Surfactant-Assisted Assembly of Dipeptide Forming a Broom-like Structure

Understanding the influence of surfactants on the assembly of peptides has a considerable practical motivation. In this paper, we systematically study the anionic surfactant-assisted assembly of diphenylalanine (FF). FF forms broom-like structures in a concentration of sodium cholate (NaC) around the CMC, and assembles into linear and unidirectional rods in the presence of low and high surfactant concentrations. FF’s improved hydrogen bonding and controlled assembly rates are appropriate for other anionic surfactants. At this stage, the use of FF as the simplest protein consequence can be helpful in the investigation of further protein–surfactant interactions.     

The Dual Function of PhOH Included in the Coordination Sphere of the Nickel Complexes in the Processes of Oxidation with Dioxygen

The role of ligands in the regulation of the catalytic activity of Ni-complexes (Ni(acac)₂) in green process-selective ethylbenzene oxidation with O₂ into α-phenyl ethyl hydroperoxide is considered in this article. The dual function of phenol (PhOH) included in the coordination sphere of the nickel complex as an antioxidant or catalyst depends on the ligand environment of the metal. The role of intermolecular H-bonds and supramolecular structures (AFM method) in the mechanisms of selective catalysis by nickel complexes in chemical and biological oxidation reactions is analyzed.     

Influence of Aliphatic Chain Length on Structural,Thermal and Electrochemical Properties of n-alkylene Benzyl Alcohols: A Study of the Odd–Even Effect

The century-old, well-known odd–even effect phenomenon is still a very attractive and intriguing topic in supramolecular and nano-scale organic chemistry. As a part of our continuous efforts in the study of supramolecular chemistry, we have prepared three novel aromatic alcohols (1,2-bis[2-(hydroxymethyl)phenoxy]butylene (Do4OH), 1,2-bis[2-(hydroxymethyl)phenoxy]pentylene (Do5OH) and 1,2-bis[2-(hydroxymethyl)phenoxy]hexylene (Do6OH)) and determined their crystal and molecular structures by single-crystal X-ray diffraction. In all compounds, two benzyl alcohol groups are linked by an aliphatic chain of different lengths (CH₂)_n; n = 4, 5 and 6. The major differences in the molecular structures were found in the overall planarity of the molecules and the conformation of the aliphatic chain. Molecules with an even number of CH₂ groups tend to be planar with an all-trans conformation of the aliphatic chain, while the odd-numbered molecule is non-planar, with partial gauche conformation. A direct consequence of these structural differences is visible in the melting points—odd-numbered compounds of a particular series display systematically lower melting points. Crystal and molecular structures were additionally studied by the theoretical calculations and the melting points were correlated with packing density and the number of CH₂ groups. The results have shown that the generally accepted rule, higher density = higher stability = higher melting point, could not be applied to these compounds. It was found that the denser packaging causes an increase in the percentage of repulsive H‧‧‧H interactions, thereby reducing the stability of the crystal, and consequently, the melting points. Another interesting consequence of different molecular structures is their electrochemical and antioxidative properties—a non-planar structure displays the highest oxidation peak of hydroxyl groups and moderate antioxidant activity.     

A relativistic density functional study of gaseous uranium tetrahalides

The molecular structures and vibrational frequencies of gaseous UX₄ (X = F, Cl, Br and I) molecules have been investigated using generalized gradient approximation (GGA) functions (BP, BLYP, PBE and RPBE) with triple-zeta polarized (TZP) basis set. Scalar relativistic effects are introduced via the zeroth-order regular approximation (ZORA) approach to the Dirac equation in the present study. Of the methods examined here the RPBE has the best performance in terms of the errors compared with experiment and reference for the vibrational frequencies. The bond dissociation energies (BDE) for U–X bonds in the UX₄ were obtained using the RPBE method, and are in good agreement with experimental values. In addition, satisfactory calculated entropies of UX₄ have also been obtained at temperatures ranging from 600 to 1200 K in 50 steps using the same method.     

Nanoassemblies with light‐responsive size and density from linear flexible polyelectrolytes

This study presents electrostatically self‐assembled nanoparticles from linear flexible polyelectrolytes (poly(diallyldimethylammonium chloride or quarternized poly(4‐vinylpyridine)) and an ionic photo‐isomerizable azo dye (Acid Yellow 38) that can change their size upon UV‐light irradiation. Assemblies with narrow size distribution are stable in aqueous solution. For samples with under‐stoichiometric dye load, UV‐light exposure triggers a size decrease, e.g. from a hydrodynamic radius of R_h = 94 nm to R_h = 62 nm for an Ay38‐PDADMAC sample with a charge ratio of l_charge = 0.7. Size changes are caused by trans‐cis isomerization of the dye, accompanied by a change in hydrophilicity, binding enthalpy and entropy. Assemblies are characterized by static and dynamic light scattering, atomic force microscopy, UV–vis spectroscopy and isothermal titration calorimetry. Zeta potential measurements give insight into the electrostatic stabilization and size‐control of the ionic nano‐assemblies, revealing a master curve of effective surface charge density versus hydrodynamic radius. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys., 2013     

A Germanate Compound Constructed from Dissymmetric Ge7 Chains and Metal Complexes

Abstract. A novel germanate compound, |[Ni(dien)₂]₃(H₂O)₃|[Ge₇O₁₃F₅]₂(designated JU‐85, dien = diethylenetriamine), was solvothermally synthesized. The structure of JU‐85 was determined by single‐crystal X‐ray diffraction and further characterized by powder X‐ray diffraction, inductively coupled plasma, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. JU‐85 has dissymmetric chains constructed from diagonally linked Ge₇ building units and various Ni(dien)₂²⁺ complexes formed in situ during the synthesis. Compared with its structural analogue, FJ‐6, JU‐85 contains less complex cations and different host‐guest assembly. Besides the diagonal linkage in JU‐85, other dissymmetric linkages of Ge₇ building units were enumerated, which could be used as the stereogenic centers for the design of novel chiral germanate compounds.     

Near-i.r. Absorption of H2O and D2O in the liquid and supercooled range

Summary Results are reported on near-i.r. absorption spectra of H₂O and D₂O down to the temperature region of supercooled liquid. No anomalous behaviour is observed when the absorbance at any given frequency is studied as a function of temperature. A critical-exponent behaviour strikingly correlating with that exhibited by transport properties is instead observed when spectral deconvolution methods are used. Results are discussed in relation with current views on water structure, based on molecular-dynamics simulation results and connectivity calculations.

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Riassunto Si riportano risultati sugli spettri di assorbimento i.r. di H₂O e D₂O fino alla regione di temperature del liquido sopraraffreddato. L'andamento dell'assorbanza a frequenza costante in funzione della temperatura non mostra alcuna indicazione di comportamento anomalo. Al contrario, quando gli spettri sono analizzati con metodo di deconvoluzione, si osserva un comportamento di tipo esponente critico, che correla straordinariamente bene con quello mostrato dalle proprietà di trasporto. I risultati sono discussi anche in relazione ai piú recenti modelli di struttura dell'acqua, derivanti dai risultati di simulazione e dai calcoli di connettività.

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Резюме Приводятся результаты для спектров инфракрасного поглощения H₂O и D₂O для температур переохлажденной жидкости. Не обнаружено аномального поведения, когда поглощательная способность при заданной частоте изучается как функция темпетатуры. Напротив, при анализе спектров с помощью спектральных методов конволюции наблюдается поведение типа критической экспоненты, которое коррелирует с поведением, определяемым транспортыми свойствами. Полученные результаты обсуждаются в связи с недавними моделями структуры воды, полученными на основе моделирования молекулярной динамики и нычислений связности.

     

Indefinite preference structures and decision analysis

It always takes time for people to digest information and make judgments. The decision maker's preference is not always clear and stable when decision analysis and decision making are performed. In this paper, we introduce a generalized preference structure to cope with indefinite preferences. We describe its general properties, its implication on value function representation, its solution concepts, and methods for obtaining the solutions.This research has been partially supported by NSF Grant No. IST-84-18863. The authors are grateful to Dr. D. J. White for his helpful comments on a previous draft.     

Transport properties of a single-quantum dot Aharonov-Bohm interferometer

We consider a two-terminal Aharonov-Bohm (AB) interferometer with a quantum dot inserted in one path of the AB ring. We investigate the transport properties of this system in and out of the Kondo regime. We utilize perturbation theory to calculate the electron self-energy of the quantum dot with respect to the intradot Coulomb interaction. We show the expression of the Kondo temperature as a function of the AB phase together with its dependence on other characteristics such as the linewidth of the ring and the finite Coulomb interaction and the energy levels of the quantum dot. The current oscillates periodically as a function of the AB phase. The amplitude of the current oscillation decreases with increasing Coulomb interaction. For a given temperature, the electron transport through the AB interferometer can be selected to be in or out of the Kondo regime by changing the magnetic flux threading perpendicular to the AB ring of the system.     

Generalized Transvectants-Rankin–Cohen Brackets

We introduce o(p+1q+1)-invariant bilinear differential operators on the space of tensor densities on Rⁿ generalizing the well-known bilinear sl₂-invariant differential operators in the one-dimensional case, called Transvectants or Rankin–Cohen brackets. We also consider already known linear o(p+1q+1)-invariant differential operators given by powers of the Laplacian.