Solid-phase triester synthesis of modified triuridylates using an effective condensing agent

Triuridylates containing 2-deoxyuridine, 5-bromouridine, and 6-azauridine in various positions of the sequence have been synthesized by the use of an O-nucleophilic nucleotide condensation catalyst — 4-ethoxypyridine N-oxide — under the conditions of the solid-phase triester method.Institute of Molecular Biology and Genetics, Ukrainian SSR Academy of Sciences, Kiev. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 416–421, May–June, 1988.     

Preparation of copolyesters from diols and bisphenols by the solution polycondensation with TsCl/DMF/Py as a condensing agent

A novel synthetic method for the preparation of copolyesters comprised of diols and bisphenols using tosyl chloride (TsCl)/DMF/pyridine (Py) as a condensing agent has been developed. A variety of combinations of monomers could produce relatively high molecular weight copolymers, and better results were obtained by initial oligomerization of diols followed by bisphenols. In order to demonstrate usefulness of this method, copolymers comprised of IPA/TPA (50/50), bis(2‐hydroxyethyl)terephthalate (BHET),and several bisphenols were prepared and compared to the poly(ethylene terephthalate) (PET) modified by TPA and 2,2‐bis(4‐hydroxyphenyl)propane (BPA) diacetate in terms of their thermal properties. The length of mesogenic unit segments in the thermotropic IPA/TPA (50/50)‐BHET/ 4,4′‐dihydroxybenzophenone (4,4′‐DHBP) (50/50) copolymer was changed by initial reaction of BHET followed by dropwise addition of 4,4′‐DHBP in the two‐stage polycondensation and also by varying the amounts of BHET used at the initial and final stages in the three‐stage copolycondensation, and the results were studied by NMR and their thermal properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1270–1276, 2000     

Chromatographic behaviour and purification of linear lambda phage and plasmid DNA molecules on 2-hydroxyethyl methacrylate-ethylene dimethacrylate-based supports

The HEMA-BIO 1000 support, which is based on a copolymer of 2-hydroxyethyl methacrylate and ethylene dimethacrylate, was used for separation of lambda DNA and its fragments and plasmid pBR322 DNA. The separation of fragments greater than 6.6 kbp was demonstrated according to the slalom chromatography mechanism on column for size-exclusion chromatography in the case of linear lambda DNA fragments. The influence of particle size of column packing, mobile phase rate, and KCl concentration in mobile phase is discussed. The purification of plasmid DNA pBR322 using size-exclusion chromatography was more rapid compared to gel electrophoresis. The presence of salts in the eluate is not disadvantageous. DNA can be recovered from the eluate by ethanol precipitation. Plasmid DNA pBR322 isolated in this way was suitable for different biological applications (cleavage with restrictases, electrotransformation into bacterial cells).     

Nucleosides and Nucleotides. Part 18. p-nitrobenzenesulfonyl nitroimidazole as a new condensing agent in the triester synthesis of oligonucleotides

p-Nitrobenzenesulfonyl nitroimidazole (p-NBSNI) ( 5 ) has been shown to be an efficient and convenient condensing agent in the coupling of protected nucleotide fragments. Its utility has been demonstrated by a direct comparison with previously-described condensing agents in the synthesis of various di- and tetradeoxy-nucleotides.     

High‐viscosity polyesters from secondary alicyclic 1,4‐cyclohexanedicarboxylic acids and hydroquinones with thionyl chloride/pyridine condensing agent

High‐viscosity polyesters can be prepared by the polycondensation of secondary aliphatic trans‐cyclohexanedicarboxylic acid (t‐CHDC) and hydroquinones using SOCl₂/pyridine condensing agent at 80°C. Incorporation of its cis‐isomer significantly affected η_inh and the thermal property of the resulting copolymers. The copolymers of t‐CHDC, hydroquinones, and p‐hydroxybenzoic acid having different monomer sequences were prepared by changing the order of introduction of monomers.     

Propagation in the two-step solution copolycondensation with p-xylyleneglycol and bisphenols with the TsCl/DMF/Py condensing agent

A two-stage solution copolycondensation of IPA/TPA (50/50), ineffective aliphatic p-xylyleneglycol (PXG), and effective bisphenols (BPs) using tosyl chloride/dimethylformamide/pyridine condensing agent was studied by examining factors, such as, kinds of BPs, reaction temperature, and the order of addition of PXG and BPs. Better results were obtained by initial reaction of PXG followed by BPs at a lower temperature (80 °C). BPs, when reacted randomly with the preformed oligomers from PXG, gave better results. These results were discussed in terms of the reaction of the preformed oligomers with PXG or BPs by measuring the distributions of growing oligomers by GPC and of PXG or BPs in the copolymers by 1H NMR.     

Molecular sieving of lambda phage DNA in polyacrylamide solutions as a function of the molecular weight of the polymer.

Electrophoresis of lambda phage DNA was carried out in solutions at various concentrations of uncrosslinked polyacrylamide of 0.6, 1, 5 and 9 x 10(6) molecular weight (Mw) with narrow Mw distribution. By inspection of mobilities in the various concentration ranges, it appears that mobilities decrease, and retardation increases, with increasing Mw. The relation between electrophoretic retardation and the Mw of the polymer was also interpreted (i) in the manner previously applied to nonlinear Ferguson plots and compatible with the Ogston model; and (ii) empirically, on the basis of the first derivatives of the functions describing the Ferguson plots at the polymer concentrations used. Interpretation (i) shows that the retardation increases linearly in the order of 0.6, 1, 5 and 9 x 10(6) Mw of polyacrylamide. Interpretation (ii) shows a nonlinear increase of retardation in the Mw range 5 to 9 x 10(6), and a decrease in retardation as Mw is raised from 0.6 to 5.0 x 10(6). Hypothetically, interpretation (ii) can be explained mechanistically by a progressive change, as the polymer size is increased, from a collision with the surface of the polymer fiber to one occurring after permeation in the interior of a random-coiled fiber. Interpretation (i) may fail to detect that change due to the large difference between DNA mobility in solutions of the smallest polymer and the free mobility. DNA peak detection in all of the four size classes of polyacrylamide in solution is limited to relatively narrow ranges of polymer concentration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of methyl sidegroup on the extent of hydrogen bonding and modulus of polyurethane elastomers

The effects of methyl sidegroup on the properties of polyurethane elastomers, mainly hydrogen bonding and elastic properties, were studied. Polyurethanes of almost equal crosslinking density and urethane group concentration, but with different side methyl groups, were prepared by a prepolymer method. The extent of hydrogen bonding was determined by an infrared technique. The density and Young's modulus are decreased by the introduction of methyl sidegroup, swelling ratio and T_g are increased, but the extent of hydrogen bonding is not affected.     

Polycondensation of aromatic dicarboxylic acids and bisphenols with a new tosyl chloride/triphenylphosphine oxide/pyridine condensing agent

A new condensing agent comprised of tosyl chloride (TsCl) and triphenylphosphine oxide (TPPO) in pyridine was very effective for the preparation of polyesters of aromatic dicarboxylic acids and bisphenols with higher molecular weight than those obtained from TsCl/dimethylformamide in pyridine. Among the phosphorus compounds examined TPPO was most effective, and the reaction using half an equivalent with respect to the carboxyl groups yielded the most favorable results at temperatures of more than 100°C.     

Purification and characterization of a nuclease from Lentinus edodes.

An endonuclease with 3'-nucleotidase activity (nuclease Le1) was purified from fruit bodies of Lentinus edodes in a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The apparent molecular weight of nuclease Le1 was about 27000. The nuclease was inactivated in the presence of ethylenediaminetetraacetic acid (EDTA) and reactivated by the addition of Zn2+. Hydrolysis of poly U by the nuclease showed many intermediate size oligomers prior to the formation of 5'-uridine monophosphate (UMP). Therefore, it was concluded that nuclease Le1 was a Zn(2+)-endonuclease similar to P1-nuclease from Penicillium citrinum. The nuclease was very sensitive to ionic strength, but pH-profiles of the hydrolysis of four 3'-nucleotides were very similar to those of P1 nuclease from P. citrinum.     

5H-3-oxa-Octafluoropentanesulfonyl fluoride: a novel and efficient condensing agent for esterification, amidation and anhydridization

The use of 5H-3-oxa-octafluoropentanesulfonyl fluoride (HCF₂CF₂OCF₂CF₂SO₂F) as a novel and efficient condensing reagent for esterification of carboxylic acids with alcohols and amidation of carboxylic acids with amines in the presence of 1,3-diazabicyclo[5.4.0]-undec-7-ene (DBU) is reported. HCF₂CF₂OCF₂CF₂SO₂F cannot serve as a condensing agent for anhydridization of carboxylic acids, however, HCF₂CF₂OCF₂CF₂SO₂F/(CH₃)₃SiCN system can mediate anhydridization of some aromatic carboxylic acids.     

Effects of NaOH treatment of cereal starch granules on the extent of granular starch hydrolysis

Effect of NaOH treatment on granular hydrolysis of cereal starches was studied and granular starch hydrolyzing enzyme is used to hydrolyze native and NaOH-treated starch for 24?h. The dextrose equivalent value of NaOH-treated starch increased significantly compared to native starch, i.e., 28–38?% for corn, 7–37?% for rice, but no significant increase for corn starch. Scanning electron microscopy micrographs showed that NaOH treatment caused an enlargement of pores and degrades the surface of starch granules. Hydrolyzed-treated starch exhibited rougher surface and more porous granules compared to native starch. The swelling power and pasting properties of NaOH-treated starches were markedly altered after hydrolysis. X-ray pattern of all starches showed no changes and the amylose content decrease significantly after hydrolysis, which could due to extensive degradation of amorphous region. Evidently, NaOH treatment below gelatinization temperature was effective in enhancing the degree of granular starch hydrolysis.     

Gas-liquid chromatographic assay of a new antineoplastic agent, 1,3,3,5,5-pentakis-(azaridino)lambda 6-2,4,6,3 lambda 5, 5 lambda 5-thiatriazadiphosphorine-1-oxide. Application to pharmacokinetic studies

A method for the assay of 1,3,3,5,5-pentakis-(azaridino)-lambda 6,2,4,6,3 lambda 5,5 lambda 5-thiatriazadiphosphorine-1-oxide (SOAz), a new anticancer drug of which the clinical trials are in progress, is described. This method is based on capillary gas chromatography using a thermionic detector. The lower detection limit was 100 pg per injection and a coefficient of variation smaller than 5% could be obtained when parathion was used as external standard. The method is suitable for biological samples and therefore has been proposed for clinical pharmacokinetic studies as well as for the determination of patterns of SOAz distribution in several organs of the mouse. A preliminary clinical study showed that the serum decay curves of SOAz could be fitted to an open two-compartment model for drug disappearance.     

载体表面氧化程度对Ni/SiC甲烷化催化剂性能的影响

采用等体积浸渍法制备了Ni/SiC甲烷化催化剂, 研究了SiC载体表面氧化程度对催化剂低温活性和高温稳定性的影响, 并采用热重-差示扫描量热、N₂物理吸附、傅立叶变换红外光谱、氨程序升温脱附、X射线衍射、氢程序升温还原和氢化学吸附技术对样品进行了表征. 结果表明, 随着载体氧化温度的提高, 催化剂的比表面积和镍分散度降低, 但还原性和反应稳定性提高. 未氧化载体所负载催化剂的高温稳定性最差, 其原因在于载体对镍粒子的固定作用最弱. 负载于500和700℃处理的SiC载体上的催化剂具有较好的低温活性和高温稳定性, 这是因为适度氧化后的载体能较好地分散并固定镍粒子. 900℃处理的载体因过度氧化形成了低活性的氧化层, 使负载的镍粒子变大, 因而催化剂的低温活性最差.