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At least 145 records · Page 8Linked to original sources
PubMed1984

[Effect of 1-(chloromethyl)silatrane on biochemical indices in the tissue of experimental gastric ulcer].

It has been demonstrated in rats with experimental gastric ulcer that 1-(chloromethyl) silatrane intensifies the development of granulation-fibrous tissue and favours optimization of the ratio of collagens and glycosaminoglycans, the main connective tissue biopolymers. Furthermore, 1-(chloromethyl) silatrane produces a more pronounced effect on hexosamine-containing glycoproteins in the ulcer tissue as compared with methyluracil and oxyferriscorbon. At the same time, judging by the time course of sialoproteins, the antiulcerous drugs, methyluracil and oxyferriscorbon, are much more effective antiinflammatory agents than 1-(chloromethyl)silatrane.

2,3-Diketogulonic Acid↗
PubMedDate not supplied

Silatrane-based surface chemistry for immobilization of DNA, protein-DNA complexes and other biological materials.

The procedure of surface functionalization based on the use of 1-(3-Aminopropyl)silatrane (APS) instead of our early procedure utilizing aminopropyl triethoxy silane (APTES) is described. Unlike APTES, APS is less reactive and extremely resistant to hydrolysis and polymerization at neutral pH. The kinetics of DNA adsorption to APS-mica was studied. The results are consistent with a diffusion controlled mechanism suggesting that DNA molecules bind irreversibly with the surface upon immobilization. This conclusion is supported by the data on imaging of supercoiled DNA, the labile conformations of which are very sensitive to the conditions at the surface-liquid interface. In addition, we demonstrated directly that the segments of DNA molecules could move along the surface if the sample is imaged in aqueous solution without drying of the sample. Using the time-lapse mode of AFM imaging we visualized the transition of purine-pyrimidine sequence in supercoiled DNA from intramolecular triple-helical conformation (H-form) into the B-helix upon the change of pH from acidic (pH 5) to neutral. The mechanisms of the H-to-B transitions and the correlation of the local structural transitions with a global DNA conformation are discussed.

Adsorption↗
PubMed2005

Highly fluorescent solid-state asymmetric spirosilabifluorene derivatives.

A series of four asymmetrically aryl-substituted 9,9'-spiro-9-silabifluorene (SSF) derivatives, 2,2'-di-tert-butyl-7,7'-diphenyl-9,9'-spiro-9-silabifluorene (PhSSF), 2,2'-di-tert-butyl-7,7'-dipyridin-2-yl-9,9'-spiro-9-silabifluorene (PySSF), 2,2'-di-tert-butyl-7,7'-dibiphenyl-4-yl-9,9'-spiro-9-silabifluorene (BPhSSF), and 2,2'-di-tert-butyl-7,7'-bis(2',2' '-bipyridin-6-yl)-9,9'-spiro-9-silabifluorene (BPySSF) are prepared through the cyclization of the corresponding 2,2'-dilithiobiphenyls with silicon tetrachloride. These novel spiro-linked silacyclopentadienes (siloles) form transparent and stable amorphous films with relatively high glass transition temperatures (T(g) = 203-228 degrees C). The absorbance spectrum of each compound shows a significant bathochromic shift relative to that of the corresponding carbon analogue as a result of the effective sigma-pi conjugation between the sigma orbital of the exocyclic Si-C bond and the pi orbital of the oligoarylene fragment. Solid-state films exhibit intense violet-blue emission (lambda(PL) = 398-415 nm) with high absolute photoluminescence quantum yields (phi(PL) = 30-55%).

Biphenyl Compounds↗
PubMed2000

Oxy-cope rearrangements of bicyclo[3.2.0]heptenones. Synthesis of bicyclo[4.2.1]non-1(4)-en-6-ones and bicyclo[5.2. 1]dec-1(10)-en-5-ones.

6-exo-Methylbicyclo[3.2.0]hepten-7-ones and their 2-alkylidene analogues are readily prepared from dialkyl squarates. These compounds undergo facial oxy-Cope ring expansions upon treatment with vinyllithium; the former leads to bicyclo[4.2. 1]non-1(4)-en-6-ones and the latter to the first examples of bicyclo[5.2.1]dec-1(10)-en-5-ones, compounds having exceptionally strained bridgehead double bonds. The transformations are controlled by the 6-exo-methyl group in the starting material along with the substituent at position-1 (bridgehead) which force attack of the lithium reagent from the concave face of the starting material, thus allowing the cyclopentenyl or alkylidene groups to participate in the sigmatropic event.

Bridged Bicyclo Compounds↗
PubMed1984

Benzamidomethaneboronic acid: synthesis and inhibition of chymotrypsin.

Benzamidomethaneboronic acid (2) has been synthesized unambiguously from the reaction of dibutyl iodomethaneboronate and N-lithiohexamethyldisilazane to form dibutyl [bis(trimethylsilyl)amino]methaneboronate (4), which was desilylated, benzoylated, and hydrolyzed to 2. It has been shown that 2 is a strong competitive inhibitor of alpha-chymotrypsin (Ki = 8.1 X 10(-6) M, pH 7.5). The reaction product from dibutyl iodomethaneboronate and sodiobenzamide, previously shown to be a potent inhibitor of chymotrypsin, was shown by this work to be O-linked isomer, benzimidoxy-methaneboronic acid (3). The pH-Ki profile over the pH range 6.5-9.5 was consistent with the formation of an enzyme-inhibitor complex which resembled the metastable tetrahedral reaction intermediates occurring during acylation and deacylation of chymotrypsin-catalyzed hydrolysis.

Acylation↗
PubMed1990

Investigations on the mechanism of the hypocholesterolemic action of 1-ethoxysilatrane.

Intraperitoneal administration of the nontoxic silicon compound, 1-ethoxysilatrane, to the rat did not cause proliferation of hepatic mitochondria or of endoplasmic reticulum, nor did it affect mitochondrial oxidative phosphorylation. The activities of cholesterol 7 alpha-hydroxylase in hepatic microsomes and of cholesterol oxidase in mitochondria respectively were unaffected by silatrane treatment. The rate of release of bile, whose composition remained unchanged, also was not increased in silatrane-treated animals. The results indicated that the compound did not affect the pathway of cholesterol degradation. A progressive decrease in the activity of hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase was observed on administration of the compound over a period of three weeks. Consistent with this, cholesterol biosynthesis in liver as measured by incorporation of radioactive precursors, acetate and water but not mevalonate, was significantly decreased in silatrane-treated animals. However, enzyme-linked immunosorbent assay revealed that the concentration of HMGCoA reductase protein was not decreased by the treatment indicating that inactivated enzyme was also present in such microsomes. Addition of silatrane to microsomes in the assay system did not cause inhibition indicating that the inactivation is by an indirect mechanism. It is concluded that the hypocholesterolemic action of the compound rested entirely on the inhibition of cholesterol biosynthesis in vivo by inactivation of the rate-limiting enzyme HMGCoA reductase.

AMP-Activated Protein Kinases↗
PubMed2002

Stereoselective and improved syntheses and anticancer testing of 3'-O-silatranylthymidines.

A stereoselective synthesis of 3'-O-((R,R,R)-trimethylsilatranyl)thymidine (R,R,R-1) and synthesis of 3'-O-silatranylthymidine (5) via an improved silatranylation procedure using tetrakis(dimethylamino)silane are reported. Diastereomeric mixture 1 showed more activity than R,R,R-1 or 5 in a primary anticancer screen against breast, CNS, and lung cell lines; demonstrating the import of the configuration and presence, respectively, of the silatrane methyl groups for growth inhibition.

Antineoplastic Agents↗
PubMed1989

Syntheses and comparison of three reagents for allyldimethylsilylation of prostaglandins and steroids: a gas chromatographic method.

Three reagents used for allyldimethylsilylation of prostaglandins and steroids have been prepared: N,O-bis(allyldimethylsilyl)trifluoroacetamide, N-methylallyl-dimethylsilyltrifluoroacetamide and allyldimethylsilyl-N,N-diphenylamine. The reaction kinetics of the reagents have been studied at room temperature in several solvents, and the optimal conditions for the derivatization of prostaglandins and steroids are discussed.

Acetamides↗
PubMedDate not supplied

[An analysis of the action of metalloatranes on the hypothalamic neurons of rats].

Neurophysiological effects of different metal derivatives of atranes at single and repeated introduction into rats have been studied. Spontaneous activity of separate hypothalamic neurons was found to change at introduction of atranes. Discharge activity of hypothalamic [correction of pretubercular] cells changed both in phasic and in tonic mode in response to single injection of atranes. The data obtained allow to conclude that metal derivatives of atranes do not exert specific effect on hypothalamic neurons.

Animals↗
PubMed1985

Gas chromatography-mass spectrometry of carboxylic acids in tissues as their tert.-butyldimethylsilyl derivatives.

Krebs cycle and related acids were isolated from liver, pancreas and stomach of rats by pulverizing frozen tissue samples in liquid nitrogen with an aqueous solution of perchloric acid and methoxylamine hydrochloride. Perchloric acid and basic and neutral compounds were removed by ion-exchange chromatography on DEAE-Sephadex and SP-Sephadex columns. Phosphate was removed without loss of citrate by partition chromatography on Sephadex G-25 in a butanol--water system. Loss of acids during evaporation of water was prevented by keeping the temperature low and by addition of ammonia and tetrabutyl-ammonium bromide. tert.-Butyldimethylsilyl derivatives were prepared, purified by chromatography on a Sephadex LH-20 column and separated by gas chromatography on a non-polar capillary column. Recoveries in the procedure were above 45% for all acids except acetoacetate (25%). The mass spectrometric fragmentation of the methoxime-tert.-butyldimethylsilyl derivatives was studied by analysis of the derivatives of deuterated acids. The intense ions at M-57 present in all spectra appeared to contain all original hydrogen atoms. Thus, the method should be suitable for quantitation by isotope dilution and in metabolic studies with deuterated compounds.

Animals↗
PubMed1984

Pharmacokinetics of compound 58-112, a potential skeletal muscle relaxant, in man.

The pharmacokinetics of 4-[(3-methoxyphenyl)methyl] -2,2,6,6-tetramethyl-1-oxa-4-aza-2,6-disilacyclohexane (Sandoz compound 58-112), a new chemical entity with a unique myotonolytic effect, was studied in 12 healthy male volunteers who received an oral dose of 50 or 100 mg of the 14C-labeled drug. Serial blood and breath samples and complete urine and feces were collected for 120 hours after dosing. All samples were analyzed for total radioactivity while the blood and urine were also assayed for unchanged compound 58-112. Measurable blood radioactivity levels were observed at 0.5 hour, and peak concentrations were attained at 1 to 2 hours after dosing. The absorption of the radioactive doses was complete and appeared linear in the 50-100 mg range, as indicated by blood 14C levels that were proportional to the dose. The 50- and 100-mg doses also resulted in virtually identical excretion patterns, with 95 per cent of the administered radioactivity recovered within 9 hours, almost exclusively in the urine. However, the disproportionately higher blood concentrations of unchanged compound 58-112 after the 100-mg dose could suggest saturable presystemic metabolism in the liver. Simultaneous fitting of all data in the 100-mg dose study to a pharmacokinetic model showed that unchanged compound 58-112 was distributed into a central and a peripheral compartment and was eliminated entirely by metabolism, the distribution and elimination half-lives being 0.5 and 3.9 hours, respectively. The metabolite(s) was distributed into one homogeneous space, and its elimination half-life was 0.1 hour, with a renal:fecal clearance ratio of approximately 96:4.

Adult↗
PubMed2004

Novel fluoropolymer functionalized silsesquioxanes for nanoscale architecture of hybrid composites.

Condensation of octa(aminophenyl)silsesquioxane with 4-(trifluorovinyloxy)benzoyl chloride affords new fluoroolefin functionalized silsesquioxanes in good yield. The new octa-trifluorovinyl functionalized monomer undergoes thermal copolymerization with established trifluorovinyl aryl ether terminated perfluorocyclobutyl (PFCB) oligomers, giving the first example of silsesquioxane functionalized PFCB materials. The new hybrid polymers offer a versatile building block toward a variety of nanocomposite applications including low loss photonics.

Aniline Compounds↗