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A facile synthesis of dehydroepiandrosterones derived by C-16 spiro-pyrrolidine and their cytotoxic evaluation are reported. Seven derivatives, 3a–3g, were prepared by the [3 + 2] cycloaddition reaction of the 16-arylidene dehydroepiandrosterone and the azomethine ylide, where the azomethine ylide was generated in situ from 11H-indeno[1,2-b]quinoxalin-11-one and sarcosine. Their cytotoxicity was evaluated on brine shrimp assay and the bioactivities represented by LC50 values were found in the range of 6.19–27.2 µg/mL. Among them, the activities of 3d and 3g are the best, as manifested by LC50 values less than 10 µg/mL. All products were confirmed by NMR, HR MS and X-ray analysis. Graphic abstract

Proton transfer processes of 15 benzimidazole compounds are studied by density functional theory methods, and natural orbital energy index (NOEI) is introduced. Here, NOEI and nucleus independent chemical shift (NICS) are applied to estimate the π-electron localization and delocalization, respectively. Proton transfer potential energy surfaces are calculated to explore these processes, and the results show that the changes of the π-electron delocalization of the phenyl (pyridyl) is the main factors for the stability of keto form. There is high correlation between the π-electron delocalization and the proton transfer barrier. When the π-electron localization is considered, the regression increases the correlation coefficient, increasing from 0.9663 to 0.9864. NOEI index is sensitive to π-electron localization; it is a beneficial and useful complement to NICS.

Hypochlorite (ClO − ) and temperature play crucial roles in a wide range of physiological processes, and they are also implicated in various diseases, including cancer, inflammation of tissues and so on. Therefore, it is of great importance to explore a novel method to detect ClO − and temperature instantly. In this study, we developed a silica nanoparticle-based dual-responsive ratiometric fluorescent sensor (DRFS), whose correlative dual emissions can response to ClO − and temperature independently and sensitively. The detection limit of DRFS can reach to as low as 26 nM for the detection of ClO − . And further research demonstrates that DRFS possesses excellent anti-interference feature when other possible interferents exist, and has been successfully applied in ClO − detection in human serum and recognition of exogenous/endogenous ClO − in HeLa cells and macrophages by fluorescence microscopic imaging. Moreover, DRFS can also be used as a ratiometric temperature sensor, and the fluorescence intensity ratio (I 576 /I 445 ) exhibits a linear temperature response in the range from 20 to 60 °C with a change ratio as large as a factor of 5. Based on the above research, the DRFS can be used as versatile fluorescence sensor in various physiological and environmental systems.

Mercury pollutant brings huge threat to human health and the environment because of its bioaccumulation and permanent damage. Thus, highly selective and ratiometric detection and imaging of Hg2+ in organisms is quite important. Herein, we report on a polymer nanoparticle-based ratiometric fluorescent probe (NP3) for highly selective recognition of Hg2+ in totally aqueous solution and imaging in living cells. This probe comprises the reference fluorescent dye (4-ethoxy-9-allyl-1,8-naphthalimide: EANI), which resides in the core of nanoparticle, and the Hg2+-recognition group (fluorescein derivative: AEMH-FITC) on the surface of nanoparticle. It displays distinct dual emissions at 432 nm and 528 nm under a single-wavelength excitation. The fluorescence of the FITC moieties can be effectively quenched by Hg2+ due to photoinduced electron transfer (PET) mechanism, while that of the EANI remains constant, resulting in a ratiometric fluorescent detection of Hg2+. The as-prepared NP3 not only shows favorable water dispersibility, excellent long-term photostability, but also exhibits highly selective ratiometric detection of Hg2+ over other interfering ions (such as Cu2+, Na+, Mg2+, Zn2+, Co2+, Mn2+, K+, Ca2+, Fe3+, Cd2+, Ag+, Fe2+), and quite low detection limit (∼75 nM). Furthermore, intracellular fluorescence imaging experiments demonstrate that NP3 has good permeability of cell-membrane, and is able to facilitate visualization of Hg2+ changes in living cells.

Superior photoswitchable fluorescent polymer nanoparticles (PFPNs) are highly desirable for photo-rewritable data storage and ultrahigh-resolution bioimaging. Herein, 2-(3′,3′-dimethyl-6-nitrospiro[chromene-2,2′-indolin]-1′-yl)ethyl 2-(((dodecylthio)-carbonothioyl)thio)-2-methylpropanoate (SPTTC), a novel photochromic spiropyran-based reversible addition–fragmentation chain transfer (RAFT) reagent, and 5-dimethylaminonaphthalene-N-allyl-1-sulfonamide (DNS), the energy-level matched green fluorescent dye, were firstly synthesized. Then, they are used as donor and acceptor of the designed fluorescence resonance energy transfer (FRET) system to help fabricate superior dual-color PFPNs via a simple one-pot RAFT miniemulsion method. Thanks to its multiple merits such as the photochromic property, improved miscibility, and the ability to control polymerization rate, not only did the designed SPTTC provide the PFPNs with superior photoswitchable fluorescence properties such as high energy transfer efficiency (up to 91%), high dual-color contrast (green and red), rapid photoresponsiveness (2–4 min) and outstanding photoreversibility upon irradiation with UV and visible light, but it also endowed PFPNs with controllable molecular weight and narrow polydispersity index (PDI), excellent cell membrane permeability and long-term fluorescence stability. Moreover, the as-prepared PFPNs were successfully used for rewritable fluorescence patterning and intracellular dual-color imaging due to its prominent properties.

The development of an effective method for imaging of lysosomal hypochlorous acid (HClO) is of great significance to better understand the roles of HClO-related diseases. Herein, we report on the fabrication of fluorescence resonance energy transfer (FRET)-based fluorescent polymer dots (FPD) for the ratiometric imaging of lysosomal HClO in living cells via a simple co-precipitation method. This FRET-based construction strategy takes the advantage of flexible design by incorporating target-inert fluorogen (donor) and target-sensitive fluorogen (acceptor) into the nanoparticle to avoid leakage and photobleaching problems. The as-prepared FPD exhibits good water dispersibility, fast response ( 15 weeks). Moreover, the resultant FPD with good membrane permeability could mainly locate in the lysosomes and act as a probe for the ratiometric imaging of lysosomal HClO in living HeLa cells.

The detection of copper ion (Cu 2+ ) and sulfide anion (S 2− ) is of vital importance since the abnormal level of Cu 2+ or S 2− can lead to many diseases. Herein, a highly sensitive and selective fluorescent sensor, 1,4,8,11-tetraazacyclotetradecane (Cyclam)-functionalized carbon dots (CCDs), has been designed, synthesized and evaluated for Cu 2+ and S 2− . For this nanoprobe, a specific fluorescence resonance energy transfer (FRET) process can be effectively take place between carbon dots and the surface Cu 2+ -Cyclam complex, the as-prepared CCDs display high sensitivity (detection limit: 100 nM) and selectivity toward Cu 2+ among many other metal cations (such as Mg 2+ , Co 2+ , Pb 2+ , Ni 2+ , Mn 2+ , Hg 2+ , Fe 2+ , Ca 2+ and Zn 2+ ) in 100% aqueous solution. Moreover, it is worth to point out that the subsequent addition of S 2− can extract Cu 2+ from the CCDs-Cu 2+ complex and recover the fluorescence of carbon dots, the detection limit for S 2− can reach to 130 nM in the aqueous medium. And no statistically significant interference was observed among the other 10 anions (HCO 3 − , SO 4 2− , NO 3 − , Cl − , CO 3 2− , S 2 O 3 2− , F − , Br − , HPO 4 − , ClO 4 − ) for S 2− through the study. In addition, the novel type of multifunctional fluorescent sensor has a relatively wide pH range (pH 4–10). At the same time, it exhibited remarkable longterm fluorescence stability (≥35 days) for Cu 2+ detection. In addition, this nanoprobe exhibits very low cytotoxicity and can easily permeate the cell membrane and realize Cu 2+ and S 2− monitoring and imaging in live cells. Therefore, this novel approach can be used in various fields, such as the detection of multiplex analytes in biological applications and environment, and it will reveal great application prospects.

Photoswitchable fluorescent polymeric nanoparticles (PFPNs) with controllable molecular weight, high contrast, biocompatibility, and prominent photostability are highly desirable but still scarce for rewritable printing, super-resolution bioimaging, and rewritable data storage. In this study, novel amphiphilic BODIPY-based PFPNs with considerable merits are first synthesized by a facile one-pot RAFT-mediated miniemulsion polymerization method. The polymerization is performed by adopting polymerizable BODIPY and spiropyran derivatives, together with MMA as monomer, and mediated by utilizing biocompatible PEO macro-RAFT agent as both control agent and reactive stabilizer. The amphiphilic BODIPY-based PFPNs not only exhibit reversibly photoswitchable fluorescence properties under the alternative UV and visible light illumination through induced intraparticle fluorescence resonance energy transfer (FRET) but also display controllable molecular weight with narrow polydispersity index (PDI), high contrast of fl...

A non-catalytic condensation of NiII β-aminonorcorrole with aryl aldehydes is shown to produce a family of pyrromethane dimers that undergo deaminative cyclization to yield pyridine-fused bis(norcorrole)s comprising two antiaromatic macrocycles communicating by an aromatic moiety. The new compounds were characterized by spectroscopic, structural, and electrochemical methods supported by DFT calculations, all of which revealed unexpected antiaromaticity enhancement in the fused system.

In this study, amphiphilic diblock copolymers were designed and synthesized via the incorporation of reversible addition-fragmentation chain transfer radical polymerization (RAFT) and a subsequent grafting technique. Subsequently, Hg

Aromaticity is a key concept in physical organic chemistry. The aromatic order of the classic heterobenzenes was reported in experiment early. However, the unambiguous criteria used to validate the aromaticity of that were controversial or inadequate in theory. In this work, the global aromaticity of the compounds has been studied using the ELF, NICS and ISE. NICS(max)(zz) was calculated based on the maximum NICS contribution to the out-of-plane zz tensor component. Two types of bonds are observed. The correlations between NICS(max)(sigma zz) and NICS(max)(pi zz) with respect to aromaticity are demonstrated, specifically between NICS(max)(pi zz), and ELF pi (cc = 0.98) for pi bonds. For a bonds, the different electron delocalization of sigma bonds out of the plane of the ring predicted well the discrepancies between NICS(max)(sigma zz) and ELF sigma. The sigma aromatic order of the classic heterobenzenes (C6H5N > C6H6 > C5H5P > C5H5As > C5H5Bi, C5H5Sb) was proved via the level of electronic delocalization. (C) 2014 Elsevier B.V. All rights reserved.

This work concerns the interaction of prenoxine sodium (PRX) and bovine serum albumin (BSA), which was conducted by spectroscopic means: fluorescence spectra, ultraviolet-visible spectra (UV-vis) and circular dichroism spectra (CD spectra) in physiological conditions. The results revealed the PRX can quench the fluorescence of BSA remarkably in aqueous solution. The quench mechanism has been obtained after corrected the fluorescence intensities for inner filter effects. The binding constants (Ka) were calculated according to the relevant fluorescence data at different temperatures. Moreover, from a series of analyses, we have obtained the binding sites, the binding distance and binding force. The effect of PRX on the conformation of BSA has been analyzed using synchronous fluorescence under experimental conditions. In addition, the CD spectra proved that the secondary structure of BSA changed in the presence of PRX in aqueous solution.

In a one-pot synthesis, 1′-methyl-2,3″-dioxo-5″-aryl-1,2,5a″,7″,8″,9a″-hexahydro-5″H,6″H-dispiro[indole-3,2′-pyrrolidine-3′,2″-pyrano[2,3-d][1,3]thiazolo[3,2-a]pyrimidine]-4′-carboxylic acid methyl ester was prepared via the sequential reaction of 4-aryl-octahydro-pyrano[2,3-d]pyrimidine-2-thione, dimethyl acetylenedicarboxylate (DMAD), and a mixture of isatin and sarcosine. All the novel spiro compounds, in moderate yields, were characterized thoroughly by infrared, NMR, mass spectromentry, and elemental analysis together with x-ray crystallographic analysis.

Quantum mechanics and molecular dynamics are used to simulate guanidinium ionic liquids. Results show that the stronger interaction exists between guanidine cation and chlorine anion with interaction energy about 109.216 kcal/mol. There are two types of spatial distribution for the title system: middle and top. Middle mode is a more stable conformation according to energy and geometric distribution. It is also verified by radial distribution function. The continuous increase of carbon dioxide (CO2) does not affect the structure of ionic liquids, but CO2 molecules are always captured by the cavity of ionic liquids.

A microporous acylamide-functionalized MOF with a 2-fold interpenetrated and methyl decorated framework (HNUST-4) has been designed and synthesized from [Cu2(COO)4] motifs and a C2-symmetric acylamide-linking tetracarboxylate, which exhibits good water stability, permanent porosity as well as high and selective CO2 uptake at ambient temperature.

The fluorescence and ultraviolet-visible (UV-Vis) spectroscopy were explored to study the interaction between Tropicamide (TA) and bovine serum albumin (BSA) at three different temperatures (292, 301 and 310K) under imitated physiological conditions. The experimental results showed that the fluorescence quenching mechanism between TA and BSA was static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process is spontaneous, hydrogen binds and vander Waals were the main force to stabilize the complex. According to Förster non-radiation energy transfer theory, the binding distance between TA and BSA was calculated to be 4.90 nm. Synchronous fluorescence spectroscopy indicated the conformation of BSA changed in the presence of TA. Furthermore, the effect of some common metal ions (Mg(2+), Ca(2+), Cu(2+), and Ni(2+)) on the binding constants between TA and BSA were examined.

A microporous oxalamide-functionalized NbO-type metal–organic framework, HNUST-3, has been designed and synthesized by self-assembling [Cu2(COO)4] paddlewheel SBUs and a novel tetracarboxylate ligand with linking oxalamide groups. HNUST-3 represents the first example of a porous oxalamide-functionalized MOF, which exhibits a high BET surface area of 2412 m2·g–1, large H2 uptake (unsaturated total capacity of 6.1 wt % at 20 bar and 77 K), and excellent CH4 storage (135.8 cm3(STP)cm–3 at 20 bar and 298 K) as well as high CO2 adsorption capacity (20.2 mmol·g–1 at 20 bar and 298 K) with good selectivity for CO2 over CH4 (7.9) and N2 (26.1) at 298 K.

The characters (geometries, interaction energies, and electronic properties, etc.) of the intermolecular interactions between heteroaromatic rings (C5H5N, C4H4O and C4H4S) and Lewis acids (LiCN, LiNC) have been studied at the MP2/aug-cc-pVTZ level. Two types of interactions are observed: N/O⋯Li (type I) and π⋯Li (type II) bonded interactions. The calculated interaction energies show that type I structures are more stable. The nature of the intermolecular interactions has been also investigated by natural bond orbital (NBO), atoms in molecules (AIMs) and symmetry adapted perturbation theory (SAPT) methods, and the results demonstrate that the type I interactions are predominantly electrostatic in nature, while the induction forces dominate the type II interactions.

The 1,3-dipolar cycloaddition of azomethine ylide generated in situ from isatin and sarcosine to 2-arylmethylidene-2,3-dihydro-1H-pyrrolizin-1-ones afforded novel 1′-methyl-4′-(aryl)-1″H-dispiro[indole-3,2′-pyrrolidine-3′,2″-pyrrolizine]-1″,2(1H)-diones in good yields. The structures of all the products were characterized thoroughly by NMR, infrared spectroscopy, mass spectrum, and elemental analysis.

National Natural Science Foundation of China [21201062, 21172066]; Scientific Research Fund of Hunan Provincial Education Department [12K101, 12C0115]; Hunan Provincial Natural Science Foundation of China [11JJ2007]; State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) [201309]; Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province

The design of effective tools for detecting copper ion (Cu2+) and sulfide anion (S2-) is of great importance due to the abnormal level of Cu2+ and S2- has been associated with an increase in risk of many diseases. Herein, we report on the fabrication of fluorescence resonance energy transfer (FRET) based fluorescent probe PF (PEI-FITC) for detecting Cu2+ and S2- in 100% aqueous media via a facile one-pot method by covalent linking fluorescein isothiocyanate (FITC) with branched-polyethylenimine (b-PEI). PF could selectively coordinate with Cu2+ among 10 metal ions to form PF-Cu2+ complex, resulting in fluorescence quenching through FRET mechanism. Furthermore, the in situ generated PF-Cu2+ complex can be used to selectively detect S2- based on the displacement approach, resulting in an off-on type sensing. There is no obvious interference from other anions, such as Cl-, NO3-, ClO4-, SO42-, HCO3-, CO32-, Br-, HPO42-, F- and S2O32-. In addition, PF was successfully used to determine Cu2+ and S2- in human serum and tap water samples. Therefore, the FRET-based probe PF may provide a new method for selective detection of multifarious analysts in biological and environmental applications, and even hold promise for application in more complicated systems.

Fluorescence and ultraviolet spectroscopies were applied to investigate the interaction between five N-benzyl piperidones (NBP) and bovine serum albumin (BSA) under imitated physiological conditions. The experimental results show that these NBPs have a static fluorescence quenching effect on the endogenous fluorescence of BSA at the temperatures 302 and 310 K. According to the fluorescence quenching theory, the Stern–Volmer quenching constant (K SV), the binding constant (K a), and the number of binding sites (n) were obtained. Also, the effect of substituents on the binding capacity between NBP and BSA is in the order: C6H5

The interaction between thiazolo[2,3-b]pyrimidine (TZPM) analogues and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and UV–Vis spectroscopy at two different temperatures (299 and 307 K) under imitated physiological conditions. The results indicate that both static quenching and dynamic quenching contribute to the fluorescence quenching of BSA by TZPM. The binding constant ( K a ) and binding sites ( n ) were calculated from the obtained spectra. Based on the Forster non-radiation energy transfer theory, the average binding distance between BSA and TZPM was estimated. The synchronous fluorescence spectra indicate that the conformation of BSA has been changed. The comparison of binding potency of TZPM and BSA suggests that the substituents on the benzene ring enhance the binding affinity of TZPM and BSA. We investigated the possible sub-domains on BSA that bind TZPM by displacement experiments. Furthermore, to explore the effect of molecular structure on the binding, a study on quantitative structure–property relationship (QSPR) was performed, the quantitative relationship equation of R 0 , r and K a were obtained. We observed that R 0 , r and K a between BSA and TZPM is connected with the margin of the highest and the lowest occupied orbital energy (Δ E ), dipole moment ( μ ), Molar Volume ( V m ), Mole Mass ( M ).

Spiro pyrrolidines, which were proved with diverse and potent biological activities and they were discovered widespread in nature. In this paper, using fluorescence and ultraviolet spectroscopy, we investigated the interactions between novel spiro pyrrolidine (NSP) and bovine serum albumin (BSA) under the imitated physiological condition. The results show that the NSP binds to BSA molecules. Static quenching and non-radiation energy transfer are the main reasons for fluorescence quenching. We calculated the binding constant (K(a)) and binding sites (n) at different temperatures and obtained the binding distance between the tryptophan residue in BSA and the NSP based on the Förster theory of non-radiation energy transfer. In addition, using synchronous fluorescence spectra, we demonstrated conformation changes of BSA caused by NSP. The comparison of binding potency of NSP and BSA suggests that the substituent on the benzene ring influences the binding ability of NSP and BSA.

Novel multicolor and photoswitchcable fluorescent polymer nanoparticles were prepared by one-step miniemulsion via methyl methacrylate (MMA) copolymerization with 4-ethoxy-9-allyl-1,8-naphthalimide (EANI), allyl-(7-nitro-benzo[1,2,5]oxadiazol-4-yl)-amine (NBDAA) and spiropyran-linked methacrylate (SPMA). Under visible-light conditions, SPMA moieties in polymer nanoparticles are colorless and nonfluorescent, by varying the incorporating ratio of two dyes (EANI and NBDAA), fluorescence resonance energy transfer (FRET)-mediated emission signatures can be tuned so that the nanoparticles exhibit multiple colors under a single wavelength excitation. Moreover, the fluorescence emission of EANI and NBDAA dyes in nanoparticles can be reversibly switched "on" and "off" through the FRET process by the alternating irradiation of UV and visible light. This class of novel photoswitchable multicolor fluorescent polymer nanoparticles may find potential applications in multiplexed bioanalysis.

The fluorescence and ultraviolet spectroscopies were explored to study the interaction between edaravone (EDA) and bovine serum albumin (BSA) under imitated physiological condition. The experimental results show that the fluorescence quenching mechanism between EDA and BSA is a combined quenching (dynamic and static quenching). The binding constants, binding sites, and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) of the interaction system were calculated at different temperatures. According to Forster non-radiation energy transfer theory, the binding distance between EDA and BSA was calculated to be 3.10 nm. The effect of EDA on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effects of some common metal ions Mg2+, Ca2+, Cu2+, and Ni2+ on the binding constant between EDA and BSA were examined.

Novel photoswitchable fluorescent nanoparticles were fabricated by a facile one-step mini-emulsion polymerization, in which fluorescence resonance energy transfer (FRET) donor, 9,10-diphenylanthracene (DPA), and photoswitchable acceptor, spiropyran derivate, were simultaneously embedded in polymer matrix during the polymerization process. The prepared fluorescent nanoparticles exhibit the typical absorption properties of both DPA dye and spiropyran moiety, indicating that the two chromophores have been incorporated into the polymer nanoparticles. The obtained fluorescent nanoparticles exhibited superior photoswitchable fluorescent performance due to the effective photoinduced interparticle FRET. Moreover, the novel photoswitchable fluorescent nanoparticles also revealed small size (ca. 60 nm), high intensity, relatively fast photoresponsive property and good photoreversibility in aqueous media.

The 1,3-dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and isatin to 7-arylmethylidene-3-aryl-3,4-dihydro-2H-thiazolo[3,2-a][1,3,5]triazin-6(7H)-ones afforded novel dispiro[oxindole-pyrrolidine]-thiazolo[3,2-a][1,3,5]triazines in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, and elemental analysis. The results of experiment indicated that this 1,3-dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity. J. Heterocyclic Chem., (2011).

The ground- and excited-state intramolecular proton transfer processes of 2-(2-R (ROH, NH2, SH) phenyl (or pyridyl)) benzoxazoles (or benzothiazoles) are investigated by the DFT methods. The calculated results indicate that in the ground state there is a high correlation (R=0.9950) between the proton transfer barrier and the intramolecular hydrogen bonds (IMHB) strength. The increase of the strength of IMHB in the proton transfer processes leads to a larger barrier contributions. Intramolecular proton transfer process pathway is along with the minimal difference of change value in the IMHB angle. In the excited-state, there is a similar relationship between the IMHB and the barrier.

A new class of spiro thiazolo[3,2-a]pyrimidine compounds were synthesized by the one-pot sequential 1,3-dipolar cycloaddition of azomethine ylide (generated from isatin and sarcosine)–nitrile oxide to 2-arylmethylidene-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidin-3-ones in moderate yields. The structures of all the products were characterized thoroughly by NMR, MS, IR, elemental analysis, and NMR together with X-ray crystallographic analysis. J. Heterocyclic Chem., (2011).

The 1,3-dipolar cycloaddition reactions of nitrilimine with thiazolo[3,2-a]pyrimidine derivatives was investigated. Bis-cycloadducts were obtained through a domino 1,3-dipolar cycloaddition/ring-opening/ring-opening/1,3-dipolar cycloaddition processes. The structures of the products were characterized thoroughly by NMR, IR, MS, elemental analysis together with X-ray crystallographic analysis.

Both lomefloxacin (LOM) and ofloxacin (OFL) have a powerful ability to quench the fluorescence of bovine serum albumin (BSA). The fluorescence quenching action is much stronger when the two drugs coexist. The synergism between LOM and OFL was studied using fluorescence and ultraviolet spectroscopy under imitated physiological conditions. The results show that static quenching and non-radiation energy transfer are the main reasons for the fluorescence quenching. The synergism results in both the reduction of the binding stability between drugs and BSA and an increase of the free drug concentration, which will increase the efficacy of drugs. The thermodynamic parameters at different temperatures were calculated and the binding distances r between the drugs and BSA were obtained based on Forsters theory of non-radiation energy transfer. The synchronous fluorescence spectra indicated that the effect of synergism affected the conformation of BSA.

In this study, two hydrophobic fluorescent dyes, nitrobenzoxadiazolyl (NBD) and 9-(diethylamino)benzo[a]phenoxazin-5-one (NR) with different doping ratios were incorporated into polymer nanoparticles to constitute novel polymer nanoparticle-based fluorescence resonance energy transfer (FRET) systems via a facile one-step mini-emulsion polymerization. Spectroscopic characteristics demonstrate that the two fluorophores have been successfully embedded into the nanoparticles, and the fluorescence emission intensity of the two hydrophobic dyes can be greatly enhanced in aqueous media. The as-prepared fluorescent nanoparticles also display a uniform small size (ca. 55 nm), high dye load, intense fluorescence, as well as controllable amount and ratio of the two dyes. The observed FRET efficiencies (16.0–75.2%), as well as the distance (r) between NBD (donor) and NR (acceptor), is closely correlated to the doping ratio of two dyes. Moreover, by varying the doping ratio of two dyes, the fluorescent nanoparticles w...

The 1,3-dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and acenaphthenequinone to 7-arylmethylidene-3-aryl-3,4-dihydro-2H-thiazolo[3,2-a][1,3,5]triazin-6(7H)-ones afforded novel dispiro[acenaphthylene-1,2′-pyrrolidine]-3′,7′ ′-[1,3]thiazolo[3,2-a][1,3,5]triazines in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, elemental analysis and X-ray crystallographic analysis. The results of experiment indicated that this 1,3-dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity.

The interaction between dihydromyricetin (DMY) and bovine serum albumin (BSA) was investigated using fluorescence and ultraviolet spectroscopy at different temperatures under imitated physiological conditions. The experimental results revealed that dynamic quenching, static quenching and non-radiation energy transfer led to the fluorescence quenching. The obtained binding constants, binding sites and corresponding thermodynamic parameters at different temperatures indicate that hydrophobic forces play a major role in the interaction of DMY with BSA. According to Forster non-radiation energy transfer theory, the binding distance between BSA and DMY was found to be 3.26 nm. Synchronous fluorescence spectroscopy and FT-IR spectra showed the conformation of BSA changed in the presence of DMY. In addition, the effect of some common metal ions Cu 2+ , Ca 2+ , Mg 2+ , and Zn 2+ on the binding constant between DMY and BSA was examined.

To understand the effects of benzimidazole substitution on reaction equilibrium, the interactions between a series of benzimidazole-like ligands and [OV(O2)2(D2O)]−/[OV(O2)2(HOD)]− in solution were explored by a combination of multinuclear (1H, 13C, and 51V) magnetic resonance and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological condition. Some direct NMR data are reported for the first time. These results show that the relative reactivity among the organic ligands is 2-methyl-1H-benzo[d]imidazole > (1H-benzo[d]imidazol-2-yl)methanol > 1-(1H-benzo[d]imidazol-2-yl)ethanol > 1H-benzo[d][1,2,3]triazole. Both the steric effect and the electron effect of the 2-position substituted groups in benzimidazole ring affect the reaction equilibrium. The competitive coordination results in the formation of a series of new six-coordinated peroxovanadate species [OV(O2)2L]− (L = benzimidazole-like ligands). Moreover, the results of density functional calculations provided a reasonable explanation on the relative reactivity of the benzimidazole-like ligands as well as the important role of solvation in these reactions.

Fluorescence tunable polymer nanoparticles were prepared by incorporating two hydrophobic fluorescent dyes (9, 10-diphenylanthracene: DPA and nitrobenzoxadiazolyl: NBD) into polymethylmethacrylate (PMMA) nanoparticles via one-step mini-emulsion polymerization method. The prepared fluorescent nanoparticles exhibit the spectral properties of both DPA and NBD dye, indicating that the two fluorophores have been incorporated into the nanoparticles. The nanoparticles greatly enhance the fluorescence emission of the two hydrophobic dyes in aqueous media probably by providing good protection of the dye molecules in the polymer nanoparticles matrix. Moreover, by varying the doping ratio of the two hydrophobic dyes, the polymer nanoparticles exhibit tunable and distinguishable emission characteristics under a single wavelength excitation via occuring fluorescence resonance energy transfer (FRET).

The 1,3-dipolar cycloaddition of azomethine ylides derived from isatin and amino acids viz. sarcosine and proline to 2-arylmethylidene-5,6-dihydroimidazo[2,1-b]thiazol-3(2H)-ones afforded novel spiro pyrrolidines and pyrrolizidines regio- and stereoselectively in moderate yields. The products were characterized thoroughly by IR, MS, NMR together with elementary analysis.

Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, Hunan Province College Key Laboratory of QSAR/QSPR, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China *E-mail: pgyi@hnust.edu.cn Received December 27, 2009 DOI 10.1002/jhet.443 Published online 26 July 2010 in Wiley Online Library (wileyonlinelibrary.com).

A new class of [1,2,4]oxadiazolo[4,5-a]thiazolo[2,3-b]pyrimidin-9(10H)-one was prepared in moderate yields by the reaction of nitrile oxide with 2-arylmethylidene-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidin-3-one. The reaction site of dipolarphile is the CN of thiazolo[3,2-a]pyrimidin-3-one rather than the expected CC of arylmethylidene. The structures of the products were characterized thoroughly by IR, elemental analysis, MS, and NMR analysis.

We develop a controllable approach to prepare ordered–CdTe quantum dots (QDs) polyamidoamine (PAMAM) nanocomposites (NCPs) by self-assembly growth of simple CdTe– PAMAM in aqueous solution. The sphere and network CdTe NCPs were obtained at pH 4.7 for growing 15 h and 79 h respectively. As the NCPs ceased growing over pH 8 immediately, we can conveniently control their size and morphology by adjusting pH of the solution to tune the growth time. The morphology change of CdTe-PAMAM nanocomposites was characterized by TEM images. The fluorescent intensity and photostability of ordered–CdTe–PAMAM have been improved significantly.

To understand the 4-substituting group effects of organic ligands in pyridine ring on the reaction equilibrium, the interactions between a series of 4-picoline-like ligands and [OV(O(2))(2)(D(2)O)](-)/[OV(O(2))(2)(HOD)](-) in solution were explored by the combined use of multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, DOSY, and variable-temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological condition. Some direct NMR data are given for the first time. The reactivity among the 4-picoline-like ligands is 4-picolineisonicotinateisonicotinamideethyl isonicotinate. The competitive coordination results in the formation of a series of new six-coordinated peroxovanadate species [OV(O(2))(2)L](n-) (L=4-picoline-like ligands, n=1 or 2). The results of density functional calculations provide a reasonable explanation on the relative reactivity of the 4-picoline-like ligands. Solvation effects play an important role in these reactions.

The 1,3-dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and isatin to 1-benzyl-3,5-diarylmethylidene-piperidin-4-ones afforded novel di-spiro-indolo/pyrrolidino/piperidines in moderate yields. Further cycloaddition of these di-spiro compounds to nitrile oxide afforded tri-spiro-indolo/pyrrolidino/piperadino/isoxazolines in moderate yields with high regio- and stereoselectivity.

A new class of N1-substituted 1,2,3,6-tetrahydropyrimidin-2-ones was prepared in moderate yields by the reaction of nitrile oxide with thiazolo[3,2-a]pyrimidine derivatives via a domino 1,3-dipolar cycloaddition/ring-opening/ substitution process. The structures of the products were characterized thoroughly by IR, elemental analysis, MS, NMR together with X-ray crystallographic analysis.

Gold nanorods coated with a multiplex component, namely Au(2)S/AuAgS coated gold nanorods, are produced without precipitation and aggregation among the nanorods. Both the thickness of the shell and size of the core can be readily controlled by this technique allowing one to tune the plasmon resonance of the nanocomposites over a range of several hundred nanometers. These Au(2)S/AuAgS coated gold nanorods exhibit interesting optical properties and are suitable for many biological sensing applications. Functionalization of the Au(2)S/AuAgS coated gold nanorods is achieved by manipulating the affinity between the Au(2)S/AuAgS and thiol compounds. Biomolecules can be covalently attached via the NH(2) bond of the antibodies to the NHS-terminated nanorods. The longitudinal peaks of the Au(2)S/AuAgS coated gold nanorods are extremely sensitive to the refractive index changes induced by target binding, suggesting that they are excellent sensors for target-specific binding events and have the potential to achieve single-molecule sensitivity in microspectroscopy.

A novel diperoxovanadate complex NH(4)[OV(O(2))(2)(picolinamide)].H(2)O was synthesized from aqueous solution under physiological conditions. The solution structure of the complex was characterized by multinuclear ((1)H, (13)C, (14)N, and (51)V), variable temperature as well as two-dimensional (DOSY) NMR techniques in the interaction system of NH(4)VO(3)/H(2)O(2)/picolinamide at room temperature. The crystal structure of the complex was determined at 223K by single-crystal X-ray diffraction method. It belongs to the monoclinic space group P21/c with a=7.323(3)A, b=14.255(7)A, c=10.022(5)A, beta=99.524(9) degrees , V=1031.7(8)A(3), and Z=4. The crystal is composed of ammonium ions, picolinamide oxodiperoxovanadate(V) ions, and water molecules, which are held together by ionic and hydrogen bond forces. The species [OV(O(2))(2)(picolinamide)](-) is seven-coordinated with a distorted pentagonal bipyramidal geometry both in solution and in crystal.

We describe the fabrication and characterization of a localized surface plasmon resonance (LSPR) biosensor that utilizes gold nanorods immobilized as the optical transducer which requires the intensity change at a single wavelength to be monitored as a function of receptor–analyte binding at the nanorod surface. In contrary to free gold nanorods suspended in an aqueous solution with high sensitivity to the longitudinal plasmon wavelength to the surrounding environment, the intensity of the longitudinal plasmon band based on immobilized gold nanorods is more sensitive to changes in the surrounding dielectric properties than the change in the longitudinal plasmon wavelength. Quantitative calculation gives a linear equation between the concentration ( X ) of the test sample and intensity of LPB ( Y ) as Y = 0.0881 + 12.9502 X and 0.1 pM anti-goat can be detected using this IgG probe in this study. This sensor chip made of immobilized gold nanorods is very stable. The immobilized gold nanorods preserved under 4 °C for 1 year yield almost the same extinction spectrum as the original nanorods. This study reveals a reliable and sensitive method to measure the intensity of longitudinal plasmon bands based on the highly stable LSPR substrate. Moreover, the performance is comparable to dynamic SPR measurements in immunoassays and can monitor the receptor–analyte reactions in real time.