Study of interaction of a fluorescent probe with DNA

The zinc complex of 2-[2-(3, 5-bis(2-pyridylmethyl)aminomethyl-4-hydroxy-phenyl) ethylene]-5-methylpyrazine (1) could bind with the calf thymus deoxyribonucleic acid (ct-DNA). The binding behaviors between them were studied by fluorescence and absorption spectral assay. The absorption titration of 1-Zn with ct-DNA showed no bathochromic shift and hypochromic effect. No anisotropy increase was observed when ct-DNA was added to 1-Zn solution. They both proved the lack of intercalation interaction between 1-Zn and ct-DNA. The ionic strength experiment, Scatchard plot, study of interaction between 1-Zn and denatured ct-DNA all revealed that the interaction mode between 1-Zn and ct-DNA was electrostatic interaction. Binding constant was estimated to be 7.96×10⁴ L moL⁻¹.     

A Galactosidase-Activatable Fluorescent Probe for Detection of Bacteria Based on BODIPY

Pathogenic E. coli infection is one of the most widespread foodborne diseases, so the development of sensitive, reliable and easy operating detection tests is a key issue for food safety. Identifying bacteria with a fluorescent medium is more sensitive and faster than using chromogenic media. This study designed and synthesized a β-galactosidase-activatable fluorescent probe BOD-Gal for the sensitive detection of E. coli. It employed a biocompatible and photostable 4,4-difluoro-3a,4a-diaza-s-indancene (BODIPY) as the fluorophore to form a β-O-glycosidic bond with galactose, allowing the BOD-Gal to show significant on-off fluorescent signals for in vitro and in vivo bacterial detection. This work shows the potential for the use of a BODIPY based enzyme substrate for pathogen detection.     

分子内电荷转移双重荧光体识别阴离子研究

设计合成阴离子受体是近年来超分子化学中一个颇为活跃的研究领域[1～ 7] .其中荧光法以其高灵敏度和高选择性等特点使发光受体的设计合成备受关注 [6 ,7] .分子内电荷转移 (Intramolecular charge transfer,ICT)原理已被成功地用于构筑阳离子荧光传感体系[8] ,但将其应用于阴离子识别的研究尚鲜见报道[9～ 12 ] .本文设计合成了 ICT荧光体对二甲氨Scheme 1　 The structures of anion receptors基苯甲酰肼 (DMABH,结构见 Scheme 1 ) ,研究了 DMABH与阴离子如 HSO- 4,Ac O- ,H2 PO- 4,Cl O- 4,NO- 3,Cl- 和 Br- 等结合后的光…     

A novel thiourea-based dual fluorescent anion receptor with a rigid hydrazine spacer

[structure: see text] A neutral receptor with a rigid hydrazine spacer, N-p-(dimethylamino)benzamido-N'-phenylthiourea, was prepared, and its dual fluorescence in acetonitrile was found to show response toward the presence of anions such as AcO(-), H(2)PO(4)(-), HSO(4)(-), Br(-), Cl(-), F(-), and ClO(4)(-) with high sensitivity and selectivity toward AcO(-).     

Semi-quantitative Surface Enhanced Raman Scattering Spectroscopic Creatinine Measurement in Human Urine Samples

This paper presents the development of a semi-quantitative method of measuring the creatinine biomolecule in human urine by the surface enhanced Raman scattering (SERS) technique. Creatinine is one of the major components of urine and can be used to represent the metabolic and renal function of the human body. The Raman signal of creatinine is enhanced by 50 nm Au nanoparticles. Raman spectra between 1400 and 1500 cm^?1 were analyzed to obtain the relationship between the SERS band area and creatinine concentration. The square of the correlation coefficient is 0.99 in artificial urine over the creatinine range 38.4–153.6 mg/dl. In a human urine experiment, a good linear correlation is observed over the creatinine concentration range 2.56–6.4 mg/dl. The square of correlation coefficient is 0.96.     

苯乙烯三嗪衍生物的合成及在重金属离子识别中的应用

合成了2,4-二(2-噻吩乙烯基)-6-(4′-N,N-二甲氨基苯乙烯基)-1,3,5-均三嗪(2)并鉴定了其结构。在乙腈-水混合介质中,化合物2在355和416 nm处呈现双吸收峰,加入Cu2+,Hg2+和Fe3+后,均在520 nm附近形成新的吸收峰。化合物2与Cu2+、Hg2+和Fe3+均形成1∶1型配合物,其结合常数分别为1.9×105L·mol-1,6.6×103L·mol-1,2.7×103L·mol-1。对照化合物4与金属离子的光谱响应与化合物2相似,仅吸收峰的位置不同。因此,可认为化合物2和4中三嗪环中的N和噻吩环中的S与Cu2+、Hg2+和Fe3+共同配位形成了稳定的金属配合物。     

2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine -4-hydroxy-phenyl) ethylene] pyrazine zinc complex as fluorescent probe for labeling proteins

The binding characteristics between 2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine -4-hydroxy-phenyl) ethylene] pyrazine (1) or its complex (1-Zn) and serum albumins were studied by fluorescence spectroscopy in pH 7.4 aqueous solution. 1-Zn emitted weak fluorescence at 580 nm in a pH 7.4 Tris-HCl buffer solution when excited at 435 nm, however, the fluorescence intensity increased upon addition of serum albumins with the blue shift of emission peak to 524 nm. The binding constants were estimated as 8.40 x 10(7) and 3.03 x 10(6)mol(-1)L for bovine serum albumin (BSA) and human serum albumin (HSA) respectively, and the number of binding sites was 1 for each. The quenching mechanism of fluorescence of serum albumins by 1-Zn was considered as a static quenching process. The binding distance between 1-Zn and serum albumins and the energy transfer efficiency were obtained based on the theory of F?rester spectroscopy energy transfer. The effect of 1-Zn on the conformation of serum albumins was further analyzed using synchronous fluorescence spectrometry. The experiment results clearly showed that 1-Zn is a highly sensitive protein sensor.     

Enhanced anion binding of N-(anilino)thioureas. Contribution of the N-anilino-NH proton acidity

We report here that N-anilino-N'-phenythioureas in general function as a new family of thiourea-based efficient anion receptors superior to classical N-alkyl(aryl)thioureas, when the N-anilino-NH proton is acidic enough; that is, the N-phenyl substituent is not less electron-withdrawing than m-Cl. Changes due to anion binding in the absorption spectra of these N-anilinothioureas are much more substantial than those of N-alkyl(aryl)thioureas, and anion binding constants in MeCN, at 10(6)-10(7) mol(-1) L order of magnitude for AcO(-) for example, are much higher despite a similar acidity of the thioureido-NH protons. Crystal structure and (1)H NMR data show that the N-aniline chromophore is electronically decoupled from the thiourea anion binding site by the N-N bond, and an intramolecular hydrogen bond exists in MeCN but not in DMSO between the N-anilino-NH nitrogen atom and the other thioureido-NH proton. Conformation changes in the N-anilinothioureas upon anion binding were assumed to occur and lead to a much higher increment in the electron-donating ability in the N-aniline chromophore that the charge transfer (CT) is enhanced or switched on, compared to not switching on a CT in the case of N-phenylthioureas. The anion binding constant shows a stronger dependence on the N-phenyl substituent than on the N'-phenyl substituent, opposite to that observed with N-benzamidothioureas, and the CT band position of the anion binding complex depends much more on the N-phenyl substituent than that of the anion binding complexes of N-benzamidothioureas. The implications of these findings for new anion-receptors design and thiourea-based organocatalysts development are discussed.     

A unique NH-spacer for N-benzamidothiourea based anion sensors. Substituent effect on anion sensing of the ICT dual fluorescent N-(p-dimethylaminobenzamido)-N'-arylthioureas

A series of N-(p-dimethylaminobenzamido)-N'-(substituted-phenyl)thioureas (substituent = p-CH3, H, p-Cl, p-Br, m-Br, m-NO2, and p-NO2) were designed as anion sensors in order to better understand the -NH-spacer via a substituent effect investigation. In these molecules the dual fluorescent intramolecular charge transfer (ICT) fluorophore p-dimethylaminobenzamide as the signal reporter was linked to the anion-binding site, the thiourea moiety, via an N-N single bond. Correlation of the NMR signals of the aromatic and -NH protons with substituents in these molecules indicated that the N-N single bond stopped the ground-state electronic communication between the signal reporter and the anion-binding site. Dual fluorescence was observed in highly polar solvents such as acetonitrile with the former five derivatives. The fact that the CT emission wavelength and the CT to LE emission intensity ratio of the sensors were independent of the substituent existing in the anion-binding moiety suggested that the substituent electronic effect could not be communicated to the CT fluorophore in the excited-state either. Yet in acetonitrile both the CT dual fluorescence and the absorption of the sensors were found to be highly sensitive toward anions. A conformation change around the N-N bond in the sensor molecules was suggested to occur upon anion binding that established the electronic communication between the signal reporter and the anion-binding site. The anion binding constants of the N-(p-dimethylaminobenzamido)thiourea sensors were found higher than those of the corresponding traditional N-phenylthiourea counterparts and the substituent effect on the anion binding constant was much higher than that in the latter. "-NH-" was shown to be a unique spacer that affords N-benzamidothiourea allosteric anion sensors.     

Functionalized manganese-doped zinc sulfide core/shell quantum dots as selective fluorescent chemodosimeters for silver ion

Zinc sulfide quantum dots doped with Mn(II) ions and coated with a shell of zinc sulfide were prepared, and their surface was modified with iminodiacetic acid to form a QDs-conjugate (QDs-IDA). Such modification effectively improves the water-solubility and luminescence quantum yield of the quantum dots. The optical properties and structural features were characterized by photometry, ¹H NMR and fluorescence spectroscopy. The results displayed that QDs-IDA selectively respond to Ag (I) ion in phosphate buffer solution (pH 7.3) in quenching the fluorescence of QDs-IDA. A good linear relationship exists in the concentration range from 5.0?×?10^?7 mol·L^?1 to 4.5?×?10^?6 mol·L^?1 and the detection limit is 2.6?×?10^?7 mol·L^?1. The sensing mechanism was assumed to result from complex formation between the iminodiacetic acid of QDs-IDA and silver (I) ion which promoted photo-induced electron transfer.