Robust and simple interface for microchip electrophoresis-mass spectrometry

A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was developed using a spray nozzle connected to the exit of the separation channel of the microchip. The spray nozzle was attached to the microchip using a polyether ether ketone screw without adhesive, thus allowing easy replaced. Sample injection and electrophoretic separation was performed by control of the voltage only. The analysis of a few basic drugs was performed using the optimized MCE-MS system. The separation was improved by using a high-viscosity separation buffer and a spray nozzle with a small bore size. This system was also applied to the separation of peptides and protein-trypsin digests. Sample adsorption was minimized by adding acetonitrile to the separation buffer when using a quartz microchip.     

The photochemical characteristics of aromatic enediyne compounds substituted with electron donating and electron withdrawing groups

trans- and cis-1-(4-Dimethylaminophenyl)-6-(4-nitrophenyl)hex-3-ene-1,5-diynes (trans- and cis-DANE) were synthesized and their photochemical properties were studied. The absorption spectra of trans-DANE red-shifted compared with the parent compound bisphenylethynylethene (BEE) due to intramolecular charge transfer. The fluorescence spectra, Stokes shift, fluorescence lifetime, fluorescence quantum yield, and quantum yield of trans-to-cis photoisomerization of trans-DANE showed strong dependence upon the solvent polarity in the less-polar region. No fluorescence emission from trans-DANE was observed in medium-polar and polar solvents. The quantum yield of cis-to-trans isomerization was almost solvent independent. The donor-acceptor substituents shifted the equilibrium between the trans perpendicular triplet state and the trans planar triplet state to the trans triplet state, and resulted in an increase in the triplet lifetime. Comparison of the photochemical properties of trans-DANE with trans-4-dimethylamino-4'-nitrostilbene (DANS) suggests that trans-DANE is a possible fluorescent probe in the non-polar region.     

Epoxidation of Allylic Alcohols with Hydrogen Peroxide Catalyzed by [PMO12O40]3-[C5H5N+(CH2)15CH3]3

Applicatims a Mo- and W-based heteropoly acids (HPA) as a catalyst in the oxidation of olefins have extensively been investigated¹. However, a patent work is only attempted concerning the evoxidatim of olefins with H₂0₂ by HPA²⁾ since the oxirane ring is cleaved because of a strong acidity of HPA itself. Herein, an effective epoxidatim of some allylic alcohols with H₂0₂ by a new Mo-species (MPCP), which was prepared from 12-molybdatophosphoric acid (H₃PMo₁₂0₄₀) and cetylpyridinium chloride (C₅H₅N (CH₂), ₁₅CH₃- C1^-) under two-phase conditions using chloroform as an organic solvent, is described.     

Modeling Thioredoxin Reductase-Like Activity with Cyclic Selenenyl Sulfides: Participation of an NH⋅⋅⋅Se Hydrogen Bond through Stabilization of the Mixed Se−S Intermediate

At the redox-active center of thioredoxin reductase (TrxR), a selenenyl sulfide (Se−S) bond is formed between Cys497 and Sec498, which is activated into the thiolselenolate state ([SH,Se⁻]) by reacting with a nearby dithiol motif ([SH^Cys59,SH^Cys64]) present in the other subunit. This process is achieved through two reversible steps: an attack of a cysteinyl thiol of Cys59 at the Se atom of the Se−S bond and a subsequent attack of a remaining thiol at the S atom of the generated mixed Se−S intermediate. However, it is not clear how the kinetically unfavorable second step progresses smoothly in the catalytic cycle. A model study that used synthetic selenenyl sulfides, which mimic the active site structure of human TrxR comprising Cys497, Sec498, and His472, suggested that His472 can play a key role by forming a hydrogen bond with the Se atom of the mixed Se−S intermediate to facilitate the second step. In addition, the selenenyl sulfides exhibited a defensive ability against H₂O₂-induced oxidative stress in cultured cells, which suggests the possibility for medicinal applications to control the redox balance in cells.     

An Alternative Method for the Stereospecific Synthesis of Conjugated Alkenynes Via the Copper (I) Iodide Assisted Cross-Coupling Reaction of 1-Akyens with Haloalkenes

Conjugated alkenynes were prepared stereospecifically in moderate to good yields by heating haloalkenes with 1-alkynes in the presence of copper(I) iodide in hexamethylphosphoric triamide (HMPA).     

Acceleration of Proliferative Response of Mouse Fibroblasts by Short-Time Pretreatment with Polyphenols

Under the hypothesis that photo-irradiated proanthocyanidin could accelerate wound healing through reactive oxygen species (ROS) formation, we examined the effect of proanthocyanidin on 3T3-L1 mouse fibroblasts with or without photo-irradiation. As a result, irrespective of presence or absence of photo-irradiation, only 1 min exposure of the cells to proanthocyanidin resulted in accelerated proliferation of the cells in a concentration-dependent manner. Similarly to proanthocyanidin, 1 min pretreatment with catechin, caffeic acid, and chlorogenic acid accelerated the proliferative response, but gallic acid, epicatechin gallate, epigallocatechin, and epigallocatechin gallate failed. If incorporated active ingredient such as proanthocyanidin for such a short time as 1 min accelerates the proliferation response, a bioassay was conducted by utilizing antioxidant potential of proanthocyanidin. That is, intracellular oxidation of 2′,7′-dichlorodihydrofluorescin induced by H₂O₂ was significantly inhibited when the cells were pretreated with proanthocyanidin for 1 min, suggesting that incorporated proanthocyanidin into the cells exerted antioxidant effect. This was also supported by a liquid chromatography/mass spectrometry analysis in which incorporation of proanthocyanidin components such as catechin monomers and dimers into the cells within 1 min was confirmed. These results suggest that active polyphenolic compounds such as proanthocyanidin, catechin, caffeic acid, and chlorogenic acid incorporated into the cells in such a short time as 1 min could accelerate the proliferative response of the cells.     

Complexation Constants of Lanthanide Ions with Poly(Methacrylic Acid) and its Copolymers

Complexation of some lanthanide ions with poly(methacrylic acid) and its copolymers was studied by potentiometric titration. Poly [methacrylic acid-co-oligo(ethylene oxide)methacrylate] and poly(methacrylic acid-co-acrylamide) formed tris-carboxylate coordinate lanthanide complexes with large overall complexation constants, while poly-(methacrylic acid)s and copolymer with higher content of the methacrylic acid residue formed bis-coordinate ones. It was concluded that the comonomer residues in the copolymer chains decreased the steric hindrance for the complexation and/or acted as co-coordinating groups of the carboxylic group to lanthanide ions. Very large positive and favorable entropy changes were observed for the complexation with poly(methacrylic acid) and its copolymers. This contribution of thermodynamic parameters to the complexation was contrary to that for the analogous monomeric methacrylic acid complex and is assumed to be induced by dehydration of the polymers through the lanthanide ion complexation.     

Biosynthetic Conclusions from the Functional Dissection of Oxygenases for Biosynthesis of Actinorhodin and Related Streptomyces Antibiotics

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Highlights? ActVA-ORF5 is a flavin-dependent monooxygenase required for actinorhodin biosynthesis ? ActVA-ORF5 and its three close homologs were functionally dissected ? ActVA-ORF5 and Gra-21 are bifunctional at C-6/C-8, while Med-7 acts only for C-6 ? AlnT exhibits different regiospecificity for oxidation of tricyclic substrates     

Excited state intramolecular hydrogen atom transfer of phenylethynyl-substituted 2′-hydroxychalcones

(E)-1-[2-Hydroxy-4-(phenylethynyl)phenyl]-3-[4-(phenylethynyl)phenyl]prop-2-en-1-one (1), (E)-1-[2-hydroxy-4-(phenylethynyl)phenyl]-3-phenylprop-2-en-1-one (2), and (E)-1-(2-hydroxyphenyl)-3-[4-(phenylethynyl)phenyl]prop-2-en-1-one (3), which belong to a new class of 2′-hydroxychalcones with phenylethynyl group(s) at the para position of the phenyl ring, were synthesized, and their photochemical properties were investigated. The lowest energy absorption band of 1 peaks at a longer wavelength (383 nm) with a much larger molar extinction coefficient (5.0 × 10⁴ M ^?1 cm^?1) than that of the parent 2′-hydroxychalcone (2′HC) (2.0 × 10⁴ M ^?1 cm^?1 at 318 nm). Upon photoexcitation, all three compounds underwent excited-state intramolecular hydrogen atom transfer (ESIHT) to produce an excited tautomer that emitted fluorescence with a large Stokes shift in the longer wavelength region at 600–700 nm. The quantum yield of the tautomer fluorescence of 1 was not high at 298 K (Φ _f = 9.1 × 10^?5), but was highest among 2′HC and its analogues. The Φ _f values of 1–3 increased 10–30 fold upon reducing the temperature from 298 to 77 K.