ENHANCEMENT OF ULTRAVIOLET-DNA REPAIR IN den V GENE TRANSFECTANTS and T4 ENDONUCLEASE V-LIPOSOME RECIPIENTS

The phage T4 denV gene, coding for the pyrimidine-dimer specific T4 endonuclease V, was transfected into human repair-proficient fibroblasts, repair-deficient xeroderma pigmentosum fibroblasts, and into wild type CHO hamster cells. Transfectants maintained denV DNA and expressed denV mRNA. Purified T4 endonuclease V encapsulated in liposomes was also used to treat repair-proficient and -deficient human cells. The denV transfected clones and liposome-treated cells showed increased unscheduled DNA synthesis and enhanced removal of pyrimidine dimers compared to controls. Both denV gene transfection and endonuclease V liposome treatment enhanced post-UV survival in xeroderma pigmentosum cells but had no effect on survival in repair-proficient human or hamster cells. The results demonstrate that an exogenous DNA repair enzyme can correct the DNA repair defect in xeroderma pigmentosum cells and enhance DNA repair in normal cells.     

UV-DNA Damage in Mouse and Human Cells Induces the Expression of Tumor Necrosis Factor α

Ultraviolet light induces the expression of tumor necrosis factor α (TNFα) in many mammalian cells. We have examined the signal for this induction in a human DNA repair-deficient cell line carrying a transgene composed of the murine TNF regulatory sequences fused to the chloramphenicol acetyltransferase (CAT) structural gene. When compared by fluence, UVC was a more efficient inducer of CAT than was UVB, but they were equivalent inducers when compared by the frequency of cyclobutyl pyrimidine dimers produced by each source. Further, treatment of UV-irradiated cells with the prokaryotic DNA repair enzyme T4 endonuclease V in-creased the level of repair of dimers and concomitantly reduced CAT gene expression. Membrane-bound TNFα expression was increased by UV and reduced by repair of dimers. Finally, in the TNFcat transgene system, DNA damage directly to the cell with the transgene was required as cocultivation of unirradiated TNFcat cells with UV-irradiated cells did not increase CAT activity. These results show that DNA damage is a signal for the induction of TNFa gene expression in mouse and human cells.     

Some new organoxy (alkyl) ethynylsilanes

Conclusions Some ethynyl(organoxy)silanes were obtained by the transetherification of CH₃O(CH₃)₂SiC CH with 1,3 dichloroisopropanol, 4-iodophenol, and 3, 5-xylenol, of CH₃O(CH₃)Si(C CH)₂ with ethanol, of CH₃O(CH₃)Si(CH = CH₂) (C CH) with ethanol and propanol, and of CH₃(CH₃O)₂SiC CH with butanol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 450–451, February, 1977.     

Photoprotection by topical DNA repair enzymes: molecular correlates of clinical studies

A new approach to photoprotection is to repair DNA damage after UV exposure. This can be accomplished by delivery of a DNA repair enzyme with specificity to UV-induced cyclobutane pyrimidine dimers into skin by means of specially engineered liposomes. Treatment of DNA-repair-deficient xeroderma pigmentosum patients or skin cancer patients with T4N5 liposome lotion containing such DNA repair liposomes increases the removal of DNA damage in the first few hours after treatment. In these studies, a DNA repair effect was observed in some patients treated with heat-inactivated enzyme. Unexpectedly, it was discovered that the heat-inactivated T4 endonuclease V enzyme refolds and recovers enzymatic activity. These studies demonstrate that measurements of molecular changes induced by biological drugs are useful adjuvants to clinical studies.     

New polyunsaturated organosilicon dendrimers based on 1,1-diethynyl-and 1-vinyl-1-ethynylsilacycloalkanes

1,1-Dichloro-and 1-vinyl-1-chlorosilacyclanes were prepared by reactions of tetrachlorosilane or vinyltrichlorosilane with magnesium and 1,4-dibromobutane or 1,5-dibromopentane. The reactions of the products obtained with ethynylmagnesium bromide or bis(bromomagnesio)acetylene yield the corresponding ethynylsilacyclanes. Condensation of 1,1-diethynylsilacyclanes or bis(ethynylsilacyclopentyl)ethyne with an equimolar amount of ethylmagnesium bromide and methylbis(trimethylsilylethynyl)fluorosilane gave the corresponding highly unsaturated mono-and binuclear first-generation dendrimers with the cores formed by the silicon atoms incorporated in silacycloalkane fragments. The ¹H, ¹³C, and ²⁹Si NMR spectra of all the compounds obtained were studied. The key parameters and the chemical graph of the new dendrimers are presented.     

1-ethynyl-3-chloromethyltetramethyldisiloxane and some of its reactions

Conclusions The cohydrolysis of CH CSi(CH₃)₂OC₂H₅ with ClSi(CH₃)₂CH₂Cl gave the previously unknown 1-ethynyl-3-chloromethyltetramethyldisiloxane. The bromomagnesium derivatives of the latter were reacted with CH₂O, CH₃COCH₃, Br₂, and ClSi(CH₃)₃. In addition, the compound was subjected to hydrosilylation, entered into the diene condensation with hexachlorocyclopentadiene, and reacted with NaI, morpholine, and piperidine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1877–1880, August, 1976.     

1-(2′-triethylsilylethyl)-, 1-(2′-triethylsilylvinyl)-, and 1′-(2′-triethylsilylethynyl)-silatranes

Conclusions The reaction of 2-triethylsilyl-substituted ethyl-, vinyl-, and ethynyltrialkoxysilanes with triethanolamine gave 1-substituted silatranes possessing neurotropic activity.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2611–2613, November, 1984.     

Cyclosilethynes containing exocyclic cyclopentyl and cyclohexyl groups

The reaction of BrMgCCSiMe₂CCSiMe₂CCSiMe₂CCSiMe₂CCMgBr with chloro(cyclopentyl)(methyl)silane in a large excess of THF gave 1-cyclopentyl-1,4,4,7,7,10,10,13,13-nonamethyl-1,4,7,10, 13-pentasilacyclopentadeca-2,5,8,11,14-pentayne. Similarly, 1,10-di(cyclopentyl)- or 1,6-di(cyclopentylmethyl)-1,4,4,7,7,10,13,13,16,16-decamethyl-1,4,7,10,13,16-hexasilacyclooctadeca-2,5,8,11,14,17-hexaynes were synthesized from BrMgCCSiMe₂CCSiMe₂CCMgBr and dichloro(cyclopentyl)methylsilane or dichloro(cyclopentylmethyl)(methyl)silane. Condensation of Me₂Si(CCMgBr)₂ with dichloro(cyclohexyl)-methylsilane afforded 1,7-di(cyclohexyl)-1,4,4,7,10,10-hexamethyl-1,4,7,10-tetrasilacyclododeca-2,5,8,11-tetrayne.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1282–1284.Original Russian Text Copyright © 2004 by O. Yarosh, Zhilitskaya, N. Yarosh, Albanov, Klyba, Voronkov.This revised version was published online in April 2005 with a corrected cover date.     

Mass spectra of 3,6-dihalo-4,4-dimethyl-1,4-selenasilafulvenes and 2,4-dihalo-2-dihalomethyl-3,3-dimethyl-1-selena-3-silacyclopent-4-enes

The behavior of new heterocyclic systems, viz., 3,6-dihalo-4,4-dimethyl-1,4-selena- silafulvenes 1a, b and 2,4-dihalo-2-dihalomethyl-3,3-dimethyl-1-selena-3-silacyclopent-4-enes 2a, b (Hal =Cl, Br), was studied under conditions of electron ionization and thermal decomposition. Their fragmentation is accompanied by skeletal rearrangements, and the positive charge is localized mainly on ions containing silicon. Selenasilafulvenes 1a, b form stable molecular ions. Selenasilacyclopent-4-ene 2a decomposes partially and compound 2b decomposes completely in the gas phase with the elimination of a hydrogen halide and a halogen molecules.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 639–642, March, 2005.The term “contribution” implies the ratio of the sum of peak intensities of all isotope varieties of the ion under consideration to the total ion current.     

Noncombustible adhesive compositions based on brominated epoxide resins for production of structural film adhesives and adhesive prepregs

This paper presents a composition developed for use both as a film adhesive with a working temperature up to 150°C and as a binder for production of fiberglass with a working temperature up to 120°C. The composition is autoextinguishing and contains bromated epoxy resins. It is shown that the strength property indices of the fiberglass bound with the created composition are up to those for modern structural materials.