Analysis of melamine cyanurate in urine using matrix-assisted laser desorption/ionization mass spectrometry.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was applied to the direct analysis of melamine cyanurate (MC). The three commonly used MALDI matrixes, namely, alpha-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA), and 2,5-dihydroxybenzoic acid (DHB), were able to desorb/ionize melamine from MC upon N(2) laser irradiation, with CHCA showing the highest detection sensitivity in the positive mode. Only DHB and SA were able to desorb/ionize cyanuric acid from MC in the negative mode but with remarkably lower sensitivity.

Mitogen-activated protein kinase (MAPK) pathway mediates the oestrogen-like activities of ginsenoside Rg1 in human breast cancer (MCF-7) cells.

Background And Purpose: The present study was designed to determine how ginsenoside Rg1, an active ingredient in ginseng root, exerts its oestrogenic effects. We hypothesize that Rg1 may exert oestrogen-like actions in MCF-7 cells by activating the mitogen-activated protein kinase (MAPK) pathway in a ligand-independent manner.

Experimental Approach: MCF-7 cells were co-incubated with the MAPK inhibitor PD98059 to determine whether the stimulant effects of Rg1 on cell proliferation, the induction of IGF-IR and pS2, the functional transactivation of oestrogen receptor-alpha (ERalpha), as well as ERalpha phosphorylation are dependent on MAPK.

Flavonoid dimers as bivalent modulators for p-glycoprotein-based multidrug resistance: structure-activity relationships.

We recently described the modulatory activities of apigenin homodimers linked by ethylene glycol units in multidrug- resistant breast cancer and leukemic cells overexpressing ABCB1 (P-glycoprotein, P-gp). To further improve the potency of these dimers, a small library of flavonoid homodimers and heterodimers were synthesized, and their in vitro activity in reversing cellular resistance to paclitaxel, along with structure-activity relationships (SAR), were evaluated using a P-gp-expressing human breast cancer cell line. Among these synthesized homodimers, many showed more potent reversing activity than that of the parent compound and verapamil.

Inter- and intramolecular [4 + 3] cycloadditions using epoxy enol silanes as functionalized oxyallyl cation precursors.

Using epoxy enol triethylsilanes as oxyallyl cation precursors, [4 + 3] cycloadditions with various dienes occur under catalysis by silyl triflates and acids in good yields. The intramolecular [4 + 3] cycloaddition proceeds under mild conditions and generate hydroxylated cycloadducts with high diastereoselectivity and yields. Enantiomerically pure epoxy enol silanes have been shown to give excellent yields of the optically pure cycloadduct bearing multiple stereocenters.

Electron-deficient alkynes as cleavable reagents for the modification of cysteine-containing peptides in aqueous medium.

An efficient method has been developed for the chemoselective cysteine modification of unprotected peptides and proteins in aqueous media through the formation of a vinyl sulfide linkage by using electron-deficient alkynes, including alkynoic amides, esters and alkynones. The terminal alkynone-modified peptides could be converted back into the unmodified peptides (81% isolated yield) by adding thiols under mild conditions. The usefulness of this thiol-assisted cleavage of the vinyl sulfide linkage in peptides has been exemplified by the enrichment of a cysteine-containing peptide (71% recovery) from a mixture of cysteine-containing and non-cysteine-containing peptides.

Biomimetic total synthesis of (+/-)-pallavicinolide A.

Piecing it together: The first total synthesis of naturally occurring diterpene pallavicinolide A was achieved. Notable features are highlighted by three key biomimetic transformations: a base-promoted Grob fragmentation, a singlet oxygen oxidation, and an intramolecular Diels-Alder cycloaddition.

Highly efficient and regioselective platinum(II)-catalyzed tandem synthesis of multiply substituted indolines and tetrahydroquinolines.

A special advantage: The platinum(II)-catalyzed tandem cyclization of aminoalkynes with 1,3-diketones offers a new and highly efficient method for the synthesis of indolines and tetrahydroquinolines (see scheme; M.S. = molecular sieves).

Cyclometalated platinum(II) complexes as highly sensitive luminescent switch-on probes for practical application in protein staining and cell imaging.

Protein-staining platinum: The luminescent switch-on characteristic of the platinum(II) complex can be utilized for staining a series of proteins in sodium dodecyl sulfate-polyarcylamide gels, to give emissive gel images directly under UV light (see figure). The detection sensitivity for BSA protein is down to 6.0 ng, revealing potential practical applications of luminescent platinum(II) complexes in the luminescent signaling of biomolecules.

Novel classes of dimer antitumour drug candidates.

Polyvalency in the biological world is defined as the simultaneous binding of multiple ligands to one receptor. Polyvalency can increase the affinity of the polyvalent ligand by 100-1000 fold over the monovalent ligand. Such phenomenon has been employed to design polyvalent toxin inhibitors.

Palladium-indolylphosphine-catalyzed Hiyama cross-coupling of aryl mesylates.

Aryl mesylates are found to be applicable as electrophiles in organosilicon-mediated coupling reactions. The catalyst system comprising 2 mol % of Pd(OAc)(2) and CM-phos supporting ligand is highly effective in catalyzing Hiyama cross-coupling of various aryl and heteroaryl mesylates. Interesting acid additive effects show that the presence of 0.

Palladium-catalyzed cross coupling reaction of benzyl bromides with diazoesters for stereoselective synthesis of (E)-alpha,beta-diarylacrylates.

A Pd-catalyzed cross-coupling reaction of benzyl bromides with alpha-aryldiazoesters is described, and E-alpha,beta-diarylacrylates were obtained in good yields and excellent E-to-Z selectivity (>20:1).

Timosaponin A-III induces autophagy preceding mitochondria-mediated apoptosis in HeLa cancer cells.

Timosaponin A-III (TAIII), a saponin isolated from the rhizome of Anemarrhena asphodeloides, exhibits potent cytotoxicity and has the potential to be developed as an anticancer agent. Here, we provide evidence that TAIII induces autophagy in HeLa cells followed by apoptotic cell death. TAIII-induced autophagy was morphologically characterized by the formation of membrane-bound autophagic vacuoles recognizable at the ultrastructural level.

Persistence of camptothecin analog-topoisomerase I-DNA ternary complexes: a molecular dynamics study.

Topoisomerase I (top1) is the sole chemotherapeutic target for the anticancer alkaloid camptothecin and its analogs (CPTs). The CPTs mediate cytotoxicity by binding reversibly to transient top1-DNA covalent complexes. There is significant variation in the persistence of the resultant CPTs-top1-DNA ternary complexes formed.

Platinum(II) complexes with dipyridophenazine ligands as human telomerase inhibitors and luminescent probes for G-quadruplex DNA.

A series of platinum(II) complexes containing dipyridophenazine (dppz) and C-deprotonated 2-phenylpyridine (N-CH) ligands were prepared and assayed for G-quadruplex DNA binding activities. [PtII(dppz-COOH)(N-C)]CF3SO3 (1; dppz-COOH = 11-carboxydipyrido[3,2-a:2',3'-c]phenazine) binds G-quadruplex DNA through an external end-stacking mode with a binding affinity of approximately 10(7) dm3 mol-1. G-quadruplex DNA binding is accompanied by up to a 293-fold increase in the intensity of photoluminescence at lambdamax = 512 nm.

Trityl-derivatized carbohydrates immobilized on a polystyrene microplate.

Carbohydrate biosensors, including carbohydrate arrays, are attracting increased attention for the comprehensive and high-throughput investigation of protein-carbohydrate interactions. Here, we describe an effective approach to fabricating a robust microplate-based carbohydrate array capable of probing protein binding and screening for inhibitors in a high-throughout manner. This approach involves the derivatization of carbohydrates with a trityl group through an alkyl linker and the immobilization of the trityl-derivatized carbohydrates (mannose and maltose) onto microplates noncovalently to construct carbohydrate arrays.

Structures and solvatochromic phosphorescence of dicationic terpyridyl-platinum(II) complexes with foldable oligo(ortho-phenyleneethynylene) bridging ligands.

A series of binuclear organoplatinum(II) complexes, [(tBu3tpy)Pt--(C[triple chemical bond]C--1,2-C6H4)n--C[triple chemical bond]C--Pt(tBu3tpy)][ClO4]2 (1-7, n=1, 2, 3, 4, 5, 6, 8; tBu3tpy=4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine) with foldable oligo(ortho-phenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 32.5 CH3OH, 5CH3CN, and 64 CH3CN, each of the bridging ortho-phenyleneethynylene ligands has a partially folded conformation.

Primary and secondary phosphine complexes of iron porphyrins and ruthenium phthalocyanine: synthesis, structure, and P-H bond functionalization.

Reduction of [Fe(III)(Por)Cl] (Por = porphyrinato dianion) with Na2S2O4 followed by reaction with excess PH2Ph, PH2Ad, or PHPh2 afforded [Fe(II)(F20-TPP)(PH2Ph)2] (1a), [Fe(II)(F20-TPP)(PH2Ad)2] (1b), [Fe(II)(F20-TPP)(PHPh2)2] (2a), and [Fe(II)(2,6-Cl2TPP)(PHPh2)2] (2b). Reaction of [Ru(II)(Pc)(DMSO)2] (Pc = phthalocyaninato dianion) with PH2Ph or PHPh2 gave [Ru(II)(Pc)(PH2Ph)2] (3a) and [Ru(II)(Pc)(PHPh2)2] (4). [Ru(II)(Pc)(PH2Ad)2] (3b) and [Ru(II)(Pc)(PH2Bu(t))2] (3c) were isolated by treating a mixture of [Ru(II)(Pc)(DMSO)2] and O=PCl2Ad or PCl2Bu(t) with LiAlH4.

Suzuki-Miyaura coupling of aryl tosylates catalyzed by an array of indolyl phosphine-palladium catalysts.

A family of indolyl phosphine ligands was applied to Suzuki-Miyaura cross-coupling of aryl tosylates. Catalyst loading can be reduced to 0.2 mol % for coupling of nonactivated aryl tosylate.

A new family of tunable indolylphosphine ligands by one-pot assembly and their applications in Suzuki-Miyaura coupling of aryl chlorides.

This study describes a new class of indolylphosphine ligands, which can be easily accessed by a simple one-pot assembly from commercially available indoles, acid chlorides, and chlorophosphines. A combination of these three starting materials provides a high diversification of the ligand structure. The application of this ligand array in palladium-catalyzed Suzuki-Miyaura coupling reaction of aryl chlorides with arylboronic acids is described.

Mitochondrial dysfunction contributes to the increased vulnerabilities of adiponectin knockout mice to liver injury.

Unlabelled: Adiponectin is an adipocyte-derived hormone with a wide range of beneficial effects on obesity-related medical complications. Numerous epidemiological investigations in diverse ethnic groups have identified a lower adiponectin level as an independent risk factor for nonalcoholic fatty liver diseases and liver dysfunctions. Animal studies have demonstrated that replenishment of adiponectin protects against various forms of hepatic injuries, suggesting it to be a potential drug candidate for the treatment of liver diseases.

Hepatocyte nuclear factor 1 binding element within the promoter of microsomal triglyceride transfer protein (MTTP) gene is crucial for MTTP basal expression and insulin responsiveness.

Insulin inhibits the transcription of the microsomal triglyceride transfer protein (MTTP), which plays a pivotal role in lipoprotein assembly and secretion. Here, we provide evidence that a hepatocyte nuclear factor 1 binding element (HNF1A element) within the MTTP promoter serves as a novel negative insulin-responsive element. Deletion/mutation mapping of the MTTP gene promoter identified a modified HNF1A element that is crucial to the negative insulin effect.

Gold(I)-catalyzed intermolecular hydroarylation of alkenes with indoles under thermal and microwave-assisted conditions.

An efficient method for intermolecular hydroarylation of aryl and aliphatic alkenes with indoles using a combination of [(PR(3))AuCl]/AgOTf as catalyst under thermal and microwave-assisted conditions has been developed. The gold(I)-catalyzed reactions of indoles with aryl alkenes were achieved in toluene at 85 degrees C over a reaction time of 1-3 h with 2 mol% of [(PR(3))AuCl]/AgOTf as catalyst. This method works for a variety of styrenes bearing electron-deficient, electron-rich, and sterically bulky substituents to give the corresponding products in good to high yields (60-95%).

A non-cross-linked soluble polystyrene-supported ruthenium catalyst for carbenoid transfer reactions.

Ruthenium nanoparticles supported on non-cross-linked soluble polystyrene were prepared by reacting [RuCl(2)(C(6)H(5)CO(2)Et)](2) with polystyrene in open air. They effectively catalyze intra- and intermolecular carbenoid insertion into C-H and N-H bonds, alkene cyclopropanation, and ammonium ylide/[2,3]-sigmatropic rearrangement reactions. This supported ruthenium catalyst is much more reactive than [RuCl(2)(p-cymene)](2) and [Ru(Por)CO] for catalytic intermolecular carbenoid C-H bond insertion into saturated alkanes.