Kinetics of lipid layer formation at interfaces

A formal kinetic model of lipid layer formation at an interface in contact with a liposomal suspension is developed and investigated. Neglecting diffusion (for sufficiently high bulk concentrations) the kinetic scheme consists of two consecutive processes: (I) irreversible transformation of ‘soluble’ intact vesicles from the ‘subsurface’ layer into ‘adsorbed’ ones (‘defected’ or ‘ruptured’ liposomes, ‘mesophases’); and (II) irreversible transformation of the ‘adsorbed’ vesicles into a lipid monolayer. The resulting set of two differential equations is analyzed making use of the ‘steady-state concentration’ approach (with ‘adsorbed’ vesicles as intermediate compound). Numerical results illustrate the predicted kinetic behavior which depends on the relative magnitude of the rates of the two consecutive processes. Approximate analytical solutions in the case of a much slower process I are obtained in some limiting cases. The model is used to estimate rate constants from previously established experimental kinetic data at the air/water interface.     

Role of the Residue Q1919 in Increasing Kinase Activity of G2019S LRRK2 Kinase: A Computational Study

Mutations in multi-domain leucine-rich repeat kinase 2 (LRRK2) have been an interest to researchers as these mutations are associated with Parkinson's disease. G2019S mutation in LRRK2 kinase domain leads to the formation of additional hydrogen bonds by S2019 which results in stabilization of the active state of the kinase, thereby increasing kinase activity. Two additional hydrogen bonds of S2019 are reported separately. Here, a mechanistic picture of the formation of additional hydrogen bonds of S2019 with Q1919 (also with E1920) is presented using ‘active’ Roco4 kinase as a homology model and its relationship with the stabilization of the ‘active’ G2019S LRRK2 kinase. A conformational flipping of residue Q1919 was found which helped to form stable hydrogen bond with S2019 and made ‘active’ state more stable in G2019S LRRK2. Two different states were found within the ‘active’ kinase with respect to the conformational change (flipping) in Q1919. Two doubly-mutated systems, G2019S/Q1919A and G2019S/E1920 K, were studied separately to check the effect of Q1919 and E1920. For both cases, the stable S2 state was not formed, leading to a decrease in kinase activity. These results indicate that both the additional hydrogen bonds of S2019 (with Q1919 and E1920) are necessary to stabilize the active G2019S LRRK2.     

Correlations between electrochemical and spectral properties of alkyl-substituted diphthalocyanine lanthanide complexes

The electrochemical behavior and spectral properties of a series of symmetrical 2,3,9,10,16,17,23,24,2’,3’,9’, 10’,16’,17’,23’,24’-hexadecaalkyl-substituted lanthanide complexes (R₈Pc)₂Ln (R = H, Me, Et, Buⁿ; Ln = Eu, Dy, Lu) were studied. Regularities of changing the parameters under study were established, depending on the nature of lanthanide and substituents in the phthalocyanine macroligands. The position of the intervalence band of the complexes in the near-IR region depends on the effective distance between the macroligands and also on the electronic effect of the substituents. Correlations between the electrochemical and spectral properties of the complexes were found.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 184–189, January, 2005.     

Combinatorial enumeration of ethane derivatives as three-dimensional chemical structures,not as graphs. A systematic approach for enumerating and characterizing stereoisomers of tartaric acids and related compounds

Fujita’s proligand method is applied to the enumeration of ethane derivatives, where the counting of stereoisomers of tartaric acids is examined in detail as a probe for testing the versatility of the method. The cycle index with chirality fittingness (CI-CF) for enumerating ethane derivatives is obtained by Fujita’s proligand method and compared with the CI-CF derived alternatively by the direct calculation of permutations of substitution positions. The two CI-CFs are identical with each other so that the methodology underlying in Fujita’s method is demonstrated in a concrete fashion. The enumeration results are compared with those derived by Pólya’s corona. Fujita’s proligand method is shown to be capable of enumerating stereoisomers, whereas Pólya’s corona is concluded to enumerate graphs, but not stereoisomers. The conceptually change from graphs to three-dimensional (3D) chemical structures is discussed, where the superiority of Fujita’s proligand method is demonstrated.     

L’importance des phénomènes d’oxydo-réduction dans le verreImportance of oxidoreduction phenomena in glass.

Oxydo-reduction phenomenon concerns glass manufacturing as well as its properties. Various oxidation scales have been used by glassmakers, the most widely used being the ratio between Fe²⁺ and the total iron content. Comparisons are made with others, such as the partial pressure of oxygen or the redox potential. The influence of the chemical composition of the glass is also studied as well as that of the temperature, through the results obtained in Saint-Gobain Recherche and in other laboratories. In industrial glass manufacturing, the oxidation equilibrium is usually achieved during the fining process, an intense ‘bubbling’ being necessary to obtain a homogeneous glass. Thus, the oxidoreduction state of the glass does not depend on the atmosphere under which it was made, but depends on the mixture of gases generated during the fining process, which is described through the reactions generated by the two main fining systems, arsenic oxide or antimony oxide + sodium nitrate and sodium sulphate + a reducing agent. The former provides oxygen and the latter, a mixture of oxygen and sulphur dioxide. Consequently, a glass melted with arsenic oxide is more oxidised than a glass melted with sodium sulphate. The equilibrium constant used to interpret the latter system, mostly used for soda lime silica glasses fining, is given as a function of the temperature and some of the consequences are examined. Obviously, the coloration by iron oxide impurities is influenced by the manufacturing process. Some other colouring oxides are submitted to a change of oxidation state and thus to a modification of their colouring action. A quick review is done of the transition metal coloration, of the electron-charge-transfer absorption due to sulphides or selenides, and of aggregate formation inducing the well-known red ruby glass, for instance.

Résumé

Les phénomènes d’oxydo-réduction concernent aussi bien l’élaboration du verre que ses propriétés. Plusieurs échelles d’oxydo-réduction ont été utilisées par les verriers, la plus courante étant le rapport entre Fe²⁺ et la teneur totale en fer. Nous faisons la comparaison entre les différents systèmes, comme la pression partielle d’oxygène. Dans l’élaboration des verres industriels, l’équilibre redox est réalisé habituellement pendant le processus d’affinage, un « bullage » intense étant indispensable à l’obtention d’un verre homogène. L’état redox du verre ne dépend pas de l’atmosphère sous laquelle il a été élaboré, mais du mélange de gaz généré durant le processus d’affinage. Les deux systèmes affinants principaux sont l’oxyde d’arsenic ou d’antimoine couplé au nitrate de sodium ou bien le sulfate de sodium couplé à un agent réducteur. Le premier génère de l’oxygène et le second un mélange d’oxygène et de dioxyde de soufre. En conséquence, un verre élaboré avec de l’oxyde d’arsenic est plus oxydé qu’un verre élaboré avec du sulfate de sodium. La coloration par l’impureté oxyde de fer est évidemment fortement influencée par le procédé. D’autres oxydes colorants subissent aussi des changements d’état d’oxydo-réduction et voient leur action colorante modifiée en fonction des conditions d’élaboration.     

Effects of activation conditions on the electrochemical capacitance of activated carbon nanotubes

The effects of different activation conditions (including KOH/CNTs ratio, activation temperature, activation time and nitrogen flow rate) on the electrochemical capacitance of activated carbon nanotubes (CNTs) have been investigated. All the four factors can affect the activated CNTs’ electrochemical capacitance. And the effects on the activated CNTs’ electrochemical capacitance carried out by virtue of their effects on activated CNTs’ BET specific surface area and graphitized degree.     

The synergistic effect of cobalt-dicarbollide anions on the extraction of M lanthanide cations by Calix[4]arenes: a molecular dynamics study at the water–‘oil’ interface

We report molecular dynamics studies on the effect of CCD^– (chlorinated cobalt-dicarbollide) anions on the Eu³⁺ lanthanide cation extraction by a calix[4]arene-CMPO ligand L, focusing on the water–‘oil’ interface, where ‘oil’ is modelled by chloroform. The free L ligand and its EuL³⁺ complex are found to adsorb and to concentrate at the interface, but are too hydrophilic to be extracted. Addition of CCD^– anions in diluted conditions (either covalent linked to L or as separated CCD^– H₃O⁺ ions) also leads to adsorption of these species at the interface. However, at high concentrations, CCD^– anions saturate the interface and promote the extraction of EuL³⁺ to the oil phase. Another important feature concerns the uncomplexed Eu(CCD)₃ salt: accumulation of CCD^– anions at the interface creates a negative potential which attracts the hydrated Eu³⁺ ions, therefore facilitating their complexation by interfacial ligands. These features allow us to better understand the synergistic effect of lipophilic anions in the assisted liquid-liquid extraction of trivalent M³⁺ lanthanide or actinide cations. To cite this article: B. Coupez, G. Wipf, C. R. Chimie 7 (2004).

Résumé

Synergie due aux anions dicarbollides lors de l’extraction d’ions lanthanides M³⁺ par des calix[4]arènes : simulations de dynamique moléculaire à l’interface eau–« huile ». Nous étudions par simulations de dynamique moléculaire l’effet de synergie dû aux anions CCD^– (cobalt-dicarbollides) lors de l’extraction de Eu³⁺ par un calix [4]arène L, en se focalisant sur l’interface eau–« huile », l’huile étant modélisée par du chloroforme. On montre que le ligand L et son complexe EuL³⁺ s’adsorbent à l’interface, mais sont trop hydrophiles pour être extraits. L’addition d’anions CCD^– (qu’ils soient sous la forme d’ions CCD^– H₃O⁺ séparés ou greffés de façon covalente au calixarène) conduit aussi à l’adsorption de ces espèces à l’interface. Cependant, aux plus fortes concentrations, les anions CCD^– saturent l’interface et induisent l’extraction du complexe EuL³⁺ vers l’huile. Un autre résultat remarquable concerne les sels Eu(CCD)₃ : l’accumulation des anions CCD^– à l’interface y crée un potentiel négatif, ce qui attire les cations Eu³⁺ et facilite ainsi leur complexation par des ligands à l’interface. Ces résultats permettent de mieux comprendre l’effet de synergie dû aux anions CCD^– lors de l’extraction d’ions lanthanides ou actinides M³⁺ et, d’une manière générale, ce qui se passe à l’interface entre l’eau et des liquides non miscibles. Pour citer cet article : B. Coupez, G. Wipf, C. R. Chimie 7 (2004).     

Asymmetric synthesis of 2-substituted butane-1,4-diols by hydrogenation of homochiral fumaramide derivatives

Diastereoselective hydrogenation of homochiral fumaramides 1 derived from (2R)-Oppolzer’s sultam was observed by analysis of the ¹H NMR spectra of the succinamide mixtures with de’s of 77–88%. Reduction of these succinamides using LiAlH₄ gave the corresponding (2S)-butane-1,4-diols and established that addition of hydrogen takes place selectively on the re-face of fumaramides 1. The stereoselectivity was confirmed by estimating the ee’s from the ¹⁹F NMR spectra of the Mosher’s diesters of the diols. This methodology was applied to the synthesis of selected pyrrolidine natural products in homochiral form.     

Facile route to synthesis of functionalised poly(methylalkoxy)siloxane under mild and aerobic conditions in the presence of platinum catalysts

A facile and high yield method of synthesis of novel and functional poly(methylalkoxy) siloxanes is reported. The Si–H groups of poly(methylhydrogen) siloxanes (PMHS) were treated with various simple (primary, secondary, tertiary) alcohols (1a–10a) in the presence of platinum based catalysts (Speier’s and Karstedt’s catalysts). Also oxyethylene, aldehyde, epoxide, halogen and allyl grafted polysiloxane were smoothly and quantitatively prepared by the alcoholysis between linear siloxanes polymer and functional alcohols (11a–20a) with use of Karstedt’s catalysts. It is found that alcoholysis reaction in the presence of the Karstedt’s catalyst proceed faster than Speier’s catalyst .In addition, the rate of alcoholysis reaction is dependent on amount of the catalyst and reaction temperature. The polymers prepared were characterized by IR, NMR spectroscopy and GPC analysis.     

人教版高中化学必修模块教科书实验活动的分析与比较*——以2019年版教科书“实验”和“实验活动”栏目为例

以人教版高中化学必修模块教科书(2019年版)“实验”和“实验活动”栏目的实验活动为研究对象,采用Herron修正的“实验活动探究层次分类法”(LOLA)和笔者提出的“学生实验行为要求分类法”(RSBLA)对其进行分析,并与2007年版教科书进行对比。研究发现,2019年版教科书的实验活动探究层次处于层次1和层次2,学生行为要求为“观察”“记录实验现象”“回答与实验有关的问题”和“设计实验”。卡方检验表明,2019年版教科书和2007年版教科书“实验”栏目的实验活动探究层次分布比例和学生实验行为要求均存在显著性差异。     

In silico fight against novel coronavirus by finding chromone derivatives as inhibitor of coronavirus main proteases enzyme

Structural Chemistry - Novel coronavirus, 2019-nCoV is a danger to the world and is spreading rapidly. Very little structural information about 2019-nCoV make this situation more difficult for drug...     

A CASSCF/icMRCI study of the electric field gradient in low-lying electronic states of N2/N2

The electric field gradients (EFG’s) at the nucleus are calculated as a function of internuclear separation in the X²Σ_g⁺ and B²Σ_u⁺ electronic states of the nitrogen molecule cation using the internally contracted multireference configuration interaction (icMRCI) method. The EFG’s and potential energy functions (PEF’s) are used to estimate the ¹⁴N nuclear quadrupole coupling constants (NQCC’s) in the two electronic states as functions of vibrational and end-over-end rotational quantum numbers. The dependences of the computed constants on the basis set and reference configuration space are investigated. Since no counterpart for comparison of the calculated NQCC’s exists, the N₂⁺ results are supported by analogous calculations on the X¹Σ_g⁺ and A³Σ_u⁺ states of N₂, for which established data are available. The overall good quality of the icMRCI wave functions is further corroborated by a favorable agreement of spectroscopic constants derived from the corresponding PEF’s and experimental data. Variations of the EFG with internuclear separation are explained in terms of wave function composition, and used for gaining specific insight into the chemical bonding in N₂⁺ and N₂.     

Comment on “Theoretical Investigations on Geometrical and Electronic Structures of Silver Clusters”

We would like to make a few comments on the results reported in a recent paper in this journal by Tsuneda, J. Comput. Chem, 2019, 40, 206. The structures of some pure silver clusters were not correctly assigned. © 2019 Wiley Periodicals, Inc.     

Influence of Surfactants on Structuring of Molding Blends Based on ZnO

The correlation between the surfactant sorption and structural mechanical properties of molding blends and granulated sorbents was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 240–244.Original Russian Text Copyright © 2005 by Prokof’ev, Il’in, Basova.     

Conformational Mobility of 4,4′-Bisdimethyl-Aminobenzophenone in the Excited State

Quantum-chemical calculations on various conformational states of the molecule of Michler’s ketone have been carried out by semi-empirical and non-empirical methods (HyperChem 7.0 suite of programs and Gaussian 98). The influence of solvation on the relative levels of different orbital types and on the spin states of the molecule has been examined. The possibility of the TICT process occurring in polar media, which may have an important effect on the spectral characteristics of Michler’s ketone, has been investigated.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 3, pp. 185–189, May–June, 2005.     

Synthesis of 3,4-bis(2,5-dimethyl-3-thienyl)furan-2,5-dione from mucobromic acid

Palladium-catalyzed cross-coupling between 2,5-dimethyl-3-thienylboronic and mucobromic acids under phase transfer catalysis (PTC) conditions gave the expected 3,4-bis(2,5-dimethyl-3-thienyl)-5-hydroxyfuran-2-one in 32% yield. The by-product was 2,2’,5,5’-tetramethyl-3,3’-bithiophene. The oxidation of the obtained hemiacylal with potassium permanganate under PTC conditions afforded 3,4-bis(2,5-dimethyl-3-thienyl)furan-2,5-dione in high yield.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2238–2240, October, 2004.     

化学教育，情暖隆德——厦门大学“化在宁夏”暑期社会实践

2019年7月20日至7月28日,厦门大学"化在宁夏"实践队前往宁夏隆德县进行以教育为主旨的暑期社会实践,其中包含三个具体的实践方向:科普化学知识、帮扶学生学业、增长爱国情怀。     

General strategy for a short and efficient synthesis of 3-hydroxy-4-methylprolines (HMP)

The non-proteinogenic amino acid 3-hydroxy-4-methylproline (HMP) is an active constituent of some potent antimicrobials including echinocandins, nostopeptins, pneumocandins, sporiofungin and mulundocandins. A synthesis has been achieved in 10 steps with 29% overall yield; the Evans’ aldol reaction using Crimmins’ modified method was pivotal to the success of the strategy.     

Molecular docking and dynamic simulation of approved drugs targeting against spike protein (6VXX) of 2019-nCoV (novel coronavirus)

The 2019-nCoV has triggered a global public health emergency due to its rapid spread, resulting in a pandemic situation. Because of its ability to bind with the host cell receptor ACE-2, the spike protein of the 2019-nCoV is a critical factor in viral infection. The current study aims to investigate the molecular-docking of the spike protein (6VXX) using PyRx for FDA-approved drugs available for the treatment of SARS-1 and MERS, with the hypothesis that these drugs could be suggested for the treatment of 2019-nCoV or not. A phylogenetic analysis of 2019-nCoV in relation to SARS-1 and MERS confirmed the validation. The positive result urged the Multiple Sequence Alignment analysis of the top five affected countries, with China serving as a control, using WHO available reference data to determine the rate of mutant variation. The docking results revealed that the top ten drugs with the highest binding affinity rate are also used for Hepatitis-C virus treatment, and the Molecular Dynamic Simulation was carried out for the drug Paritaprevir, which had the highest binding affinity rate, using Gromacs. The results indicated that the drug Paritaprevir could be used as a potential target against the 2019-nCoV Spike protein.     

Synthesis of Sulfides by Reactions of 1,1-Dichloro-2-chloro-methylcyclopropane with S-Nucleophiles

1,1-Dichloro-2-chloromethylcyclopropane reacts with thiolates to give 2,2-dichlorocyclopropylmethyl sulfides via replacement of the side-chain chlorine atom. The resulting sulfides are readily oxidized to the corresponding sulfones.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 3, 2005, pp. 381–386.Original Russian Text Copyright © 2005 by Mikhed’kina, Nedel’ko, Prezhdo.