Search

Polymyxin is a critical antibiotic against the infection caused by multidrug-resistant gram-negative bacteria. Neurotoxicity is one of main dose-limiting factors. The present study aimed to investigate the underlying molecular mechanism on colistin induced peripheral neurotoxicity using a mouse model. Forty mice were divided into control, colistin 1-, 3- and 7-day groups, the mice were intravenously injected with saline or colistin (sulfate) at the dose of 15 mg/kg/day for 1, 3 and 7 days, respectively. The results showed that, colistin treatment for 7 days markedly resulted in the demyelination, axonal degeneration and mitochondria swelling in the mice’s sciatic tissues. Colistin treatment induces oxidative stress as well as the increases of mitochondrial permeability transition, decreases of membrane potential (ΔΨm) and activities of mitochondrial respiratory chain in the mice’s sciatic nerve tissues. Furthermore, in the colistin-7 day group, adenosine-triphosphate (ATP) level Na+/K+-ATPase activity decreased to 75.2% (p

The migratory insertion of isonitriles into metal C bonds is a potentially important method for the formation of C C bonds in organic and pharmaceutical syntheses. In this context, the reaction mechanism of Cp * (pentamethylcyclopentadienyl)(Cl)Zr(diene) with isonitriles was studied using density functional theory calculations. Zr imido complexes and α-methylene cyclopentenimines are the confirmed products for N-t Bu-, N -2,6-diMePh-, and N -1-adamantyl-substituted isonitriles, whereas six-membered zirconacycles are the thermodynamically favored products for Me- and Et-substituted isonitriles. The β-H elimination pathway is responsible for the formation of α-methylene cyclopentenimines and zirconacycles. The kinetically favored products for MeNC and EtNC are diazazirconacyclopentanes ( σ complexes), which are formed via an isomerization pathway. The effects of substituents on the isonitrile nitrogen atom in the main elementary reactions are also discussed.

A density functional theory study is performed on the reactions of α,β-unsaturated oxime pivalates and alkenes through Cp*RhIII-catalyzed (Cp* = pentamethylcyclopentadienyl) C–H activation. The catalytic cycle involves reversible metalation–deprotonation, migratory alkene insertion, pivaloyl transfer to the Rh center, and reductive elimination, among other steps. The results show that the migratory alkene insertion is rate-determining and that the reductive elimination to form the product-ligated species makes the reaction irreversible (exergonic by 60 kcal/mol). If the electron-donating ability of the substituents on the cyclopentadienyl (Cp) ligand is increased or an electron-withdrawing group is introduced into the terminus of the alkene, the apparent activation energy of the reaction increases. In contrast, if a stronger electron-donating group is introduced at the 2-position of the α,β-unsaturated oxime pivalate, the apparent activation energy of the reaction decreases greatly, and the reaction can be performed at room temperature. On the other hand, for phenyl groups at the 2-position, the introduction of a more electron-deficient p-CF3-phenyl group increases the apparent activation energy. Finally, the diastereoselectivity of the reaction with cyclohexylethylene as the substrate is attributable to a clash between the cyclohexyl group and the α,β-unsaturated oxime pivalate.

In spite of their widespread use as catalysts, 1,2,3,4,5-pentamethylcyclopentadienyl (Cp*) iridium complexes have been rarely employed in the synthesis of pyridine derivatives. Herein, we used density functional theory (DFT) calculations to predict the [Cp*Ir(OAc)]+-catalysed synthesis of 2,3-dihydropyridines, which are important starting materials for pharmaceuticals, from α,β-unsaturated oxime pivalates and alkenes. The corresponding Cp*Rh complex-catalysed processes were discussed in comparison. The simulated catalytic cycle consists of several elementary reactions, such as reversible acetate-assisted metalation–deprotonation, migratory insertion of the alkene, pivaloyl transfer, and reductive elimination. The migratory insertion of the alkene is identified as the rate-determining step, and the reductive elimination to furnish the product-ligated species makes the reaction irreversible (exergonic by about 48 kcal mol−1). The stabilities of the intermediates and the energy barrier of migratory insertion of the alkene can be affected by introducing substituent groups with different electronic characteristics into Cp* and the 2-position of α,β-unsaturated oxime pivalates, as well as by using polarised alkenes. The apparent activation energy of the reaction can be increased by increasing the electron-donating ability of the substituent group on Cp*, and by introducing electron-withdrawing groups into the terminus of alkenes. When a strong electron-donating group such as the amido group is introduced into the 2-position of α,β-unsaturated oxime pivalates, the apparent activation energy is greatly reduced so that the reaction can occur at room temperature. In contrast, changing phenyl into the highly electron-deficient p-CF3-phenyl makes the reaction more difficult. Diastereoselectivity of the reaction was examined using cyclohexylethylene as a substrate, and a method for enhancing diastereocontrol was suggested.

The migratory insertion of isonitriles into the metal–C bond is important for constructing C–C bonds in organic and pharmaceutical syntheses. We examine the reaction of Cp*(Cl)Ti(diene) with isonitriles using density functional theory calculations. At room temperature, the bis-insertion reaction occurs easily for N-tert-butyl (tBu), methyl (Me), ethyl (Et), 2,6-dimethylphenyl (Ar), and N-1-adamantyl (1-Ad)-substituted isonitriles. The elementary reactions include the isomerisation of Cp*(Cl)Ti(diene), migratory insertion of the first isonitrile into a Ti–C bond, C–C reductive elimination, β-H elimination, migratory insertion of the second isonitrile into a Ti–H bond, and C–C reductive coupling. Two reliable fragmentation mechanisms are suggested for the bis-insertion products. For the bulkier tBuNC, ArNC, and 1-AdNC, the β-H elimination reaction pathway is dominant. For the smaller MeNC and EtNC, the γ-H elimination reaction pathway competes with the β-H elimination. For ArNC, the isomerisation reaction pathway to a newly predicted “σ complex” is kinetically favourable.

The adsorption and separation of hazard metal ions, radioactive nuclides, or minor actinides from wastewater and high-level radioactive waste liquids using functional silica-based nano/micro-particles modified with various inorganic materials or organic groups, has attracted significant attention since the discovery of ordered mesoporous silica-based substrates. Focusing on inorganic and organic modified materials, the synthesis methods and sorption performances for specific ions in aqueous solutions are summarized in this review. Three modification methods for silica-based particles, the direct synthesis method, wetness impregnation method, and layer-by-layer (LBL) deposition, are usually adopted to load inorganic material onto silica-based particles, while the wetness impregnation method is currently used for the preparation of functional silica-based particles modified with organic groups. Generally, the specific synthesis method is employed based on the properties of the loading materials and the silicon-based substrate. Adsorption of specific toxic ions onto modified silica-based particles depends on the properties of the loaded material. The silicon matrix only changes the thermodynamic and mechanical properties of the material, such as the abrasive resistance, dispersibility, and radiation resistance. In this paper, inorganic loads, such as metal phosphates, molybdophosphate, titanate-based materials, and hydrotalcite, in addition to organic loads, such as 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix{4}arene (Calix {4}) arene-R14 and functional 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines(BTP) are reviewed. More specifically, we emphasize on the synthesis methods of such materials, their structures in relation to their capacities, their selectivities for trapping specific ions from either single or multi-component aqueous solutions, and the possible retention mechanisms. Potential candidates for remediation uses are selected based on their sorption capacities and distribution coefficients for target cations and the pH window for an optimum cation capture.

A novel sheet-like Zn2+ doped Bi2MoO6 photocatalyst was fabricated through a facile hydrothermal strategy. The morphologies and chemical compositions of the samples were investigated with the help of powder X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), energy dispersive X-ray analysis (EDS), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman and FT-IR spectra. These experimental results indicated that Zn2+ ions could be incorporated into the crystal lattices of Bi2MoO6 and substituted the Bi3+ ions. Photocatalytic experiments revealed that the as-obtained Zn2+ doped Bi2MoO6 nanosheets possessed excellent UV-visible light induced photocatalytic ability for the decomposition of Rhodamine B (RhB) molecules by comparison with undoped Bi2MoO6. The effect of some scavengers on the photocatalytic efficiency was assessed. Moreover, a possible enhancement mechanism of photocatalytic activity over Zn2+ doped Bi2MoO6 nanosheets was presented based on the systematical characterization results.

Development of highly functional cesium selective adsorbents for the decontamination of high-activity-level water (HALW) from the Fukushima NPP-1 accident is very urgent. In order to selectively adsorb the radioactive cesium, three kinds of novel porous silica gels loaded with insoluble ferrocyanides (SLFC) were prepared using a successive impregnation/precipitation method. Based on the results of previous research, the SLFC composites have relatively large uptake ratio above 95%, distribution coefficients (K d) above 103 cm3/g, and excellent adsorption kinetics even in seawater. The solidification results also indicate that zeolites have an excellent Cs immobilization characteristic, gas-trapping and self-sintering abilities, and low leachability. We chose three kinds of SLFC composites to achieve the optimization of solidification by mixing with nine kinds of additives at high temperatures (up to 1200 °C). The Cs contents in the three composites were estimated to be below 30% of the initial contents and decreased with the three stages at calcination temperatures ranging from 25 to 1200 °C. By contrast, the Cs immobilization ratio was markedly lowered by mixing with additives: of those, allophane had the best immobilization result. By increasing the additive ratio to 50 wt%, the Cs immobilization ratio became almost 100% and no volatilization of Cs was detected even after calcination at 1200 °C. This result indicates that calcination of the mixture of SLFC composites after adsorbing Cs+ ions and specific additives under appropriate ratio is effective for stable solidification.

pea starch and acrylamide were used as the raw materials, potassium peroxodisulfate and sodium sulfite were used as the initiator, EDTA (Ethylene Diamine Tetraacetic Acid) and urea were used as the auxiliaries to make starch grafting acrylamide polymer flocculating agent by the method of aqueous solution polymerization. The influence of reaction temperature, concentration of initiator and raw material ratio on the flocculating performance of products was analyzed by ternary quadratic orthogonal regression rotational combination experiment. The result shows that the flocculation effect will be the best when the reaction temperature is 60°C, the initiator is 5.00 ml, and the raw material ratio is 2.25.

We report on the enhanced interfacial adhesion of diamond coating on copper substrate modified by a small fraction of Al. For pure copper substrate, the diamond coating formed tends to crack and delaminate, primarily caused by a slight accumulation of detrimental graphite intermediate layer and thermal stress induced by mismatch of the coefficients of thermal expansion. Additions of 1 and 3 at.% Al to the copper substrate gradually decrease the intermediate graphitic phase. At the higher Al concentration, an aluminium oxide forms at the coating–substrate interface, and graphitic/amorphous carbon is completely inhibited, leading to significantly enhanced interfacial adhesion of diamond coating. The electron structure of copper is not observed to significantly alter on this Cu–Al dilute alloy. The alumina barrier layer preferentially formed on copper surface is believed to play a key role in preventing graphitization and adhesion enhancement.

Bamboo vinegar and sulfuric acid are used as acidifier and the method of precipitation is adopted to synthesize the antibacterial white carbon black. Orthogonal experiment was carried out to investigate the influence of reaction temperature, the amount of bamboo vinegar, additive amount of polyethylene glycol, the concentration of sodium silicate and amount of priming water on the oil absorption value of white carbon black. The analysis of orthogonal experimental results shows that influence of temperature, amount of priming water and the additive amount of PEG on oil absorption value is extremely remarkable. The influence of the amount of bamboo vinegar is remarkable, but the concentration of sodium silicate is indistinctive. It is verified through experiments that the specific surface area and oil absorption value of product is high, and its antibacterial effect is good.

Raman spectra of Al- and N-doped 6 H-SiC crystal samples with different doping levels were measured. The first-order Raman spectra of the samples were shifted to higher frequency when the doping concentrations were increased. Compared with Al-doped samples, the intensity of A 1 longitudinal optical mode of N-doped ones changed obviously, which reflected the different doping concentrations. The second-order Raman spectra were not dependent on the doping types and concentrations.

Two types of donor(D)–acceptor(A) calix[4]arenes have been theoretically studied using DFT//B3LYP/6-31G(d) method and ZINDO/CISD method. The calculations show that the substitution of CC by the conjugation bridge CC and NN plays an important part in altering one-photon absorption (OPA) and two-photon absorption (TPA) properties. The maximum OPA wavelengths of all studied compounds are less than 400 nm, which means high transparency. The geometry of the calixarenes strongly influences the TPA properties of the studied compounds. In addition, the nitro derivatives have a wider TPA response range than other non-nitro derivatives. The tetrasubstituted calix[4]arenes (type B calixarenes) have a larger TPA cross-section values than the bisubstituted calix[4]arenes (type A calixarenes). Copyright © 2009 John Wiley & Sons, Ltd.

Two series of porphyrin-thiophene chromophores were theoretically studied that exhibit large two-photon absorption cross-section in the visible region. The density functional theory (DFT) associated with ZINDO/SDCI methods has been used to calculate the molecular geometries, electronic structures, one-photon and two-photon absorption properties. The results show that the number of thiophene units affects the properties of one-photon absorption (OPA) and two-photon absorption (TPA). Porphyrin-thiophene chromophores featuring two or three thiophene units have wide TPA response ranges; they can be applied to many nonlinear optical areas, such as optical limiting. Intervening ethynyl unit is beneficial to extend the conjugated pathway, and increase the two-photon absorption cross-section. At the same time, the OPA and TPA wavelengths are bathochromically shifted. From viewpoint of the high transparency and large nonlinear optical response, porphyrin-thiophene chromophores will be promising TPA materials.

The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G(d) and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400{600 nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.

Two series of bis(styryl)benzene derivatives (BSBD), namely the single-BSBD and the double-BSBD, were investigated. The equilibrium geometries and electronic structures were obtained by using the density functional theory B3LYP and 6-31G basis set. In succession, the one- and two-photon absorption properties of all the molecules were studied theoretically with a ZINDO-SOS (sum-over-states) method in detail. It can be seen that the double-BSBDs have larger two-photon absorption (TPA) cross sections in the visible-IR range than the corresponding single-BSBDs, demonstrating that increasing the molecular dimension is a very effective method to enhance the values of the TPA cross sections. On the other hand, it can be also noticed that the values of the TPA cross sections are correlative with the ability of donating (accepting) electrons of the terminal substituent groups R [N(CH3)2, CH3, H and CF3] in these molecules. That is, the intramolecular charge transfer is also a factor for the enhancement of the TPA efficiency. To sum up, the idea of increasing the molecular dimension to enhance the TPA cross section value is a helpful direction to explore better TPA materials for practical applications. And the double-BSBD molecules are promising TPA materials for the further investigation from the standpoint of the high transparency and the larger TPA cross sections.

The equilibrium geometries, electronic structures, one- and two-photon absorption (TPA) properties of a series of octupolar complexes with the Cu(I), Zn(II) and Al(III) as coordinate centers and the bis-cinnamaldimine as ligands have been studied using the B3LYP/6-31G(d) and ZINDO-SOS methods. Compared with the dipolar metal complexes, all the octupolar metal complexes (including tetrahedral and octahedral complexes) have relatively large TPA cross-sections, indicating that building octupolar metal complex is an effective route to design of promising TPA material. Lewis acidity of metal center and molecular symmetry are two important factors for enhancement of TPA cross-section of metal complex. Due to the stronger Lewis acidity of Zn(II) than Cu(I) as well as Al(III) than Zn(II), the tetrahedral Zn(II) complex exhibits a TPA cross-section larger than that of the tetrahedral Cu(I) complex, the maximum TPA position of the octahedral Al(III) complex is red-shifted relative to the octahedral Zn(II) complex, and at the same time, the octahedral Al(III) complex has a large TPA cross-section. Compared with the tetrahedral complexes, the TPA cross-sections of the octahedral complexes are enhanced due to the increased number of ligands.

On the basis of the equilibrium geometric structures obtained at the B3LYP/6-31G level, the one-photon absorption (OPA) and two-photon absorption (TPA) properties of donor/acceptor-functionalized tetrakis(phenylethynyl)benzenes (TPEBs) and bis(dehydroben-zoannuleno) benzenes (bisDBAs) have been determined by using ZINDO-SOS method. The influence of the molecular structures on OPAs and TPAs have been discussed. Among the donor/acceptor substituted regioisomers, the ortho- and meta-substituted compounds have the largest two-photon responses, mainly due to the existence of the larger dipole moment differences between the ground states and the intermediate states. The diacetylene bridges in bisDBAs result in the red-shift of OPAs and TPAs and decrease of TPA cross-sections. From the point of view of transparency/nonlinearity, the TPEBs and bisDBAs are promising candidates for TPA materials.

SiC single crystals were grown on the seeds with different root-mean-square (RMS) roughness by physical vapor transport (PVT) method. Green and yellow zones appeared in the same wafer. Decreasing the RMS roughness, the yellow zone was increased and the wafer was uniform. The green and yellow zones corresponded to 6H and 4H polytype, respectively. Based on Raman spectra and structural characterization, SiC polytype formation mechanism was discussed. It was found that the polytype was dependent on the seed RMS roughness.

The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the meso – meso singly, the meso -β doubly and the meso – meso β–β β–β triply linked Zn II -porphyrin dimers and trimers have been comparatively studied by using the hybrid B3LYP functional combined with the 6-31G basis set and ZINDO-SOS methods. The results show that on going from the dimers to the trimers, due to the increased conjugation chain, the maximum TPA positions are red-shifted and the maximum TPA cross sections produce a remarkable enhancement. The calculated maximum TPA cross sections of the studied molecules are in the range of 25.4–616.3 × 10 −48 cm 4 s/photon. Compared with the meso – meso singly linked Zn II -porphyrin derivatives, the meso -β doubly and the meso – meso β–β β–β triply linked Zn II -porphyrin derivatives have larger TPA cross sections at 700–1000 nm. They are promising candidates for TPA materials.

Two series of dimethylfluorene core derivatives, which have different conjugation length or different peripheral substituted groups, are theoretically investigated in the paper. Using the density functional theory B3LYP with 6-31G basis set, we have obtained the equilibrium geometries and electronic structures for all the studied molecules. On the basis of the geometrical and electronic structures, the one- and two-photon absorptions properties are studied theoretically with ZINDO-SOS method in detail. The computational results are in good agreement with the available experimental values. According to our calculations, from the series I molecule to the series II counterparts, the maximum one-photon absorption (OPA) intensities and the maximum two-photon absorption (TPA) cross sections values δmax are obviously increased as the conjugation length increases. And for both series the maximum OPA wavelength λ max ( 1 ) and δmax values are increased with the stronger electron-donating or electron-accepting capability. This demonstrates that the conjugation length and the different substituent groups play important roles in the OPA and the TPA cross section.

Using density-functional theory and ZINDO-SOS method, we carry out a comparative study of the two-photon absorption (TPA) properties of a new octupolar compound—sumanene 3O derivative and relative molecules. The results indicate that the TPA cross sections of the octupolar compounds increase with the electron-accepting ability of the center. Sumanene 3O is a stronger electron-acceptor than 1,3,5-tri(nitro)benzene. Compared with the conventional octupolar compounds, the sumanene 3O derivative, which has the largest TPA cross section among the studied molecules here, is a more promising TPA material.

The electronic structures and the one- and two-photon absorption (TPA) properties of two series of the olefin-linked paracyclophane (pCp) oligomers have been studied using AM1 and ZINDO-SOS methods. The relationship between the TPA cross sections and the molecular chain length is obtained. The maximum TPA cross section increases in proportion to Nα (N denotes the number of repeat units) and the values of α depend on different molecular structures. The olefin-linked pCp oligomers, which have good transparency and large TPA cross sections, are promising candidates for TPA materials.Key words: two-photon properties, paracyclophane oligomer, AM1, ZINDO-SOS.

Electronic structures, one- and two-photon absorption (TPA) properties of zinc(II)-porphyrin compound (ZH), meso–meso singly-linked zinc(II)-diporphyrin compound (Z2H) and zinc(II) meso,meso-coupled porphyrin dimer (Z2H-G) via intermolecular hydrogen bonding interactions have been comparatively studied by using ZINDO–SOS method. The results show that formation of hydrogen bondings between carboxyl groups and cyclic urea reduces the dihedral angle between the adjacent porphyrin planes in Z2H-G, leading to increased electronic interactions between the two porphyrin planes and increased couplings between electronic states. Electronic spectrum of ZH can be described with the four-orbital model, while the descriptions of the electronic spectra of Z2H and Z2H-G need eight frontier orbitals. Theoretical calculations reveal that TPA cross sections increase on going from ZH to Z2H to Z2H-G due to increase of the couplings between electronic states through transition dipole moments.

On the basis of the equilibrium geometric structures obtained by using the hybrid B3LYP functional combined with the 6-31G basis set, the electronic structures, one- and two-photon properties of triphenylamine (boron, aluminum)-cored dendritic compounds have been studied by using ZINDO/SDCI and sum-over-states (SOS) formula. The dentritic structure–TPA property relationship has been discussed. These compounds exhibit large TPA cross-sections and good transparency. They are promising TPA materials for optical power limiting.

The equilibrium geometries and one- and two-photon absorption (TPA) properties of a series of tetra-paracyclophane derivatives have been determined by using the hybrid B3LYP combined with 6-31G basis set and ZINDO–SOS methods. The results show that the tetra-paracyclophane derivatives have large TPA cross-sections, which are about two times larger than that of the corresponding linear counterparts. The introduction of donor/acceptor groups has improved the TPA cross sections of paracyclophane derivatives. In particular, the increased molecular chain plays a crucial role in increasing TPA cross section, according to the three-state model, due to the larger transition dipole moment between the ground state and intermediate state. The calculated results also reveal that the dimers of D–π–A (D and A denote donor and acceptor, respectively) chromophore have relatively large TPA cross sections among studied compounds.

A series of heterocycle-based molecules using π-deficient (pyridinium) and π-excessive (pyrrole) heteroaromatic rings as acceptor and donor, respectively, have been designed and their two-photon absorption properties have been investigated theoretically by using the AM1 and ZINDO methods. On the basis of correct geometries and UV-VIS spectra, the positions and strengths of two-photon absorption of these molecules were reported. Our calculated results reveal that molecule F, which has the largest two-photon cross-section (2457.29×10−50 cm4 s photon−1) among studied molecules, is a more promising two-photon absorption material.

6H-SiC single crystal was grown by physical vapor transport (PVT). The duplications of several types of stacking fault (SF) such as SF , SF , and SF were observed by high-resolution transmission electron microscopy (HRTEM). First-principle calculations revealed that the formation energies of single SF and SF are very low while that of SF is much higher. Further calculations demonstrated that the continuous SFs possessed larger stress along the c-axis than the separated SFs. This suggests that the stress should be the reason for the SF duplication, and the SF can be duplicated under higher c-axis stress.

A mechanism for the dehydrogenation reaction of 1,2,3,4-tetrahydroquinoline to quinoline derivatives, catalyzed by a Cp*Ir complex containing a 2-pyridonate ligand, is proposed and supported by theoretical calculations at the B3LYP level. The proposed mechanism involves two stages which are all thermodynamically unfavorable (endothermic by 36.3 kcal mol(-1) and 18.4 kcal mol(-1), respectively). The apparent activation energies of the first and second stages of the reaction are 30.8 kcal mol(-1) and 34.0 kcal mol(-1), respectively, and are considered overestimates of the entropy change of reaction. Owing to a decrease in the oxidative ability of iridium(III) coordinated to large electronegative nitrogen and chlorine, ligand promoted hydrogen abstraction is crucial at both stages of dehydrogenation, in which the oxidation state of iridium(III) does not change, and the ligand 2-pyridonate is converted to 2-hydroxypyridine. Cp*Ir(C(5)NH(4)OH)ClH, an important intermediate, releases hydrogen through an energy barrier of 23.5 kcal mol(-1).

There are two molecules in the asymmetric unit of the title compound, C19H15NO2, in which the dihedral angles between the naphthalene ring system and the pyridine ring are 40.5 (3) and 41.2 (4)°. In the crystal, C—H...O hydrogen bonds link the molecules.

The molecular equilibrium structures, electronic structures, and one- and two-photon absorption (TPA) properties of C2v (Zn(II), Fe(II) and Cu(I)) dipolar and D2d (Zn(II) and Cu(I)) and D3 (Zn(II)) octupolar metal complexes featuring different functionalized bipyridyl ligands have been studied by the ZINDO-SOS method. The calculated results show that one- and two-photon absorption properties of metal complexes are strongly influenced by the nature of the ligands (donor end groups and pi linkers) and metal ions as well as by the symmetry of the complexes. The length of the pi-conjugated backbone, the Lewis acidity of the metal ions, and the increase of ligand-to-metal ratio result in a substantial enhancement of the TPA cross sections of metal complexes. Substitution of C=N and N=N for C=C plays an important role in altering the maximum TPA wavelengths and the maximum TPA cross sections of metal complexes. Of them, the C=N substituted metal complexes have relatively large TPA cross sections. Replacing styryl with thienylvinyl makes the one-photon absorption wavelength red shift and at the same time leads to a great decrease of the maximum TPA cross sections of metal complexes. The possible reason is discussed. In the range 500-1250 nm, octupolar metal complexes exhibit intense TPAs and therefore are promising candidates for TPA materials.

The electronic structures, one-photon absorption (OPA), and two-photon absorption (TPA) properties of a series of ferrocene-based chromophores with TCF-type acceptors (TCF = 2-dicyanomethylene-3-cyano-4-methyl-2,5-dihydrofuran) have been studied by using the ZINDO-SOS method. The results have revealed that OPA and TPA of ferrocenyl derivatives are affected by the strength of the acceptor, especially the pi-bridge conjugation length. The TPA cross section increases with increasing acceptor strength and pi-bridge conjugation length. The TCF-type acceptor with a phenyl group can lead to a larger TPA cross section. Quadrupole molecules have the largest TPA cross sections (2000-3000 GM), which are about 4 times that of the corresponding dipolar molecules, indicating larger interactions between the top and bottom branches. Finally, the origins of the two-photon excitations for ferrocenyl derivatives are analyzed. The calculations show that ferrocenyl derivatives with TCF-type acceptors (especially quadrupole molecules) are promising candidates for TPA materials.

The synthesis of SiC hollow spheres is reported. The shell of the spheres is formed through a solid–gas reaction rather than traditional chemical methods. The sphere size can be modulated from the microscale to the nanoscale, and the shell thickness can be finely tuned by adjusting the experimental parameters. This technique presents a new paradigm in the preparation of hollow spheres. Based on this technique, other carbide hollow spheres could also be synthesized.

Background Porcine reproductive and respiratory syndrome (PRRS) is an important pig endemic disease in pork-producing countries worldwide. The etiology, porcine reproductive and respiratory syndrome virus (PRRSV), is characterized by fast antigen variability. Glycosylated protein 4 (GP4) is a minor protein in PRRSV virion, but contributes to induce protective immune responses. However, the antigenic characterization of PRRSV GP4 and the role of the mutations in this protein in PRRSV evolution are not clear. Methods Peptides chip scanning and peptide based ELISA was used to analyze the antigenic characterization of HP-PRRSV GP4. A total of 142 peptides printed on a chip were used to reveal the antigen reaction characteristics of the HP-PRRSV. The reactions of these peptides with HP-PRRSV-specific pig serum were scanned and quantified using the software PepSlide® Analyzer by fluorescence intensity. The active reaction regions (AR) were identified based on the scanning results and then the amino acids (aa) sequences of AR(s) is aligned among PRRSV strains for further identify the key aa site(s) impact the antigenicity of the protein. Peptide based ELISA is then reacted with PRRSV positive sera derived from pig inoculated with different PRRSV strains for further analysis the role of specific amino acid in AR. Results The intensity plot was used to show the reactions of the peptides with PRRSV serum and it showed that enormously different response happened to various parts of GP4. The highest reaction intensity value reached 6401.5 against one peptide with the sequence DIKTNTTAASDFVVL. An AR from S29 to G56 was identified. Sequence alignment revealed various mutations in site 43 and possibly played an important role in this AR. Peptides ELISA reaction with sera from pigs inoculated with different PRRSV strain revealed that the change of aa in site 43 reduced the reaction of the peptide with PRRSV positive sera derived from pigs inoculated with the peptide related PRRSV strains. Conclusion In this study, one AR covering S29 to G56 was identified in GP4. The aa in site 43 play an important role in determining the antigenic character of GP4. The continual mutations (S → G → D → N) occurred in this site alter the antigenicity of PRRSV GP4. Electronic supplementary material The online version of this article (doi:10.1186/s12985-016-0586-3) contains supplementary material, which is available to authorized users.