Langmuir and Langmuir–Blodgett Films from Amphiphilic Pillar[5]arene‐Containing [2]Rotaxanes

Amphiphilic pillar[5]arene‐containing [2]rotaxanes have been prepared and fully characterized. In the particular case of the [2]rotaxane incorporating a 1,4‐diethoxypillar[5]arene subunit, the structure of the compound was confirmed by X‐ray crystal structure analysis. Owing to a good hydrophilic/hydrophobic balance, stable Langmuir films have been obtained for these rotaxanes and the size of the peripheral alkyl chains on the pillar[5]arene subunit has a dramatic influence on the reversibility during compression–decompression cycles. Indeed, when these are small enough, molecular reorganization of the rotaxane by gliding motions are capable of preventing strong π–π interactions between neighboring macrocycles in the thin film.     

Mechanism of oligomerization reactions of silica

The mechanism of the oligomerization reaction of silica, the initial step of silica formation, has been studied by quantum chemical techniques. The solvent effect is included by using the COSMO model. The formation of various oligomers (from dimer to tetramer) was investigated. The calculations show that the anionic pathway is kinetically preferred over the neutral route. The first step in the anionic mechanism is the formation of the SiO-Si linkage between the reactants to form a five-coordinated silicon complex, which is an essential intermediate in the condensation reaction. The rate-limiting step is water removal leading to the oligomer product. The activation energies for dimer and trimer formation ( approximately 80 kJ/mol) are significantly higher than those of the subsequent oligermerization. The activation energies for the ring closure reaction ( approximately 100 kJ/mol) are even higher. The differences in activation energies can be related to the details in intra- and intermolecular hydrogen bonding of the oligomeric complexes.     

A model study on the mechanism and kinetics for the dissociation of water anion

Quantum chemical computations using both density functional theory (B3LYP functional) and wavefunction (MP2 and CCSD(T)) methods, with the 6-311++G(3df,2p) and aug-cc-pVnZ (n = D,T,Q) basis sets, in conjunction with a polarizable continuum model (PCM) method for treating structures in solution, were carried out to look again at a series of small negatively charged water species [(H₂O)_n]^•–. For each size n of [(H₂O)_n]^•– in aqueous solution with n = 2, 3, and 4, two distinct structural motifs can be identified: a classical water radical anion formed by hydrogen bonds and a molecular pincer in which the excess electron is directly interacting with H atoms. In aqueous solution, both motifs have comparable energy content and likely coexist and compete for the ground state. Some water anion isomers can dissociate when interaction with a water molecule, [(H₂O)_n]^•– + H₂O → H^•(H₂O)_m + OH^–(H₂O)_n–m, through successive hydrogen transfers with moderate energy barriers. This reaction can also be regarded as a water-splitting process in which the H transfers involved take place mainly within a water trimer, whereas other water molecules tend to stabilize transition structures through microsolvation rather than direct participation. Calculated absolute rate constants for the reversed reaction H^•(H₂O)₂ + OH^–(H₂O)₂ → [(H₂O)₄]^•־ + H₂O with both H and D isotopes agree well with the experimentally evaluated counterpart and lend a kinetic support for the involvement of a tetramer unit.     

New Polyenes from the Marine-Derived Fungus Talaromyces cyanescens with Anti-Neuroinflammatory and Cytotoxic Activities

Three new polyene compounds, talacyanols A–C (1–3), along with two known compounds, ramulosin (4) and eurothiocin A (5), were isolated from the marine fungus Talaromyces cyanescens derived from a seaweed Caulerpa sp. Structures of 1–5 were established by one-dimensional and two-dimensional (1D/2D) NMR, HR-ESIMS, and the modified Mosher’s methods, as well as comparison with previously reported literature data. All the compounds (1–5) were tested for their in vitro cytotoxic and anti-neuroinflammatory activities. Among them, 1 showed moderate cytotoxic activity against a panel of cancer cell lines (HCT-15, NUGC-3, NCI-H23, ACHN, PC-3, and MDA-MB-231) with GI₅₀ values ranging from 44.4 to 91.6 μM, whereas compounds 2 and 5 exhibited anti-neuroinflammatory effect without cytotoxicity against all the tested cell lines.     

A new benzofuran derivative from the leaves of Ficus pumila L.

A new benzofuran derivative, pumiloside (1), together with seven known flavonoid glycosides, afzelin (2), astragalin (3), quercitrin (4), isoquercitrin (5), kaempferol 3-O-rutinoside (6), rutin (7) and kaempferol 3-O-sophoroside (8) were isolated from the leaves of Ficus pumila. Their structures were established by spectroscopic data and comparison with the literature values.     

“Printing” DNA Strand Patterns on Small Molecules with Control of Valency,Directionality, and Sequence

The incorporation of synthetic molecules as corner units in DNA structures has been of interest over the last two decades. In this work, we present a facile method for generating branched small molecule‐DNA hybrids with controllable valency, different sequences, and directionalities (5′–3′) using a “printing” process from a simple 3‐way junction structure. We also show that the DNA‐imprinted small molecule can be extended asymmetrically using polymerase chain reaction (PCR) and can be replicated chemically. This strategy provides opportunities to achieve new structural motifs in DNA nanotechnology and introduce new functionalities to DNA nanostructures.     

When can the Ogston-Morris-Rodbard-Chrambach model be applied to gel electrophoresis?

The Ogston-Morris-Rodbard-Chrambach theory of gel electrophoresis is consistent with predictions from the volume averaging method with respect to the equivalence of the accessible volume fraction to the ratios of gel mobility to free solution mobility and the gel diffusion coefficient to free solution diffusion coefficient for the limiting case of small molecule electrophoresis with low electrical fields, low gel concentrations, and nonconductive gel fibers. When these conditions are not valid, more extensive calculations are required to determine the mobility and diffusion coefficient ratios as functions of the geometry and electrical field within the gel. The volume averaging theory shows that it is important to account for the electrical conductivity properties of the fibers that make up a gel electrophoresis medium, and this aspect is consistent with early theories of transport phenomena in gel electrophoresis.     

Enhanced adsorption of methylene blue onto graphene oxide-doped XFe<Subscript>2</Subscript>O<Subscript>4</Subscript> (X = Co,Mn, Ni) nanocomposites: kinetic,isothermal, thermodynamic and recyclability studies

The nanocomposites XFe₂O₄/GO with various metal sites (X = Co, Mn, and Ni) were successfully synthesized via the polymerized complex method. The XFe₂O₄/GO family was characterized using X-Ray diffraction analysis, scanning electron microscopy (SEM), and a vibrating sample magnetometer. We also investigated the effect of three fundamental parameters (initial concentration, dosage, and pH) on the removal of methylene blue using the response surface methodology. A high F value, very low P value (< 0.00001), a non-significant lack of fit, and the determination coefficient (R ² > 0.95) demonstrated a strong correlation between experimental and predicted values of the responses. The predicted optimal conditions for maximum removal efficiency were easily determined to adhere to the following trend for actual test experiments: MnFe₂O₄/GO (60.1%) < CoFe₂O₄/GO (80.3%) < NiFe₂O₄/GO (87.7%). Moreover, the adsorption behavior was well-described by the Langmuir isotherm and a pseudo-second-order kinetic model. The maximum capacity for adsorption of methylene blue onto XFe₂O₄/GO was found from 42.2 to 80.6 mg/g. Moreover, the XFe₂O₄/GO could be regenerated for several cycles without a considerable decrease in removal yield, suggesting that this highly promising XFe₂O₄/GO could be applied as an efficient and novel adsorbent.     

Analysis of isomeric long-chain hydroxy fatty acids by tandem mass spectrometry: application to the diagnosis of long-chain 3-hydroxyacyl CoA dehydrogenase deficiency

Acetyl trimethylaminoethyl ester iodide derivatives have been used to selectively analyze isomeric long-chain hydroxy fatty acids by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The binary derivatives of 2-, 3-, 12- and 16-hydroxypalmitic acids afford remarkably different product ion spectra. Further discrimination between isomers is possible by acylating with pivaloyl chloride. 2- and omega-Hydroxy long-chain fatty acids form pivaloyl esters in quantitative yield whereas other secondary alcohols only partially react. Cotton-based filter paper used for blood collection contains substantial amounts of esterified long-chain hydroxy fatty acids. From the product ion spectra of the acetyl trimethylaminoethyl esters the hydroxydocosanoic and -tetracosanoic acids are >90% omega-hydroxy. All remaining saturated and unsaturated hydroxy acids are >90% 2-hydroxy acids. A method for the quantification of free 3-hydroxypalmitic acid in plasma by ESI-MS/MS for the diagnosis of long-chain 3-hydroxyacyl CoA dehydrogenase deficiency (LCHAD) is described. Median plasma concentrations of 0.43 micromol/L (control, n = 22) and 12.2 micromol/L (LCHAD, n = 3) were obtained from 5 microL plasma samples.