A zwitterion of 1,5‐bis­(2‐hydroxy­benzamido)‐3‐aza­pentane: a two‐dimensional hydrogen‐bonding network involving dimers

The title compound, 2‐{N‐[2‐(2‐hydroxy­benzamido)ethyl­ammonio­ethyl]amino­carbon­yl}phenolate, C₁₈H₂₁N₃O₄, crystallizes in a zwitterionic form as a result of inter­molecular proton transfer and possesses a negatively charged phenolate group and a protonated amino group. The 2‐hydroxy­benzamide and 2‐(amino­carbonyl)­phenolate moieties attached to the two ends of the C—C—N—C—C backbone adopt a cis conformation in relation to this backbone. All N‐ and O‐bound H atoms are involved in hydrogen‐bond formation; the zwitterions are first linked into head‐to‐tail dimers, which are further organized into a two‐dimensional network parallel to the crystallographic bc plane.     

Asymptotic stability of some quasilinear parabolic equations in divergence form. L∞ results

In this paper we study the behavior of solutions of some quasilinear parabolic equations of the form

$\text{(}\text{?u}\text{?t}\text{) ?}\text{∑}\text{i=1}\text{n}\text{(}\text{d}\text{dx}{}_{\mathrm{i}}\text{) a}{}_{\mathrm{i}}\text{(x, t, u, u}{}_{\mathrm{x}}\text{) + a(x, t, u, u}{}_{\mathrm{x}}\text{)u + f(x, t) = O,}$

as t → ∞. In particular, the solutions of these equations will decay to zero as t → ∞ in the L^∞ norm.     

Separation of metal ions by capillary electrophoresis

A number of experimental parameters have been optimized for the separation of 26 metal ions, including alkali, alkaline earth, transition and lanthanide metal ions. Experimental parameters that were evaluated included nature of indirect-detection reagent, pH of electrolyte, concentration of complexing agent and nature of the surface of the capillary; unbonded and C₁ and C₁₈ bonded phases were studied. In addition the effect of internal diameter on linearity and signal-to-noise ratio was examined, and separation efficiency was determined for a variety of experimental conditions. Detection limits (signal-to-noise RATIO = 3) were ca. 1 μg/ml for the lanthanides, ca. 0.6 μg/ml for transition and alkaline earth ions and ca. 0.1–0.8 μg/ml for alkali metal ions. The average relative standard deviations of were 3.7, 5.1 and 2.5% on unbonded, C₁ and C₁₈ capillaries, respectively. Whereas conventional regression analysis suggested that the calibration curves were linear over the range of 1·10⁻⁵ to 4·10⁻⁴ mol/l, sensitivity plots showed that the results were actually linear to within 6% only over the range of 2.5·10⁻⁵ to 4·10⁻⁴ mol/l.     

Reversible replication between ordered mesoporous silica and mesoporous carbon

Highly ordered mesoporous silica can be regenerated from a mesoporous carbon CMK-3 that is a negative replica of mesoporous silica SBA-15, indicating reversible replication between carbon and inorganic materials.     

Quantum chemical studies on electrophilic addition

The geometries of the 2-chloroethyl and ethylenechloronium cations, two possible intermediates in the electrophilic addition of chlorine to ethylene, have been fully optimized using ab initio molecular orbital calculations employing the split valence shell 4-31G basis set.These geometries were then used to compute more accurate wave functions using Dunning's double-zeta basis set. The bridged chloronium ion was found to be more stable by 9.35 kcal/mole, the opposite order of stability from the C₂H₄F⁺ ions. Interconversion of the two C₂H₄Cl⁺ cations was computed to have a barrier of 6.25 kcal/mole.The activation energy for this chlorination reaction, using the ethylenechloronium cation and a chlorine anion at infinite separation as the model for the activated complex, was computed to be 128.7 kcal/mole, showing that this is not a feasible gas phase reaction.     

Isolation of a potent anti-MRSA sesquiterpenoid quinone from Ulmus davidiana var. japonica

A highly potent anti-MRSA sesquiterpenoid has been isolated from Ulmus davidiana var. japonica, which has been traditionally used to treat infectious diseases in Korea. This naturally occurring antibiotic was identified as mansonone F (1). This compound has been found to be highly active specifically against MRSA and showed an MIC range of 0.39-3.13 microg/ml which is comparable to that of vancomycin.     

Synthesis of new 1,3-bis（phenylethynyl）disilazanes

Three new 1,3-bis(phenylethynyl)disilazanes were synthesized from the reaction of 1,3-dichlorodisilazanes with (phenylethy- nyl)lithium,and characterized by infrared (IR) spectra,nuclear magnetic resonance (NMR) and mass spectrometry (MS).     

Characterization and epitope mapping of two monoclonal antibodies against human CD99

CD99 plays a critical role in the diapedesis of monocytes, T cell differentiation, and the transport of MHC molecules. Engagement of CD99 by agonistic monoclonal antibodies has been reported to trigger multifactorial events including T cell activation as well as cell-cell adhesion during hematopoietic cell differentiation. In this study, to identify the functional domains participating in the cellular events, we mapped the epitopes of CD99, which are recognized by two agonistic CD99 monoclonal antibodies, DN16 and YG32. Using recombinant fusion proteins of GST with whole or parts of CD99, we found that both antibodies interact with CD99 molecules independently of sugar moieties. DN16 mAb detected a linear epitope located in the amino terminal region of CD99 while YG32 mAb bound another linear epitope in the center of the extracellular domain. To confirm that the identified epitopes of CD99 are actually recognized by the two mAbs, we showed the presence of physical interaction between the mAbs and the fusion proteins or synthetic peptides containing the corresponding epitopes using surface plasmon resonance analyses. The dissociation constants of DN16 and YG32 mAbs for the antigen were calculated as 1.27 x 10(-7) and 7.08 x 10(-9) M, respectively. These studies will help understand the functional domains and the subsequent signaling mechanism of CD99.     

Liquid chromatography/electrospray ionization mass spectrometry for the characterization of twenty-three flavonoids in the extract of Dalbergia odorifera

A method incorporating high-performance liquid chromatography (HPLC) with electrospray ionization and tandem mass spectrometry, with parallel analysis by HPLC with UV detection using a diode-array detector, was developed for the qualitative characterization of flavonoids in D. odorifera. Twenty-three flavonoids, including six isoflavones, six neoflavones, four isoflavanones, three flavanones, two chalcones, one isoflavanonol and one pterocarpan, were unambiguously identified by comparing their retention times, UV and MS spectra with those of authentic compounds. Furthermore, the collision-induced dissociations of the [M-H]- ions were studied to clarify the MS behavior of the different types of flavonoids. In negative ion ESI-MS all the flavonoids yielded prominent [M-H]- ions in the first order mass spectra. Fragments involving losses of CH3*, H2O, CO, C2H2O, and CO2 were observed in the MS/MS spectra. Each of the seven types of flavonoid showed characteristic MS/MS fragmentation patterns. The isoflavanones, flavanones and chalcones were observed to undergo retro-Diels-Alder fragmentations. The spectra of almost all the neoflavonoids unexpectedly exhibited only [M-H-CH3]-* radical anions as base peaks without any further fragmentation. Substitution positions also remarkably influenced the fragmentation behavior, which could assist in distinction among the flavonoid isomers. The fragmentation rules deduced here could aid in the characterization of other flavonoids of these types.