Synthesis and structural aspects of N-triflylphosphoramides and their calcium salts--highly acidic and effective Brønsted acids

Recently, 1,1′‐bi‐2‐naphthol (BINOL)‐based N‐triflylphosphoramides emerged as a new class of potent Brønsted acid catalysts. In this paper we describe the efficient synthesis of various BINOL‐based N‐triflylphosphoramides and their calcium salts. Furthermore, X‐ray crystal structure analysis combined with energy‐dispersive X‐ray spectroscopy (EDX) measurements confirmed that the synthesised chiral N‐triflylphosphoramides are highly acidic metal‐free catalysts.     

A Reusable DNA Single‐Walled Carbon‐Nanotube‐Based Fluorescent Sensor for Highly Sensitive and Selective Detection of Ag+ and Cysteine in Aqueous Solutions

Here we report a reusable DNA single‐walled carbon nanotube (SWNT)‐based fluorescent sensor for highly sensitive and selective detection of Ag⁺ and cysteine (Cys) in aqueous solution. SWNTs can effectively quench the fluorescence of dye‐labeled single‐stranded DNA due to their strong π–π stacking interactions. However, upon incubation with Ag⁺, Ag⁺ can induce stable duplex formation mediated by C–Ag⁺–C (C=cytosine) coordination chemistry, which has been further confirmed by DNA melting studies. This weakens the interactions between DNA and SWNTs, and thus activates the sensor fluorescence. On the other hand, because Cys is a strong Ag⁺ binder, it can remove Ag⁺ from C–Ag⁺–C base pairs and deactivates the sensor fluorescence by rewrapping the dye‐labeled oligonucleotides around the SWNT. In this way, the fluorescence signal‐on and signal‐off of a DNA/SWNT sensor can be used to detect aqueous Ag⁺ and Cys, respectively. This sensing platform exhibits high sensitivity and selectivity toward Ag⁺ and Cys versus other metal ions and the other 19 natural amino acids, with a limit of detection of 1 nM for Ag⁺ and 9.5 nM for Cys. Based on these results, we have constructed a reusable fluorescent sensor by using the covalent‐linked SWNT–DNA conjugates according to the same sensing mechanism. There is no report on the use of SWNT–DNA assays for the detection of Ag⁺ and Cys. This assay is simple, effective, and reusable, and can in principle be used to detect other metal ions by substituting C–C base pairs with other native or artificial bases that selectively bind to other metal ions.     

Immunosuppressive Resveratrol Aneuploids from Hopea chinensis

Two novel resveratrol aneuploids, hopeachinols A ( 1 ) and B ( 2 ), as well as a potent immunosuppressive polyphenol diptoindonesin G ( 3 ) were characterized from the ethanol extract of Hopea chinensis stem barks. The structure of the polyphenols was accommodated by comprehensive spectroscopic analysis with the absolute stereochemistry determined by the CD approach coupled with theoretical ECD spectra computer‐generated through the Gaussian 03 program. The distinct structure and biological profile of 3 recommended it as a starting molecule for the relevant drug discovery.     

On-line coupling of in-tube boronate affinity solid phase microextraction with high performance liquid chromatography-electrospray ionization tandem mass spectrometry for the determination of cis-diol biomolecules

Boronate affinity solid phase microextraction (BA-SPME) is a new format appeared recently with great potential for specific extraction of cis-diol-containing compounds. Unlike conventional SPME, BA-SPME relies on covalent interactions and thereby features with specific selectivity, eliminated matrix effect and manipulable capture/release. However, only on-fiber BA-SPME and its off-line combination with high performance liquid chromatography (HPLC) have been reported so far. In this study, we report on-line coupling of in-tube BA-SPME with HPLC-electrospray ionization tandem mass spectroscopy (in-tube BA-SPME-HPLC-ESI-MS/MS) for the specific and sensitive determination of cis-diol-containing biomolecules. A boronate affinity extraction phase was prepared onto the inner surface of the capillary by copolymerization of vinylphenylboronic acid (VPBA) and ethylene glycol dimethacrylate (EDMA). The extraction conditions were optimized by choosing appropriate extraction/desorption solutions and extraction time. The extraction capacity, linear range, reproducibility and life-time were investigated. The developed method was successfully applied for the determination of dopamine in urine samples. Since many cis-diol-containing compounds are of great biological importance, the in-tube BA-SPME-HPLC method can be a promising tool.     

Three New Sesquiterpenoids from Echinops ritro L.

From the whole plants of E. ritro L., the three new sesquiterpenoids (3α,4α,6α)‐3,13‐dihydroxyguaia‐7(11),10(14)‐dieno‐12,6‐lactone ( 1 ), (3α,4α,6α,11β)‐3‐hydroxyguai‐1(10)‐eno‐12,6‐lactone ( 2 ), and (11α)‐11,13‐dihydroarglanilic acid methyl ester (=(4β,6α,11α)‐4,6‐dihydroxy‐1‐oxoeudesm‐2‐en‐12‐oic acid methyl ester; 3 ), together with eight known sesquiterpenoids, were isolated. Their structures were elucidated through analysis of spectroscopic data including extensive 2D‐NMR.     

Spectroscopic Studies on the Interaction of 2,4-Dichlorophenol with Bovine Serum Albumin

The interaction between 2,4-dichlorophenol (DCP) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-vis absorption and circular dichroism (CD) spectroscopy under simulative physiological conditions. The experiment results show that the fluorescence intensity of BSA is dramatically decreased owing to the formation of a DCP–BSA complex. The corresponding effective quenching constants (K _a) between DCP and BSA at four different temperatures (292, 298, 304 and 310 K) were determined to be 10.08×10⁴, 9.082×10⁴, 8.177×10⁴, and 7.260×10⁴ L?mol^?1, respectively. The thermodynamics parameters enthalpy change (ΔH) and entropy change (ΔS) were calculated to be ?13.64 kJ?mol^?1 and 49.08 J?mol^?1?K^?1, which suggested that hydrophobic interaction was the predominant intermolecular force. Site marker competitive experiments indicated that the binding of DCP to BSA primarily takes place in subdomain IIA. The binding distance (r) between DCP and the tryptophan residue of BSA ias 4.09 nm according to Förster’s theory of non-radioactive energy transfer. The conformational investigation demonstrated that the presence of DCP decreased the α-helical content of BSA and induced a slight unfolding of the polypeptides of protein, which confirmed the occurrence some micro environmental and conformational changes of BSA molecules.     

A novel method for D-arabinitol determination based on a nano-structured sensing film by one-step electrodeposition

Copper nanoparticles (Cu-NPs) were incorporated into chitosan hydrogel to form a film on the surface of a glassy carbon electrode (GCE) leading to a sensing element for D-arabinitol with excellent oxidative catalytic activity. The electrochemical response to D-arabinitol was studied by cyclic voltammetry and differential pulse voltammetry. Operational parameters affecting the response were examined and optimized, and a simple and sensitive method was established for the determination of D-arabinitol. Response is linear in the concentration range from 10 μmol·L^?1 to 10 mmol·L^?1, and the limit of detection is 1.0 μmol·L^?1. The method may be combined with separation techniques in order to analyze for the ratio of D- and L-arabinitol which is a diagnostic marker for candidiasis.     

Dual functional polyelectrolyte multilayer coatings for implants: permanent microbicidal base with controlled release of therapeutic agents

Here we present a new bifunctional layer-by-layer (LbL) construct made by combining a permanent microbicidal polyelectrolyte multilayered (PEM) base film with a hydrolytically degradable PEM top film that offers controlled and localized delivery of therapeutics. Two degradable film architectures are presented: (1) bolus release of an antibiotic (gentamicin) to eradicate initial infection at the implant site, or (2) sustained delivery of an anti-inflammatory drug (diclofenac) to cope with inflammation at the site of implantation due to tissue injury. Each degradable film was built on top of a permanent base film that imparts the implantable device surface with microbicidal functionality that prevents the formation of biofilms. Controlled-delivery of gentamicin was demonstrated over hours and that of diclofenac over days. Both drugs retained their efficacy upon release. The permanent microbicidal base film was biocompatible with A549 epithelial cancer cells and MC3T3-E1 osteoprogenitor cells, while also preventing bacteria attachment from turbid media for the entire duration of the two weeks studied. The microbicidal base film retains its functionality after the biodegradable films have completely degraded. The versatility of these PEM films and their ability to prevent biofilm formation make them attractive as coatings for implantable devices.     

Establishment of a High Expression of α1A Adrenergic Receptor Cell Membrane Chromatography-RPLC Method for Screening Target Components from Radix Caulophylli

We describe here an analytical method of HEK293 α_1A AR cell membrane chromatography (HEK293 α_1A AR/CMC) combined with reverse phase liquid chromatography (RPLC) for recognition, separation and identification of target components from Traditional Chinese Medicines (TCMs) Radix Caulophylli. The HEK 293 α_1A cells with high expressing α_1A adrenergic receptors were used to prepare the stationary phase in the CMC model. Retention fractions on the α_1A AR–CMC model were collected using an automated fraction collection and injection module (FC/I). And each fraction was analyzed by RPLC under optimized conditions. 5-Methylurapidil (5-MU) and tamsulosin hydrochloride were used as standard compounds to investigate the suitability and reliability of the HEK 293 α_1A AR–CMC–RPLC method prior to screening target component from Radix Caulophylli total alkaloid. The results indicated that caulophine was the target component acting on the α_1A AR. This method could be an efficient way in drug discovery using natural medicinal herbs as a source of novel compounds.