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Recently, the Cu-based catalyst has attracted wide attention for the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) due to its high catalytic activity and it is low cost. However, its poor stability, ease of agglomeration, and the short life of the catalyst restrict its further development in industrial applications. Here, we constructed a novel MOF-derived Cu/SiO2 catalyst (MOF-CmS for short) with a controllable distribution of Cu active sites for the hydrogenation of the DMO to EG reaction. The catalyst was prepared by a hydrothermal method with the HKUST-1 uniformly coated on the surface of the silica microspheres. After the calcination, the highly dispersed and uniform Cu species were loaded on the surface of the silica. The resulted MOF-CmS catalyst showed a 100% conversion of DMO and over 98% selectivity of EG at 200 °C and 2 MPa while a traditional Cu/SiO2 catalyst exhibited serious agglomeration of Cu active sites and low catalytic activity (DMO conversion of 86.9% and EG selectivity of 46.6%). It is believed that the highly dispersed active metal center and the interaction between the active metal and carrier were the main reasons for higher catalytic activity of the MOF-CmS catalyst. Therefore, the developed method opened another avenue to synthesize highly dispersed and stable Cu-based catalysts.

What happens first between a corporate social responsibility (CSR) communication and a crisis can result in different levels of perceived cognitive dissonance and corporate hypocrisy depending on whether there is information inconsistency between the CSR communication and the crisis. This paper presents the findings from an experimental study and an online survey conducted and administered to investigate the contingency influence on consumer perceptions in response to inconsistent information. The results indicate that consumers experience greater cognitive dissonance and perceive more corporate hypocrisy when they are exposed, first, to a CSR initiative and then to a crisis, than when the order is reversed, provided that the CSR initiative and the crisis are congruent with the same social issue. However, there are no significant differences when the CSR initiative is incongruent with the crisis. Further, the findings of the study suggest that consumer cognitive dissonance not only directly influences the perceived corporate reputation, but also indirectly affects the perceived corporate reputation through a mediating effect of perceived corporate hypocrisy. The theoretical contribution of this study lies in providing a better understanding of consumer perceptions (including cognitive dissonance, perceived corporate hypocrisy and corporate reputation) in response to inconsistent CSR information. Meanwhile, the managerial contribution of this study stands by providing insights into the use of CSR communication strategies.

The stabilization of suspended planar lipid membranes, or black lipid membranes (BLMs), through polymerization of mono- and bis-functionalized dienoyl lipids was investigated. Electrical properties, including capacitance, conductance, and dielectric breakdown voltage, were determined for BLMs composed of mono-DenPC, bis-DenPC, mono-SorbPC, and bis-SorbPC both prior to and following photopolymerization, with diphytanoyl phosphocholine (DPhPC) serving as a control. Poly(lipid) BLMs exhibited significantly longer lifetimes and increased the stability to air-water transfers. BLM stability followed the order: bis-DenPC > mono-DenPC ≈ mono-SorbPC > bis-SorbPC. The conductance of bis-SorbPC BLMs was significantly higher than that of the other lipids, which is attributed to a high density of hydrophilic pores, resulting in relatively unstable membranes. The use of poly(lipid) BLMs as matrices for supporting the activity of an ion channel protein (IC) was explored using α – hemolysin (α-HL), a model IC. Characteristic i-V plots of α-HL were maintained following photopolymerization of bis-DenPC, mono-DenPC, and mono-SorbPC, demonstrating the utility of these materials for preparing more durable BLMs for single channel recordings of reconstituted ICs.

Polymerization of substrate-supported bilayers composed of dienoyl phosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability, however the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl phosphatidylcholine (mono-SorbPC), bis-dienoyl phosphatidylcholine (bis-DenPC) and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lβ phase for each lipid. In all cases, polymerization reduced membrane fluidity, however measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate inter-leaflet bonding. The D values measured after polymerization were 0.1 to 0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases, and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.

Immobilized and site-specifically labeled proteins are becoming invaluable tools in proteomics. Here, we describe a strategy to attach a desired protein to a solid surface in a covalent, site-specific manner. This approach employs an enzymatic posttranslational modification method to site-specifically label a target protein with an azide; an alternative substrate for protein farnesyl transferase containing an azide group was developed for this purpose. A bio-orthogonal Cu(I)-catalyzed cycloaddition reaction is then used to covalently attach the protein to agarose beads bearing an alkyne functional group. We demonstrate that both the azide incorporation and the capture steps can be performed on either a purified protein target or on a protein present within a complex mixture. This approach involves the use of a four-residue tag which is significantly smaller than most other tags reported to date and results in covalent immobilization of the target protein. Hence it should have significant applicability in protein science.

A pyrrolidino[60]fullerene 1 with pyrrolidine group was synthesized and characterized. The UV-Vis spectra showed that the blue shift of absorption peaks was first observed when strong organic acids such asp-toluene sulfonic or trifluoroacetic acid were added to the solution of pyrrolidino[60]fullerene 1 in dichloromethane. The results indicated that the pyrrolidino[60]fullerene derivatives without pyrrolidine group also possess the same phenomenon. Experiments and computation with the MOPAC 7.0 semi-empirical PM3 method demonstrated the reason that some energy gaps on [60] fullerene skeleton were increased because electronic charges on [60] fullerene framework transferred to pyrrolidine ring when strong organic acids were added into pyrrolidino[60]fullerene derivatives’ solution; as the result, the complexes could be formed and some absorption wavelengths blue shifted in the UV-Vis spectrum.

The results of characterization had shown that it was [1+2] cycloaddition reaction when [60,70]fullerene reacted with 4,4,5,5-tetramethylidazoline-2-thione (1) and dl-valine by FT-IR, FD-mass, 1H NMR, 13C NMR, UV–Vis spectra. [60]fullerene reacting with 4,4,5,5-tetramethylidazoline-2-thione (1) and other α-aminoacids such as l-leucine and α-aminoisobutyric acid had been also done in order to understand the reaction better, and the possible mechanism was put forward based on the results of characterization. In this reaction, reaction temperature was very important due to the reactivity of different α-aminoacids and the result of the experiment had also shown that the reactivity of dl-valine was more reactive than that of other two α-aminoacids.

Oxidization of those [60] and [70] fulleropyrolidine obtained from the reaction of C60 and C70 with diketone and 2-aminoisobutyric acid by m-chloroperoxybenzoic acid to give two new nitroxides integrated into C60 and C70. The magnetic property of the nitroxide based on C60 was measured by SQUID.

Two [60]fullerene derivatives (compounds 1 and 2) have been synthesized. Their redox properties have been measured by cyclic voltammetry. The photoconductivities of poly(N-vinylcarbazole) (PVK) doped with [60] fullerene and with their derivatives have been studied to explore the possible relationship between the reductibility of fullerenes and the photoconductivity of fullerenes-doped PVK. The charge generation efficiencies of PVK doped with [60]fullerene and with its derivatives have changed remarkably: the diversity of charge generation efficiency is obvious in different doping systems. The result indicates that there is charge transfer between fullerenes and PVK.

The electrochemical properties of four C60 derivatives (compounds 1∼4) were investigated with cyclic voltammetry (CV), and compared with that of C60. The reduction potentials of compound 1∼3 shifted to more negative positions than C60, and their oxidation peaks appeared at the lower potentials. Significantly, the reduction potentials of compound 4 shifted to more positive positions than C60, which is advantageous to form charge-transfer complexes with more donors. So the reduction properties in different solvents and in situ NIR absorption spectra of compound 4 were studied in more details. In addition, the AM1 molecular orbital calculation was performed on C60 and compound 1∼4 for the explanation of the potential shifts. The reduction potentials of these compounds exhibited good linear relationships with the calculation LUMO or LUMO+1 energy levels.

A monoadduct of [60]Fulleropyrrolidine having a 15-crown-5 structure has been prepared and characterised. It is found that the absorption spectrum of this crowned fullerene can be regulated hypsochromically by metal ions complexation.

Substantial effect of A site local moment exhibited by rare earth ions on the ferromagnetic transition temperature T-c is presented through comparative study of two series of samples, i.e. (La1-ySmy)(1/3)Nd1/3Sr1/3MnO3 and La1/3Nd1/3(Ca1-xSrx)(1/3)MnO3 in which x and y are chosen to make the respective samples have the same average A site ionic radius (r(A)) It is found that, contrary to the prediction of the established T-c similar to [r(A)] phase diagram, for the two samples with the same [r(A)] the one with Sm substitution exhibits lower T-c than its counterpart with Ca substitution and the difference increases with Sm content. The result suggests that A site local moments weaken the double exchange interaction, hence reduce T-c. Possible reasons are discussed. (C) 1997 Published by Elsevier Science Ltd.

A novel stable nitroxide based on C60 integrated into special structures was synthesized through the oxidization of [60]fulleropyrrolidine with m-chloroperbenzoic acid. The magnetic properties of the nitroxide were measured by ESR and a SQUID-magnetometer.

C 60 or C 70 reacts with 2-aminoisobutyric acid and cyclohexanone in chlorobenzene at refluxing through 1,3-dipolar cycloaddition to give [60]fulleropyrrolidine 1 or [70]fulleropyrrolidine 3 which can be oxidized with MCPBA at room temperature to yield stable nitroxides 2 or 4 . The compounds 1 and 3 were characterized by mass spectrum, FT-i.r., n.m.r. spectra. The compounds 2 and 4 were characterized by mass spectrum, FT-i.r., e.s.r. spectra. The magnetic properties of compounds 2 and 4 were measured by SQUID-magnetometer (MPMC Quantum Design), we found that they were paramagnetic.

Exposure to perchlorate is ubiquitous in the United States and has been found to be widespread in food and drinking water. People living in the lower Colorado River region may have perchlorate exposure because of perchlorate in ground water and locally-grown produce. Relatively high doses of perchlorate can inhibit iodine uptake and impair thyroid function, and thus could impair neurological development in utero. We examined human exposures to perchlorate in the Imperial Valley among individuals consuming locally grown produce and compared perchlorate exposure doses to state and federal reference doses. We collected 24-hour urine specimen from a convenience sample of 31 individuals and measured urinary excretion rates of perchlorate, thiocyanate, nitrate, and iodide. In addition, drinking water and local produce were also sampled for perchlorate. All but two of the water samples tested negative for perchlorate. Perchlorate levels in 79 produce samples ranged from non-detect to 1816 ppb. Estimated perchlorate doses ranged from 0.02 to 0.51 µg/kg of body weight/day. Perchlorate dose increased with the number of servings of dairy products consumed and with estimated perchlorate levels in produce consumed. The geometric mean perchlorate dose was 70% higher than for the NHANES reference population. Our sample of 31 Imperial Valley residents had higher perchlorate dose levels compared with national reference ranges. Although none of our exposure estimates exceeded the U. S. EPA reference dose, three participants exceeded the acceptable daily dose as defined by bench mark dose methods used by the California Office of Environmental Health Hazard Assessment.

Introduction Protein prenylation consists of the attachment of 15 (farnesyl) or 20 (geranylgeranyl) carbon isoprenoids to proteins via a thioether linkage. The prenyl groups originate from the corresponding allylic diphosphates and are attached to their cognate target proteins by a class of enzymes called prenyltransferases (Fig. 1). This posttranslational modification has received considerable attention in recent years due to the fact that many proteins involved in signal transduction pathways including Ras are prenylated. Inhibition of protein prenylation can negate the effects of transforming mutations in Ras. This has resulted in significant interest in the prenyltransferase class of enzymes as potential targets for anticancer therapy [1].

Originally designed to block the prenylation of oncogenic Ras, inhibitors of protein farnesyltransferase currently in preclinical and clinical trials are showing efficacy in cancers with normal Ras. Blocking protein prenylation has also shown promise in the treatment of malaria, Chagas disease and progeria syndrome. A better understanding of the mechanism, targets and in vivo consequences of protein prenylation are needed to elucidate the mode of action of current PFTase (Protein Farnesyltransferase) inhibitors and to create more potent and selective compounds. Caged enzyme substrates are useful tools for understanding enzyme mechanism and biological function. Reported here is the synthesis and characterization of caged substrates of PFTase. The caged isoprenoid diphosphates are poor substrates prior to photolysis. The caged CAAX peptide is a true catalytically caged substrate of PFTase in that it is to not a substrate, yet is able to bind to the enzyme as established by inhibition studies and X-ray crystallography. Irradiation of the caged molecules with 350 nm light readily releases their cognate substrate and their photolysis products are benign. These properties highlight the utility of those analogs towards a variety of in vitro and in vivo applications.

To obtain a transition state (TS) structure for an enzyme-catalyzed prenylation reaction, SN1 and SN2 model substitution reactions with dimethylallyl chloride were first studied. 13C Kinetic isotope effects (KIEs) for the model reactions were measured by a natural abundance NMR method and used to validate the computational methods that would be used in the subsequent determination of the enzymatic TS structure. Using a primary 13C KIE and a secondary 2H KIE measured via mass spectrometry, a TS structure for the enzyme-catalyzed reaction was computed; a density functional level of electronic structure theory using the mPW1N functional in combination with the 6-31+G(d) basis set was employed for those calculations. That structure has a C−O bond length of 1.69 A and a C−S bond length of 3.70 A. While the former bond length is similar to that for a nonenzymatic SN2 reaction, the latter is considerably (0.90 A) longer, indicating that the enzyme effects catalysis via an “exploded” TS structure.

Protein farnesyltransferase (PFTase) catalyzes the attachment of a geranylazide moiety to a peptide substrate, N-dansyl-GCVIA. Because geranylazide is actually a mixture of isomeric, interconverting primary and secondary azides, incorporation of this isoprenoid into peptides can potentially result in a corresponding mixture of prenylated peptides. Here, we first examined the reactivity of geranyl azide in a model Staudinger reaction and determined that a mixture of products is formed. We then describe the synthesis of 6,7-dihydrogeranylazide diphosphate and demonstrate that this compound allows exclusive incorporation of a primary azide into a peptide. The resulting azide-containing peptide was derivatized with a triphenylphosphine-based reagent to generate an O-alkyl imidate-linked product. Finally, we show, using a series of model reactions, that the Staudinger ligation frequently produces small amounts of O-alkyl imidate products in addition to the major amide-linked products. Thus, the alkoxyimidates we have observed as the exclusive products in the reactions of peptides containing prenylated azides also appear to be a common type of product formed using other azide-containing reactants, although at greatly reduced levels. This method for chemical modification of the C-terminus of a protein should be useful for a variety of applications in protein chemistry.

Protein farnesyltransferase (PFTase) catalyzes the attachment of a geranylazide (C10) or farnesylazide (C15) moiety from the corresponding prenyldiphosphates to a model peptide substrate, N-dansyl-Gly-Cys-Val-Ile-Ala-OH. The rates of incorporation for these two substrate analogs are comparable and approximately twofold lower than that using the natural substrate farnesyl diphosphate (FPP). Reaction of N-dansyl-Gly-Cys(S-farnesylazide)-Val-Ile-Ala-OH with 2-diphenylphosphanylbenzoic acid methyl ester then gives a stable alkoxy-imidate linked product. This result suggests future generations whereby azide groups introduced using this enzymatic approach are functionalized using a broad range of azide-reactive reagents. Thus, chemistry has been developed that could be used to achieve highly specific peptide and protein modification. The farnesylazide analog may be useful in certain biological studies, whereas the geranylazide group may be more useful for general protein modification and immobilization.

Protein farnesyltransferase (PFTase) catalyzes the attachment of a geranyl azide moiety to a peptide substrate, N-dansyl–Gly–Cys–Val–Ile–Ala–OH. The resulting azide-containing peptide was derivatized with a triphenylphosphine-based reagent to generate an O-alkyl imidate-linked product, rather than the amide-linked material expected via a Staudinger reaction. Since the CAAX box recognition motif (where the internal A residues are aliphatic amino acids) modified by PFTase can be incorporated into the C-terminus of virtually any polypeptide, this two-step procedure provides a general method for incorporating a diverse range of chemical modifications specifically near the C-terminus of proteins. © 2005 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2005

C 60 reacts with dichlorodinitromethane by heat, resulting in mulitiple addition C 60 derivatives. The derivatives consist of 3–4 nitro groups, 3–5 chloro atoms per C 60 , which were characterized by elemental analysis, FTIR absorption, FAB mass spectrometry and cyclic voltammetry spectrum and the magnetic properties were measured by SQUID-magnetometer (MPMS, Quantum Design).

The new bicyclic triaminophosphine ligand P(i-BuNCH2)3CMe (3) has been synthesized in three steps from commercially available materials and its efficacy in palladium-catalyzed reactions of aryl halides with an array of amines has been demonstrated. Electron-poor, electron-neutral, and electron-rich aryl bromides, chlorides, and iodides participated in the process. The reactions encompassed aromatic amines (primary or secondary) and secondary amines (cyclic or acyclic). It has also been shown that the weak base Cs2CO3 can be employed with ligand 3, allowing a variety of functionalized substrates (e.g., those containing esters and nitro groups) to be utilized in our amination protocols. This ligand provides a remarkably general, efficient, and mild palladium catalyst for aryl iodide amination. Although 3 is slightly air and moisture sensitive, easy procedures can be adopted that avoid the need of a glovebox. Comparisons of the efficacy of 3 in these reactions with that of the proazaphosphatrane P(i-BuNCH2CH2)3N (2) reveal that in addition to the opportunity for transannulation in 2 (but not in 3), other significant stereoelectronic contrasts exist between these two ligands which help account for differences in the activities of the Pd/2 and Pd/3 catalytic systems.

At the high temperatures used for the preparation of liquid crystalline aromatic polyesters (LCPs), ketene cleavage occurred from acetoxyarenes. Ketene is known to oligomerize to colored oligomers which may be responsible for an undesirable yellow color in LCPs. Thermolysis of the model compound p-acetoxybenzoate gave ketene oligomers and methyl p-hydroxybenzoate, which oligomerized. A free-radical chain reaction mechanism for ketene formation was demonstrated by the reaction of tributyltin hydride with haloacetoxyarenes.

Black lipid membranes (BLMs) are widely used for recording the activity of incorporated ion channel proteins. However, BLMs are inherently unstable structures that typically rupture within a few hours after formation. Here, stabilized BLMs were formed using the polymerizable lipid bis-dienoyl phosphatidylcholine (bis-DenPC) on glass pipettes of approximately 10 microm (I.D.). After polymerization, these BLMs maintained steady conductance values for several weeks, as compared to a few hours for unpolymerized membranes. The activity of an ion channel, alpha-hemolysin, incorporated into bis-DenPC BLMs prior to polymerization, was maintained for 1 week after BLM formation and polymerization. These lifetimes are a substantial improvement over those achievable with conventional BLM technologies. Polymerized BLMs containing functional ion channels may represent an enabling technology for development of robust biosensors and drug screening devices.

Two new pyrrolidino[60]fullerene derivatives 2 and 4 with unsaturated bond were synthesized by [60]fullerene reacted with sarcosine and aldehydes 1 and 3 refluxing in toluene and characterized by FTIR, FD-mass, 1 HNMR, 13 CNMR and UVVis spectra