Synthesis and characterization of an anomeric sulfur analogue of CMP-sialic acid

alpha-2,3-Sialyltransferase catalyzes the transfer of sialic acid from CMP-sialic acid (1) to a lactose acceptor. An analogue of 1 was synthesized in which the anomeric oxygen atom was replaced with a sulfur atom (1S). The key step in the synthesis of 1S was a tetrazole-promoted coupling of a cytidine-5'-phosphoramidite with a glycosyl thiol of a protected sialic acid. Compounds 1 and 1S were characterized for their activity in a sialyl transfer assay. The rate of solvolysis in aqueous buffer of analogue 1S was 50-fold slower than that of 1. Analogue 1S was found to be substrate for alpha-2,3-sialyltransferase. The K(m) of 1S was just 3-fold higher than that of 1, while the k(cat) of 1S was 2 orders of magnitude lower compared to 1.     

Syntheses of new model compounds related to an antigenic epitope from Bupleurum falcatum L. and their distributions in various ganglioside-phospholipid monolayers

6-N-[2-(Tetradecyl)hexadecanamido]hexyl beta-D-glucopyranosyluronic acid-(1-->6)-beta-D-galactopyranosyl-(1-->6)-beta-D-galactopyranoside (1) and its clustering compound (2) carrying a tetravalent sugar unit, which are new model compounds related to a major antigenic epitope from antiulcer pectic polysaccharide of Bupleurum falcatum L., were synthesized and the distributions of 1 and 2 in mixed ganglioside (GM1, GD1a or GT1b)/phospholipid (DPPC) monolayers were observed using atomic force microscopy (AFM). AFM images showed that 1 was distributed in the GM1, GD1a and GT1b region of the mixed monolayers, in which 1 was miscible with GD1a. Specific distribution of 1 was observed in the mixed GM1/DPPC monolayer. Compound 2 was miscible with GM1, while 2 formed associations with GD1a and GT1b in the mixed monolayers. The distribution mode of 1 and 2 was different among the mixed ganglioside/DPPC monolayers.     

LC-MS/MS法测定大鼠血浆中人参皂苷Rb1的含量及其药代动力学研究

采用液相色谱-串联质谱法快速、灵敏地测定大鼠血浆中人参皂苷Rb1(GRb1)的含量,并将该方法应用于大鼠口服GRb1后的代谢动力学研究。血浆样品采用96孔板进行液-液萃取后,应用Agilent SB-C18色谱柱(100 mm×2.1 mm,3.5μm)进行分离,以甲醇-0.1%甲酸溶液(体积比为75∶25)为流动相进行洗脱,在正离子模式下对GRb1和内标人参皂苷Rg1(GRg1)进行检测,用于定量的离子反应分别为1131.5→365.1(GRb1),823.3→643.4(GRg1)。人参皂苷Rb1血浆样品测定方法的定量线性范围为1~500 ng/mL,线性相关系数大于0.999,定量下限为1 ng/mL,批内和批间精密度(RSD)小于9.05%,回收率为79.7%~81.0%,基质效应为96.6%~99.3%。大鼠灌胃给予Rb15 mg/kg后,大鼠体内血药浓度到达高峰时间tmax为1.53 h,半衰期t1/2为13.54 h,药时曲线面积AUC0~72为16237.76(ng·h)/mL。该方法快速、高效、灵敏,适用于人参皂苷Rb1的代谢动力学研究。     

阳离子表面活性单体DMOHAC的合成及其胶束化行为

以环氧氯丙烷、丙烯酰胺及N,N-二甲基十八烷基叔胺为原料,经开环和季铵化两步反应合成了新型阳离子表面活性单体,N,N-二甲基十八烷基(2-羟基-3-丙烯酰胺丙基)氯化铵（DMOHAC, 1）,其结构经FT-IR表征。用TG和摩尔电导率法研究了1的热稳定性和1、十八烷基三甲基氯化铵(OTAC)、1/OTAC混合胶束的CMC值。结果表明：1的热稳定性能良好,1和OTAC的CMC值分别为0.10 mmol·L^-1和0.33 mmol·L^-1。当n（1）: n（OTAC）=2 : 1时,1/OTAC混合胶束的CMC值为0.12 mmol·L^-1;当n（1）: n（OTAC）=1 : 2时,1/OTAC混合胶束的CMC值为0.21 mmol·L^-1。1/OTAC混合胶束的CMC值介于1和OTAC之间。     

生物素-亲和素体系测定雌酮

雌酮与牛血清白蛋白共价结合,合成雌酮的完全抗原。利用此抗原免疫小鼠,通过细胞融合技术制备了雌酮的单克隆抗体,经纯化表征知,抗体是IgG1型,相对分子量为164000,与固定抗的亲和常数为8.2×10^8L/mol。以生物素化的羊抗鼠免疫球蛋白及辣根过氧化物酶标记的链亲和素为标记体系,通过竞争抑制的方式测定游离的雌酮,结果表明：雌酮在10～10000pg/mL内呈线性关系。     

Suppressive components in rice husk against mutagens-induced SOS response using Salmonella typhimurium TA1535/pSK1002 umu test

The EtOAc extract from rice (Oriza sativa cv. Hinohikari) husk showed a suppressive effect on umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK1002 against the mutagen, Trp-P-1, which requires liver metabolizing enzyme. To obtain the suppressive compound, the EtOAc extract was fractionated by SiO(2) column chromatography using umu test as a bioassay guide. Suppressive compound was isolated and identified as momilactone A (1) by EIMS, IR, (1)H- and (13)C-NMR spectroscopy. Compound 1 inhibited of the SOS-inducing activity of Trp-P-1 in the umu test. Gene expression was suppressed by 32.6% at less than 0.60 mM. Compound 1 was assayed with activated Trp-P-1. The suppressive effect of Compound 1 was decreased compared with that of Trp-P-1. Furthermore, 1 was assayed with another mutagens, such as MeIQ, activated MeIQ, furylfuramide (AF-2), MNNG, and UV-irradiation. Compound 1 showed greater suppressive effect on AF-2-inducing SOS response than other mutagens.     

Direct UHV-TEM observation of palladium clusters on a silicon surface.

About 1 monolayer of palladium was deposited onto a silicon (111) 7 x 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 x 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 x 1 surface layer were directly observed by in situ plan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 x 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 x 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 x 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described.     

新型磷杂菲基反应型阻燃剂的合成及其在聚氨酯阻燃中的应用

以9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物和1,4-丁二醇二缩水甘油醚为原料,合成了一种新型的反应型阻燃剂1-（2-羟基-3-磷杂菲）丙氧基-4-环氧丙氧基丁烷(1),其结构和性能经¹H NMR, ³¹P NMR, FT-IR和TG表征。以1为封端剂,聚氨酯（PU）为基材,制备了1/PU阻燃复合材料（2）,研究了1对2阻燃性能和力学性能的影响,初步探讨了1的阻燃机理。结果表明:1具有气相和凝聚相阻燃作用,2燃烧后可形成致密光滑炭层,使点燃时间延长,改善了燃烧熔滴现象。1含量为1%时,2¹的LOI为27%, UL-94燃烧等级为V-0级。     

Comparison of the Catalytic Activities of Three Isozymes of Carnitine Palmitoyltransferase 1 Expressed in COS7 Cells

The enzyme carnitine palmitoyltransferase 1 (CPT1) catalyzes the transfer of an acyl group from acyl-CoA to carnitine to form acylcarnitine, and three isozymes of it, 1a, 1b, and 1c, have been identified. Interestingly, the 1c isozyme was reported to show no enzymatic activity, but it was not clearly demonstrated whether this inactivity was due to its dysfunction or due to its poor expression. In the present study, we (a) expressed individual CPT1 isozymes in COS7 cells, (b) evaluated quantitatively their expression levels by Western blotting using the three bacterially expressed CPT1 isozymes as standards, and (c) evaluated their catalytic activities. With these experiments, we successfully demonstrated that the absence of the enzymatic activity of the 1c isozyme was due to its dysfunction. In addition, experiments on the preparation of standard CPT1 isozymes revealed that the 1c isozyme did not show the standard relationship between migration in an SDS–PAGE gel and molecular size. We further tried to determine why the 1c isozyme was inert by preparing chimeric CPT1 between 1a and 1c, but no clear conclusion could be drawn because one of the chimeric CPT1s was not sufficiently expressed.     

The interplay of iron(II) spin transition and polymorphism

The mononuclear compound (1) [Fe(II)(L)(2)](BF(4))(2) (L = 4-ethynyl-2,6-bis(pyrazol-1-yl)pyridine) was prepared and structurally as well as magnetically characterised. The crystallisation revealed the formation of two polymorphs--the orthorhombic 1A and the tetragonal form 1B. A third, intermediate phase 1C was found exhibiting a different orthorhombic space group. Reversibility of the phase transition between 1A and 1C was studied by variable-temperature single-crystal and powder X-ray diffraction studies, while an irreversible phase transition was observed for the transition of 1B→1C. The magnetic studies show that the 1A?1C transition is accompanied by a very abrupt spin transition (ST) with 8 K hysteresis width (T(1/2)(↓) = 337 K, T(1/2)(↑) = 345 K). The ST was confirmed by M?ssbauer spectroscopy as well as by DSC studies. In contrast, the 1B polymorph remained low-spin up to 420 K. In conclusion, a full cycle of intertwined phase- and spin-conversions of three polymorphs could be proven following the general scheme 1B→1C?1A.     

Benesi-Hildebrand方程的正确性与可靠性

Benesi-Hildebrand(B-H)方程现被广泛地应用于各种非键作用体系, 特别是作用比为1:1型和1:2型的体系. 该方程可以用来确定作用体系的平衡常数以及作用比. 通过计算机模拟, 发现在某些情况下, 对于1:2型的作用体系, B-H方程会给出错误的作用比信息. 无论是弱的作用体系还是强的作用体系, 都可能会出现1:1的B-H方程曲线呈现出线性, 同时(或者)1:2的B-H方程曲线呈现出非线性的情况. 此外, 本文还研究了体系中两种作用物质的初态浓度比对于1:1型作用的平衡常数计算的影响, 发现最小的初态浓度比(r0)等于100是可以确保B-H方程近似条件C0B≈CB成立的安全阈值. 当作用很弱的时候, 比如说作用的平衡常数K小于25 L·mol-1 (C0P=4×10-4 mol·L-1)时, 则不需要对最小初态浓度比值r0进行限制, 就可以满足B-H方程的近似条件. 通过计算机模拟还分析了文献中提出的两个边界条件. 研究表明1/(KC0P)≥10可以保证处于平衡状态时的CB/C0B≥0.91. 而另一个条件KC0B>0.1 并不是确保B-H方程近似条件成立的充分条件.     

Synthesis and characterization of a new coordination compound of gold(III) with triphenylarsine oxide(TPAsO)

A new solid coordination compound of the type 1:1 of TPAsO to gold(III) was prepared firstly by means of the extraction method, but only the coordination compound of the type 2:1 was obtained by the method of direct synthesis. It was found in polar solvents that the 1:1 type coordination compound could transform to that of the 2:1 type slowly. By the data of thermoanalyses, a mechanism was suggested for thermal decomposition of the above two coordination compounds.     

Synthesis of 6-[[(hydroxyimino)phenyl]methyl]-1-[(1-methylethyl)sulfonyl]-1H-imidazo[4,5-b]pyridin-2-amine. An aza analogue of enviroxime

6-[[(Hydroxyimino)phenyl]methyl]-1-[(1-methylethyl)sulfonyl]-1H-imidazo[4,5-b]pyridin-2-amine ( 1 ), an aza analogue of enviroxime, was synthesized in eight steps from 6-hydroxynicotinic acid ( 2 ). Acid 2 was nitrated, chlorinated with phosphorus pentachloride, and subjected to Friedel-Crafts aroylation to give 6-chloro-5-nitro-3-pyridyl phenyl ketone ( 5 ). Amination of 5 was followed by reduction of the nitro group and condensation with ethoxycarbonylisothiocyanate to give 6-benzyl-2-ethoxycarbonylamino-1H-imidazo[4,5-d]pyridine ( 8 ). The ethoxycarbonyl moiety of 8 was cleaved, N-1 was isopropylsulfonylated, and the carbonyl moiety was condensed with hydroxylamine to give 1 . Compound 1 was inactive against rhinovirus 1B and poliovirus type 1 .     

Highly regioselective synthesis of 3,4-disubstituted 1H-pyrrole

A highly regioselective method for the synthesis of 3, 4-disubstituted 1H-pyrroles has been developed employing the ipso-directing property of a trimethylsilyl group. As a key starting material in this study, the known 3,4-bis(trimethylsilyl)-1H-pyrrole (3), was protected with carefully chosen groups, namely tert-butoxycarbonyl, N,N-dimethylaminosulfonyl, p-toluenesulfonyl, and triisopropylsilyl. A highly regioselective monoiodination of these 1-protected pyrroles was achieved by reaction with iodine-silver trifluoroacetate at low temperatures. Subsequent palladium-catalyzed cross-coupling reactions afforded 1-protected-4-substituted 3-trimethylsilyl-1H-pyrroles, which again underwent further room-temperature ipso-iodination and palladium-catalyzed cross-coupling reactions to provide symmetrical and unsymmetrical 1-protected-3,4-disubstituted 1H-pyrroles. Deprotection of 1-(tert-butoxycarbonyl) and 1-(N, N-dimethylaminosulfonyl) groups was found to be nontrivial. The 1-(p-toluenesulfonyl) protecting group was eventually proved to be superior to other protection groups, because it was readily removed after stepwise ipso monoiodinations and palladium-catalyzed cross-coupling reactions.     

Reactivity of 1-hydro-5-carbaphosphatrane based on tautomerization between pentavalent phosphorane and trivalent cyclic phosphonite

The reaction behavior of 1-hydro-5-carbaphosphatrane (1 a) was examined. Treatment of 1 a with oxidants such as 3-chloroperoxybenzoic acid (mCPBA) and tBuOCl gave cyclic phosphonate 2 and 1-chloro-5-carbaphosphatrane (4), respectively, via cyclic phosphonite 3, a tautomer of 1 a. Compound 4 was readily hydrolyzed to afford 2. Compound 1 a was also sulfurized via 3 by elemental sulfur to afford cyclic thioxophosphonate 5, which was also obtained by reactions in the presence of bases. Treatment of 1 a with bases also proceeded through 3 to give an equilibrium mixture of the corresponding phenoxide anion 10 and the phosphoranide anion 9, which was quenched with MeI to afford a mixture of 11 and 1-methyl-5-carbaphosphatrane (1 b). Such reactivities are typical for neutral phosphoranes. Theoretical investigations of these reactivities were also performed.     

1-甲基环丙烯与α-环糊精包合物的合成

采用溶液包结法利用α-环糊精(α-CD)对1-甲基环丙烯(1-MCP)进行包合,将气态的1-MCP固态化形成白色粉末状的1-MCP/α-CD稳定包合物,使之便于保存和应用。利用拉曼光谱(Raman)、X射线粉末衍射光谱(XRD)、气质联用测试仪(GC-MS)、核磁谱仪(NMR)等测试技术对所得包合物的结构和组成进行表征,证明了包合物的形成,同时提出了1-MCP/α-CD包合物中1-MCP含量的快速测定方法,以该法测定的包合物中1-MCP的有效质量分数约为3.6%。对1-MCP和α-CD的包合机理进行了探讨,认为1-MCP和α-CD按摩尔比1∶1进行包合。     

Binary organogelators which show light and temperature responsiveness

The gelation ability of 10 alkylammonium (CnH(2n+1)NH3+ where n=4-11, 12 and 16) anthracene-9-carboxylates (1n) has been evaluated. In cyclohexane, 1(4), 1(5), 1(6) and 1(7) only provided precipitates whereas 1(11), 1(12) and 1(16) provided very viscous solutions. In contrast, 1(8) 1(9) and 1(10) resulted in gels. The critical gelation concentration of 1(10) was very low (5.0 x 10(-4) mol dm(-3)). SEM observations showed that in the gel phase the morphology changes from straight fibrils to frizzy fibrils with the increase in n, whereas in the sol phase the formation of the sheet-like, two-dimensional aggregate is recognized. When the cyclohexane 1(10) gel was photoirradiated (lambda > 300 nm), the UV-VIS absorption bands assignable to monomeric anthracene were decreased and the gel was changed into the sol. It was confirmed by dark-field optical microscopy that the fibrillar bundles supporting the gel formation gradually disappear with photoirradiation time. When this sol was warmed at 30 degrees C in the dark, the gel was not regenerated but the precipitation of 1(10) resulted. When this sol was heated once at the bp of cyclohexane and cooled to 15 degrees C, the solution was changed into the gel again. This finding indicates that the fibrillar structure required for the gel formation is not reconstructed at 30 degrees C but obtained only when the hot cyclohexane solution is cooled.     

Enzyme immunoassay for aflatoxin B1-lysine adduct and its validation

A simple procedure was developed for in vitro synthesis and characterization of aflatoxin B1-lysine adduct using aflatoxin B1, N-alpha-acetyl lysine and m-chloroperbenzoic acid (MCPBA). At a molar ratio of 1:16 (aflatoxin B1:N-alpha-cetyl lysine), the recovery of adduct was 62%. Analysis of the adduct by thin-layer chromatography showed a single spot (Rf = 0). Absorption spectra of the adduct showed 2 peaks at 275 and 335 nm. Liquid chromatographic (LC) analysis of the AFB1-lysine adduct showed a relative retention time of 2.1 min. Using the same epoxidation procedure, BSA-AFB1 adduct and ovalbumin-AFB1 adduct were synthesized for production of antibodies and as coating antigen, respectively. Control rat serum, spiked with AFB1-lysine adduct and subjected to LC analysis showed a retention time of 2.1 min, which is similar to that of AFB1-lysine reference standard, synthesized. Further, enzymatically hydrolyzed, control rat serum spiked with BSA-AFB1 adduct showed 2 peaks with retention times of 2.1 and 2.7 min. Based on the LC analysis, recovery of BSA-AFB1 in terms of AFB1-lysine adducts was 67 +/- 5%. The major peak (2.1 min) accounted for 72% of the adduct; the second minor peak (2.7 min) accounted for 28% of the total AFB1-lysine adducts formed. Stability studies on the AFB1-lysine adduct synthesized, indicated that it was stable for 1 month. Antibody capture assay showed an absorbance of 0.9 to 1.0 at a dilution of 1:50,000 when ovalbumin-AFB1 was used as a coating antigen. Indirect competitive ELISA showed 50% displacement (IC50) of the antibodies at a concentration of 13 ng AFB1-lysine, whereas the IC50 for AFB1 was 7 ng. The recovery of AFB1-lysine adduct spiked to control rat serum followed by enzymatic hydrolysis and immunoanalysis (indirect ELISA) was 93 +/- 6%. The enzyme immunoassay was validated by a rodent model, in which the animals were exposed to aflatoxin B1 (20 microg AFB1/kg body mass/day). The level of AFB1-lysine adduct in the rat serum was 27.3 +/- 4.37 microg/mg albumin.     

A new pinoresinol-type lignan from Ligularia kanaitizensis

A new pinoresinol-type Lignan, 9alpha-angloyloxypinoresinol (1), was isolated from the roots and rhizomes of Ligularia kanaitizensis (Franch.) Hand.-Mazz, in addition to a known compound, 9alpha-hydroxypinoresinol (2). The structure of this new lignan (1) was established on the basis of 1D and 2D NMR experiments. Anti-HIV-1 RT biological assay showed that 1 was inhibitory to HIV-1 RT.     

水解动力学拆分3-(1-萘氧基)-1,2-环氧丙烷

研究了3-(1-萘氧基)-1,2-环氧丙烷[(R,S)-1]在Salen Co(Ⅲ)催化下的水解动力学拆分(HKR)。以转化率和ee值为指标,考察了催化剂用量、底物用量、反应温度、反应时间、溶剂种类等对HKR反应的影响。最佳HKR条件为:(R,S)-1 10 mmol,w[Salen Co(Ⅲ)]=0.75%,THF 1 mL,水0.5 eq,于25℃水解40 h,(R,S)-1的转化率为49.5%,(S)-1的ee为99.5%。