Polymerization of vinyl monomers in the presence of silica having surface functional groups

The surface of silica was modified by mercaptopropyl, chloropropyl, aminopropyl, and methacryloxypropyl groups by the treatment of silica with the corresponding silane coupling agents, and the effects of functional groups on the surface on the polymerization of vinyl monomers initiated by benzoyl peroxide or 2,2-azobisisobutyronitrile were investigated. Although the rate of the polymerization of vinyl monomers in the presence of silica was almost equal to that in the absence of silica, a part of polymer formed was grafted onto silica surface. The polymerization was considerably retarded in the presence of these functionalized silicas and the corresponding polymers were effectively grafted onto the surface. The molecular weight of ungrafted polymer formed in the presence of the functionalized silica was lower than that formed in the presence of unmodified silica. This indicates that the chain transfer reaction of growing polymer radical to functionalized silica surface forms radicals on the surface, which then couples with growing polymer radical and/or reinitiates the polymerization to give rise to the grafting of polymers onto the surface. In the case of silica having methacryloxypropyl groups, the grafting based on the copolymerization of vinyl monomer with the surface methacryloxypropyl groups was considered to successfully proceed.     

Highly efficient syntheses of [methyl-11C]thymidine and its analogue 4'-[methyl-11C]thiothymidine as nucleoside PET probes for cancer cell proliferation by Pd(0)-mediated rapid C-[11C]methylation

Pd(0)-mediated rapid couplings of CH(3)I (and then [(11)C]CH(3)I) with excess 5-tributylstannyl-2'-deoxyuridine and -4'-thio-2'-deoxyuridine were investigated for the syntheses of [methyl-(11)C]thymidine and its stable analogue, 4'-[methyl-(11)C]thiothymidine as PET probes for cancer diagnosis. The previously reported conditions were attempted using Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3) (1?:?4 in molar ratio) at 130 °C for 5 min in DMF, giving desired products only in 32 and 30% yields. Therefore, we adapted the current reaction conditions developed in our laboratory for heteroaromatic compounds. The reaction using CH(3)I/stannane/Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3)/CuCl/K(2)CO(3) (1?:?25?:?1?:?32?:?2?:?5) at 80 °C gave thymidine in 85% yield. Whereas, CH(3)I/stannane/Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3)/CuBr/CsF (1?:?25?:?1?:?32?:?2?:?5) including another CuBr/CsF system promoted the reaction at a milder temperature (60 °C), giving thymidine in 100% yield. Chemo-response of thiothymidine-precursor was different from thymidine system. Thus, the above optimized conditions including CuBr/CsF system gave 4'-thiothymidine only in 40% yield. The reaction using 5-fold amount of CuBr/CsF at 80 °C gave much higher yield (83%), but unexpectedly, the reaction was accompanied by a considerable amount of undesired destannylated product. Such destannylation was greatly suppressed by changing to a CuCl/K(2)CO(3) system using CH(3)I/stannane/Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3)/CuCl/K(2)CO(3) (1?:?25?:?1?:?32?:?2?:?5) at 80 °C, giving the 4'-thiothymidine in 98% yield. The each optimized conditions were successfully applied to the syntheses of the corresponding PET probes in 87 and 93% HPLC analytical yields. [(11)C]Compounds were isolated by preparative HPLC after the reaction conducted under slightly improved conditions, exhibiting sufficient radioactivity of 3.7-3.8 GBq and specific radioactivity of 89-200 GBq μmol(-1) with radiochemical purity of ≥99.5% for animal and human PET studies.     

Palladium-catalyzed Mizoroki-Heck reactions in water using thermoresponsive polymer micelles

Palladium-catalyzed Mizoroki-Heck reactions were carried out in water using thermoresponsive polymer micelles. The micelles were generated from thermoresponsive block copolymers consisting of a poly(N-isopropylacrylamide) (PNIPAAm) segment and a hydrophilic segment such as nonionic poly(ethylene glycol) (PEG) (2) and anionic poly(sodium p-styrenesulfonate) (PSSNa) (9). These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 40–50?°C and showed thermal stimuli-induced formation and dissociation of micelles. The copolymers formed micelles in aqueous solution at higher temperature, where catalytic reactions proceeded. At lower temperature, the micelles dissociated to form a clear solution, enabling efficient extraction of the products from aqueous reaction mixture. In the presence of these copolymers, palladium complexes catalyzed the coupling reactions between aryl iodides and alkene compounds inside the hydrophobic micelle cores in water under relatively milder conditions. Extraction of the products from the aqueous solution of 2 or 9 was found to be efficient enough in comparison with conventional surfactants.     

Syntheses and thermal analyses of curium trichloride

Curium trichloride was synthesized by the solid state reaction of curium nitride with cadmium chloride heated up to 748 K in a dynamic vacuum. The product was hexagonal ²⁴⁴CmCl₃, of which lattice parameters were determined to be a = 0.7385 ± 0.0005 and c = 0.4201 ± 0.0005 nm. The melting temperature of the ²⁴⁴CmCl₃ sample was determined to be 970 ± 3 K by differential thermal analyses using a gold crucible. These values are close to those reported in literature. The results show that mg-scale CmCl₃ samples for thermochemical measurements were prepared from the purified oxide sample without the use of corrosive reagents.     

The photoreaction of the photoactive yellow protein domain in the light sensor histidine kinase Ppr is influenced by the C-terminal domains

To study the role of the C-terminal domains in the photocycle of a light sensor histidine kinase (Ppr) having a photoactive yellow protein (PYP) domain as the photosensor domain, we analyzed the photocycles of the PYP domain of Ppr (Ppr-PYP) and full-length Ppr. The gene fragment for Ppr-PYP was expressed in Escherichia coli, and it was chemically reconstituted with p-coumaric acid; the full-length gene of Ppr was coexpressed with tyrosine ammonia-lyase and p-coumaric acid ligase for biosynthesis in cells. The light/dark difference spectra of Ppr-PYP were pH sensitive. They were represented as a linear combination of two independent difference spectra analogous to the PYP(L)/dark and PYP(M)/dark difference spectra of PYP from Halorhodospira halophila, suggesting that the pH dependence of the difference spectra is explained by the equilibrium shift between the PYP(L)- and PYP(M)-like intermediates. The light/dark difference spectrum of Ppr showed the equilibrium shift toward PYP(L) compared with that of Ppr-PYP. Kinetic measurements of the photocycles of Ppr and Ppr-PYP revealed that the C-terminal domains accelerate the recovery of the dark state. These observations suggest an interaction between the C-terminal domains and the PYP domain during the photocycle, by which light signals captured by the PYP domain are transferred to the C-terminal domains.     

Molecular understanding of the UCST-type phase separation behavior of a stereocontrolled poly(N-isopropylacrylamide) in bis(2-methoxyethyl) ether

The upper critical solution temperature (UCST)-type phase separation of an isotactic-rich poly( N-isopropylacrylamide) (PNiPA) in bis(2-methoxyethyl) ether (diglyme) has been investigated by turbidity measurement and infrared (IR) spectroscopy. The IR spectra of stereocontrolled PNiPAs in various solvents have clearly indicated that the amide I bands do not directly reflect the tacticity of the polymer. The relative intensity of the amide I bands changes depending upon the molecular environment around the amide groups of PNiPA, which is influenced by the tacticity. During the UCST-type phase separation of the isotactic-rich PNiPA in diglyme, the amide I band at around 1625 cm (-1) changes. To link the IR spectral change with the molecular information, quantum chemical calculations have been carried out for NiPA n-mers ( n = 1-4) with an isotactic stereosequence. The result has suggested that the amide I band at around 1625 cm (-1) arises from a helical structure formed by the isotactic stereosequences in the PNiPA main chain with the aid of intramolecular CO...H-N hydrogen bonding. The experimental IR spectra have revealed that the helical structures are unfolded as the temperature rises. The folding and unfolding of the isotactic sequences in the main chain may induce the thermal change in the solubility of the isotactic rich PNiPA in diglyme, resulting in the UCST-type phase separation of the solution.     

Solubilization of Polar Oils in Surfactant Self-Organized Structures

The cloud temperature of 2 wt% C(12)EO(8) aqueous solutions decreases upon addition of sarcosinate-lauroyl isopropyl (SLIP), 1-dodecanol, and m-xylene, whereas it increases in glycerol tris(2-ethylhexanoic) ester (TEH), isopropyl myristate (IPM), and saturated hydrocarbon systems. A three-phase microemulsion is formed at equal weights of water and oil in the IPM system, but a lamellar liquid crystal (L(alpha)) is present in the SLIP system at the balanced temperature. The effect of added oil on the phase transition of the hexagonal (H(1)) phase was also investigated by means of SAXS study. The H(1)-L(alpha) transition occurs upon addition of SLIP or 1-dodecanol whereas the H(1)-I(1) (discontinuous micellar cubic) phase transition takes place in TEH or IPM systems. These differences in phase behavior are attributed to the placement of solubilized oil in micelles: In the former systems, oil tends to penetrate in the surfactant palisade layer and induces the surfactant layer curvature in micelles to be less positive, while the penetration tendency is small and the opposite effect on the curvature is induced upon addition of the latter oils. Copyright 2001 Academic Press.     

Proteomics of Caenorhabditis elegans over-expressing human alpha-synuclein analyzed by fluorogenic derivatization-liquid chromatography/tandem mass spectrometry: identification of actin and several ribosomal proteins as negative markers at early Parkinson's disease stages

It has been known that the over-expression of alpha-synuclein, the main protein of Lewy bodies in Parkinson's disease (PD), leads to neurodegeneration in PD models. In this study, the changes in protein expression between the transgenic over-expressing human alpha-synuclein wild type (alpha-synWT) and the control Caenorhabditis elegans were elucidated by fluorogenic derivatization-liquid chromatography/tandem mass spectrometry (FD-LC-MS/MS) proteome analysis, which is a highly selective, sensitive, repeatable and quantitative method for protein identification. Because the alpha-synuclein wild-type worms showed moderate levels of dopamine loss without overt behavioral abnormalities, it was suggested that the changes in proteins in the alpha-synWT are related in the sequence of the formation of Lewy bodies. Among more than 400 protein peaks detected, actin and several ribosomal proteins were identified for the first time as negative markers at early PD stages. Actin was suggested to be one of the important targets in the elucidation of the etiology of neuronal diseases such as PD or other synucleinopathies.