.627(5), c = 12.770(4) Å, , = 101.25(4)º, V = 1793.2(12) Å3, Z = 4, , = 1.684 Mg/m3 at T = 293(2)K. The structure was solved by Patterson method and refined by full-matrix least-squares procedures to final R = 0.0387 using 2906 observed reflections. The asymmetric unit of the complex contains a mononuclear tridentate ligand, a perchlorate group and a methanol molecule. The compound crystallizes as parallel layers of polymeric complex bridged through perchloarate groups. The molecular CuN2OO,O,,2 chromophore involves an elongated rhombic octahedral structure and the Cu-ligand bond shows greater disparity. The five-membered chelate ring and the pyridine ring lie in the same plane while the six membered chelate ring assumes sofa conformation. A strong O-H,O inter molecular interaction plays a key role in the formation of dimer along b-axis. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Expression patterns of the opsin 5,related genes in the developing chicken retinaDEVELOPMENTAL DYNAMICS, Issue 7 2008Sayuri Tomonari Abstract The opsin gene family encodes G protein,coupled seven-transmembrane proteins that bind to a retinaldehyde chromophore for photoreception. It has been reported that opsin 5 is expressed in mammalian neural tissue, but its function has been elusive. As a first step to understand the function for opsin 5 in the developing eye, we searched for chicken opsin 5 -related genes in the genome by a bioinformatic approach and isolated opsin 5 cDNA fragments from the embryonic retina by RT-PCR. We found that there are three opsin 5,related genes, designated cOpn5m (chicken opsin 5, mammalian type), cOpn5L1 (chicken opsin 5 - like 1), and cOpn5L2 (chicken opsin 5 - like 2), in the chicken genome. Quantitative PCR analysis has revealed that cOpn5m is the most abundant in the developing and early posthatching neural retina. In situ hybridization analysis has shown that cOpn5m is specifically expressed in subsets of differentiating ganglion cells and amacrine cells. These results suggest that the mammalian type opsin 5 may contribute to the development of these retinal cells in the chicken. Developmental Dynamics 237:1910,1922, 2008. © 2008 Wiley-Liss, Inc. [source] Characterization and Assessment of the Microjet Electrode as a Detector for HPLCELECTROANALYSIS, Issue 9 2004Susan Cannan Abstract The microjet electrode (MJE) is characterized as a detector for high performance liquid chromatography (HPLC). Voltammetric measurements of the oxidation of hydroquinone (HQ) allow mass transport to be determined for the MJE detector configuration, and the factors controlling the conversion efficiency of the device to be well understood. The current-time response to the flow injection analysis of volumes of solution in the 10,80,,L range has been established, and the limit of detection of this method has been determined. The latter was found to approach that of UV absorbance measurements, which is particularly encouraging, given that HQ has a relatively strong chromophore (,=2,290.8,cm,1 mol,1,L). This detection system is a robust and simple arrangement with the capability of analyzing large volumes of eluent at typical analytical HPLC flow rates. [source] CE frontal analysis based on simultaneous UV and contactless conductivity detection: A general setup for studying noncovalent interactionsELECTROPHORESIS, Issue 3 2007Henrik Jensen Dr. Abstract CE frontal analysis (CE-FA) has been established as a powerful tool to study noncovalent interactions between macromolecules and small molecules such as drug substances or pharmaceutical excipients. However, when using traditional commercial CE instrumentation, a serious drawback is related to the fact that only UV-active compounds can be studied. In recent years, contactless conductivity detection has become an attractive alternative to UV detection in CE due to its high versatility. In this study, we combine contactless conductivity detection and UV detection in a highly versatile setup for profiling noncovalent interactions between low-molecular-weight molecules and macromolecules. In the case of molecules having a chromophore the setup allows determination of binding constants using two independent detectors. The new contactless conductivity detection cell is compatible with commercial CE instrumentation and is therefore easily implemented in any analysis laboratory with CE expertise. [source] Proteorhodopsin photosystem gene clusters exhibit co-evolutionary trends and shared ancestry among diverse marine microbial phylaENVIRONMENTAL MICROBIOLOGY, Issue 4 2007Jay McCarren Summary Since the recent discovery of retinylidene proteins in marine bacteria (proteorhodopsins), the estimated abundance and diversity of this gene family has expanded rapidly. To explore proteorhodopsin photosystem evolutionary and distributional trends, we identified and compared 16 different proteorhodopsin-containing genome fragments recovered from naturally occurring bacterioplankton populations. In addition to finding several deep-branching proteorhodopsin sequences, proteorhodopsins were found in novel taxonomic contexts, including a betaproteobacterium and a planctomycete. Approximately one-third of the proteorhodopsin-containing genome fragments analysed, as well as a number of recently reported marine bacterial whole genome sequences, contained a linked set of genes required for biosynthesis of the rhodopsin chromophore, retinal. Phylogenetic analyses of the retinal biosynthetic genes suggested their co-evolution and probable coordinated lateral gene transfer into disparate lineages, including Euryarchaeota, Planctomycetales, and three different proteobacterial lineages. The lateral transfer and retention of genes required to assemble a functional proteorhodopsin photosystem appears to be a coordinated and relatively frequent evolutionary event. Strong selection pressure apparently acts to preserve these light-dependent photosystems in diverse marine microbial lineages. [source] A green light-absorbing phycoerythrin is present in the high-light-adapted marine cyanobacterium Prochlorococcus sp.ENVIRONMENTAL MICROBIOLOGY, Issue 10 2005Summary In the high-light-adapted unicellular marine cyanobacterium Prochlorococcus sp. MED4 the cpeB gene is the only gene coding for a structural phycobiliprotein. The absence of any other phycoerythrin gene in the fully sequenced genome of this organism, the previous inability to detect a gene product, and the mutation of two out of four cysteine residues, normally involved in binding chromophores, suggested that MED4- cpeB might not code for a functional protein. Here, transcription of MED4- cpeB at a low level was detected and the transcriptional start site was mapped. Enrichment of the protein identified phycoerythrobilin as its sole chromophore in vivo, which was confirmed by chromophorylation assays in vitro using the recombinant protein. Phycourobilin is the major chromophore in low-light-adapted Prochlorococcus ecotypes such as strain SS120. Therefore, spectrally tuned phycoerythrins are a characteristic feature of distinct Prochlorococcus ecotypes. Further in vitro mutagenesis experiments replacing one or both cysteines C61R/C82S by arginine or serine, respectively, revealed that only Cys82 is required for chromophore binding. Thus, an unusual green light-absorbing phycoerythrin evolved in the high-light-adapted ecotypes of Prochlorococcus, which potentially serves as a photoreceptor. [source] Synthesis and Photophysical Properties of LnIII,DOTA,Bipy Complexes and LnIII,DOTA,Bipy,RuII Coordination ConjugatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2010Miguel Vázquez López Abstract The synthesis and the systematic and comparative photophysical study of a series of visible (EuIII, TbIII) and NIR-emitting (NdIII, YbIII) lanthanide complexes (Ln2L) and ruthenium,lanthanide coordination conjugates (Ln2LRu) are reported. The GdIII complex, the GdIII,RuII coordination conjugate, as well as the RuII complex of the ligand H6L have also been synthesized and photophysically studied as control systems. The ligand H6L, composed of a central bipyridine binding unit and functionalized on each 5,-position with a DOTA macrocycle, has been successfully synthesized from cyclen, 5,5,-dimethyl-2,2,-bipyridine and 1,2-ethylendiamine in a nine-step process. Detailed luminescence studies of all complexes, including the determination of the quantum yield and lifetime, were carried out on finely powdered microcrystalline samples as well as in water, deuterated water and [D6]DMSO at ambient (295 K) and low temperature (77 K). The photophysical data corroborate the existence of energy transfer in the Ln2L complexes and in the Nd2LRu coordination conjugate. However, no (or at most, very little) energy transfer is takes place from the Ru(bipy)3 chromophore to the LnIII ion in the other Ln2LRu heteropolymetallic complexes. Moreover, the photophysical studies reveal that all the complexes and coordination conjugates adopt different conformations and hydration states in solution and in the solid state, which influences the efficiency of the energy transfer between the bipy and/or Ru(bipy)3 antennae and the LnIII ions. [source] Molecular Motion and Performance Enhancement of BORAZAN Fluorescent DyesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009Tyler J. Morin Abstract The preparation of three 2,6-dipyrazolyl-4-X-anilines, H(pz2AnX) (X = p -CF3, Cl, tBu) using CuI-catalyzed amination is described. Subsequent reactions of H(pz2AnX) with triphenylboron proceeds with benzene elimination to give the corresponding Ph2B(pz2AnX) compounds in high yields. The Ph2B(pz2AnX) are more highly emissive in the solid state than the previously reported BORAZAN fluorophores, Ph2B(pzAnX), their monopyrazolyl counterparts. As with the Ph2B(pzAnX), the color of emission in Ph2B(pz2AnX) can be tuned simply by varying the para -aniline substituent where the emission of Ph2B(pz2AnX) is red-shifted relative to the corresponding Ph2B(pzAnX) derivatives. The electronic properties were studied by cyclic voltammetry and electronic absorption/emission spectroscopy as well as by density functional calculations (B3LYP/6-31G*). The di-pyrazolyl derivatives exhibit greater stability toward solvolysis and higher photoluminescent quantum yields (despite the red-shift in emission) compared to their monopyrazolyl counterparts presumably due to kinetic stabilization of the chromophore imparted by the second pyrazolyl ligand. For Ph2B(pz2AnX), evidence for intramolecular motion of the diphenylboryl moiety traversing both pyrazolyl groups was detected by variable temperature 1H NMR spectroscopy. The rate increases with increasing electron-donor abilities of the para -aniline substituent.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] A PCP-Pincer RuII,Terpyridine Building Block as a Potential "Antenna Unit" for Intramolecular SensitizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Marcella Gagliardo Abstract The redox- and photoactive mononuclear complex [Ru(PCP)(tpy,DTTANa4)]Cl {PCP = [C6H3(CH2PPh2)2 -2,6],; tpy,DTTA4, = 4,-(2,2,:6,,2,-terpyridine)-diethylenetriamine- N,N,N,,N, -tetraacetate} possesses an externally directed, vacant N3O4 polyaminocarboxylate-type binding site that coordinates to lanthanide(III) ions to give the neutral heterodinuclear RuII,LnIII complexes [Ru(PCP)(tpy,DTTA)Ln(H2O)2] (Ln = Gd3+, Eu3+). The photophysical properties of solutions of the mononuclear complex [Ru(PCP)(tpy,DTTANa4)]Cl were investigated in MeOH/EtOH (1:4) and compared to those of the solutions of heterodinuclear complexes [Ru(PCP)(tpy,DTTA)Ln(H2O)2] (Ln = Gd3+, Eu3+). Rigid matrix excitation at 77 K of the ,,* level of the ruthenium chromophore in the [Ru(PCP)(tpy,DTTA)Eu(H2O)2] complex results in a weak europium(III) emission pointing to a transfer of energy from Ru,Eu as a result of the metal-to-ligand charge-transfer (MLCT) excited state of the ruthenium component to the luminescent lanthanide ion. The excited state lifetime of the europium complex is 0.2 ms in methanol solution. In deuterated solvents, the lifetime increases to 0.4 ms, which indicates that the process is solvent-dependent as a result of the strongly coordinated molecules of water that are responsible for the quenching in nondeuterated solvents.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005Holger Stephan Abstract Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7-bis(4,-hydroxyphenyl)-1,10-phenanthroline with the corresponding Fréchet-type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper(II) has been studied by liquid,liquid extraction using the radioisotope 64Cu and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper(II) chromophore, which is shown to have the expected distorted square-planar geometry with two phenanthroline donors coordinated to the copper(II) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K , 16 in CHCl3. On the other hand, increasing generation of the dendritic Fréchet-type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper(II) salt to solutions of the higher generation ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Evidence for RPE65-independent vision in the cone-dominated zebrafish retinaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Helia B. Schonthaler Abstract An enzyme-based cyclic pathway for trans to cis isomerization of the chromophore of visual pigments (11- cis -retinal) is intrinsic to vertebrate cone and rod vision. This process, called the visual cycle, is mostly characterized in rod-dominated retinas and essentially depends on RPE65, an all- trans to 11- cis -retinoid isomerase. Here we analysed the role of RPE65 in zebrafish, a species with a cone-dominated retina. We cloned zebrafish RPE65 and showed that its expression coincided with photoreceptor development. Targeted gene knockdown of RPE65 resulted in morphologically altered rod outer segments and overall reduced 11- cis -retinal levels. Cone vision of RPE65-deficient larvae remained functional as demonstrated by behavioural tests and by metabolite profiling for retinoids. Furthermore, all- trans retinylamine, a potent inhibitor of the rod visual cycle, reduced 11- cis -retinal levels of control larvae to a similar extent but showed no additive effects in RPE65-deficient larvae. Thus, our study of zebrafish provides in vivo evidence for the existence of an RPE65-independent pathway for the regeneration of 11- cis -retinal for cone vision. [source] Specific Ca2+ Fluorescent Sensor: Signaling by Conformationally Induced PET Suppression in a Bichromophoric AcridinedioneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2009Pichandi Ashokkumar Abstract A series of acridinedione-based bichromophoric podand systems 1a,c were synthesized and characterized. Among these, bichromophore 1c shows specific binding of Ca2+ in the presence of other biologically important metal ions like Na+, K+, Mg2+, and Zn2+. The selective complexation was proved by steady-state emission, time-resolved emission, and 1H NMR titration. Signaling of the binding event was achieved by Ca2+ -induced folding of the bichromophore, resulting in PET suppression in the acridinedione chromophore. Involvement of a PET process in the optical signaling was confirmed by comparing bichromophores 1a,c with non-PET compound 2 and monochromophore model compound 3. Non-PET compound 2 failed to give optical response upon Ca2+ binding as a result of the absence of a PET process in the Ca2+ -bound complex. Monochromophore 3 shows a similar optical response, which is the same as that in 1c. Titration of the metal-ion-bound complex of 1c with EDTA released the metal ion from the complex, thereby regaining the original photophysical properties of the bichromophore.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Thermal Behavior of Free-Base and Core-Modified Bicyclo[2.2.2]octadiene-Fused PorphyrinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2008Hidemitsu Uno Abstract Multistep thermal fragmentation of quadruply bicyclo[2.2.2]octadiene-fused porphyrins giving tetrabenzoporphyrins was examined in detail. After the first extrusion of an ethylene molecule from the porphyrin derivative, the opposite bicyclo[2.2.2]octadiene moiety preferentially underwent the second retro-Diels,Alder reaction to give an opp -dibenzoporphyrin derivative rather than an adj -dibenzoporphyrin derivative. These two benzoporphyrin derivatives then decomposed to give a tribenzoporphyrin derivative in similar rates. The temperature regions of these fragmentations could not be distinguished by thermogravimetric analysis. In contrast, the third and the fourth fragmentations obviously occurred stepwise. There was a temperature region where the tribenzoporphyrin derivative preferentially existed. In the case of the 21,23-dithiaporphyrin derivative, opp -21,23-dithiadibenzoporphyrin, possessing benzo moieties fused at the pyrrole parts of the core-modified porphyrin chromophore was predominantly formed during the fragmentation. In the case of the 21-thiaporphyrin derivative, an ethylene molecule was extruded selectively from the bicyclo[2.2.2]octadiene moiety adjacent to the thiophene part to give 21-thiabenzo[q]porphyrin and then 21-thiabenzo[g,q]porphyrin derivatives. In these cases, the last ethylene extrusion also occurred very slowly. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Meroterpenoid Pigments from Albatrellus flettii (Basidiomycetes),EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2007Barbara Koch Abstract The pigments responsible for the blue colour of the North American polypore Albatrellus flettii have been isolated and their structures elucidated by spectroscopic methods. Albatrellin, a dimeric meroterpenoid with a furylbenzoquinone chromophore, is accompanied by its 16-hydroxy and 16-oxo derivatives. The latter has recently been described as grifolone B from a Japanese collection of A. caeruleoporus. Based on the idea that albatrellin is formed in nature by oxidative coupling of a grifolinquinone with the furan derivative cristatin, the blue pigment was synthesized in vitro. The reaction could be applied to the synthesis of several analogues.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis of Carrier-Transporting Dendrimers with Perylenebis(dicarboximide)s as a Luminescent CoreEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2006Jianfeng Pan Abstract Well-defined, modular dendrimers enable processing techniques and electronic properties to be tuned independently. Moreover, the dendritic topology can isolate the core chromophore, thus reducing or eliminating strong intermolecular interactions. This paper presents the synthesis of three series of flexible, dendron-functionalized dendrimers as red-light-emitting materials by a convergent approach: (1) carbazole (CZ) or oxadiazole (OXZ) terminated imide-type dendrimers, (2) cascade energy-transferring imide-type dendrimers, and (3) CZ-terminated perylene bay-type dendrimers. They all consist of the luminescent core of perylenebis(dicarboximide)s with specific functional groups of CZ or OXZ at the periphery and are constructed from flexible Fréchet-type poly(aryl ether) dendrons. The chemical structures of the dendrons and dendrimers were determined by standard spectroscopic techniques including 1H and 13C NMR spectroscopy and low/high-resolution mass spectrometry (ESI or MALDI-TOF). The dendrimers are designed on the basis of the following considerations: (1) dendron functionalization to incorporate CZ or OXZ units to realize the carrier-injection adjustment, (2) tuning or improving solubility, functionality, glass-transition temperature (Tg) with well-defined dendrons, and (3) avoiding luminescence quenching with the help of high site-isolation of dendrons to enhance core luminescence. DSC results indicate that the incorporation of Fréchet-type poly(aryl ether) dendrons can improve the amorphous properties and increase Tg. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Screening of urocanic acid isomers in human basal and squamous cell carcinoma tumors compared with tumor periphery and healthy skinEXPERIMENTAL DERMATOLOGY, Issue 10 2008Juan Manuel Decara Abstract:,Trans -urocanic acid is a major chromophore for ultraviolet (UV) radiation in human epidermis. The UV induces photoisomerization of trans -urocanic acid (tUCA) form to cis -urocanic acid (cUCA) and has been reported as an important mediator in the immunosuppression induced by UV. This immunomodulation has been recognized as an important factor related to skin cancer development. This is the first time that UCA isomers have been measured in epidermis of skin biopsies from patients with squamous cell carcinoma (SCC) and with basal cell carcinoma (BCC) and compared with the tumor periphery and biopsies of healthy photoexposed and non-photoexposed skin as controls. The UCA isomers were separated and quantified by high performance liquid chromatography. Analysis of UCA in healthy skin showed significant increase in total UCA content in non-photoexposed body sites compared with highly exposed skins. In contrast, the percentage of cUCA was higher in photoexposed body sites. Maximal levels of cUCA were found in cheek, forehead and forearm and lower levels in abdomen and thigh. No differences were found in total UCA concentration between the tumor samples and healthy photoexposed skin. However, differences were found in relation between isomers. Higher levels of cUCA were detected in SCC biopsies (44% of total UCA) compared with samples of BCC and that of healthy photoexposed skin (30%). These results suggest that the UV radiation exposure, a main factor in development of SCC can be mediated, apart from direct effect to cells (DNA damage), by immunosuppression pathways mediated by high production of cUCA. [source] In vitro expansion of DNA triplet repeats with bulge binders and different DNA polymerasesFEBS JOURNAL, Issue 18 2008Di Ouyang The expansion of DNA repeat sequences is associated with many genetic diseases in humans. Simple bulge DNA structures have been implicated as intermediates in DNA slippage within the DNA repeat regions. To probe the possible role of bulged structures in DNA slippage, we designed and synthesized a pair of simple chiral spirocyclic compounds [Xi Z, Ouyang D & Mu HT (2006) Bioorg Med Chem Lett16, 1180,1184], DDI-1A and DDI-1B, which mimic the molecular architecture of the enediyne antitumor antibiotic neocarzinostatin chromophore. Both compounds strongly stimulated slippage in various DNA repeats in vitro. Enhanced slippage synthesis was found to be synchronous for primer and template. CD spectra and UV thermal stability studies supported the idea that DDI-1A and DDI-1B exhibited selective binding to the DNA bulge and induced a significant conformational change in bulge DNA. The proposed mechanism for the observed in vitro expansion of long DNA is discussed. [source] Homologous expression of a bacterial phytochromeFEBS JOURNAL, Issue 8 2007The cyanobacterium Fremyella diplosiphon incorporates biliverdin as a genuine, functional chromophore Bacteriophytochromes constitute a light-sensing subgroup of sensory kinases with a chromophore-binding motif in the N-terminal half and a C-terminally located histidine kinase activity. The cyanobacterium Fremyella diplosiphon (also designated Calothrix sp.) expresses two sequentially very similar bacteriophytochromes, cyanobacterial phytochrome A (CphA) and cyanobacterial phytochrome B (CphB). Cyanobacterial phytochrome A has the canonical cysteine residue, by which covalent chromophore attachment is accomplished in the same manner as in plant phytochromes; however, its paralog cyanobacterial phytochrome B carries a leucine residue at that position. On the basis of in vitro experiments that showed, for both cyanobacterial phytochrome A and cyanobacterial phytochrome B, light-induced autophosphorylation and phosphate transfer to their cognate response regulator proteins RcpA and RcpB [Hübschmann T, Jorissen HJMM, Börner T, Gärtner W & deMarsac NT (2001) Eur J Biochem268, 3383,3389], we aimed at the identification of a chromophore that is incorporated in vivo into cyanobacterial phytochrome B within the cyanobacterial cell. The approach was based on the introduction of a copy of cphB into the cyanobacterium via triparental conjugation. The His-tagged purified, recombinant protein (CphBcy) showed photoreversible absorption bands similar to those of plant and bacterial phytochromes, but with remarkably red-shifted maxima [,max 700 and 748 nm, red-absorbing (Pr) and far red-absorbing (Pfr) forms of phytochrome, respectively]. A comparison of the absorption maxima with those of the heterologously generated apoprotein, assembled with phycocyanobilin (,max 686 and 734 nm) or with biliverdin IX, (,max 700 and 750 ± 2 nm), shows biliverdin IX, to be a genuine chromophore. The kinase activity of CphBcy and phosphotransfer to its cognate response regulator was found to be strictly Pr -dependent. As an N-terminally located cysteine was found as an alternative covalent binding site for several bacteriophytochrome photoreceptors that bind biliverdin and lack the canonical cysteine residue (e.g. Agrobacterium tumefaciens and Deinococcus radiodurans), this corresponding residue in heterologously expressed cyanobacterial phytochrome B was mutated into a serine (C24S); however, there was no change in its spectral properties. On the other hand, the mutation of His267, which is located directly after the canonical cysteine, into alanine (H267A), caused complete loss of the capability of cyanobacterial phytochrome B to form a chromoprotein. [source] Biochemical and spectroscopic characterization of the bacterial phytochrome of Pseudomonas aeruginosaFEBS JOURNAL, Issue 8 2005Ronja Tasler Phytochromes are photochromic biliproteins found in plants as well as in some cyanotrophic, photoautotrophic and heterotrophic bacteria. In many bacteria, their function is largely unknown. Here we describe the biochemical and spectroscopic characterization of recombinant bacterial phytochrome from the opportunistic pathogen Pseudomonas aeruginosa (PaBphP). The recombinant protein displays all the characteristic features of a bonafide phytochrome. In contrast with cyanobacteria and plants, the chromophore of this bacterial phytochrome is biliverdin IX,, which is produced by the heme oxygenase BphO in P. aeruginosa. This chromophore was shown to be covalently attached via its A-ring endo-vinyl group to a cysteine residue outside the defined bilin lyase domain of plant and cyanobacterial phytochromes. Site-directed mutagenesis identified Cys12 and His247 as being important for chromophore binding and photoreversibility, respectively. PaBphP is synthesized in the dark in the red-light-absorbing Pr form and immediately converted into a far-red-light-absorbing Pfr-enriched form. It shows the characteristic red/far-red-light-induced photoreversibility of phytochromes. A chromophore analog that lacks the C15/16 double bond was used to show that this photoreversibility is due to a 15Z/15E isomerization of the biliverdin chromophore. Autophosphorylation of PaBphP was demonstrated, confirming its role as a sensor kinase of a bacterial two-component signaling system. [source] | |||||||||||||||||||||||||||||||||||||