A novel synthetic method for 2-arylmethyl substituted imidazolines and imidazoles from 2-aryl-1,1-dibromoethenes

Various 2-arylmethylimidazolines were prepared by treating readily available 2-aryl-1,1-dibromoethenes with ethylenediamine under mild conditions and further converted into the corresponding imidazoles smoothly with Swern oxidation.     

Temperature effect on nanometer-scale physical properties of mixed phospholipid monolayers

Mixed dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) monolayers have been deposited on mica using Langmuir-Blodgett technique, as a model system for biomembranes. Nanometer-scale surface physical properties were quantitatively characterized with the gradual temperature change using the atomic force microscope. At 25 degrees C, tapping mode imaging revealed the clear phase-separation in the form of microscopic DPPC domain embedded in a DOPC matrix and the obvious step height between the higher DPPC phase and the lower DOPC phase. Surface force measurement made at 25 degrees C in contact mode showed significant contrasts in deformation elasticity, adhesion, and jump-to-surface. These physical property differences were kept below 40 degrees C, while they almost disappeared over 40 degrees C. In addition, the reversibility of the properties for the temperature change was also found.     

Electrochemical characterization of negative electrodes consisting of surface-modified Zr0.9Ti0.1(Ni1.1Co0.1Mn0.5V0.2Cr0.1)x Laves-phase alloys

Laves-phase hydrogen storage alloy has a high potential for use as negative electrode material as alternative for the misch-metal-based material. In order to improve the energy density and the rate capability of negative electrode, chemical and mechanical modification of Lavesphase alloy with different stoichiometric ratios was carried out. Discharge capacity and high-rate dischargeabilty was evaluated by electrochemical methods and the characterization of Laves-phase alloy was made by X-ray diffraction, SEM observation and PCT measurement. The best result in discharge capacity could be obtained for stoichiometric Laves-phase alloy with a composition of Zr_0.9Ti_0.1Ni_1.1Co_0.1Mn_0.5V_0.2Cr_0.1 by boiling in 10 M KOH solution. On the other hand, the high-rate dischargeability was increased remarkably by introducing mechanical grinding before alkali treatment. The cause for improved performance was discussed on the basis of thermodynamic stability of metal hydride and changes in crystal structure and surface morphology influencing on diffusion coefficient and diffusion path length of hydrogen.     

A molecular approach to rationally constructing specific fluorogenic substrates for the detection of acetylcholinesterase activity in live cells,mice brains and tissues

Acetylcholinesterase (AChE) is an extremely critical hydrolase tightly associated with neurological diseases. Currently, developing specific substrates for imaging AChE activity still remains a great challenge due to the interference from butyrylcholinesterase (BChE) and carboxylesterase (CE). Herein, we propose an approach to designing specific substrates for AChE detection by combining dimethylcarbamate choline with a self-immolative scaffold. The representative P10 can effectively eliminate the interference from CE and BChE. The high specificity of P10 has been proved via imaging AChE activity in cells. Moreover, P10 can also be used to successfully map AChE activity in different regions of a normal mouse brain, which may provide important data for AChE evaluation in clinical studies. Such a rational and effective approach can also provide a solid basis for designing probes with different properties to study AChE in biosystems and another way to design specific substrates for other enzymes.

In this work, a new approach was developed for designing the representative P10 with high selectivity and sensitivity for imaging AChE activity in the cells and normal mouse brain.     

A Family of Molecular Sieves Containing Framework‐Bound Organic Structure‐Directing Agents

Organic structure‐directing agents (OSDAs), such as quaternary ammonium cations and amines, used in the synthesis of zeolites and related crystalline microporous oxides usually end up entrapped inside the void spaces of the crystallized inorganic host lattice. But none of them is known to form direct chemical bonds to the framework of these industrially important catalysts and adsorbents. We demonstrate that ECR‐40, currently regarded as a typical silicoaluminophosphate molecular sieve, constitutes instead a new family of inorganic‐organic hybrid networks in which the OSDAs are covalently bonded to the inorganic framework. ECR‐40 crystallization begins with the formation of an Al–OSDA complex in the liquid phase in which the Al is octahedrally coordinated. This unit is incorporated in the crystallizing ECR‐40. Subsequent removal of framework‐bound OSDAs generates Al‐O‐Al linkages in a fully tetrahedrally coordinated framework.     

The Role of Methoxy Group in the Nazarov Cyclization of 1,5-bis-(2-Methoxyphenyl)-1,4-Pentadien-3-one in the Gas Phase and Condensed Phase

ESI-protonated 1,5-bis-(2-methoxyphenyl)-1,4-pentadien-3-one (1) undergoes a gas-phase Nazarov cyclization and dissociates via expulsions of ketene and anisole. The dissociations of the [M + D]⁺ ions are accompanied by limited HD scrambling that supports the proposed cyclization. Solution cyclization of 1 was effected to yield the cyclic ketone, 2,3-bis-(2-methoxyphenyl)-cyclopent-2-ene-1-one, (2) on a time scale that is significantly shorter than the time for cyclization of dibenzalacetone. The dissociation characteristics of the ESI-generated [M + H]⁺ ion of the synthetic cyclic ketone closely resemble those of 1, suggesting that gas-phase and solution cyclization products are the same. Additional mechanistic studies by density functional theory (DFT) methods of the gas-phase reaction reveals that the initial cyclization is followed by two sequential 1,2-aryl migrations that account for the observed structure of the cyclic product in the gas phase and solution. Furthermore, the DFT calculations show that the methoxy group serves as a catalyst for the proton migrations necessary for both cyclization and fragmentation after aryl migration. An isomer formed by moving the 2-methoxy to the 4-position requires relatively higher collision energy for the elimination of anisole, as is consistent with DFT calculations. Replacement of the 2-methoxy group with an OH shows that the cyclization followed by aryl migration and elimination of phenol occurs from the [M + H]⁺ ion at low energy similar to that for 1.

Nanocatalyst-based assay using DNA-conjugated Au nanoparticles for electrochemical DNA detection

Compared to enzymes, Au nanocatalysts show better long-term stability and are more easily prepared. Au nanoparticles (AuNPs) are used as catalytic labels to achieve ultrasensitive DNA detection via fast catalytic reactions. In addition, magnetic beads (MBs) are employed to permit low nonspecific binding of DNA-conjugated AuNPs and to minimize the electrocatalytic current of AuNPs as well as to take advantage of easy magnetic separation. In a sandwich-type electrochemical sensor, capture-probe-conjugated MBs and an indium-tin oxide electrode modified with a partially ferrocene-modified dendrimer act as the target-binding surface and the signal-generating surface, respectively. A thiolated detection-probe-conjugated AuNP exhibits a high level of unblocked active sites and permits the easy access of p-nitrophenol and NaBH 4 to these sites. Electroactive p-aminophenol is generated at these sites and is then electrooxidized to p-quinoneimine at the electrode. The p-aminophenol redox cycling by NaBH 4 offers large signal amplification. The nonspecific binding of detection-probe-conjugated AuNPs is lowered by washing DNA-linked MB-AuNP assemblies with a formamide-containing solution, and the electrocatalytic oxidation of NaBH 4 by AuNPs is minimized because long-range electron transfer between the electrode and the AuNPs bound to MBs is not feasible. The high signal amplification and low background current enable the detection of 1 fM target DNA.     

Disulfide bond cleavage in TEMPO-free radical initiated peptide sequencing mass spectrometry

The gas‐phase free radical initiated peptide sequencing (FRIPS) fragmentation behavior of o‐TEMPO‐Bz‐conjugated peptides with an intra‐ and intermolecular disulfide bond was investigated using MSⁿ tandem mass spectrometry experiments. Investigated peptides included four peptides with an intramolecular cyclic disulfide bond, Bactenecin (RLC RIVVIRVC R), TGF‐α (C HSGYVGVRC ), MCH (DFDMLRC MLGRVFRPC WQY) and Adrenomedullin (16–31) (C RFGTC TVQKLAHQIY), and two peptides with an intermolecular disulfide bond. Collisional activation of the benzyl radical conjugated peptide cation, which was generated through the release of a TEMPO radical from o‐TEMPO‐Bz‐conjugated peptides upon initial collisional activation, produced a large number of peptide backbone fragments in which the S? S or C? S bond was readily cleaved. The observed peptide backbone fragments included a‐, c‐, x‐ or z‐types, which indicates that the radical‐driven peptide fragmentation mechanism plays an important role in TEMPO‐FRIPS mass spectrometry. FRIPS application of the linearly linked disulfide peptides further showed that the S? S or C? S bond was selectively and preferentially cleaved, followed by peptide backbone dissociations. In the FRIPS mass spectra, the loss of ?SH or ?SSH was also abundantly found. On the basis of these findings, FRIPS fragmentation pathways for peptides with a disulfide bond are proposed. For the cleavage of the S? S bond, the abstraction of a hydrogen atom at C_β by the benzyl radical is proposed to be the initial radical abstraction/transfer reaction. On the other hand, H‐abstraction at C_α is suggested to lead to C? S bond cleavage, which yields [ion ± S] fragments or the loss of ?SH or ?SSH. Copyright © 2011 John Wiley & Sons, Ltd.     

Ultraviolet-A irradiation to the eye modulates intestinal mucosal functions and properties of mast cells in the mouse

We previously reported that topical irradiation of the eye by ultraviolet-B (UVB) activated hypothalamo-pituitary-adrenal axis (HPA-A) of the mouse to increase 3, 4-dihydroxyphenylalanine (DOPA)-positive melanocytes in the skin by an inducible nitric oxide synthase (iNOS)-dependent mechanism. This work demonstrates that irradiation of the eye by ultraviolet-A (UVA) specifically increased DOPA-positive cells in the mucosa of the jejunum and colon of C57BL/6J mice by some HPA- and iNOS-independent mechanism. UVA-induced increase in DOPA-positive cells in the intestine was inhibited by the administration of hexamethonium or prazosin plus propranolol, blockers for the sympathetic nervous system. UVA irradiation of the eye increased DOPA- and histidine decarboxylase (HDC)-positive cells in the intestinal mucosa of both C57BL/6J and WBB6F1/J mice but not in the mutant strain W/Wv of the latter that lack mast cells. UVA irradiation of the eye suppressed the intestinal peristalsis of control, hypophysectomized or iNOS(-/-) C57BL/6J mice by the mechanism that was inhibited by hexamethonium or prazosin plus propranolol. These observations suggest that UVA irradiation of the eye stimulated the sympathetic nervous system to increase the mucosal DOPA- and HDC-positive mast cells and suppressed the peristalsis of the small intestine of the mouse.     

Hydrolytic Transformation of Microporous Metal–Organic Frameworks to Hierarchical Micro‐ and Mesoporous MOFs

A new approach to the synthesis of hierarchical micro‐ and mesoporous MOFs from microporous MOFs involves a simple hydrolytic post‐synthetic procedure. As a proof of concept, a new microporous MOF, POST‐66(Y), was synthesized and its transformation into a hierarchical micro‐ and mesoporous MOF by water treatment was studied. This method produced mesopores in the range of 3 to 20 nm in the MOF while maintaining the original microporous structure, at least in part. The degree of micro‐ and mesoporosity can be controlled by adjusting the time and temperature of hydrolysis. The resulting hierarchical porous MOF, POST‐66(Y)‐wt, can be utilized to encapsulate nanometer‐sized guests such as proteins, and the enhanced stability and recyclability of an encapsulated enzyme is demonstrated.