A new insight into Fischer-Tropsch synthesis

Fischer-Tropsch (FT) reaction is an important synthetic route to convert CO and H(2) to fuels and chemicals in industry. To date, its reaction mechanism remains uncertain. With extensive density functional theory studies on FT reactions on Ru, we compare quantitatively several C/C coupling mechanisms that are likely to be involved. We found that a well-regarded CH(2) + CH(2)R (R = H or alkyl) mechanism possesses high reaction barriers, and a stepwise C + CR mechanism has been identified that may be relevant to FT synthesis.     

A new insight into the vibrational analysis of pyridine

A new proposal of vibrational assignment for pyridine is reported. Infrared spectra for the liquid and gas phases as well as Raman spectra for the liquid have been recorded and analyzed for -d(0), -d(5) and, for the first time to our knowledge, for 15N isotopomers as well. The proposal of assignment has been assessed by the calculation of a number of force fields, theoretical (ab initio, density functional theory) approaches as well as by a set of simple valence internal coordinates force constants transferred from benzene using the pure vibrational force field approximation. In all cases, the root mean square (rms) for the wavenumbers turn out to be lower than the best obtained so far, i.e. 6.6 cm(-1), as stated by Wiberg et al.     

A new method for gaining insight into the chemistry of drying mineral surfaces using ATR-FTIR

Although it is understood that the chemical environment at a drying surface is likely to be quite different from that at a fully hydrated surface, the difficulty of quantitative measurement has meant that this potentially crucial aspect of surface chemistry has gone largely overlooked. As a result, most of our understanding comes from measurement before and after drying, with a gray region of speculation in between. An interesting natural example is the paradoxical reduction of Mn oxides in moist soils as they dry, because drying is usually considered an oxidative process. This phenomenon indicates that important chemical changes are occurring during drying and an approach is needed to probe the chemistry of drying surfaces. Here we show the suitability of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy for real-time, in situ investigation of the drying solid-water interface, using the change in surface pH as an example. This was achieved by adsorbing thymol blue pH indicator (pK(a)=1.65) onto a natural Mn-rich clay and observing the real-time pH change, which dropped from pH 5 to below pH 1.65 with the removal of free water from the surface.     

A FLASH of insight into cellular chemistry: genetically encoded labels for protein visualization in vivo

Genetically encoded fluorescent labels, such as green fluorescent protein, make it possible to visualize a protein's natural distribution and environment in living cells. A new approach to protein labeling in living cells has been devised in which a small, membrane-permeable ligand binds with high affinity and specificity to a short peptide motif that can be incorporated into the protein of interest; the ligand becomes brightly fluorescent after binding to the peptide.     

新型固定化pH梯度毛细管等电聚焦方法用于蛋白分离

通过化学键合建立一种固定化pH梯度的方法,用于毛细管等电聚焦分离蛋白质.采用微流控泵驱动毛细管内的聚焦区带,通过调节泵的流量,从而调节聚焦区带的迁移速度.该方法避免了自由溶液聚焦时两性电解质所带来的影响,实现了高灵敏度及检测波长自由选择等优点,适用于两步法毛细管电泳等电聚焦分离蛋白质等两性电解质.本文考察了对牛血清白蛋白和血红蛋白两种蛋白质混合物的分离,证明了该方法可行.     

Native red electrophoresis--a new method suitable for separation of native proteins

A new type of native electrophoresis was developed to separate and characterize proteins. In this modification of the native blue electrophoresis, the dye Ponceau Red S is used instead of Coomassie Brilliant Blue to impose uniform negative charge on proteins to enable their electrophoretic separation according to their relative molecular masses. As Ponceau Red S binds less tightly to proteins, in comparison with Coomassie Blue, it can be easily removed after the electrophoretic separation and a further investigation of protein properties is made possible (e.g. an enzyme detection or electroblotting). The tested proteins also kept their native properties (enzyme activity or aggregation state).     

A new insight into palladium-catalyzed reaction of 2-alkynylphenol with carbon monoxide

A novel and efficient pathway for the generation of 3-(benzofuran-3-ylmethylene)benzofuran-2(3H)-ones via a palladium-catalyzed carbonylative reaction of 2-alkynylphenol with carbon monoxide is described. The reaction proceeds through a double insertion of triple bonds during the reaction process. The products are obtained in good yields with high selectivity. A one-pot synthesis starting from 2-iodophenol and alkyne is presented as well.     

A new method for the radiochemical separation of rubidium and cesium

The analytical reactions of bismuth iodide and stannic chloride with cesium and rubidium are used for the radiochemical separation of these two elements. The method consists in precipitating potassium, rubidium and cesium as their cobaltinitrites, selective isolation of cesium as cesium bismuth iodide from glacial acetic acid, and subsequent separation of rubidium from potassium as chlorostannate from conc. HCl. The results obtained by the present method for the rubidium and cesium contents of the different U.S.G.S. standard rock samples are compared with those reported using methods of comparable accuracy. The suitability of the method for the analysis of fall-out samples for their radiocesium (¹³⁷Cs) contents has been demonstrated.     

Rapid insight into C60 influence on biological functions of proteins

Experimental methods of investigations of nanoparticle (NP)–protein interactions are limited, because they require a high amount of samples and the NPs tend to interfere with spectral results. Therefore, molecular modeling is a commonly accepted tool in such kind of investigations. Examining the molecule toxicity on the molecular level, we usually want to know, mainly, the location of the ligand on the protein surface and what is an influence of such a contact on the biological functions of the protein. In the presented work, we demonstrate that multiple-docking of the ligand from a random start and with large grid volume, to let the ligand search the whole protein surface, allows to find the best binding sites and gives reliable results considering ligand–protein interactions. In the present work, we have constructed six models of bronchoalveolar lavage fluids proteins: α1-antitripsin, albumin, ceruloplasmin, lactoferrin, lysozyme, and transferrin with fullerene, C₆₀ utilizing molecular docking methods. The most probable results were examined with steered molecular dynamics (SMD) to see, if the simple docking method is able to predict the fullerene binding affinity. Albumin and lysozyme were already widely investigated and literature data is available for their complexes with fullerene C₆₀ and/or its derivatives. Thus, we used these two models as a reference set to validate the used molecular modeling methods. With our best knowledge, interactions of the remaining four proteins with NPs have never been investigated in detail before. Our results indicate that fullerene C₆₀ readily interacts with all studied proteins and may have a large impact on their biological functions.     

A new insight into the promoting effects of transition metal phosphides in methanol electrooxidation

The construction of highly active catalysts for methanol oxidation reaction (MOR) is central to direct methanol fuel cells. Tremendous progress has been made in transition metal phosphides (TMPs) based catalysts. However, TMPs would be partially damaged and transformed into new substances (e.g., Pt-M-P composite, where M represents a second transition metal) during Pt deposition process. This would pose a large obstacle to the cognition of the real promoting effects of TMPs in MOR. Herein, Co₂P co-catalysts (Pt-P/Co₂P@NPC, where NPC stands for N and P co-doped carbon) and Pt-Co-P composite catalysts (Pt-Co-P/NPC) were controllably synthesized. Electrocatalysis tests show that the Pt-Co-P/NPC exhibits superior MOR activity as high as 1016 mA/mg_Pt, significantly exceeding that of Pt-P/Co₂P@NPC (345 mA/mg_Pt). This result indicates that the promoting effect is ascribed primarily to the resultant Pt-Co-P composite, in sharply contrast to previous viewpoint that Co₂P itself improves the activity. Further mechanistic studies reveal that Pt-Co-P/NPC exhibits much stronger electron interaction and thus manifesting a remarkably weaker CO absorption than Pt-P/Co₂P@NPC and Pt/C. Moreover, Pt-Co-P is also more capable of producing oxygen-containing adsorbate and thus accelerating the removal of surface-bonded CO*, ultimately boosting the MOR performance.     

Improving the spectrophotometric determination of the alkylating activity of anticancer agents: A new insight into the mechanism of the NBP method

In this paper, the mechanism of the nitrobenzylpyridine (NBP) method to measure the alkylating activity of drugs originally described by Epstein et al. [J. Epstein, R.W. Rosenthal, R.J. Ess, Anal. Chem. 27 (1955) 1435-1439] and modified later by others was revisited using melphalan, m-sarcolysin, chlorambucil, cyclophosphamide and ifosfamide. Its direct application to determine the activity of these drugs in human serum and aqueous media is described and discussed.This method, based on the formation of a chromophore due to the reaction between the alkylating agent and NBP, was significantly improved by extracting as quickly as possible the reaction product(s) into chloroform before adding alkali to develop the color. This significantly limited the degradation by hydrolysis of the products and enhanced the yield of the end chromophore in the organic phase. The reaction time was optimized by monitoring each compound color development.The best reaction time for each compound was selected and a higher stability of the extracted color over at least 1 h was obtained (compared to a couple of minutes in previous studies). Most interestingly, water evaporation due to heating had little or no effect on the linearity of standard curves evaluated in the micromolar concentration range. Both the sensitivity and reproducibility of the method were therefore significantly improved.There appears to be a direct correlation between compound hydrolysis and alkylation activity; the relative reactivity is different among the compounds owing to the rate of (i) production, (ii) the relative proportions and (iii) the hydrolysis of the intermediates. A general mechanism for the nucleophilic competitive substitution is proposed.     

有机化学基本理论问题新的研究方法、新的观念和新 的思维模式

有机化学基本理论研究的总结和回顾。15年来,在国家自然科学基金委员会的支持下,为了认识电子离域的本质,在量子化学领域,我们建立和发展了新的作用能分解方法和大型计算程序,发展和完善了轨道定域化程序。我们的方法可以为任何一个共轭分子(无论是平面的还是非平面的,是含共轭双键的还是含累积双键的),提供一个π与σ体系彻底分离的片断分子轨道基组。这个轨道基组不仅满足分子特殊的对称性,而且还具有确切的电子占据数。与Hückel理论完全不同,我们强调：π电子的离域除了对它原先的定域π体系有强烈的失稳定作用外,它还可通过π-σ空间作用,对σ构架产生强烈的稳定作用。据此,我们提出了芳环化合物新的分类准则,揭示了芳香环流起因的必要条件,定义环的刚度为芳香性一个新判据。发现,分子内基团间的局部作用(CT和EX)同它们对分子整体性能的影响是完全相反的。就构象而言,稳定的CT作用是相斥的,失稳定的EX作用是相吸的;就电子转移而言,大的EX作用是电荷转移的助动力。其助动性在于,它能降低因CT作用而产生的给体自身对电荷转移的阻力。论证了,在二苯乙烯类分子中,π-π共轭,π-σ超共轭和σ-σ非键轨道作用都是失稳定的。与σ-σ和π-σ作用相比,π-π作用对于分子构像的影响是非常微弱的。与经典的思维模式相反,有机分子总是倾向于较小的失稳定,而不是较大的稳定。为了维持尽可能最稳定的电子总能量,在σ-σ作用的驱动下,共轭基团应该尽量地偏离共平面。阻止分子扭曲的(非电子作用力)是核排斥力。因此,一个空间拥挤的构象可以是能量有利的构象。在我们的研究中,经典有机结构理论的整体因果关系已经全面地被颠倒。     

A theoretical insight into the photophysics of psoralen

Psoralen photophysics has been studied on quantum chemistry grounds using the multiconfigurational second-order perturbation method CASPT2. Absorption and emission spectra of the system have been rationalized by computing the energies and properties of the low-lying singlet and triplet excited states. The S1 pipi* state has been determined to be responsible of the lowest absorption and fluorescence bands and to initially carry the population in the photophysical processes related to the phototherapeutic properties of psoralen derivatives. The low-lying T1 pipi* state is, on the other hand, protagonist of the phosphorescence, and its prevalent role in the reactivity of psoralen is suggested to be related to the elongation of the pyrone ring C3-C4 bond, where the spin density is distributed on both carbon atoms. Analysis of energy gaps and spin-orbit coupling elements indicates that the efficient photophysical process leading to the population of the lowest triplet state does not take place at the Franck-Condon region but along the S1 relaxation path.     

A new insight into the Pfitzinger reaction. A facile synthesis of 6-sulfamoylquinoline-4-carboxylic acids

The unusual formation of 6-sulfamoylquinoline-4-carboxylic acids from 5-sulfamoylisatins under the conditions of Pfitzinger reaction is described. Key step in the suggested mechanism is the reaction of in situ generated acetaldehyde with the hydrolytically cleaved isatin ring. The suggested mechanism has been confirmed by dynamic LCMS measurements and by reactions with isotopically labeled reactants.     

A new radiometric titration method based on separation by means of ion-exchange

The determination of thallium with potassium chlorate is chosen as an example for the earlier suggested new radio-oxidimetric titration procedure, in which phase separation is achieved by means of a strongly basic anion exchanger in the solution. Concentrations of thallium down to 2·10⁻⁶ M have been determined. Special care has to be taken for concentrations lower than 10⁻⁵ M as UV radiation is a disturbing factor. Other oxidizing agents have also been tested.     

An investigation on the subcellular distribution and compartmentalization of uranium in Phaseolus vulgaris L.

Phaseolus vulgaris L. (bean) is a promising species for uranium rhizofiltration with high tolerance and accumulation ability. To further understand the mechanisms involved in uranium tolerance and detoxification, the present study investigated subcellular distribution and compartmentalization of uranium in bean. Subcellular fractionation of uranium containing tissues indicated that both in roots and shoots, the concentration of uranium in each subcellular fractions increased evidently with increasing solution uranium level, and the majority of uranium was located in cytosol and cell wall fraction, while a minor part of uranium associated with the organelle fraction. Meanwhile, with uranium concentration increasing from 100 to 1,000 μM, the proportion of uranium distribution in cytosol fraction was decreased but it was increased in cell wall fraction. However, the proportion of uranium distribution in organelle fraction is always less than 5 %. These results suggest that stored in the cytosol (such as uranium compartmentalization with organo-ligands in vacuole) and bound to the cell walls (may be integrated with polyose and protein) might play an important role in tolerance and detoxification of uranium in bean.     

A new method for the radiochemical separation of copper from fission products

A new method for obtaining radiochemically pure⁶⁷Cu from highly active fission product solutions is described. The method is based on the solvent extraction of the Cu(II)-diethyldithiocarbamate complex in n-butyl acetate in the presence of hold-back carriers for Ni, Co, Mn, Mo, rare earths, Cd, Te and Sb, and subsequent purification steps involving scavengings for Ag, Ba, Sr and Fe followed by an anion-exchange purification step for decontamination from Te. Copper is finally extracted as the α-benzoin oxime complex in which form it is mounted and counted. The method has several advantages over other methods in that decontamination is very high and it is sufficiently fast considering the stringent radiochemical purity achieved. The⁶⁷Cu separated by this procedure from a one-day-old mixture of fission products arising from 10¹⁰ fissions was found to be completely free of any contamination.