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31.
We report herein, for the first time, that Europium ion (Eu3+) binds to the “apo” form of Escherichia coli methionine aminopeptidase (EcMetAP), and such binding results in the activation of the enzyme as well as enhancement in the luminescence intensity of the metal ion. Due to competitive displacement of the enzyme-bound Eu3+ by different metal ions, we could determine the binding affinities of both “activating” and “non-activating” metal ions for the enzyme via fluorescence spectroscopy. The experimental data revealed that among all metal ions, Fe2+ exhibited the highest binding affinity for the enzyme, supporting the notion that it serves as the physiological metal ion for the enzyme. However, the enzyme-metal binding data did not adhere to the Irving-William series. On accounting for the binding affinity vis a vis the catalytic efficiency of the enzyme for different metal ions, it appears evident that that the “coordination states” and the relative softness” of metal ions are the major determinants in facilitating the EcMetAP catalyzed reaction. 相似文献
32.
Two Hg2+-specific biosensors were constructed using bacterial luciferase as reporter gene and plasmid-free Pseudomonas putida X4 and Enterobacter aerogenes NTG-01 as host strains. The performance of X4 biosensor was compared with that of NTG-01 biosensor in the same assay conditions. The maximum bioluminescence for X4 (pmerRluxCDABE-Kan) biosensor was found during the midexponential phase and that for NTG-01 (pmerRluxCDABE-Kan) was at the late exponential phase. The shortest induction time of two biosensors was 30 min. The maximum light signal output for NTG-01 and X4 sensors was observed at the incubation time of 5 and 4 h, respectively. The lowest detectable concentration of mercury by the two biosensors were both of 100 pM at 28 degrees C, pH 7 and an initial cell number of 10(6) CFU ml(-1). Cd2+, Zn2+, Co2+, Cu2+, and Pb2 + ions at nanomolar level did not interfere with the measurement by the biosensors. These results show that the sensitivity of the two biosensors is sufficient for the detection of Hg2+ under most contaminated environments. 相似文献
33.
We have studied the delayed fluorescence in spinach chloroplasts produced 0.5 ms after each of a pair of (sub)-microsecond flashes. We observe an increase in the delayed fluorescence from the second flash relative to that produced by the first. This increase is proportional to the product of the first and second flash irradiances, appearing as an I2 dependence if both flashes are increased together. The enhancement is observable at very weak flash levels (roughly 1 photon absorbed/100 PS II centers). If the irradiance of the first flash is increased, but the irradiance of the second held constant, the delayed fluorescence from the second flash is observed to increase, but then to saturate well below the first flash irradiance at which the delayed fluorescence from the first flash itself saturates. For most experiments, the dark time between flashes was 30 ms. If the dark time is varied, the enhancement changes, reaching a half-maximal value for a dark time of approx. 300 μs. The enhancement is stopped by hydroxylamine, but not by gramicidin, valinomycin, DCMU, or mild heating. These experiments are consistent with the notion that there are two different types of Photosystem II centers if we assume that only one type is responsible for the induction we see and has an optical cross-section about 4-times the size of the other type of center. 相似文献
34.
The complexation of trivalent lanthanides with aliphatic dicarboxylic acids (malonic, succinic, glutaric and adipic) were studied at 25°C and 0.1 M (NaClO4) ionic strength by luminescence and absorption spectroscopy and luminescence lifetime measurements. The luminescence spectra and decay constants indicate that ML and ML2 complexes were formed. The stability constants of Eu(III) complexes with the dicarboxylic acids were calculated from the changes of the 5D0←7F0 excitation spectra of Eu(III). For the four dicarboxylic acids studied, both the stability constant and the number of water molecules released from the inner sphere of Eu(III) upon complexation decrease from malonate to adipate for both the ML and ML2 complexes. The results are interpreted as reflecting an increasing tendency from chelation to monodentation as the carbon chain length increases between carboxylate groups. The trend in the oscillator strength in the hypersensitive transition of the Nd(III)and Ho(III) complexes is the same as that in the ligand basicity. 相似文献
35.
Drew M. Dolino Swarna S. Ramaswamy Vasanthi Jayaraman 《Journal of visualized experiments : JoVE》2014,(91)
Luminescence Resonance Energy Transfer, or LRET, is a powerful technique used to measure distances between two sites in proteins within the distance range of 10-100 Å. By measuring the distances under various ligated conditions, conformational changes of the protein can be easily assessed. With LRET, a lanthanide, most often chelated terbium, is used as the donor fluorophore, affording advantages such as a longer donor-only emission lifetime, the flexibility to use multiple acceptor fluorophores, and the opportunity to detect sensitized acceptor emission as an easy way to measure energy transfer without the risk of also detecting donor-only signal. Here, we describe a method to use LRET on membrane proteins expressed and assayed on the surface of intact mammalian cells. We introduce a protease cleavage site between the LRET fluorophore pair. After obtaining the original LRET signal, cleavage at that site removes the specific LRET signal from the protein of interest allowing us to quantitatively subtract the background signal that remains after cleavage. This method allows for more physiologically relevant measurements to be made without the need for purification of protein. 相似文献
36.
Yi-Shan Song 《Inorganica chimica acta》2005,358(1):191-195
A novel chain-like luminescent samarium coordination polymer {Sm3(C8H4O4)4(C12N2H8)2(NO3)}n (C8H4O4 = phthalate, C12N2H8 = 1,10-phenanthroline) has been assembled by hydrothermal process. The title complex crystallizes in the monoclinic system, space group P2(1)/c, with lattice parameters a = 22.56(3) Å, b = 11.155(15) Å, c = 20.32(3) Å, β = 96.70(2)°, V = 5078(12) Å3, F(000) = 2964, GOF = 0.857, R1 = 0.0358, wR2 = 0.0597, Z = 4. Samarium ions exhibit different coordination modes from each other and lead to the unexpected high asymmetrical structure. To our knowledge, it is the first example of lanthanide coordination polymers comprising the three asymmetrical central Sm3+ fragments. The photophysical properties have been studied with excitation and emission spectra. 相似文献
37.
Kou-Lin Zhang Hong-Yan Gao Na Qiao Fang Zhou Guo-Wang Diao 《Inorganica chimica acta》2008,361(1):153-160
Two novel photoluminescent coordination polymers of formula [Cd(atpt)(H2O)2] · 2H2O (1) and [Zn(atpt)(H2O)2] (2) (H2atpt = 2-aminoterephthalic acid), in which the amino group of the atpt ligand coordinates to the metal(II) ions for the first time, have been synthesized through the self-assemblies of H2atpt and N-containing ligands [nicotiamide for 1 and imidazole for 2, respectively] with the metal(II) ions in the presence of NaOH. These complexes were characterized by FT-IR spectroscopy, thermogravimetric analysis (TG), elemental analysis and X-ray analysis. X-ray crystallographic studies of the complexes reveal that complex 1 is a double stranded one-dimensional chain, which further assembles into a three-dimensional supramolecular network via the interchain π-π stacking interaction and strong hydrogen bonds, while complex 2 exhibits a two-dimensional porous architecture. The extensively strong hydrogen bonds in complex 2 lead to the formation of three-dimensional supramolecular framework. Photoluminescence properties of the compounds 1 and 2 have been examined in solid state at room temperature. These compounds have been found to exhibit blue photoluminescence and may be good candidates for photoactive materials. 相似文献
38.
Ting Gao Peng-Fei Yan Guang-Ming Li Guang-Feng Hou Jin-Sheng Gao 《Inorganica chimica acta》2008,361(7):2051-2058
The stepwise synthesis of mononuclear (4f) and heterodinuclear (3d–4f) Salen-like complexes has been investigated through structural determination of the intermediate and final products occurring in the process. In the first step, reactions of ligand H2L and Ln(NO3)3 · 6H2O give rise to three mononuclear lanthanide complexes Ln(H2L)(NO3)3 [H2L = N,N′-ethylene-bis(3-methoxysalicylideneimine), Ln = Nd (1), Eu (2) and Tb (3)], in which N,N′-ethylene-bis(3-methoxysalicylideneimine) acts as tetradentate ligands with the O2O2 set of donor atoms capable of effective coordination. These species are fairly stable and have been isolated. Then, addition of Cu(Ac)2 · H2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes Cu(L)Ln(NO3)3 · H2O [Ln = Nd (4) and Eu (5)] where the Cu(II) ion is inserted to the inner N2O2 cavity. Luminescent analysis reveals that complex 3 exhibits characteristic metal-centered fluorescence of Tb(III) ion. However, the characteristic luminescence of both Sm(III) and Eu(III) ions is not observed both in solution and solid state of the complexes. 相似文献
39.
Zhong-Qiang Zhang Ru-Dan Huang Yan-Qing Xu Zhi-Wei Jiao Chang-Wen Hu 《Inorganica chimica acta》2009,362(15):5183-1524
Three new complexes, [Mn(OBt)2(H2O)4]·3H2O (1) (OBt = 1-hydroxybenzotriazole ion), [Zn2(OBt)2(BDC)(H2O)·H2O]n (2) (H2BDC = 1,4-benzenedicarboxylic acid), and [Cu3(OBt)2(BDC)(μ3-OH)2(H2O)2·2H2O]n (3) were synthesized by hydrothermal method and were characterized by elemental analysis, IR spectroscopy, TGA, XRPD, and single-crystal X-ray diffraction. The results from single-crystal X-ray diffraction indicate that 1, 2 and 3 are zero-dimensional (0D), two-dimensional (2D) and two-dimensional (2D) frameworks, respectively. In particular, there are all two crystallographically unique metal ions in the structures of complexes 2 and 3. Complex 2 possesses two helical chains in its structure. In the structure of 3, the chains that are built from tri-copper clusters and μ3-O atoms are connected with BDC2− to construct 2D grid structure. The luminescence properties of the three complexes were investigated. 相似文献
40.
Jian-Guo Lin Fang-Ming Wang Chang-Sheng Lu Pei-Heng Wu 《Inorganica chimica acta》2009,362(15):5219-5223
Employing the symmetrical ligand 1,2,3,4-tetra-(4-pyridyl)-butane (TPB) as bridges, two novel Zn(II) coordination polymers were obtained and characterized by single crystal X-ray diffraction: [Zn(TPB)0.5(NCS)2] (1) and [Zn(TPB)(N3)2] (2). Polymer 1 features a 2D network with herringbone structural motif constructed by TPB, while polymer 2 shows a dense 3D network connected by TPB and μ1,3-N3- bridges. In the former, the TPB ligand acts as a four-connector, while in the latter it acts as four-connector and linear bridge. Both 1 and 2 exhibit strong fluorescent emissions in the solid state, which may be of significance in the field of photoactive materials. 相似文献