The Photochemistry of Diazomethane the Reactions of Methylene with Methanol and Ethanol

In the photolysis of diazomethane-methanol. mixture, the reaction of methylene with methanol gives dimethyl ether and ethanol as products. The ratio of dimethyl ether to ethanol is found to be independent to pressure and to. the composition of diazomethane-methanol mixture. Methylene insertion into O—H bond is about 11 times faster than that into C—H bonds of methanol. The ratio decreases with increase of temperature. In the diazomethane-ethanol system, ethylmethyl ether, propanol-1 and propanol-2 are found as the products of insertion reaction of methylene into ethanol. The ratios of ethylmethyl ether to propanol-1 and to propanol-2 are both found to be almost constant and independent to pressure and to the composition of diazomethane-ethanol mixture. A small temperature effect on the ratios are observed. The rate of insertion of methylene into O—H bond is about 7.3 and 14.2 times faster than those into primary and secondary C—H bonds of ethanol, respectively.     

Spectral study of the conversion of porphyrins during interaction with molecular negative ions

In the interaction of ethioporphyrin and of several of its metal derivatives with negative ions of pyridine and anthracene in tetrahydrofuran solutions, an electron transfer takes place which results in the conversion of the pyridine and anthracene ions into neutral molecules, whereas the molecules of the pigment are first transformed into monovalent anions and subsequently into the di-, tri-, tetra-, and sometimes even into the hexavalent anions. In the first stage of this interaction, ferriethioporphyrin is reduced to ferro-ethioporphyrin, whereas the unmetallized pigment and its copper complex are transformed into the disodium derivative of ethioporphyrin. When the temperature is lowered, the rate of the electron transfer from pyridine ions to zinc-ethioporphyrin is decreased, and illumination leads to a substantial rate increase. The photochemical sensitivity of this system is possibly linked to the formation of stable complexes between pigment molecules and pyridine ions.     

Role of acidity on the electrochemistry of Prussian Blue at plain and Nation filmcoated electrodes

Prussian Blue (PB) coated on plain platinum (Pt) shows a redox wave at 0.44V vs SCE in addition to the two usual redox waves at 0.82 and 0.12 V vs SCE when the electrodes were dipped in acidic KC1 solution. PB incorporated into Nation film-coated on Pt electrode exhibited the same behaviour even in the presence of neutral KG solution. In acidic KC1, the additional redox wave observed for PB incorporated into Nation film shifted positively to 0.39V vs SCE and the peak separation was reduced to 30mV. The observed additional redox wave for PB coated on plain Pt electrode and incorporated into Nafion film-coated Pt electrodes was assigned to the partial reduction of PB occurring due to the insertion of protons into the film. The effect of various cations on the electrochemistry of PB incorporated into Nafion film-coated electrode was also studied.     

Development of a simple HPLC method for determination of paeoniflorin-metabolizing activity of intestinal bacteria in rat feces

A simple and reproducible HPLC method for the determination of paeoniflorin (PF)-metabolizing activity of intestinal bacteria in rat feces was developed and validated. Orally administered PF, a major active constituent of Paeoniae Radix, is metabolized into a bioactive compound, paeonimetabolin I (PM-I) by intestinal bacteria. Direct determination of the PF-metabolizing rate into PM-I is hard to achieve by HPLC due to the lack of intense chromophore in PM-I. However, when PF was incubated with Lactobacillus brevis, an intestinal bacterium, in the presence of phenylmercaptan, the metabolizing rate of PF into 8-phenylthio-paeonimetabolin I (PT-PM-I) was found to be equivalent to that of PF into PM-I. Thus, the PF-metabolizing activity of intestinal bacteria in rat feces was determined by measuring the rate of biotransformation of PF into PT-PM-I, which was detected by HPLC at 255 nm. This method can be utilized in the biopharmaceutical study of traditional Chinese formulations containing Paeoniae Radix.     

Efficiency of layered double hydroxide nanoparticle-mediated delivery of siRNA is determined by nucleotide sequence

In this paper, we report the novel finding that the cellular delivery efficiency of siRNAs or their mimic double-stranded (ds)DNA using layered double hydroxide (LDH) nanoparticles is dependent upon the nucleotide sequence. Efficacy of LDH-mediated delivery of four different siRNAs into cortical neurons and NIH 3T3 cells was found to vary widely (from 6 to 80%, and 2-11%, respectively). Our investigation into the formation of dsDNA-LDH complexes through monitoring the dsDNA:LDH mass ratio at the point of zero charge (PZC) indicated that the degree of intercalation of the individual dsDNA sequences into the LDH nanoparticles varied significantly. The dsDNA:LDH mass ratio at the PZC was found to be dependent on the nucleotide sequence. We further observed that PZC for each sequence was positively related to the extent of LDH-mediated internalization of the equivalent siRNA into neurons and fibroblasts. This novel finding therefore suggests that the mass ratio at the PZC is a useful predictive tool with which to assess the intercalation efficiency of selected siRNA sequences into the LDH interlayer and subsequent internalization into the cell cytoplasm. This finding will allow a more controlled approach to the design of suitable siRNA sequences for LDH-mediated siRNA delivery.     

The definition of core electrons

The traditional separation of electrons in molecules into core and valence types is often based on molecular orbital energies. This method is known to lead in some cases to large relative errors in correlated calculations. Instead, we propose a method based on the definition of molecular core character using separation of basis functions into core and valence types. This gives size-consistency to separation of electrons in molecules into core and valence types.     

Modification of films of heat-resistant polyimides by adding hydrosilicate and carbon nanoparticles of various geometries

The possibility of modifying the properties of poly(4,4′-oxydiphenylene)pyromellitimide films by introducing into prepolymer solutions nanoparticles of various compositions and structures [hydrosilicate nanoparticles in the form of layered structures (montmorillonite) and nanotubes; carbon nanofibers] was examined. New intercalating agents, tetranuclear aromatic diamines, were suggested for pretreatment of montmorillonite prior to introduction into heat-resistant polymers. The mechanical characteristics of the nanocomposites with hydrosilicate nanotubes can be optimized by chemical pretreatment of the nanotubes prior to introduction into the polymer matrix. Introduction of the above-named nanoparticles into the polymer matrix appreciably increases the elastic modulus of the material. The largest increase in the elastic modulus is observed with hydrosilicate nanotubes of the chrysotile structure, coated with an aromatic modifier.     

Separation of the molecular species of diacyl and alkenylacyl subclasses of the methyl ester of dinitrophenylethanolamine glycerophospholipid by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) procedure for the separation of the molecular species of alkenylacyl and diacyl subclasses after the derivatization of ethanolamine glycero-phospholipids (EGP) to the methyl ester of the dinitrophenylated lipids is described. Methyl esters of dinitrophenylethanolamine glycerophospholipids were first separated into alkenylacyl, alkylacyl and diacyl subclasses by thin-layer chromatography, then each subclass was separated into individual molecular species by reversed-phase HPLC. By converting the EGP into UV-absorbing derivatives, it proved possible to utilize the specificity of spectrophotometric detection for the determination of the individual molecular species. Alkenylacyl and diacyl derivatives were resolved into fifteen to twenty different species in a single HPLC run. The method should facilitate studies on the metabolism of the polar head group of both molecular species of alkenylacyl and diacyl glycerophosphoethanolamine in a variety of tissues using radioactive precursors.     

Application of computer simulation free-energy methods to compute the free energy of micellization as a function of micelle composition. 2. Implementation

In this paper, the implementation of the CS-FE/MT model introduced in article 1 is discussed, and computer simulations are performed to evaluate the feasibility of the new theoretical approach. As discussed in article 1, making predictions of surfactant/solubilizate aqueous solution behavior using the CS-FE/MT model requires evaluation of DeltaDeltaG for multiple surfactant-to-solubilizate or surfactant-to-cosurfactant transformations. The central goal of this article is to evaluate the quantitative accuracy of the alchemical computer simulation method used in the CS-FE/MT modeling approach to predict DeltaDeltaG for a single surfactant-to-solubilizate or for a single surfactant-to-cosurfactant transformation. A hybrid single/dual topology approach was used to morph the ionic surfactant sodium dodecyl sulfate (SDS) into the ionic solubilizate ibuprofen (IBU), and a dual topology approach was used to morph the nonionic surfactant octyl glucoside (OG) into the nonionic solubilizate p-aminobenzoate (PAB). In addition, a single topology approach was used to morph the nonionic surfactant n-decyl dimethylphosphine oxide (C10PO) into the nonionic cosurfactant n-decyl methyl sulfoxide (C10SO), the nonionic surfactant octylsulfinyl ethanol (C8SE) into the nonionic cosurfactant decylsulfinyl ethanol (C10SE), and the nonionic surfactant n-decyl methyl sulfoxide (C10SO) into the nonionic cosurfactant n-octyl methyl sulfoxide (C8SO). Each DeltaDeltaG value was computed by using thermodynamic integration to determine the difference in free energy associated with (i) transforming a surfactant molecule of type A into a cosurfactant/solubilizate molecule of type B in a micellar environment (referred to as DeltaG2) and (ii) transforming a surfactant molecule of type A into a cosurfactant/solubilizate molecule of type B in aqueous solution (referred to as DeltaG1). CS-FE/MT model predictions of DeltaDeltaG for each alchemical transformation were made at a number of simulation conditions, including (i) different equilibration times at each value of the coupling parameter lambda, (ii) different data-gathering times at each lambda value, and (iii) simulation at a different number of lambda values. For the three surfactant-to-cosurfactant transformations considered here, the DeltaDeltaG values predicted by the CS-FE/MT model were compared with DeltaDeltaG values predicted by an accurate molecular thermodynamic (MT) model developed by fitting to experimental CMC data. Even after performing lengthy equilibration and data gathering at each lambda value, physically unrealistic values of DeltaDeltaG were predicted by the CS-FE/MT model for the transformations of SDS into IBU and of OG into PAB. However, more physically realistic DeltaDeltaG values were predicted for the transformation of C10PO into C10SO, and reasonable free-energy predictions were obtained for the transformations of C8SE into C10SE and C10SO into C8SO. Each of the surfactant-to-cosurfactant transformations considered here involved less extensive structural changes than the surfactant-to-solubilizate transformations. As computer power increases and as improvements are made to alchemical free-energy methods, it may become possible to apply the CS-FE/MT model to make accurate predictions of the free-energy changes associated with forming multicomponent surfactant and solubilizate micelles in aqueous solution where the chemical structures of the surfactants, cosurfactants, and solubilizates differ significantly.     

Palladium-iminophosphine-catalysed carbostannylation of arynes: synthesis of ortho-substituted arylstannanes

Arynes were found to insert into a carbon-tin bond of alkynyl- and vinylstannanes in the presence of a catalytic amount of a palladium-iminophosphine complex to afford ortho-substituted arylstannanes, which were convertible into a wide variety of 1,2-disubstituted arenes via carbon-carbon bond forming reactions.     

颗粒流体系统的非线性行为

该文讨论颖粒流体系统的研究现状和可能的发展方向。认为非线性行为是实现颖粒流体系统定量化的难点所在,它可分为来源于颖粒流体相互作用的内在非线性和来源于外界影响和非理想物性的次生非线性。内在非线性引起系统内的自组织现象、分支现象和混沌运动,次生非线性则使得内在非线性的分析更加复杂。提出了认识非线性行为的两种可能途径:(1)把系统进行多方面的分解,即运动分解为极值和动态,能耗分解为可逆和耗散,过程分解为有序和无序,结构分解为不同尺度;(2)将该系统处理为尺度差别很大的两种介质的相互作用并进行计算机图形仿真。     

Theoretical studies on the reaction mechanism of palladium(0)-catalyzed addition of thiocyanates to alkynes

The reaction mechanism of the Pd(0)-catalyzed alkyne cyanothiolation reaction is investigated by MP2, CCSD(T) and the density functional method B3LYP. The overall reaction mechanism is examined. The B3LYP results are consistent with the results of CCSD(T) and MP2 methods for the isomerization, acetylene insertion and reductive elimination steps, but not for the oxidative addition step. For the oxidative addition, the bisphosphine and monophosphine pathways are competitive in B3LYP, while the bisphosphine one is preferred for CCSD(T) and MP2 methods. The electronic mechanisms for the oxidative addition of thiocyanate HS-CN to Pd(PH(3))(2) and Pd(PH(3)) and for the acetylene insertion into Pd-S and Pd-CN are discussed in terms of the electron-donation and back-donation. The chemo-selectivity that acetylene inserts into the Pd-S bond rather than into the Pd-CN bond is due to the involvement of the S p orbital. It is the doubly occupied S p unhybridized orbital that donates an electron to the alkylene pi* anti-bonding orbital, which makes insertion into Pd-S bond more favorable than into the Pd-CN bond. During the insertion into the Pd-S bond, the S sp(2) hybrid orbital and unhybridized p orbital transform into each other, while the C sp hybrid orbital shifts its direction for insertion into Pd-CN bond. By using the monosubstituted acetylenes (CN, Me and NH(2)), the influence of substituents at acetylene on the chemo- and regio-selectivities is analyzed.     

Ring opening and closing reactions of imidazoles and other 1,3-diazaheterocycles with vinyl chloroformate and phenyl chloroformate

Treatment of imidazole and benzimidazole with vinyl chloroformate or phenyl chloroformate in weakly alkaline aqueous solution leads to their conversion into the corresponding imidazol-2-ones; in weakly acidic solutions these chloroformates convert adenine into isoguanine, 6-methylaminopurine into 1-methylisoguanine and pyrimidine into an acyclic product.     

Reactivity of a Stable Phosphinonitrene towards Small Molecules

The room‐temperature stable phosphinonitrene 1 undergoes a thermal rearrangement into heterocycle 2 through a process involving a nitrene insertion into a CH bond. In the presence of acetonitrile, a nitrene–acetonitrile adduct has been isolated; then it first rearranges into a ketenimine and subsequently into a rare example of diazaphosphete. Compound 1 also splits water, carbon dioxide, carbon disulfide, and elemental sulfur, although it reacts with white phosphorus, leading to a P₅N cluster formally resulting from the insertion of the PN moiety into a P?P edge of the P₄ tetrahedron.     

Transportation of silver nanopaticles in nanochannels of carbon nanotubes with supercritical water

Supercritical water (SCW) as a highly destructive environment has been utilized to open multiwall carbon nanotubes (MWNTs) and to break silver aggregates into nanoparticles (diameter 2-20 nm). Water was drawn into open-ended MWNTs by capillary suction, pulling Ag nanoparticles into the MWNTs. The Ag nanoparticles (solid), presumably transported in the nanochannels of MWNTs by the fluidity of SCW, stacked, and fused to form nanorods, suggesting SCW associated with MWNTs (hollow interior) might be exploited as a nanoreactor.     

Spectroscopic and Spectroelectrochemical Studies of Interaction of Nile Blue with DNA

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Biomimetic fabrication of 3D structures by spontaneous folding of tapes

This paper describes a biomimetic strategy for the fabrication of 3D structures-including an electrically functional light detector-modeled on the folding of biological macromolecules into globular shapes. The process started by fabricating precursors to 3D, millimeter-sized structures using flexible polymer tapes. These tapes were patterned with metal features supporting liquid solder, crimped into strings of 3D corrugations, and attached to flat polymer tapes to generate linear 3D structures. Capillary interactions between droplets of molten solder on adjacent faces of the crimped tapes resulted in folding of the precursors into quasi-3D and truly 3D structures.     

Macroscale assembly of peptide nanotubes

Simple oligopeptides that self-assemble into homogeneous nanotubes can be directed to further assemble into macroscale parallel arrays through protein "salting out" strategies.     

The dynamics of the accumulation of the alkaloids of the genus Ungernia

Summary A study ofU. victoris, U. tadshicorum, andU. trisphaera with respect to the vegetation periods and growth sites has shown that the maximum accumulation of alkaloids takes place in the early vegetation period and that naturally dried leaves do not contain alkaloids. The alkaloid content also depends on the growth site.In the period of the vigorous development of the epigeal part, some alkaloids are possibly converted into one another (hippeastrine into lycorine, galanthamine into narwedine, and narwedine into galanthamine).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 60–64, January, 1971.     

Artificial polymeric receptors on the cell surface promote the efficient cellular uptake of quantum dots

In our previous paper, secondary-amine appended cationic polymer 1 was used as a scaffold to display artificial receptors on a cell surface (R. Kamitani et al., ChemBioChem, 2009, 10, 230). This polymer can be retained on the cell surface for more than 30 min before being slowly internalized into the cells. In this study, our aim is to achieve the efficient internalization of quantum dots (QDs) into target cells via artificial receptors on the polymer. As a receptor molecule, N-acetylglucosamine (GlcNAc) moieties were introduced into the polymer, and GlcNAc binding protein-displaying QDs were used as a ligand. We found that ligand-presenting QDs could be internalized effectively into cells via polymer-mediated endocytosis, whereas QDs were not internalized into untreated cells. These data suggest that our method based on cell-surface engineering using polymers affords a new approach to the delivery of various poorly permeable nanoparticles into cells.