Preparation of polystyrene-grafted titanate nanotubes by <Emphasis Type="Italic">in situ</Emphasis> atom transfer radical polymerization

This work successfully prepared nanohybrids by in situ atom transfer radical polymerization (ATRP) of styrene from titanate nanotubes (TNTs). Fourier-transform infrared (FT-IR), pronton nuclear magnetic resonance spectroscopy (¹H NMR), and thermal gravimetric analysis (TGA) were used to verify the successful graft of polystyrene (PS) chains from TNTs. Transmission electron microscopy (TEM) displayed that the obtained PS-g-TNTs nanohybrids had a core-shell structure of TNT core and PS shell. The grafted PS content was well controlled and increased with increasing of the monomer/initiator ratio. Further copolymerization of tert-butyl acrylate (tBA) from the surface of PS-g-TNTs was studied, illustrating the “living” characteristics of the surface-induced ATRP method used in this work. Supported by the Special Funds for Major State Basic Research Projects (Grant No. 2005CB623803), the National Basic Research Program (Grant Nos. 2007CB808000 & 2009CB930400), the National Natural Science Foundation of China (Grant Nos. 50633010 & 20874060), the Program for New Century Excellent Talents in University (Grant No. NCET-07-0558), the Basic Research Foundation of Shanghai Science and Technique Committee (Grant No. 07DJ14004), and Shanghai Leading Academic Discipline Project (Grant No. B202).     

Theoretical studies on cation-π interactions (I)—Densityfunctional theory investigation on the configurations and interaction for ammonium cation-benzene complex

Density-functional theory (DFT) approach of B3LYP/6-31G* has been employed to calculate the six possible configurations of ammonium cation-benzene complex (NH₄ ⁺ -C₆H₆). The calculation result released that the asymmetrical configuration of this complex with two hydrogen atoms pointing to the benzene ring was the most stable structure. Structural characteristics, molecular interaction fashion and thermodynamic parameters indicated that NH₄ ⁺ was bound to benzene through hydrogen bonding interaction. Project supported by the “863” High Technology Program of China (Grant No. 863-103-04-01) and the National Natural Science Foundation of China (Grant No. 29403027)     

Michael addition reactions of cyclanones with acrylamides: Producing 2-carbamoylethyl derivatives or ene-lactams

The electron-withdrawing groups (EWGs) in the electrophilic alkenes employed in the Michael addition reaction are almost only CO2R, CN, COR, NO2, and SO2Ph. Although amides (CONR1R2) are also typical electron-withdrawing groups and are of great importance in organic synthesis, they are scarcely em-ployed as the EWGs of the electrophilic alkenes in the Michael addition reaction. In this work, the Mi-chael reactions of acrylamide and its derivatives with cyclanones were successfully carried out in the presence of enough radical inhibitors. The amide groups play a key role in producing the preferred products. The N-substituted acrylamides, including N-monosubstituted and N,N-disubstituted acryla-mides could react with cyclohexanone (CHn) to give the expected 2-carbamoylethyl derivatives; how-ever, acrylamide reacting with cyclohexanone only produced ene-lactam. Cyclanones also have effects on the products, while the ring size of cyclanones influences the reaction yield and the α-substituent decides the ratio of resulting isomeric ene-lactams.     

Sulfonate-based fluorescent probes for imaging hydrogen peroxide in living cells

Based on the mechanism of H₂O₂-mediated hydrolysis of sulfonates, two fluorescein disulfonates compounds (FS-1 and FS-2) were designed and synthesized as the highly selective and sensitive fluorescent probes for imaging H₂O₂ in living cells. The probes were detected with elemental analysis, IR, ¹H NMR and ¹³C NMR. Upon reaction with H₂O₂, the probes exhibit strong fluorescence responses and high selectivity for H₂O₂ over other reactive oxygen species and some biological compounds. Furthermore, the sulfonate-based probes, as novel fluorescent reagents, are cell-permeable and can detect micromolar changes in H₂O₂ concentrations in living cells by using confocal microscopy. Supported by the National Basic Research Program of China (Grant No. 2007CB936000), the National Natural Science Funds for Distinguished Young Scholar (Grant No. 20725518), Major Program of the National Natural Science Foundation of China (Grant No. 90713019), the National Natural Science Foundation of China (Grant No. 20875057), the Natural Science Foundation of Shandong Province, China (Grant No. Y2007B02), and the Science and Technology Development Programs of Shandong Province, China (Grant No. 2008GG30003012)     

Photoelectrocatalytic oxidation of GMP on an ITO electrode modified with clay/[Ru(phen)<Subscript>2</Subscript>(dC18bpy)]<Superscript>2+</Superscript> hybrid film

An indium tin oxide (ITO) electrode modified with monolayer clay/[Ru(phen)₂(dC18bpy)]²⁺ (phen=1,10-phenanthroline, dC18bpy = 4,4′-dioctadecyl-2,2′ bipyridyl) hybrid film has been fabricated by the Langmuir-Blodgett (LB) method. Atomic force microscopy revealed that the single-layered hybrid film of clay/[Ru(phen)₂(dC18bpy)]²⁺ (denoted as Clay-Ru) was closely packed at a surface pressure of 25 mN·m⁻¹ and had a thickness of 3.4±0.5 nm. Cyclic voltammograms showed that the redox current of Ru(II) complex decreased when incorporated into the clay film, suggesting that the clay layer acts as a barrier against electron transfer. When applied to oxidizing the mononucleotide of guanosine 5′-monophosphate (GMP), a large catalytic oxidative current was achieved on the Clay-Ru(II) modified ITO electrode at the external potential above 900 mV (vs. Ag|AgCl|KCl) and, more significantly, this response was further enhanced by light irradiation (λ>360 nm), in which the photocurrent is increased about 11 times in comparison with that of a bare ITO. Mechanism of the photoelectrocatalytic effect was proposed in terms of the reduction of the photoelectrochemically generated Ru(III) complex in the Clay-Ru film by GMP. Supported by the National Natural Science Foundation of China (Grant Nos. 20471043 and 20843007), Zhejiang Provincial Natural Science Foundation (Grant Nos. Y404118 and Y408177), the “151” Distinguished Person Foundation of Zheji-ang Province of China, Zhejiang Technology Project Foundation (Grant No. 2007C21134) and Wenzhou Technology Project Foundation (Grant No. N2004B040)     

Effect of inorganic positive ions on the adsorption of surfactant Triton X-100 at quartz/solution interface

The electrode-separated piezoelectric sensor (ESPS), an improved setup of quartz crystal microbalance (QCM), has been employed to investigate the adsorption behavior of nonionic surfactant Triton X-100 at the hydrophilic quartz-solution interface in mineralized water medium in situ, which contained CaCl2 0.01 mol·L?1, MgCl2 0.01 mol·L?1, NaCl 0.35 mol·L?1. In a large scale of surfactant concentration, the effects of Ca2 , Mg2 and Na on the adsorption isotherm and kinetics are obviously different. In aque-ous solution containing NaCl only, adsorption of Triton X-100 on quartz-solution interface is promoted, both adsorption rate and adsorption amount increase. While in mineralized water medium, multivalent positive ions Ca2 and Mg2 are firmly adsorbed on quartz-solution interface, result in the increasing of adsorption rate and adsorption amount at low concentration of surfactant and the peculiar desorption of surfactant at high concentration of Triton X-100. The results got by solution depletion method are in good agreement with which obtained by ESPS. The "bridge" and "separate" effect of inorganic positive ions on the adsorption and desorption mechanism of Triton X-100 at the quartz- solution interface is discussed with molecular dynamics simulations (MD), flame atomic absorption spectrometry (FAAS) and atomic force microscopy (AFM) methods.     

3D-QSAR and docking studies of estrogen compounds based on estrogen receptor β

Close attention has been paid to estrogen compounds because these chemicals may pose a serious threat to the health of humans and wildlife. Estrogen receptor (ER) exists as two subtypes, ERα and ERβ. The difference in amino acids sequence of the binding sites of ERα and ERβ might lead to a result that some synthetic estrogens and naturally occurring steroidal ligands have different relative affinities and binding modes for ERα and ERβ. In this investigation, comparative molecular similarity indices analysis...     

Theoretical observation of hexaatomic molecules containing pentacoordinate planar carbon

The smallest molecules up to date containing a D5h pentacoordinate planar carbon (PPC) atom, CBe5 and CBe54-, are presented by means of ab initio calculations. To gain a better understanding about which electronic factors contribute to their stabilization, natural bond orbital (NBO) analysis and the nucleus independent chemical shifts (NICS) were calculated. The data reported here suggest that D5h CBe5 is σ aromaticity in nature, while in D5h CBe54- π aromaticity is dominating. The classical octet rule is well satisfied in both molecules, and is one of the fundamental reasons to understand the stability of the pentagon structures. The Be5 ring serves as σ donor in D5h CBe5, and π-acceptor in D5h CBe54-. The D5h CBe54- possessing 18 valence electrons with a closed-shell electron configuration is the most plau-sible candidate for experimental detection.     

The enzyme-amplified amperometric DNA sensor using an electrodeposited polymer redox mediator

A highly sensitive method for the detection of a breast cancer-associated BRCA-1 gene is reported. The detection is based on a classical sandwich-type assay using horseradish peroxidase (HRP) as a catalytic label and electrodeposited Os^2+/3+ conducting polymer (PAA-PVI-Os) as a redox mediator. Target DNA could be detected by the HRP-catalyzed reduction of H₂O₂, leading to a limit of detection as low as 10 fM. Supported by the National Natural Science Foundation of China (Grant Nos. 20725516, 20704043, 20873175 & 20805055), Shanghai Municipal Commission for Science and Technology (Grant Nos. 0752nm021 & 07ZR14136), Ministry of Science and Technology (Grant Nos. 2006CB933000, 2007CB936000 & 2007AA06A406), Ministry of Health (Grant No. 2009ZX10603), and China Postdoctoral Science Foundation and Shanghai Postdoctoral Scientific Program (Grant No. 07R214160).     

Statistical theory for hydrogen bonding fluid system of AaDd type (Ⅲ): Equation of state and fluctuations

The equation of the state of the hydrogen bonding fluid system of A_aD_d type is studied by the principle of statistical mechanics. The influences of hydrogen bonds on the equation of state of the system are obtained based on the change in volume due to hydrogen bonds. Moreover, the number density fluctuations of both molecules and hydrogen bonds as well as their spatial correlation property are investigated. Furthermore, an equation describing relation between the number density correlation function of “molecules-hydrogen bonds” and that of molecules and hydrogen bonds is derived. As application, taking the van der Waals hydrogen bonding fluid as an example, we considered the effect of hydrogen bonds on its relevant statistical properties. Supported by the National Natural Science Foundation of China (Grant Nos. 20303006 and 20574016), the Natural Science Foundation of Hebei Province (Grant Nos. B2006000959 and B2004000093) and the Natural Science Foundation of Education Committee of Hebei Province (Grant No. 2003101)     

Discussions about whether radioactive half life can be changed by mechanic motion

In this essay, some discussions and comments about the paper entitled “Can the decay rate of ³²P be changed by mechanic motion?” (Ding et al., Science in China Series B: Chemistry (Chinese version), 2008, 38(11):1035–1037) are given. It was strongly suggested that its experimental methods, data calculations and conclusion should be reconsidered. After the data were recalculated, the new results supported that the chiral mechanic motion could induce the changes of radioactive half life. Supported by the National Natural Science Foundation of China (Grant Nos. 20571085, and 20877099), Fund of the President of Chinese Academy of Sciences (Grant No. 0521021T04), 2005/2006 USA Li’s Foundation Merit Prize Fund, Fund of Graduate University of Chinese Academy of Sciences (Grant No. 065101HM03), and Fund of the Key Laboratory of Nuclear Analysis of the Institute of High Energy Physics of Chinese Academy of Sciences (Grant No. K129)     

Planar or quasi-planar octa- and ennea-coordinate aluminum and gallium in boron rings

An ab initio theoretical investigation has been performed on planar or quasi-planar octa-and ennea-coordinate Al and Ga centered in X@B8- and X@B9 (X=Al, Ga). These high symmetry molecular wheels all turned out to be true minima of the systems and σ+π double aromatic in nature, similar to the previously characterized D8h B@B8- both electronically and geometrically. Adiabatic and vertical detachment energies of the anions and the ionization potentials of the neutrals have been calculated to aid their eventua...     

Highly sensitive and selective ratiometric fluorescent copper sensors: Different binding affinities modulated by three separate side chains of naphthalimide

A series of compounds 1-11 with different side chains of naphthalimide as fluorescent copper sensors were designed and synthesized. Compounds 1, 9, 10 and 11 presented a high selectivity to Cu2+ in a neutral aqueous environment. Here 1, 9 and 10 showed selectivity and affinity to Cu2+ with an association constant of about ～106. It gave somewhat response to Ag+, Co2+, Ni2+ and Fe2+ while 1 detected copper. 9 and 10 displayed better selectivity by changing their hydrophobic side chains to the hydrophilic ones...     

Direct electrochemistry behavior of Cytochrome c on silicon dioxide nanoparticles-modified electrode

A newfangled direct electrochemistry behavior of Cytochrome c (Cyt c) was found on glassy carbon (GC) electrode modified with the silicon dioxide (SiO2) nanoparticles by physical adsorption. A pair of stable and well-defined redox peaks of Cyt c′ quasi-reversible electrochemical reaction were obtained with a heterogeneous electron transfer rate constant of 1.66×10-3 cm/s and a formal potential of 0.069 V (vs. Ag/AgCl) (0.263 V versus NHE) in 0.1 mol/L pH 6.8 PBS. Both the size and the amount of SiO2 nanoparticles could influence the electron transfer between Cyt c and the electrode. Electrostatic interaction which is between the negative nanoparticle surface and positively charged amino acid residues on the Cyt c surface is of importance for the stability and reproducibility toward the direct electron transfer of Cyt c. It is suggested that the modification of SiO2 nanoparticles proposes a novel approach to realize the direct electrochemistry of proteins.     

Immobilization and hybridization of DNA based on magnesium ion modified 2,6-pyridinedicarboxylic acid polymer and its application for label-free PAT gene fragment detection by electrochemical impedance spectroscopy

A new approach for a simple electrochemical detection of PAT gene fragment is described. Poly(2,6-pyridinedicarboxylic acid) (PDC) modified glassy carbon electrode (GCE) was prepared by potential scan electropolymerization in an aqueous solution. Mg2 ions were incorporated by immer-sion of the modified electrode in 0.5 mol/L aqueous solution of MgCl2 to complete the preparation of a generic "activated" electrode ready for binding the probe DNA. The ssDNA was linked to the conduct-ing polymer by forming a bidentate complex between the carboxyl groups on the polymer and the phosphate groups of DNA via Mg2 . DNA immobilization and hybridization were characterized with dif-ferential pulse voltammetry (DPV) by using methylene blue (MB) as indicator and electrochemical im-pedance spectroscopy (EIS). The EIS was of higher sensitivity for DNA detection as compared with voltammetric methods in our strategy. The electron transfer resistance (Ret) of the electrode surface in EIS in [Fe(CN)6]3-/4- solution increased after the immobilization of the DNA probe on the Mg/PDC/GCE electrode. The hybridization of the DNA probe with complementary DNA (cDNA) made Ret increase further. The difference between the Ret at ssDNA/Mg/PDC/GCE and that at hybridization DNA modified electrode (dsDNA/Mg/PDC/GCE) was applied to determine the specific sequence related to the target PAT gene with the dynamic range comprised between 1.0 × 10-9 and 1.0 × 10_5 mol/L. A detection limit of 3.4 × 10-10 mol/L of oligonucleotides can be estimated.     

Nanosilver resonance scattering spectral method for determination of hydroxyl radical and its application

Silver nanoparticles were prepared under a microwave high-pressure condition using citric acid sodium as a reducer while the excess citrate was removed under high speed centrifugation. There is a resonance scattering (RS) peak at 470 nm for silver nanoparticles. In a pH 4.0 HAc-NaAc buffer solution, hydroxyl radicals from the Fenton reaction can oxidize silver nanoparticles to Ag , resulting in the RS intensity decreasing. The decreased RS intensity at 470 nm (△I 470 nm) is linear with respect to the concentration of H2O2 (C) in the range of 0.27-7.56 μmol/L with a detection limit of 0.23 μmol/L. Its regression equation is △I 470 nm = 24.3 C 13.8 with a correlation coefficient of 0.9959. This method was applied to screening the antioxidants with satisfactory results.     

Application of peptide nucleic acids containing azobenzene self-assembled electrochemical biosensors in detecting DNA sequences

Hybridization of peptide nucleic acids probe containing azobenzene (NH₂-TNT₄, N-PNAs) with DNA was performed by covalently immobilizing of NH₂-TNT₄ in sequence on the 3-mercaptopropionic acid self-assembled monolayer modified gold electrode with the helps of N-(3-dimethylaminopropy1)-N′-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), and the hybrid was coded as N-PNAs/DNA. Using [Fe(CN)₆]^4−/3− (1:1) as the electrochemical indicator, the electrochemical properties of the N-PNAs self-assembled monolayer (N-PNAs-SAMs) and N-PNAs/DNA hybridization system under the conditions of before and after UV light irradiation were characterized with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectra (EIS). Results showed that the redox currents decreased with the increase of irradiation time, suggesting that the ability of the charge transfer on the electrode surface was weakened and the conformation of hybrid system had been changed, and the control of PNAs/DNA hybridization could be realized by UV light irradiation. Supported by the National Natural Science Foundation of China (Grant No. 50572107) and “Top Hundred Talents Program” of Chinese Academy of Science     

Potential energy curves for the X1∑ g, B1△g and B''''1∑ g states of C2 using MRCI and approximate CI methods

The potential energy curves for the X1∑ g, B1△g and B′1∑ g states of C2 have been studied by using MRCI and approximate CI methods, and are benchmarked against the calculations of full configuration interaction (FCI). The results obtained by MRCI method agree with the FCI very well, and even are accurate enough to compare other approximate methods as benchmark, when the calculations of FCI are not feasible. The approximate CI methods mentioned in this paper are reliable for treating chemical problems.     

Design of artificial nucleases and studies of their interaction with DNA

The design of artificial nucleases and nuclease mimics has attracted extensive attention and made great progress due to their significant scientific meanings and potential application in the field of gene medicine and molecular biology. This paper reviews recent progress in the investigation of artificial nuclease, including “bifunctional cooperative catalysis”, “dinuclear synergistic catalysis”, “metal-free catalysis”, and especially, the studies of aza-crown ethers as artificial nucleases and their interaction with DNA. Supported by the National Natural Science Foundation of China (Grant Nos. 20872061 & 20372032) and the National Basic Research of China (Grant No. 2007CB925103)     

Resonance-enhanced photon excitation spectroscopy of the even-parity autoionizing Rydberg states of Kr

Kr atoms were produced in their metastable states 4p⁵5s [3/2]₂ and 4p⁵5s’ [1/2]₀ in a pulsed DC discharge in a beam, and subsequently excited to the even-parity autoionizing Rydberg states 4p⁵ np′ [3/2]_1,2, [1/2]₁ and 4p⁵ nf′ [5/2]₃ using single photon excitation. The excitation spectra of the even-parity autoionizing resonance series from the metastable Kr were obtained by recording the autoionized Kr⁺ ions with time-of-flight ion detection in the photon energy range of 29000–40000 cm⁻¹. A wealth of autoionizing resonances were newly observed, from which more precise and more systematic spectroscopic data of the level energy and quantum defects were derived. Supported by the National Natural Science Foundation of China (Grant No. 20673107), the National Key Basic Research Special Foundation of China (Grant No. 2007CB815203), and Chinese Academy of Sciences (Grant No. KJCX2-SW-H08)