A Benzothiazole-Based Fluorescence Turn-on Sensor for Copper(II)

A new benzothiazole-based chemosensor BTN (1-((Z)-(((E)-3-methylbenzo[d]thiazol-2(3H)-ylidene)hydrazono)methyl)naphthalen-2-ol) was synthesized for the detection of Cu²⁺. BTN could detect Cu²⁺ with “off-on” fluorescent response from colorless to yellow irrespective of presence of other cations. Limit of detection for Cu²⁺ was determined to be 3.3 μM. Binding ratio of BTN and Cu²⁺ turned out to be a 1:1 with the analysis of Job plot and ESI-MS. Sensing feature of Cu²⁺ by BTN was explained with theoretical calculations, which might be owing to internal charge transfer and chelation-enhanced fluorescence processes.

     

Fluorescence of a Histidine-Modified Enhanced Green Fluorescent Protein (EGFP) Effectively Quenched by Copper(II) Ions

Two histidines were introduced by site-directed mutagenesis into the structure of Enhanced Green Fluorescent Protein, replacing the serine at position 202 and the glutamine at position 204 for increasing the sensitivity of the protein towards different metal ions by creating possible metal binding sites near the chromophore group. There is no appreciable difference between the absorbance and fluorescence spectra of the two proteins (wild type and the double-histidine mutant) indicating that the mutation does not change the environment of the fluorophore. Fluorescence quenching was measured at different pH (6.5–8) and temperatures (20–45 °C) varying the concentration of metal ions. Under optimal conditions (pH?=?7.5, 20 °C) the mutant’s K_d is 16 nM, it binds copper more than 200fold stronger than the wild type EGFP.     

An NBD-based Sensitive and Selective Fluorescent Sensor for Copper(II) Ion

A new 7-nitrobenz-2-oxa-1,3-diazole (NBD) derived fluorescent probe (1) exhibiting high selectivity for Cu²⁺ detection, produced significant fluorescence quenching in the presence of Cu²⁺ ion, while the metal ions Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ produced only minor changes in fluorescence. The apparent association constant (K _a) for Cu²⁺ binding in chemosensor 1 was found to be 1.22 × 10³ M⁻¹. The maximum fluorescence quenching activity caused by Cu²⁺ binding to 1 was observed over the pH range 6–10.     

Salicylaldehyde Phenylhydrazone: A New Highly Selective Fluorescent Lead (II) Probe

The fluorescence intensity of salicylaldehyde phenylhydrazone (L), in 1:1 (v/v) CH₃OH:H₂O was enhanced by ca. 100 times with a blue shift in emission maximum, on interaction with Pb²⁺ ion. No enhancement in fluorescent intensity of L was observed on interaction with metal ions - Na⁺, K⁺, Ca²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Hg²⁺. This signal transduction was found to occur via photoinduced electron transfer (PET) mechanism. A 1:1 complexation between Pb²⁺ and L with log β?=?7.86 has been proved from fluorescent and UV/Visible spectroscopic data. The detection limit of Pb²⁺ was calculated to be 6.3?×?10^?7?M.     

Synthesis,Characterization, DNA Binding Properties,Fluorescence Studies and Toxic Activity of Cobalt(III) and Ruthenium(II) Polypyridyl Complexes

The new ligand 4-(isopropylbenzaldehyde)imidazo[4,5-f ][1,10]phenanthroline (ippip) and its complexes [Ru(phen)₂(ippip)]²⁺(1),[Co(phen)₂(ippip)]³⁺(2),[Ru(bpy)₂(ippip)]²⁺(3),[Co(bpy)₂(ippip)]³⁺(4)(bpy=2,2-bipyridine) and (phen=1,10-phenanthroline) were synthesized and characterized by ES⁺-MS, ¹H and ¹³C NMR. The DNA binding properties of the four complexes were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that complexes bind to calf thymus DNA (CT-DNA) through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than 2, 3, 4 complexes under comparable experimental conditions. Furthermore, photocleavage studies reveal that singlet oxygen (¹O₂) plays a significant role in the photocleavage.     

Synthesis and Antitumor,Antioxidant Effects Studies of N-Ethylpiperazine Substitute Thiourea Ligands and Their Copper(II) Complexes

A series of N-ethylpiperazine substitute thioureas [C₆N₂H₁₃NHCSNHR], where R = -C₃H₅ (L ₁ ), -C₁₀H₇ (L ₂ ), and -C₇H₇ (L ₃ ), and their copper (II) complexes have been synthesized. These ligands and complexes have been characterized by elemental analyses, IR, ¹H and ¹³C-NMR spectra, UV-Vis, magnetic susceptibility, thermogravimetrical analyses, and MALDI-TOF MS. In vitro antitumor activity of ligands and their complexes has been screened toward several tumor cell lines. The effects on these complexes of the growth of L1210 and MCF7 were studied comparatively with that of free ligands. Antioxidant and radical scavenging activities of synthesized compounds were determined by various in vitro assays including 1,1-diphenyl-2-picryl-hydrazyl free radicals (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radicals (ABTS+), and ferrous ion (Fe²⁺) chelating activities. Moreover, these activities were compared to synthetic and standard antioxidant trolox. The results showed that the synthesized compounds had effective antioxidant power.     

Spectroscopic Studies of Oxygen-Bridged Copper (II) Cluster Somplexes; (II) Trinuclear Copper (II) Complex of Pyridine-2-Carbaldehyde Oxime

Abstract

Power electron paramagnetic resonance spectrum of the trinuclear complex Cu3L3 (OM)X2, xH20 (L=pyridine-2-carbaldehyde oxime, X=1/2 S04^2?, x=16.3) was recorded in the X-band region and interpreted in terms of a quarte (S=3/2) spin system.

Vibrational studies of the complex has also been undertaken and an assignment was made of the bands observed it the low frequency infrared and Raman spectra. It was shown that the central metallic core has a C3v syametry. Theoretical calculations of the frequencies of the vibrations related to this skeleton were performed and the results are it agreement with the experimental data.     

A Novel Highly Sensitive and Selective Fluorescent Sensor for Imaging Copper (II) in Living Cells

In this work, we designed and synthesized a novel quinolin-based derivative which exhibited signaling behaviors for Cu²⁺. Upon the addition of Cu²⁺ to the solution of the molecule, it displayed an obvious fluorescence quenching in a linear fashion due to the formation of a 1:1 metal–ligand complex. This fluorescent sensor exhibited a rare sensitivity toward Cu(II) (the level of magnitude could be 6?×?10^?8), a rapid response (<10 s) and also high selectivity toward Cu²⁺ over other metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Fe³⁺, Mn²⁺, Hg²⁺, Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, Zn²⁺ and Al³⁺. Simultaneously, the cell imaging experiments and filter paper test demonstrated its extensive applicability.     

Bis(Naphthalimide-Piperazine)-Based Off-On Fluorescent Probe for Acids

A bis(naphthalimide-piperazine) derivative (1) was synthesized as a pH-sensitive Off-On fluorescent probe. Operation mechanism of 1 is based on photo-induced electron transfer (PET) and its pH-dependent optical changes were investigated by using absorption and fluorescence spectroscopy. In the pH range of 11–4.5, this probe undergoes PET process from the piperazine to the naphthalimide moiety, leading to a fluorescence quenching. However, in the pH range of 4.5–1, the PET is inhibited to give a fluorescence enhancement. Moreover, the fluorescence ‘turn-on’ response of 1 is highly selective for protons (H⁺) over other metal cations, biomolecules and it shows a good reversibility between acidic and basic conditions.

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Graphical Abstract ?

     

Iron (II) Complex of Benzylpenicillin,Synthesis and Infrared Structural Characterisation

Synthesis and IR spectrum of iron (II), benzylpenicillin complexe are reported. The alterations observed between the ligand and iron complexe IR spectra allow us to specify the coordination modes. The benzylpenicillin is bounded to iron through carboxylate group and thazolidinic nitrogen.     

N,N,N,N-tetradentate Macrocyclic Ligand Based Selective Fluorescent Sensor for Zinc (II)

N,N,N,N-tetradentate macrocyclic ligand (L) has been synthesized by the condensation of benzil and semicarbazide and characterized. On excitation by light of wavelength 350?nm, L exhibited a fluorescent peak at λ(max)?=?454?nm, which showed ca 6 times enhancement in intensity with a blue shift on interaction with Zn(2+). L has been found to act as a selective fluorescent sensor for zinc(2+) ion over a host of other metal ions such as- Cd(2+), Pb(2+), Hg(2+), Ca(2+), Fe(2+), Na(2+), Co(2+), Mn(2+), Cu(2+) and Ni(2+), in 1:1 CH(3)OH:H(2)O. A 1:1 complex formation between L and Zn(2+) was proved. The enhancement in the fluorescence could be explained on the basis of Photo induced electron transfer (PET) mechanism with log β?=?1.86.     

A Novel Single-Labeled Fluorescent Oligonucleotide Probe for Mercury(II) Ion Detection: Using the Inherent Quenching of Deoxyguanosines

A novel single-labeled fluorescent oligonucleotide (OND) probe for the detection of nanomolar mercury(II) ion in aqueous solution is developed based on the inherent quenching of deoxyguanosines. The formation of hairpin structure of OND-Hg²⁺ complex brings deoxyguanosines close to dye, resulting in decreased dye fluorescence due to photoinduced electron transfer from dye to deoxyguanosines.     

Determination of Copper(II) Ion Concentration by Lifetime Measurements of Green Fluorescent Protein

The understanding of cellular processes and functions and the elucidation of their physiological mechanisms is an important aim in the life sciences. One important aspect is the uptake and the release of essential substances as well as their interactions with the cellular environment. As green fluorescent protein (GFP) can be genetically encoded in cells it can be used as an internal sensor giving a deeper insight into biochemical pathways. Here we report that the presence of copper(II) ions leads to a decrease of the fluorescence lifetime (τ _fl) of GFP and provide evidence for Förster resonance energy transfer (FRET) as the responsible quenching mechanism. We identify the His₆-tag as the responsible binding site for Cu^2?+? with a dissociation constant K _d ?=?9 ±2 μM and a Förster radius R ₀?=?2.1 ±0.1 nm. The extent of the lifetime quenching depends on [Cu^2?+?] which is comprehended by a mathematical titration model. We envision that Cu^2?+? can be quantified noninvasively and in real-time by measuring τ _fl of GFP.     

Spectroscopic Studies of Oxygen-Bridged Copper (II) Cluster Complexes; (I) Dimeric Copper (II) Complexes of 2-Aminopyridine and Pentane-2,4-Dionate

X-band E.P.R and also the far infrared spectra of alkoxy-bridged dimeric copper (11) complexes of 2-aminopyridime and pentane-2, 4-dionate were recorded and the two sets of data thus obtained have been correlated.

The E.P.R spectra were analysed in terms of an axial (S=1) spin Hamiltonian. Zero-field splitting parameter (D) was calculated for each complex and an attempt was made in order to correlate the obtained values with the magnetic coupling constants (J) of some compounds with analogous structures.

An assignment has been made of the bands related to the central Cu202 bridging skeleton and the observed similarity in the frequency magnitude of a strongly CuOCu angle dependent mode has been proposed to arise from nearly equal angles in the seri of complexes.

The correlative results indicated in the above have therefore enabled the identification of a ferromagnetic exchange mechanism in the seri of complexes with J values larger than 242.5 cm-1.     

谷胱甘肽比率荧光探针分子的设计合成及其光谱性能

将喹啉和丹磺酰胺两种荧光基团同时引入配体L1,利用L1与锌离子自组装构筑三核锌有机-金属大环化合物H-1(比率荧光探针),实现了对生物分子谷胱甘肽(GSH)的有效识别。利用紫外光谱、荧光光谱、~1H NMR、ESI-MS等表征方法研究了H-1对生物分子谷胱甘肽(GSH)的光谱识别作用。紫外滴定光谱表明,当向H-1中加入谷胱甘肽分子后,425 nm处的吸收峰强度降低,320 nm处的吸收峰强度增大,等吸收点为355 nm。利用320 nm处的吸光度值模拟计算平衡常数,lg K为4.03±0.11,说明H-1与GSH形成了1∶1的包合物。荧光光谱分析表明,当向H-1中加入GSH后,以340 nm光激发,波长为513 nm处丹磺酰胺的荧光强度下降,并且发生红移,而396 nm处喹啉基团的荧光强度增大。利用喹啉基团与丹磺酰胺基团荧光发射峰强度变化的比值可以精准检测谷胱甘肽分子,检测限可达到2.5×10~(-6)mol·L~(-1)。     

酮类甲醛荧光探针的合成及其光学性质

设计合成了两种化合物4-氨基4-（4-甲氧基苯基）-3-丁烯-2-酮（1b）和4-氨基-4-（1,3-亚甲二氧基苯基-5-基）-3-丁烯-2-酮（2b）,测试了其在不同甲醛含量下的紫外吸收光谱及单光子荧光光谱。当含有100 μmol/L和5 μmol/L的甲醛时,化合物1b和2b的紫外吸收峰强度分别达到其最大值。在单光子荧光方面,化合物1b的荧光发射峰位置在384 nm,与紫外吸收峰相比红移50 nm。化合物2b的荧光发射峰呈现出双峰形状,其发射峰位置分别在384 nm及411 nm左右。当加入15 μmol/L的甲醛时,化合物2b的411 nm处的荧光发射峰明显增强,两峰的重叠程度降低,可作为检测甲醛的特征变化。以上数据表明,化合物1b和2b不仅能够对微量甲醛产生响应,也可作为一种理想平台为更进一步拓宽化合物1b和2b在监测生物体系中甲醛荧光生物成像上的应用奠定理论基础。