Structural studies of the melibiose permease of Escherichia coli by fluorescence resonance energy transfer. II. Identification of the tryptophan residues acting as energy donors

In the accompanying paper, we demonstrated the presence of a fluorescence resonance energy transfer (FRET) between the tryptophans of the melibiose permease (MelB) of Escherichia coli and a fluorescent sugar, 2'-(N-5-dimethylaminonaphthalene-1-sulfonyl)aminoethyl-1-thio-beta-D- galactopyranoside (Dns2-S-Gal) bound at the sugar-binding site (Maehrel, C., Cordat, E., Mus-Veteau, I., and Leblanc, G. (1998) J. Biol. Chem. 273, 33192-33197). To identify the tryptophans that transfer their energy to the fluorescent sugar, we analyzed the FRET properties of MelB mutants carrying the replacement of each of the eight MelB tryptophans by a phenylalanine. The data indicate that Trp64, localized in loop 2-3 from the N-terminal domain, and Trp299, localized in helix IX in the C-terminal domain, are responsible for up to 80% of the FRET signal. Moreover, by assuming that only Trp299 transfers energy to Dns2-S-Gal in mutant W64F, whereas only Trp64 transfers energy to Dns2-S-Gal in mutant W299F, we calculated that Trp299 and Trp64 are about 14 and 20 A away from the probe, respectively. In addition, we observed that mutating Trp342, localized in helix X of the C-terminal domain, produces a significant increase of the polarity of the fluorescent sugar environment, suggesting its proximity to the sugar-binding site. Taken together, these data provide additional support for the suggestion that (i) the sugar-binding site is localized in the C-terminal part of the transporter, probably close to membrane segments IX and X, and (ii) the N-terminal domain, and particularly cytoplasmic loop 2-3, is also close to the sugar-binding site.     

Potential photosensitizers for photodynamic therapy. IV. Photophysical and photochemical properties of azaporphyrin and azachlorin derivatives

The photophysical and photochemical properties of a 5-azaprotoporphyrin derivative ([5]AZPP), a zinc-15-azaporphyrin derivative (Zn-[15]AZIDP) and an E-Z isomeric mixture of a 5-azachlorin derivative ([5]AZCH) were studied in various solvents. The quantum yields of fluorescence phi F0, S1-T1 intersystem crossing phi T0 and singlet oxygen (1 delta g) formation phi delta were measured and the Stern-Volmer constants for the quenching of the S1 states by oxygen and the rate constants of quenching of O2(1 delta g) by the different azaporphyrinoid compounds were obtained. The fluorescence quantum yield (phi F0 = 0.23), the strong absorption in the red (lambda max = 674 nm, epsilon max = 66,000 M-1 cm-1) and the high value of the quantum yield for singlet oxygen (1 delta g) formation (phi delta = 0.65) observed for [5]AZCH recommend azachlorin derivatives as potential markers and photosensitizers for tumour therapy.     

Structural studies of the melibiose permease of Escherichia coli by fluorescence resonance energy transfer. I. Evidence for ion-induced conformational change

Further insight into the cosubstrate-induced structural change of the melibiose permease (MelB) of Escherichia coli has been sought by investigating the binding and spectroscopic properties of the fluorescent sugar 2'-(N-5-dimethylaminonaphthalene-1-sulfonyl)aminoethyl 1-thio-beta-D-galactopyranoside (Dns2-S-Gal) and related analogs (Dns3-S-Gal or Dns6-S-Gal with a propyl or hexyl instead of an ethyl linker, respectively) interacting with MelB in membrane vesicles or in proteoliposomes. The three analogs efficiently inhibit melibiose transport and bind to MelB in a sodium-dependent fashion. Their dissociation constants (Kd) are in the micromolar range in the presence of NaCl and an order of magnitude higher in its absence. In the presence of NaCl and Dns2-S-Gal, sample excitation at 335 or 297 nm gives rise to a fluorescent signal at around 465 nm, whereas Dns3-S-Gal or Dns6-S-Gal emits a fluorescence light at 490 or 506 nm, respectively. Detailed study of the Dns2-S-Gal signal elicited by a 297 nm illumination indicates that a tryptophan-mediated fluorescence resonance energy transfer phenomenon is involved in the response. All fluorescence signals below 500 nm are prevented by addition of melibiose in excess, and the kinetic constants describing their dependence on the probe or NaCl concentrations closely correlate with the probe binding constants. Finally, the Dns2-S-Gal signal recorded in sodium-free medium is red shifted by up to 25 nm from that recorded in the presence of NaCl. Taken together, these results suggest (i) that the fluorescence signals below 500 nm arise from Dns-S-Gal molecules bound to MelB, (ii) the presence of a highly hydrophobic environment close to or at the sugar-binding site, the polarity of which increases on moving away from the sugar-binding site, and (iii) that the interaction of sodium ions with MelB enhances the hydrophobicity of this environment. These results are consistent with the induction of a cooperative change of the structure of the sugar-binding site or of its immediate vicinity by the ions.     

Luminescent Properties of Bi-Rare Earth Complexes with m-methylbenzoic Acid and 1, 10-phenanthroline

Ｔｈｅｒｅｈａｓｂｅｅｎａｇｒｏｗｉｎｇｉｎｔｅｒｅｓｔｉｎｔｈｅｌｕｍｉｎｅｓｃｅｎｃｅｐｒｏｐｅｒｔｉｅｓｏｆｌａｎｔｈａｎｉｄｅｃｏｍｐｌｅｘ ｅｓｗｉｔｈｏｒｇａｎｉｃａｃｉｄｓ ,ｓｕｃｈａｓａｒｏｍａｔｉｃａｃｉｄｓｏｒｐｈｔｈａｌｉｃａｃｉｄｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌｃｈｅｍｉｃａｌａｎｄｂｉｏｌｏｇｉｃａｌａｐｐｌｉｃａｔｉｏｎｆｏｒｐｒｏｂｅｓａｎｄｌａｂｅｌｓ .Ｅｕ3 + ａｎｄＴｂ3 + ｈａｖｅｍｏｒｅｅｘｃｅｌ ｌｅｎｔｌｕｍｉｎｅｓｃｅｎｃｅｐｒｏｐｅｒｔｉ…     

Paternal care enhances male reproductive success in pine engraver beetles

His117 of the D2 protein of photosystem II (PS II) is a conserved residue in the second transmembrane region of the protein and has been suggested to bind chlorophyll. Nine site-directed mutations were introduced at residue 117, using both photosystem I (PS I)-containing and PS I-less background strains of the cyanobacterium Synechocystis sp. PCC 6803. Of these nine, four (H117C, H117M, H117N, and H117T) were photoautotrophic in the PS I-containing background. The other mutants (H117F, H117L, H117P, H117R, and H117Y) did not accumulate appreciable amounts of PS II in their thylakoids. The type of residues that can functionally replace His117 support the notion of His117 serving as a chlorophyll ligand. The properties of the H117N and H117T mutants were characterized in more detail. Whereas the properties of the H117N mutant were close to those of wild type, in the H117T mutant the 77-K fluorescence emission spectrum shows a much smaller amplitude at 695 nm than expected on the basis of the amount of PS II that is present. Moreover, in H117T, the amount of light needed to half-saturate O2-evolution rates was twofold higher than in the control strain, and the variable fluorescence yield was quenched. However, O2 evolution rates at saturating light intensity and electron-transport kinetics were normal in the mutant. Also, the radical accessory chlorophyll (Chlz+) formed by donation of an electron to the PS-II reaction center could be generated normally by illumination at low temperature in the H117T mutant. We conclude that the chlorophyll associated with residue 117 of the D2 protein is important for efficient excitation transfer between the proximal antenna and the PS II reaction center. A possible mechanism involving a chlorophyll cation to explain the quenching in the H117T mutant is discussed.     

Influence of B2O3 on Spectroscopic Properties of Er^3＋/Yb^3＋ Co-Doped Tungsten-Tellurite Glasses

A series of novel Er^3＋/Yb^3＋ co-doped （85- x ） TeO2-15WO3-xB2O3 （TWB;x=2%,5%,8%（mole fraction） ） glasses were prepared. Influence of B203 on the spectroscopic properties of Er^3＋/Yb^3＋ co-doped tungsten-tellurite glasses were investigated. It is found that the intensity of 1.5μm fluorescence, lifetime of the ^4I13/2 level and upconversion fluorescence all decrease with the increase of B2O3 content. The product of full width at half maximum （FWHM） and stimulated emission cross-section （σe^peak） of Er^3＋ ：^4I13/2→^4I15/2 transition has an optimum when B203 is 5% （mole fraction）. The emission spectra of Er^3＋ ： ^4I13/2→^4I15/2 transition was analyzed using peak-fit routine, and an equivalent four-level system was proposed to estimate the stark splitting for the 411512 and ^4I13/2 levels of Er^3＋ ions in TWB glasses at room temperature.     

Upconversion properties of Y2O3：Er films prepared by sol-gel method

Y2O3:Er3+ films were prepared by a simple sol-gel process. The structural properties of Y2O3:Er3+ flints were characterized with X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The results indicated that the Y2O3:Er3+ f'rims might have high upconversion efficiency because of their low vibrational energy. Under 785 and 980 nm laser excitation, the samples showed green (2H11/2→4I15/2, 4S3/2→4I15/2) and red (4F9/2→4I15/2) upconversion emissions. The upconversion mechanisms were stud-led in detail through laser power dependence. Excited state absorption and energy transfer process were discussed as possible upconversion mechanisms. The cross relaxation process in Er3+ was also investigated.     

Comparison of D2O and ethanol dilutions in total body water measurements in humans

Total body water was measured by ethanol dilution and D2O stable isotope dilution in a group of 20 healthy volunteers (5 females and 15 males), predominantly 23- to 31-year-old students. Both indicator substances were given orally with an ethanol burden of 0.8 g/kg body weight and a D2O burden of 0.1 g/kg body weight after 12-h food and fluid restriction. This first direct comparison of total body water (TBW) from ethanol and D2O dilutions revealed the ethanol compartments to be smaller than those of D2O. The quotient of TBW (ethanol)/TBW (D2O) was 97.7%, which is the order of the quotient TBW (H2(18)O)/TBW (D2O) ( = 97%), well known from the literature and taken to represent relatively exactly the value of TBW overestimation (based on H/D exchange for acid protons) following D2O dilution [36]. Thus the value of TBW (ethanol) is almost identical to that of H2(18)O, which provides direct evidence that ethanol is distributed only in the body water.     

Principles of magnetic resonance angiography

A strongly fluorescing 7-hydroxycoumarin (umbelliferone, U) oxidized in dilute (10 mumol/L-O, 1 mol/L) aqueous solution with CIO- or CIO- + H2O2 (but not with H2O2 alone) produces a strong chemiluminescence (CL). Light emission kinetics depends on the pH of solution (4.0-10.5) and the reaction has a low activation energy Ea = 31 +/- 2 kJ/mol (285-310 K). The spectrum covers the fluorescence of umbelliferone (400-550 nm, lambda max 460 nm). No red emission typical of 1 delta g, 1 sigma g, 1 sigma+g (O2)2 is observed either in the umbelliferone+CIO- or the umbelliferone +CIO- + H2O2 solution. The possible mechanism of CL and concomitant degradative oxidation of umbelliferone is discussed.     

Fluorescence studies of human semi-beta-hemoglobin assembly

The intrinsic fluorescence properties of human alpha apohemoglobin at protein concentrations from 1 to 5 microM in 0.1 M potassium phosphate buffer, pH 7 or 8 at 5 degrees C were monitored in the absence and presence of a fixed concentration (5 microM) of a fluorescence quenching heme-containing native or Des (146-His, 145-Tyr) beta chain partner. These "reverse quenching" studies revealed that the emission intensity changes observed correlated well with protein concentration and theoretical extent of semi-beta-hemoglobin assembly. Furthermore, the relative quenching efficiencies were calculated to be 0.32, 0.25 and 0.61 for beta (pH 7), beta (pH 8) and Des beta (pH 7) chains, respectively. Thus, heme-mediated quenching was sensitive to the expected pH induced alpha apohemoglobin conformational change and to alteration in beta chain structure. Intramolecular changes induced by carboxylterminal modification (decreased "beta chain self-quenching") appeared to enhance the intermolecular rearrangements (increased "alpha chain partner quenching") seen upon subunit assembly.     

Hydrothermal synthesis and crystal structure study of two novel 3-D mellitates {Nd2[C6(COO)6](H2O)6} and {Ho2[C6(COO)6](H2O)6}

Two novel 3-D coordination compounds, Nd2[C6(COO)6](H2O)6(1)and Ho2[C6(COO)6](H2O)6(2), were hydrothermally synthe-sized from mellitic acid and neodymium perchlorate (or holmium perchlorate) in the alkaline aqueous solution and characterized with ele-mental analysis, TG, IR spectrum, and single crystal X-ray diffraction. The two compounds were isostructural and crystallized in the ortho-rhombic system, space group Pnnm, with a=1.3531 (4) nm, b=0.6687 (2) nm, c=1.0224(3) nm, V=0.92523(5) nm3, Z=4, D=2.630 g/cm3, F(000)=696.0, Goof=1.052. Final R indices [I 2Σ(I)]: R1=0.0195, wR2=0.0382 for 1; a=1.3411(2) nm, b=0.6586(1) nm, c=1.0116(2) nm, V=0.8935(3) nm3, Z=4, D=2.877 g/cm3, F(000)=724.0, Goof=1.061. Final R indices [I 2Σ(I)]: R1=0.0200, wR2=0.0479 for 2. In the two compounds 1 and 2, the mellitic acid ligand, in which all the carboxylate groups were deprotonated, had only one kind of coordination mode to bridge metal ions to form four-connected three-dimensional diamondiod networks.     

Physical and functional independency of p70 and p58 natural killer (NK) cell receptors for HLA class I: their role in the definition of different groups of alloreactive NK cell clones

Natural killer (NK) cells express clonally distributed receptors for different groups of HLA class I alleles. The Z27 monoclonal antibody described in this study recognizes a p70 receptor specific for HLA-B alleles belonging to the Bw4 supertypic specificity. Single amino acid substitutions in the peptide-binding groove of HLA-B2705 molecules influenced the recognition by some, but not all, p7O/Z27+ clones. This suggests the existence of a limited polymorphism within the p7O family of receptors. The pattern of reactivity of monoclonal antibody Z27 revealed that Bw4-specific receptors may be expressed alone or in combination with different (GL183 and/or EB6) p58 molecules. Analysis of NK clones coexpressing p58 and p7O receptors allowed us to demonstrate that the two molecules represent physically and functionally independent receptors. The expression of p7O molecules either alone or in combination with EB6 molecules provided the molecular basis for understanding the cytolytic pattern of two previously defined groups of "alloreactive" NK cell clones ("group 3" and "group 5").     

Isolation and characterizations of quinone analogue-resistant mutants of bo-type ubiquinol oxidase from Escherichia coli

Cytochrome bo is a member of the heme-copper terminal oxidase superfamily and serves as a four-subunit ubiquinol oxidase in the aerobic respiratory chain of Escherichia coli. To probe the location and structural properties of the ubiquinol oxidation site, we isolated and characterized five or 10 spontaneous mutants resistant to either 2,6-dimethyl-1,4-benzoquinone, 2,6-dichloro-4-nitrophenol, or 2,6-dichloro-4-dicyanovinylphenol, the potent competitive inhibitors for the oxidation of ubiquinol-1 [Sato-Watanabe, M., Mogi, T., Miyoshi, H., Iwamura, H., Matsushita, K., Adachi, O., and Anraku, Y. (1994) J. Biol. Chem. 269, 28899-28907]. Analyses of the growth yields and the ubiquinol-1 oxidase activities of the mutant membranes showed that the mutations increased the degree of the resistance to the selecting compounds. Notably, several mutants showed the cross-resistance. These data indicate that the binding sites for substrate and the competitive inhibitors are partially overlapped in the ubiquinol oxidation site. All the mutations were linked to the expression vector, and 23 mutations examined were all present in the C-terminal hydrophilic domain (Pro96-His315) of subunit II. Sequencing analysis revealed that seven mutations examined are localized near both ends of the cupredoxin fold. Met248Ile, Ser258Asn, Phe281Ser, and His284Pro are present in a quinol oxidase-specific (Qox) domain and proximal to low-spin heme b in subunit I and the lost CuA site in subunit II, whereas Ile129Thr, Asn198Thr, and Gln233His are rather scattered in a three-dimensional structure and closer to transmembrane helices of subunit II. Our data suggest that the Qox domain and the CuA end of the cupredoxin fold provide the quinol oxidation site and are involved in electron transfer to the metal centers in subunit I.     

Protein rotational dynamics investigated with a dual EPR/optical molecular probe. Spin-labeled eosin

An acyl spin-label derivative of 5-aminoeosin (5-SLE) was chemically synthesized and employed in studies of rotational dynamics of the free probe and of the probe when bound noncovalently to bovine serum albumin using the spectroscopic techniques of fluorescence anisotropy decay and electron paramagnetic resonance (EPR) and their long-lifetime counterparts phosphorescence anisotropy decay and saturation transfer EPR. Previous work (Beth, A. H., Cobb, C. E., and J. M. Beechem, 1992. Synthesis and characterization of a combined fluorescence, phosphorescence, and electron paramagnetic resonance probe. Society of Photo-Optical Instrumentation Engineers. Time-Resolved Laser Spectroscopy III. 504-512) has shown that the spin-label moiety only slightly altered the fluorescence and phosphorescence lifetimes and quantum yields of 5-SLE when compared with 5-SLE whose nitroxide had been reduced with ascorbate and with the diamagnetic homolog 5-acetyleosin. In the present work, we have utilized time-resolved fluorescence anisotropy decay and linear EPR spectroscopies to observe and quantitate the psec motions of 5-SLE in solution and the nsec motions of the 5-SLE-bovine serum albumin complex. Time-resolved phosphorescence anisotropy decay and saturation transfer EPR studies have been carried out to observe and quantitate the microseconds motions of the 5-SLE-albumin complex in glycerol/buffer solutions of varying viscosity. These latter studies have enabled a rigorous comparison of rotational correlation times obtained from these complementary techniques to be made with a single probe. The studies described demonstrate that it is possible to employ a single molecular probe to carry out the full range of fluorescence, phosphorescence, EPR, and saturation transfer EPR studies. It is anticipated that "dual" molecular probes of this general type will significantly enhance capabilities for extracting dynamics and structural information from macromolecules and their functional assemblies.     

Synthesis and Structural Determination of Eight Coordinate NH_4[Yb(Ⅲ)(Cydta)(H_2O)_2]·5H_2O

ｅｃａｕｓｅｓｏｍｅｒａｒｅｅａｒｔｈｍｅｔａｌｃｏｍｐｏｕｎｄｓｈａｖｅｔｈｅｐｒｏｍｏｔｉｖｅａｃｔｉｏｎｔｏｔｈｅｇｒｏｗｔｈｏｆａｎｉ ｍａｌｓａｎｄｐｌａｎｔｓ[1 ] ,ａｎｄｔｈｅｆｕｎｃｔｉｏｎｏｆａｎｔｉｉｎ ｆｌａｍｍａｔｉｏｎ ,ａｎｔｉｂａｃｔｅｒｉｕｍ ,ａｎｔｉｃｏａｇｕｌａｎｔｉｏｎａｎｄａｎｔｉｃａｎｅｒ[2 ] ,ｔｈｅｉｎｖｅｓｔｉｇａｔｉｏｎｏｎｔｈｅｓｙｎ ｔｈｅｓｅｓａｎｄｓｔｒｕｃｔｕｒｅｓｏｆｔｈｅｅｖｅｒｙｋｉｎｄｓｏｆｒａｒｅｅａｒｔｈｍｅｔａｌｃｏｍｐｏｕｎｄｓ…     

CdTe量子点-双硫腙荧光开关测定铜

CdTe量子点表面包覆双硫腙,由于双硫腙与CdTe量子点之间发生荧光共振能量转移使得CdTe量子点荧光猝灭,铜的加入与双硫腙形成双齿螯合物,使得CdTe量子点荧光能量转移被阻止,CdTe量子点荧光强度得以恢复,由此建立了一种荧光开关测定痕量铜的新方法。在最佳条件下,0.5 mL双硫腙@CdTe 量子点(Dit@CdTe),1.5 mL pH 7.5的Tris-HCl缓冲溶液中加入不同浓度的Cu²⁺,放置10 min,于激发波长/发射波长为431 nm/591 nm下进行荧光测定,荧光增强强度与Cu²⁺浓度在0.01~10.0 μmol/L范围内呈良好线性关系,相关系数为0.990 3,检出限为0.004 μmol/L。方法用于实际水样中铜的测定,相对标准偏差小于6.8%,回收率在97%～105%之间,并且测定结果与电感耦合等离子体质谱法(ICP-MS)测定结果一致。     

The effect of magnesium ions on action spectra for reactions mediated by photosystems I and II in spinach chloroplasts

Action spectra were measured for positive changes in variable fluorescence (emission greater than 665 nm) excited by a beam of 485 nm chopped at 75 HZ. The action of two further beams were compared, one being variable, the other (reference) constant with respect to wavelength and intensity. Comparison was achieved by alternating the reference and the variable wavelength beams at 0.3 HZ and adjusting the intensity of the latter such as to cancel out any 0.3 HZ component in the 75 HZ fluorescence signal. The relative action then was obtained as the reciprocal of the intensity of the variable wavelength beam. Similarly, action spectra were measured for O2 evolution with ferricyanide/p-phenylenediamine as electron acceptor, and for O2 uptake mediated by methyl viologen with ascorbate 3-(p-chlorophenyl)-1,1-dimethylurea as electron donor in the presence of 2,6-dichlorophenolindophenol. Addition of 5 mM MgCl2 increases the relative action around 480 nm for the change in variable fluorescence and p-phenylenediamine-dependent O2 evolution, and decreases it for methyl viologen-mediated O2 uptake with 2,6-dichlorophenolindo-phenol/ascorbate as electron donor in the presence of 3-(p-chlorophenyl)-1,1-dimethylurea. The change in variable fluorescence and O2 evolution are stimulated by MgCl2, whereas O2 uptake is inhibited by it. The results are discussed in terms of a model assuming a tripartite organization of the photosynthetic pigments (Thornber, J. P. and Highkin, H. R. (1974) Eur. J. Biochem. 41, 109-116; Butler, W. L. and Kitajima, M. (1975) Biochim. Biophys. Acta 396, 72-85). MgCl2 is thought to promote energy transfer to Photosystem II from a light-harvesting pigment complex serving both photosystems.     

The binding of ethyl carbamate to DNA of mouse liver in vivo: the nature of the bound molecule and the site of binding

Ethyl carbamate, labelled at C1 with 14C, bound in vivo to liver DNA of intact and partially hepatectomised mice. Isotope (18O) enrichment was not detected in the oxygen of liver DNA of mice injected with [18O] ethyl carbamate, C2H5--18O--CO--NH2. This suggests that it was the ethyl group and not the ethoxy group which bound to DNA. Chromatographic analysis of acid hydrolysates of liver DNA from mice treated with [1-14C] ethyl carbamate provided no evidence of alkylation or other form of binding to purine or pyrimidine bases. On relatively mild acid hydrolysis the alkyl group remained bound to the "apurinic acid" fraction, while more vigorous hydrolysis lead progressively first to its separation as highly ionisable hydrophilic non-volatile compounds and then to its loss as a volatile compound. DNAase I followed by phosphodiesterase hydrolysis also split off the 14C-containing group as a volatile compound. The volatile compound was identified as ethanol. These results suggest that the alkyl group was bound as an ester to a phosphate group in the DNA chain. Results with DNA from partially hepatectomised mice did not differ from those with DNA from intact mice.     

Synthesis and Crystal Structure of a 4f-3d Complex [La(DMF)_6(H_2O)_3][Cr(CN)_6]·2H_2O

Ｒｅｃｅｎｔｌｙ ,ｔｈｅｒｅｈａｓｂｅｅｎｃｏｎｓｉｄｅｒａｂｌｅｉｎ ｔｅｒｅｓｔｉｎｌａｎｔｈａｎｉｄｅ(Ⅲ )ｈｅｘａｃｙａｎｏｆｅｒｒａｔｅｓａｎｄｔｈｅａｎａｌｏｇｏｕｓｃｏｂａｌｔ(Ⅲ )ａｓｗｅｌｌａｓｃｈｒｏｍｉｕｍ(Ⅲ )ｃｏｍｐｌｅｘｅｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌａｓｃａｔａｌｙｔｉｃ ,ｓｅｍｉｃｏｎｄｕｃｔｉｖｅ ,ａｎｄｍａｇｎｅｔｉｃｍａｔｅ ｒｉａｌｓ[1～ 4] .Ｆｏｒｅｘａｍｐｌｅ ,ｍａｇｎｅｔｉｃｓｔｕｄｉｅｓｏｎａｓｅｒｉｅｓｏｆｔｈｒｅｅ ｄｉｍｅｎｓｉｏ…     

Synthesis, Structure and Fluorescence Properties of Tb(Ⅲ) Complex with Isonicotinic Acid and Biphenyl-2,2''-Dicarboxylic Acid

Terbium perchlorate reacted with isonicotinic acid (Hpya) and biphenyl-2,2'-dicarboxylic acid (H2dpa) under hydrothermal condition, a new ternary terbium complex [Tb(pya)(dpa)(H2O)]n (1) was synthesized. The structure of the ternary complex was determined by X-ray single crystal diffraction and characterized by elemental analysis, fluorescence measurement. The fluorescence spectrum shows the title complex emits strong green light. The crystal data for the complex: monoclinic, P21/n space group, a=0.8908(5) nm, b=1.0569(6) nm, c=2.0969(11) nm, β=98.446(8)°, V=1.9528(18) nm3, Z=4, R=0.0241, wR2=0.0534. The center Tb3 ion is eight coordinated. The coordination polyhedron around Tb3 ion can be described as a distorted square antiprism. The complex forms an infinite one-dimensional alternating chain polymer by bridging carboxyl groups of pya and dpa.