1,1-Dihydroperoxycyclododecane as a new, crystalline non-hygroscopic oxidizer for the chemical synthesis of oligodeoxyribonucleotides

A new oxidation method for DNA synthesis was developed by the use of 1,1-dihydroperoxycyclododecane in CH₂Cl₂-EtOAc under anhydrous conditions. This new oxidizer was successfully applied to the synthesis of oligodeoxyribonucleotides that involves an oxidation step for conversion of phosphite intermediates to phosphate derivatives.     

Synthesis and hybridization properties of 2′-O-(tetrazol-5-yl)ethyl-modified oligonucleotides

2′-O-(1H-Tetrazol-5-yl)ethyladenosine was synthesized using 2′-O-cyanoethyladenosine derivative as a key intermediate. The 2′-O-(1H-tetrazol-5-yl)ethyl modifications exhibited intriguing properties such as the change in the structure of the tetrazole residue between a protonated and a deprotonated form. The T_m experiments of various oligodeoxynucleotides having a 2′-O-(1H-tetrazol-5-yl)ethyl-modified adenosine showed reduced hybridization affinity in comparison to the unmodified oligonucleotides toward their complementary oligodeoxynucleotides. The mechanism of the reduced hybridization affinity was discussed on the basis of the structure and the physicochemical properties of the tetrazole moiety.     

Flow injection determination of trace amounts of copper based on its catalytic effect on the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine by cumene hydroperoxide

A sensitive and selective flow-injection method has been developed for the catalytic determination of copper(II). The method is based on the oxidation of 3,3′,5,5′-tetramethylbenzidine by cumene hydroperoxide as an organic oxidant in an acidic medium. A highly sensitivity has been achieved by adding 2,9-dimethyl-1,10-phenanthroline as an activator and benzyldimethyltetradecylammonium chloride (zephiramine) as a surfactant. The reaction was spectrophotometrically monitored by measuring the increase in absorbance of oxidation product of 3,3′,5,5′-tetramethylbenzidine at 650 nm. The calibration curve was linear over the range of 0.5–3.0 ng mL^?1 at a rate of 30 samples h^?1. Most of the diverse ions did not interfere with the determination of copper up to at least 50-fold excess. The serious interference by iron(III) was eliminated by addition of fluoride. The method was successfully applied to the determination of copper in water samples.     

95Tc and96Tc production by (γ, xn) reactions

The⁹⁹Tc (, 3n)⁹⁶Tc and⁹⁹Tc (, 4n)⁹⁵Tc reactions were studied by irradiation of target⁹⁹Tc with bremsstrahlung from the linear electron accelerator of Tohoku University, up to 50 MeV -energy. The resulting⁹⁶Tc (4.3 d) and⁹⁵Tc (20 h) activities were determined by -spectrometry. The -flux was monitored by the⁹⁹Tc (, )^99mTc reaction. Metallic copper and gold foils were used as additional flux monitors in front of and behind the samples. Their measured radioactivity was utilized for normalizing bremsstrahlung flux calculations, in order to determine reaction cross sections. Cross sections were also determined theoretically, performing calculations in the framework of a neutron cascade evaporation model. Above the (, 3n) and (, 4n) threshold energies the neutron emission channel was supposed to be the only open channel for deexcitation following photoabsorption. The preeguilibrium contribution was considered negligible. The experimental results obtained for the integrated cross section at 30 and 50 MeV fit reasonably well the calculated curves.     

Synthesis and physical properties of high birefringence phenylacetylene liquid crystals containing a cyclohexyl group

We have synthesized new phenylacetylene-based liquid crystals containing a cyclohexyl or cyclohexylethyl group and evaluated their physical properties in order to develop a range of materials having high value of birefringence. The cyclohexyl-containing compounds exhibited nematic behaviour near room temperature and moderate values of δn of around 0.3. The cyclohexylethyl-containing compounds had a very wide nematic range with a high T_NI and very high values of δn of over 0.4. They also exhibited low viscosities. The order parameter was not affected by introducing either a cyclohexyl or a cyclohexylethyl group and the values of δn based on calculated polarizabilities were obtained experimentally.     

Synthesis and radical crosslinking reaction of poly (vinylcyclopropanone acetal)s

Synthesis and radical crosslinking reaction of poly (vinylcyclopropanone acetal)s ( 4 ), volume change on the crosslinking, and thermal analysis of 4 and the crosslinked polymers were carried out. 4 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane with sodium dialkoxides. Radical crosslinking of 4a was carried out in the presence of AIBN, BPO, or DTBP at 60, 80, or 120°C, respectively. 4a afforded no dichloromethane-insoluble part in the crosslinking in chlorobenzene but afforded in 37% yield in bulk at 120°C. On the other hand, 4b afforded dichloromethane-insoluble part in 33% yield in the crosslinking in chlorobenzene at 120°C. Volume shrinkage of 4a and 4b on crosslinking at 120°C was 4.11 and 3.55%, respectively. Glass transition temperatures of the crosslinked polymers obtained from 4a and 4b were 28 and 163°C, respectively, which were 32 ～ 49°C higher than those before crosslinking. © 1994 John Wiley & Sons, Inc.     

Sequence-specific gene silencing in mammalian cells by alkylating pyrrole-imidazole polyamides

Gene silencing was examined by sequence-specific alkylation of DNA by N-methylpyrrole (Py)-N-methylimidazole (Im) hairpin polyamides. Polyamides ImImPyPygammaImImPyLDu86 (A) and ImImPyPygammaImPyPyLDu86 (B) selectively alkylated the coding regions of the renilla and firefly luciferases, respectively, according to the base pair recognition rule of Py-Im polyamides. Two different plasmids, encoding renilla luciferase and firefly luciferase, were used as vectors to examine the effect of alkylation on gene silencing. Transfection of the alkylated luciferase vectors-by polyamide A or B-into HeLa, 293, and NIH3T3 cells demonstrated that these sequence-specific DNA alkylations lead to selective silencing of gene expression. Next, the vectors were cotransfected into HeLa cells and the cells were treated with polyamide A or B. Selective reduction of luciferase activities was caused by both polyamides. On the basis of this sequence-specific alkylation and gene silencing activity, these alkylating Py-Im polyamides thus have potential as antitumor drugs to target specific gene expression in human cells.     

Selective Targeting of the KRAS Codon 12 Mutation Sequence by Pyrrole–Imidazole Polyamide seco‐CBI Conjugates

Mutation of KRAS is a key step in many cancers. Mutations occur most frequently at codon 12, but the targeting of KRAS is notoriously difficult. We recently demonstrated selective reduction in the volume of tumors harboring the KRAS codon 12 mutation in a mouse model by using an alkylating hairpin N‐methylpyrrole–N‐methylimidazole polyamide seco‐1,2,9,9a‐tetrahydrocyclopropa[1,2‐c]benz[1,2‐e]indol‐4‐one conjugate (conjugate 4 ) designed to target the KRAS codon 12 mutation sequence. Herein, we have compared the alkylating activity of 4 against three other conjugates that were also designed to target the KRAS codon 12 mutation sequence. Conjugate 4 displayed greater affinity for the G12D mutation sequence than for the G12V sequence. A computer‐minimized model suggested that conjugate 4 could bind more efficiently to the G12D match sequence than to a one‐base‐pair mismatch sequence. Conjugate 4 was modified for next‐generation sequencing. Bind‐n‐Seq analysis supported the evidence showing that conjugate 4 could target the G12D mutation sequence with exceptionally high affinity and the G12V mutation sequence with much higher affinity than that for the wild‐type sequence.     

Star‐shaped cyclopolymers: A new category of star polymer with rigid cyclized arms prepared by controlled cationic cyclopolymerization and subsequent microgel formation of divinyl ethers

The combination of living/controlled cationic cyclopolymerization and crosslinking polymerization of bifunctional vinyl ethers (divinyl ethers) was applied to the synthesis of core‐crosslinked star‐shaped polymers with rigid cyclized arms. Cyclopolymerization of 4,4‐bis(vinyloxymethyl)cyclohexene ( 1 ), a divinyl ether with a cyclohexene group, was investigated with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in toluene at 0 °C. The reaction proceeded quantitatively to give soluble poly( 1 )s in organic solvents. The content of the unreacted vinyl groups in the produced polymers was less than ～3 mol%, and therefore, the degree of cyclization of the polymers was determined to be ～97%. The number‐average molecular weight (M_n) of the polymers increased in direct proportion to monomer conversion and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that living cyclopolymerization of 1 occurred. The chain linking reactions among the formed living cyclopolymers with 1,4‐bis(vinyloxy)cyclohexane ( 3 ) as a crosslinker in toluene at 0 °C produced core‐crosslinked star‐shaped cyclopoly( 1 )s [star‐poly( 1 )s] in high yield (100%). Dihydroxylation of the cyclohexene double bonds of star‐poly( 1 ) gave hydrophilic water‐soluble star‐shaped polymers with rigid arm structure [star‐poly( 1 )‐OH] with thermo‐responsive function in water. T_gs of star‐poly( 1 ) and star‐poly( 1 )‐OH were 135 °C and 216 °C, respectively; these values are very high as vinyl ether‐based star‐shaped polymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1094–1102     

Synthesis of poly(vinyl ether)‐based,ABA triblock‐type thermoplastic elastomers with functionalized soft segments and their gas permeability

The ABA‐type triblock copolymers consisting of poly(2‐adamantyl vinyl ether) [poly(2‐AdVE)] as outer hard segments and poly(6‐acetoxyhexyl vinyl ether) [poly(AcHVE)], poly(6‐hydroxyhexyl vinyl ether) [poly(HHVE)], or poly(2‐(2‐methoxyethoxy)ethyl vinyl ether) [poly(MOEOVE)] as inner soft segments were synthesized by sequential living cationic polymerization. Despite the presence of polar functional groups such as ester, hydroxyl, and oxyethylene units in their soft segments, the block copolymers formed elastomeric films. The thermal and mechanical properties and morphology of the block copolymers showed that the two polymer segments of these triblock copolymers were segregated into microphase‐separated structure. Effect of the functional groups in the soft segments on gas permeability was investigated as one of the characteristics of the new functional thermoplastic elastomers composed solely of poly(vinyl ether) backbones. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1114–1124