Effective disruption of phosphoprotein-protein surface interaction using Zn(II) dipicolylamine-based artificial receptors via two-point interaction

Protein phosphorylation is ubiquitously involved in living cells, and it is one of the key events controlling protein-protein surface interactions, which are essential in signal transduction cascades. We now report that the small molecular receptors bearing binuclear Zn(II)-Dpa can strongly bind to a bis-phosphorylated peptide in a cross-linking manner under neutral aqueous conditions when the distance between the two Zn(II) centers can appropriately fit in that of the two phosphate groups of the phosphorylated peptide. The binding property was quantitatively determined by ITC (isothermal titration calorimetry), induced CD (circular dichroism), and NMR. On the basis of these findings, we demonstrated that these types of small molecules were able to effectively disrupt the phosphoprotein-protein interaction in a phosphorylated CTD peptide and the Pin1 WW domain, a phosphoprotein binding domain, at a micromolar level. The strategy based on a small molecular disruptor that directly interacts with phosphoprotein is unique and should be promising in developing a designer inhibitor for phosphoprotein-protein interaction.     

Determination of erythromycin A in rat plasma and urine by high-performance liquid chromatography with chemiluminescence detection using Tris(2,2'-bipyridine)ruthenium(II)

A simple and sensitive method was developed for the determination of erythromycin A (EA), decladinosyl erythromycin A (dClEA) and erythromycin B (EB) in rat plasma and urine by high-performance liquid chromatography with electrogenerated chemiluminescence detection using Tris(2,2'-bipyridine)ruthenium(II). The recovery rates of EA, dClEA and EB were 97, 94 and 85% from rat plasma and 89, 83 and 93% from rat urine, respectively. The calibration curves were linear over the concentration ranges 0.05-5 microg/mL for plasma and 0.5-50 microg/mL for urine. The precision and accuracy for all analytes in rat plasma were < or =9.0 and -6.3-7.2%, and those in urine were < or =9.4% and -6.1-7.6%, respectively. This method proved to be a powerful tool for determination of EA, dClEA and EB concentrations in samples from rats.     

A combinatorial sample-preparation robot system using the volumetric-weighing method

We have developed a new automatic sample-preparation robot system with use of the volumetric-weighing method. In this system, slurries, aqueous solutions, and other wet reagents are employed as starting materials and 64 (8×8) samples at the maximum are prepared on a library plate of 35 mm × 35 mm size. Volumetric-weighing and mixing of the starting materials and distributing reaction mixtures to the library plate are automatically performed by computer-controlled mechanisms with an easy-to-use programming software interface. While this robot is designed in terms of space saving and portability, it is able to equip with an atmosphere-controlled furnace to sinter the samples on the library plate. Typical preparation time for a library plate of 36 (6×6) samples is less than 40 min. This robot system is promising in enhancing throughput of wet-chemically synthesized materials researches.     

Hydroxylated surface of GaAs as a scaffold for a heterogeneous Pd catalyst

A novel use of GaAs, namely, as a scaffold for a heterogeneous palladium catalyst, is proposed. Hydroxy groups on the GaAs surface play important roles. During the adsorption of Pd(OAc)(2) on the GaAs surface, the hydroxy groups attract Pd(ii) species by anion exchange. A subsequent redox reaction proceeds to generate Pd(0) nanoparticles, which are stabilized on the GaAs surface. This process is confirmed by surface-sensitive measurements: diffuse reflection IR spectroscopy and X-ray photoelectron spectroscopy. Moreover, a more bulk-sensitive measurement, hard X-ray photoemission spectroscopy with synchrotron radiation, also supported our considerations. The amounts of Pd(0) nanoparticles on the surface were evaluated by catalytic activity, yield, and recyclability in the Heck reaction, in addition to the deposit test.     

Fluorescence response of 3-trifluoroacetylaminophthalimide to a Li(+)-I(-) ion pair induced by 254 nm photolysis in acetonitrile

A 3-trifluoroacetylaminophthalimide selectively distinguished LiI from other alkaline-metal iodides and lithium halides by a marked fluorescence colour change, from orange-yellow to sky-blue, subsequent to 254 nm photolysis.     

One‐Pot Synthesis of 4‐Substituted 3,4‐Dihydro‐3‐methoxyisocoumarins via Carboxylation of α‐Substituted 2‐Lithio‐β‐methoxystyrenes with Carbon Dioxide

A new type of isocoumarins (=1H‐isochromen‐1‐ones=1H‐2‐benzopyran‐1‐ones), 4‐substituted 3,4‐dihydro‐3‐methoxyisocoumarins 2 , can be obtained by a one‐pot process from α‐substituted 2‐bromo‐β‐methoxystyrenes 1 . Thus, lithium 2‐(1‐aryl(or methyl)‐2‐methoxyethenyl)benzoates are conveniently generated via the Br/Li exchange between 1 and BuLi, followed by the action of CO₂ on the resulting α‐substituted 2‐lithio‐β‐methoxystyrenes. Upon treating with concentrated HCl at room temperature, these lithium benzoates undergo lactonization to provide the desired 3,4‐dihydroisocoumarins 2 in relatively good yields.     

蓝藻Trichodesmium thiebautii细胞外多糖的单糖组成分析

蓝藻Trichodesmium thiebautii细胞外多糖经过DEAE-sephaeel柱层析后,经TLC、GLC．^1H-NMR分析,推定为硫酸化多糖,其组成单糖主要为D-半乳糖,其次是D-葡萄糖、D-木糖、2-脱氧核糖、L-鼠李糖,并含有葡萄糖醛酸和丙酮酸．     

Raman spectroscopy of the BC3 phase obtained under high pressure and high temperature

A direct transformation of the g‐BC₃ phase to a new diamond‐like d‐BC₃ phase was observed in a diamond‐anvil cell (DAC) at high temperature, 2033 ± 241 K, and high pressure, 50 GPa. Analysis of the peak positions of the d‐BC₃, B₄C, α‐boron, and the boron‐doped diamond leads to the conclusion that the positions of the peaks of the d‐BC₃ are more similar to the peak pattern of the boron‐doped diamond rather than that of boron carbide, α‐boron. Copyright © 2007 John Wiley & Sons, Ltd.     

Quantized conductance behavior of Pt metal nanoconstrictions under electrochemical potential control

We studied the quantized conductance behavior of mechanically fabricated Pt nanoconstrictions under electrochemical potential control in H₂SO₄, Na₂SO₄, and NaOH solutions. There was no clear feature in the conductance histogram, when the electrochemical potential of the nanoconstrictions was kept at the double layer or the under potential deposited hydrogen potential. At the hydrogen evolution potential, the conductance histograms showed clear features around 0.5 and 1 G₀ in the H₂SO₄ solution. In Na₂SO₄, and NaOH solutions, a 1 G₀ feature with a shoulder appeared in the histogram. The quantized conductance behavior of Pt nanoconstrictions could be controlled by the electrochemical potential and solution pH.