Stereospecific construction of a trans-1,4-diphosphacyclohexane skeleton

trans-1,4-Diphosphacyclohexanes were successfully synthesized by the stereospecific intramolecular coupling reaction of the optically active bisphosphine. This is a new route for the construction of the trans-1,4-diphosphacyclohexane skeleton. A cis isomer was also prepared along with the trans isomer from a mixture of rac- and meso-bisphosphines. The coordinated boranes were easily removed to afford the corresponding 1,4-diphosphacyclohexanes.     

Biodegradable nanogels prepared by self-assembly of poly(L-lactide)-grafted dextran: entrapment and release of proteins

We showed previously that poly(L-lactide)-grafted dextran could form biodegradable nanogels in water. In this paper, various properties of Dex-g-PLLA nanogels were compared with Dex-Chol (dextran-cholesterol conjugate) nanogels to investigate the effects of hydrophobic units. Dex-g-PLLA nanogels exhibited significantly lower CAC and higher colloidal stability, indicating a strong tendency to form nanogels. We prepared lysozyme-loaded Dex-g-PLLA nanogels, and they exhibited a sustained release of lysozyme for 1 week without denaturation in PBS at 37 degrees C. The Dex-g-PLLA nanogels therefore have great potential as a delivery vehicle for therapeutic protein.     

Rhodium‐Catalyzed Allylation of Aldehydes with Homoallylic Alcohols by Retroallylation and Isomerization to Saturated Ketones with Conventional or Microwave Heating

The treatment of an aldehyde with a tertiary homoallylic alcohol at 100–250 °C in the presence of cesium carbonate and a rhodium catalyst leads to allyl transfer from the homoallylic alcohol to the aldehyde. The process includes Rh‐mediated retroallylation to form an allyl rhodium species as the key intermediate. The homoallylic alcohol formed initially through allyl transfer is converted under the reaction conditions into the corresponding saturated ketone when bulky ligands are used. Microwave heating at 250 °C accelerates the reaction significantly.     

Letter: correlation between phosphorylation ratios by matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis and enzyme kinetics

To identify the correlation between the phosphorylation ratios by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-ToF MS) analysis and enzyme kinetics (K(m), V(max), and V(max)/K(m)) is important to understand whether MALDI-TOF MS can be applied for monitoring the properties of peptides that are substrates of protein kinases. The correlation between phosphorylation ratios and enzyme kinetics was examined using peptides for protein kinase C (PKC) and for 60 kDa phosphoprotein, encoded by the cellular sarcoma gene (c-Src). Phosphorylation ratios, analyzed by MALDI-ToF MS, showed higher correlation coefficient (r = > +0.7) for V(max)/K(m) compared with that (r = < -/+0.6) for K(m) or V(max). For ion modes, a higher correlation coefficient between phosphorylation ratios and V(max)/K(m) was identified in the positive mode (r = > +0.7) compared to that in the negative mode (r = < +0.5). These results suggest that MALDI-ToF MS is a useful tool to evaluate V(max)/K(m) of peptides for protein kinases.     

First acid dissociation at an aqueous H2SO4 interface with sum frequency generation spectroscopy

The vibrational sum frequency generation (SFG) spectra of the air-liquid interface of H2SO4-H2O solutions over a wide range of concentrations are measured in the SO stretching region (1000-1300 cm(-1)). The analogy of the concentration dependence of Raman and SFG is indicative of a nearly identical behavior of the first acid dissociation at the air-liquid interface as in the bulk.     

Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate + water mixtures studied by infrared vibrational spectroscopy

Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration.     

Preparation of hollow poly(divinyl benzene) particles with multiple holes in the shell by microsuspension polymerization with the SaPSeP method

Hollow polymer particles with multiple holes in the shell were prepared by aqueous microsuspension polymerization of micrometer-sized, monodisperse divinylbenzene/n-hexadecane droplets in the presence of sodium dodecyl sulfate (SDS) at concentrations above 4 mM utilizing the Self-assembling Phase-Separated Polymer (SaPSeP) method developed by the authors. The total surface area of the holes per particle increased with an increase in the SDS concentration. At [SDS] = 10 mM, “flower-like” non-spherical particles were formed. Part CCCXV of series “Studies on Suspension and Emulsion”     

Water properties in the super-salt-resistive gel probed by NMR and DSC

The so-called "super-salt-resistive gel", or poly(4-vinylphenol) (P4VPh) hydrogel, of different water contents ( H = 97-51%) was prepared by cross-linking with different amounts of ethylene glycol diglycidyl ether. 1H NMR spectroscopy was used to investigate the dynamic properties of water in the gel samples in terms of the spin-spin relaxation. The T2 values in those hydrogels were analyzed by assuming a two-component system, namely, T 2(long) and T2(short), and their fractions were obtained. In the higher water content region (75% < or = H < or = 97%), T2(long) for P4VPh gel was almost constant or even slightly increased with decreasing temperature. On the other hand, T2(long) for poly(vinyl alcohol) (PVA) gel (80% < or = H < or = 96%) significantly decreased with decreasing temperature, showing a natural behavior for water mobility in common hydrogels. Water in P4VPh gels of lower water contents ( H = 70% and 51%) also showed intriguing behaviors: the T2 values are much larger than those of gels with higher water contents and decreased with decreasing temperature only in the lower temperature range (<10 degrees C). The fraction of T2(long) values of P4VPh gel showed another contrast to those of PVA gel; the latter decreased with decreasing water content (normal behavior), while in the former gel the highest fraction (ca. 60% at 20 degrees C) was observed for a sample with the lowest water content ( H = 51%). On the other hand, the results of DSC measurements for P4VPh gel were less specific than those of T2 and comparable to those of common hydrogels such as PVA; with decreasing water content, the total amounts of free water and freezable bound water per polymer mass (g/g) decreased, while the amount of nonfreezing water per polymer also decreased.     

Preparation of high performance nanocomposite elastomer: effect of reaction conditions on in situ silica generation of high content in natural rubber

Effect of amines on an in situ silica generation in natural rubber was investigated, and n-hexylamine, n-heptylamine and n-octylamine were found to increase the in situ silica content. The nanometer sized silica particles up to ca. 80 parts per hundred rubber by weight were generated in situ in the rubber matrix via a sol–gel reaction of tetraethoxysilane. Additionally, dispersion of the silica in the rubbery matrix was more homogeneous than that of commercial silica dispersed by a conventional mechanical mixing. In this in situ silica generation, the polarity and solubility in water of amine were influential factors for controlling the in situ silica content in the rubbery matrix. The obtained high in situ silica filled natural rubber was useful to prepare high performance nanocomposite elastomers.