Pd/C-catalyzed one-pot Suzuki-Miyaura cross-coupling/hydrogenation of pyridine derivatives

Using bromopyridines and methoxyphenyl boronic acid as starting materials, consecutive Suzuki-Miyaura cross-coupling and hydrogenation reactions were undertaken using a heterogeneous Pd/C catalyst in one-pot manner under mild conditions (balloon-pressure at room temperature for hydrogenation) with excellent yield. To counter Pd leaching as well as catalyst poisoning, addition of an appropriate amount of H₂O was crucial to achieving successful AcOH-promoted hydrogenation, which ensured a selective reduction of the pyridine rings to the corresponding piperidines.     

Efficient Catalytic Promiscuity for Chemically Distinct Reactions

High catalytic proficiencies observed for the native and promiscuous reaction of the Pseudomonas aeruginosa arylsulfatase (PAS; the picture shows transition states of the two substrates with corresponding binding constants K_tx) suggest that the trade‐off between high activity and tight specificity can be substantially relaxed.

     

Effect of the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions on barrier properties of mice skin for transdermal permeation of tetracaine hydrochloride: in vitro

Effect of composition of lecithin water-in-oil and oil-in-water microemulsion on in vitro transdermal permeation of tetracaine hydrochloride was studied on mice model. The results were compared with an aqueous solution of tetracaine hydrochloride (2.7 mg/ml). In vitro skin flux and permeability coefficients were obtained using the Franz diffusion cell. Differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) were used to study the mechanism of action of the microemulsion. Micrographs of TEM and CLSM studies were analyzed by using Image Pro Plus image software. Skin flux of tetracaine hydrochloride was found to be dependent on the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions. At lower Km ratio (i.e. 0.5:1 and 0.8:1) of microemulsion, the rate of permeation of tetracaine hydrochloride was higher when compared to the microemulsion of higher Km ratio (1:1 and 1.5:1). Image analysis of TEM micrograph, 6h after application of lecithin microemulsion, showed 3.5+/-0.75-fold (p<0.001) increase in the intercellular space in the epidermis and 3.8+/-0.4-fold (p<0.001) enhancement in upper dermis. CLMS results show that sweat gland and hair follicles also provided path for permeation of the drug through the skin.     

A Local Expansion Theorem for the Löwner Equation

If W(z) is a power series with complex coefficients which represents an injective function bounded by one in the unit disk and which vanishes at the origin then a Grunsky space $\mathcal{G}(W)$ exists. It is contained contractively in the Dirichlet space for the unit disk. In this paper an admissible family of weighted Dirichlet spaces is used as in the proof of Bieberbach conjecture to construct a Local Grunsky space. An expansion theorem is presented for such a Local Grunsky space. The proof relies on the reproducing kernel function for coefficients of powers of z and Löwner differential equation.     

Suppression of soliton self-frequency shift by upshifted filtering

We consider the effects of stimulated Raman scattering on ultrashort light pulses propagating in long-haul fiber transmission lines. We propose an efficient method for suppressing the soliton self-frequency shift by use of upshifted filters without any compromise in signal-to-noise ratio and with the pulse stability preserved.     

An inorganic phosphate (Pi) sensor triggers ‘turn-on’ fluorescence response by removal of a Cu ion from a Cu-ligand sensor: determination of Pi in biological samples

A fluorescent ligand that displays a high selectivity for Cu²⁺ has been synthesized. On complexation with Cu²⁺, the fluorescence of the ligand is quenched. Inorganic phosphate ions decomplex Cu²⁺ displaying a fluorescence enhancement that can even be seen with naked eyes. The method was successfully used in quantitative determination of inorganic phosphates in serum, urine, and saliva samples.     

Photoreversible Assembly–Disassembly of a Polymeric Structure by Using an Azobenzene Photoswitch and Al3+ Ions

A nonmacrocyclic azobenzene‐based photochromic receptor in its E isomer forms an extended polymeric assembly with Al³⁺ ions. Exposure of the E form to UV light at λ=366 nm causes a disassembly of the polymeric structure due to the change in the molecular geometry of the ligand. The linear polymeric structure was regenerated on exposure to visible light.     

Kinetics and mechanism of biphasic substitution reactions of a platinum(II) complex with thioglycollic acid and 4-methyl-3-thiosemicarbazide in aqueous solution

The kinetics of interactions between cis-diaqua(2-aminomethylpyridine)platinum(II) perchlorate (1) [Pt(pic)(OH₂)₂](ClO₄)₂, thioglycollic acid (TGA), and 4-methyl-3-thiosemicarbazide (MTSC) have been studied spectrophotometrically in aqueous medium as a function of the [complex (1)] as well as [TGA] or [MTSC], pH and temperature at constant ionic strength. The observed pseudo-first-order rate constants were proportional to [TGA] or [MTSC]. At pH 4.0, the interactions of (1) with both TGA and MTSC show two distinct consecutive steps; the first step is dependent and second independent of [TGA] or [MTSC]. The association equilibrium constant (K _E) for the outer sphere complex formation has been evaluated, along with the rate constants for the two steps. The first step is assigned to ligand-assisted anation and the second to chelation of TGA or MTSC. The activation parameters for both the steps were evaluated using Eyring’s equation. On the basis of the kinetic observations and evaluated activation parameters, an associative mechanism is proposed for both the reactions.     

Non‐Equilibrium Polymerization of Cross‐β Amyloid Peptides for Temporal Control of Electronic Properties

Hydrophobic collapse plays crucial roles in protein functions, from accessing the complex three‐dimensional structures of native enzymes to the dynamic polymerization of non‐equilibrium microtubules. However, hydrophobic collapse can also lead to the thermodynamically downhill aggregation of aberrant proteins, which has interestingly led to the development of a unique class of soft nanomaterials. There remain critical gaps in the understanding of the mechanisms of how hydrophobic collapse can regulate such aggregation. Demonstrated herein is a methodology for non‐equilibrium amyloid polymerization through mutations of the core sequence of Aβ peptides by a thermodynamically activated moiety. An out of equilibrium state is realized because of the negative feedback from the transiently formed cross‐β amyloid networks. Such non‐equilibrium amyloid nanostructures were utilized to access temporal control over its electronic properties.