Modeling Lanthanide Complexes: Towards the Theoretical Design of Light Conversion Molecular Devices

Theoretical techniques have been developed and/or improved to predict the molecular structure of lanthanide complexes which were used to calculate their electronic properties, in particular, their electronic spectra and energy levels necessary to calculate the rates of energy transfer from the ligands to the metal ion. The molecular structure has been obtained by the SMLC/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes – Austin Model 1) model where the lanthanide ion is simulated by a sparkle implemented into the AM1 Hamiltonian used to perform a HF-SCF (Hartree-Fock Self-Consistent Field) calculation. The previous implementation of the SMLC/AM1 model (sparkle/1) involving only two parameters has been generalized to be consistent with the AM1 Hamiltonian and the new model (sparkle/2) significantly improved the prediction of molecular structures of Eu(III) complexes. For the electronic spectra and energy level calculations of the lanthanide complexes the model replaces the metal ion by a point charge with the ligands held in their positions as determined by the SMLC/AM1 model, and uses a INDO/S-CI (intermediate neglect of differential overlap/spectroscopic-configuration interaction) model. A preliminary study of the solvent effects on the absorption spectra of the free ligand is also presented. For the ligand-lanthanide ion energy transfer Fermi's golden rule is used with the multipolar and exchange mechanisms being implemented and tested for several complexes. These theoretical techniques have been applied to several complexes yielding very good results when compared to experimental data as well as predictions for the molecular and electronic structures and the relative contributions of the mechanisms for the energy transfer rates. This revised version was published online in June 2006 with corrections to the Cover Date.     

The role of the nicotinamide and adenine subsites in the negative co-operativity of coenzyme binding to glyceraldehyde-3-phosphate dehydrogenase.

The interaction of 3-aminopyridine-adenine dinucleotide, an NAD ⁺ 2 analogue which is fluorescent at the pyridine end of the molecule, with rabbit muscle glyceraldehyde-3-phosphate dehydrogenase was investigated. The fluorescence properties of the AAD⁺ molecule were used to monitor the nicotinamide subsites ou the GPDHase tetramer, the fluorescent aminopyridine moiety of the molecule serving as an intrinsic probe. Although the binding of AAD⁺ wag found to be negatively co-operative, no conformational changes induced at the nicotinamide subsite upon coenzyme binding were found to be transmitted to neighboring subunits. These findings, in conjunction with our earlier findings and with the observation that different NAD⁺ analogues which differ in the chemistry of the pyridine moiety bind with different extents of co-operativity, enable us to offer specific roles for the nicotinamide and the adenine subsites in generating the negative co-operativity.It is suggested that the structure of the pyridine moiety of the coenzyme controls the mode of binding of the pyridine moiety to the nicotinamide subsite. This, in turn, controls the orientation of the adenine moiety with respect to its subsite, thereby determining the mode of the interactions between the adenine and its binding domain. As the propagation of conformational changes caused by these interactions to neighboring subunits is believed to be the cause of the negative co-operativity exhibited by this enzyme towards coenzyme binding, the structure of the pyridine moiety controls this phenomenon.     

Extraction and analysis of superoxide free radicals (·O−2) from whole mammalian liver

Extraction of whole lobes of normal rat liver with dimethyl sulphoxide (DMSO) under N₂ gives extracts which contain 5—10 μmol/l·O^?₂ (50-100 nmol·O^?₂ per 10 ml extract per 4 g liver; 1.25-2.50 nmol·O^?₂ per millilitre per gram liver). Evidence for ·O^?₂ in the extracts is given by: (1) electron spin resonance signals (ESR), (2) differential pulse polarography (DPP), (3) chemiluminescence (CL), and (4) nitroblue tetrazolium reduction (NBT). All tests yield results identical with those obtained with authentic ·O^?₂. Extraction of ·O^?₂ is enhanced by tetrabutyl ammonium ion, and is maximal at 1-3 min. These results raise the possibility that substantial amounts of ·O^?₂ are normally sequestered in protective membranous sites in vivo.     

Tunable luminescence of a synthesized furophenanthraquinone derivative: interactions with different solvents

The synthesis is described of a luminescent furophenanthraquinone derivative, 9‐methoxyphenanthro[4,3‐b]furan‐4,5‐dione (MPFD). The biological importance of tetracyclic furophenanthraquinones was considered and the tunable luminescence of MPFD in different solvents was studied to explore the nature of the specific interactions between MPFD and solvents. Observation of dual emission bands and identical nature of the fluorescence excitation spectra of MPFD monitored at the emission wavelength in polar solvents indicated the formation of two different types of species in the excited state, probably due to proton transfer from the solvent to MPFD. Luminescence intensity due to anionic species was found to be increased and the corresponding peak was red shifted with increase in the proton‐donating ability of the solvents, acting as an acid with respect to MPFD. Availability of more acidic protons in the solvent facilitated this phenomenon occurring in the excited state. MPFD also interacted with halogen‐containing solvents by forming electron donor–acceptor charge transfer (CT) complexes. This CT complex formation was dependent on the number of chlorine atoms; the position of the corresponding luminescence band varied with the polarity of the solvent. Extent of the CT increased with increase in the number of chlorine atoms in the dichloro, trichloro and tetrachloro solvents, whereas the luminescence peak due to the CT complex was found to be blue shifted with decrease in solvent polarity. Interaction of the synthesized bioactive MPFD with different solvents deserves biological importance as proton transfer and CT play pivotal roles in biology.     

铽(Ⅲ)离子及其复合物:从发光特性到传感应用

稀土元素也称镧系元素,因其独特的发光性质和配位性质,其发光复合物被广泛研究于生物技术领域。其中稀土铽(Ⅲ)离子复合物因具有优异的光谱特性,关于其研究呈现出快速的发展趋势。主要从其发光特性的角度出发,探讨了其发光机理,并对铽(Ⅲ)离子与不同有机化合物结合形成的发光铽配合物以及铽(Ⅲ)离子及其配合物与不同纳米材料形成的复合物进行了分类综述。此外,还详细地阐述了铽离子及其复合物在荧光探针、生物传感器、药物递送、细胞成像、癌症治疗等相关领域的应用。最后,对其今后发展趋势和潜在的研究价值进行了展望。     

Gaussia分泌型萤光素酶的研究进展及其应用

Gaussia分泌型萤光素酶是近年发现的一种来源于海洋桡脚类动物Gaussia princeps的新型分泌型萤光素酶,是目前已知的可自然分泌的最小萤光素酶,因其分子小、灵敏度高、半衰期短和可高效分泌,而成为一种理想的报告基因,广泛应用于体内外研究。我们就Gaussia分泌型萤光素酶的发光原理、荧光特性及其应用等进行简要综述。     

Energy transfer between Ce3+ → Gd3+ or Tb3+ in KNaSO4 microphosphor

KNaSO₄ microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO₄ has a 5‐µm particle size detected by SEM. KNaSO₄:Ce³⁺,Tb³⁺ showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb³⁺ due to ⁵D₄ → ⁷F_J (J = 4, 5, 6) transitions. KNaSO₄:Ce³⁺,Gd³⁺ showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce³⁺ → Gd³⁺ and Ce³⁺ → Tb³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Gd³⁺ or Tb³⁺ (green emission). Ce³⁺ emission weakened and Gd³⁺ or Tb³⁺ enhanced the emission significantly in KNaSO₄. This paper discusses the development and understanding of photoluminescence and the effect of Tb³⁺ and Gd³⁺ on KNaSO₄:Ce³⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of highly fluorescent nitrogen and phosphorus doped carbon dots for the detection of Fe3+ ions in cancer cells

Highly fluorescent nitrogen and phosphorus‐doped carbon dots with a quantum yield 59% have been successfully synthesized from citric acid and di‐ammonium hydrogen phosphate by single step hydrothermal method. The synthesized carbon dots have high solubility as well as stability in aqueous medium. The as‐obtained carbon dots are well monodispersed with particle sizes 1.5–4 nm. Owing to a good tunable fluorescence property and biocompatibility, the carbon dots were applied for intercellular sensing of Fe³⁺ ions as well as cancer cell imaging. Copyright © 2015 John Wiley & Sons, Ltd.     

Classification of Chinese herbs based on the cluster analysis of delayed luminescence

Traditional Chinese material medica are an important component of the Chinese pharmacopeia. According to the traditional Chinese medicinal concept, Chinese herbal medicines are classified into different categories based on their therapeutic effects, however, the bioactive principles cannot be solely explained by chemical analysis. The aim of this study is to classify different Chinese herbs based on their therapeutic effects by using delayed luminescence (DL). The DL of 56 Chinese herbs was measured using an ultra‐sensitive luminescence detection system. The different DL parameters were used to classify Chinese herbs according to a hierarchical cluster analysis. The samples were divided into two groups based on their DL kinetic parameters. Interestingly, the DL classification results were quite consistent with classification according to the Chinese medicinal concepts of ‘cold’ and ‘heat’ properties. In this paper, we show for the first time that by using DL technology, it is possible to classify Chinese herbs according to the Chinese medicinal concept and it may even be possible to predict their therapeutic properties. Copyright © 2015 John Wiley & Sons, Ltd.     

Nondestructive evaluation of photosynthesis by delayed luminescence in Arabidopsis in Petri dishes

Nondestructive evaluation of photosynthesis is a valuable tool in the field and laboratory. Delayed luminescence (DL) can reflect charge recombination through the backflow of electrons. However, DL detection has not yet been adapted for whole plants in Petri dishes. To compensate for differences in DL decay between sibling Arabidopsis plants grown under the same conditions, we developed a time-sequential double measurement method. Using this method, we examined the influence of photosynthetic electron flow inhibitors, and differences in the DL decay curves were categorized by considering the initial and late phases of the decay curves, as well as their intermediate slopes. The appearance of concavity and convexity in DL curves in Arabidopsis was different from unicellular algae, suggesting complexity in the photosynthetic machinery of higher plants. This detection method should be invaluable for evaluating photosynthetic defects in higher plants under sterile conditions without interrupting plant culture.