Synthesis of p-Trifluoroacetamidophenylethyl O-(2-Acetamido-2-Deoxy-β-D-Galactopyranosyl)-(1→4)-O-β-D- Galactopyanosyl-(1→4)-O-β-D-Glucopyranoside,Containing the Trisaccharide Portion of the Asialo-GM2 Glycolipid

ABSTRACT

The p-trifluoroacetamidophenylethyl β-glycoside 9 of the trisaccharide O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-(1→4)-O-β-D-galactopyranosyl-(1→4)-D-glucopyranose (gangliotriose, asialo-GM2) was synthesised. The key step was coupling of a suitably protected lactose derivative with a galactosamine thioglycoside derivative using sulfuryl chloride/trifluoromethanesulfonic acid activation.     

Synthesis and Characterization of Silica Gel Particles Functionalized with Bioactive Materials

Bioactive materials (having an amino acid, Ac-Tryptophan, A or a peptide, Ac-Trp-Ala-Ala, B) were anchored onto silica particles. A photoactive linker (N,N′-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (DPN)) was initially attached to the particles and next the amino acids were bound by using both Zr/P chemistry and 1,3-diisopropylcarbodiimide/1-hydroxybenzotriazole coupling. In A derivative extensive complexation of Trp with DPN was observed. Photolysis studies showed the presence of excited state reactions on the silica particles, moreover the radical species (DPN^.−, TrpH^.+, Trp^.) remained alive ∼100 times longer on the particle surface than in solution. These studies show that the formation rate of these radicals is a function of the supramolecular structures of the peptide and of the amino acid derivative on the silica particle. This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18–21 July, 2004.     

Aromatic amine coupling ofaspergillus niger lactase to controlled-pore silica witho-dianisidine

Lactose (β-galactosidase) derived fromAspergillus niger was immobilized on controlledpore silica with an average pore diameter of 425 Å. The coupling of this enzyme to the surface of the silica was accomplished by reacting the surface of the silica with o-dianisidine followed by the functionalization of the residual amine with glutaraldehyde or with nitrite to form the diazonium salt. The PH profiles of the immobilized enzymes were determined and compared. Continuous reactor studies of the glutaraldehyde-functionalized, immobilized enzyme indicated a half-life of 52 days at 50°C with a 5% lactose feed at pH 3.5.     

以N-乙酰基-5-N,4-O-噁唑烷酮保护的唾液酸对甲基苯硫苷给体合成神经节苷脂GM3三糖甲苷衍生物

详细研究了N-乙酰基-5-N,4-O-噁唑烷酮保护的唾液酸对甲基苯硫苷给体1与四种苄基或苯甲酰基保护的半乳糖甲苷二醇的唾液酸化反应, 以较高的产率(72%～89%)得到了相应的唾液酸化产物, α/β＝(1.6～2.0)∶1. 在此基础上, 以乳糖为原料通过7步反应以19%的总产率制得了2,3,6,2’,6’-五-O-苯甲酰基-β-乳糖甲苷17, 使用唾液酸给体1将化合物17唾液酸化, 成功地得到神经节苷脂GM3三糖甲苷衍生物18, 产率68%, α/β＝1.6∶1.     

Large Scale Synthesis of A Derivative of An α-Galactosyl Trisaccharide Epitope Involved in the Hyperacute Rejection of Xenotransplantation

ABSTRACT

A derivative of an α-galactosyl trisaccharide xenoactive antigen, (2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-(1→3)-(2,4,6-tri-O-acetyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-acetyl-β-D-glucopyranosyl azide (5), was synthesized on a large scale (50 gram). The synthesis involved a high yielding and highly stereoselective (α/β>20:1) glycosylation reaction utilizing a thiogalactoside as the donor and a selectively protected lactose azide as the acceptor. This derivative serves as a versatile intermediate that can be transformed into a variety of α-Gal containing glycoconjugates highly desired in xenotransplantation research and pharmaceutical development.     

A novel method for the preparation of C18 ester-bonded RP-HPLC packings

Summary A novel procedure had been developed for the preparation of RP packings. A C₁₈ alkyl-chain was bound onto spherical silica (particle size d_p=5 μm, s=300 m²g⁻¹) with glycidoxypropyltrimethoxysilane as coupling agent. Elemental analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) and chromatographic evaluation confirmed the bonding of the packings and their RP behavior.     

全衍生化羟丙基-β-环糊精固定相的制备及应用

研究了3, 5-二甲基苯基异氰酸酯对羟丙基-β-环糊精固定相的手性识别影响.通过异氰酸丙基三乙氧基硅烷作偶联剂,将羟丙基-β-环糊精键合到3-氨丙基硅烷化硅胶上,再用3, 5-二甲基苯基异氰酸酯对β-环糊精和硅胶其余羟基进行衍生化,制得一种新型的3, 5-二甲基苯基氨基甲酸酯全衍生化羟丙基-β-环糊精键合硅胶手性固定相.在反相色谱条件下,对9种手性药物进行了拆分,结果表明,3, 5-二甲基苯基氨基全衍生化固定相较之羟丙基-β-环糊精固定相有更好的分离效果.     

单分散SiO2/PS复合粒子的制备

聚合物包覆无机物的核一壳结构复合粒子研究长期以来受到关注,源于其应用广泛．根据表面性质要求对无机相或者有机相表面进行功能化,可使得到的复合粒子与不同的应用体系相匹配．这类聚合物包覆无机物的有机／无机复合粒子,已在光学器件、分离、药品、农业、涂料等很多领域有广泛和潜在应用．本文制备这类复合粒子用于石油工业模型催化剂和助剂．     

Synthesis of composite latex particles filled with silica

Encapsulation of silica nanoparticles was performed by dispersion polymerization of styrene, butyl acrylate and butyl methacrylate in aqueous alcoholic media. Following previous works^1‐3), the silica beads were first modified by reacting on their surface the 3‐trimethoxysilyl propyl methacrylate coupling agent (MPS). In every case, the silica beads are all surrounded by polymer giving composite latex particles filled with silica. Each composite particle contains from one to a great number of silica beads. Changing the size or the concentration of the silica beads, and the experimental conditions for the synthesis of the polymer particles enables to control this number. One can take benefit of this to synthesize model composite particles with controlled compositions.     

Preparation of hemispherical hollow silica microcapsules with different affinity surface by using spherical vaterite calcium carbonate as template

We developed a method to prepare hemispherical hollow silica microcapsules (HHSM) with different affinity surfaces using spherical vaterite calcium carbonate (SVCC) as a template. The preparation process composed of the adhesion of calcium carbonate onto the surface of methyl methacrylate (MMA) droplets followed by suspension polymerization, the partial etching of calcium carbonate on the polymethyl methacrylate (PMMA) mother particle, the formation of silicon dioxide powder by sol–gel reaction and their deposition onto the etched flat surface of calcium carbonate, the surface modification of deposited silicon dioxide with silane coupling agent, the removal of the mother particle with acetone, the formation of silicon dioxide powder by sol–gel reaction and deposition onto the exposed hemispherical surface of calcium carbonate, and the surface modification of deposited silicon dioxide with silane coupling agent. The synthesized microcapsules had a complete hemispherical structure and both hydrophilic and hydrophobic surfaces. Copyright © 2007 John Wiley & Sons, Ltd.     

An efficient synthesis of a biantennary sialooligosaccharide analog using a 1,6-anhydro-β-lactose derivative as a key synthetic block

An efficient and versatile method for the synthesis of a biantennary octasaccharide derivative was established by combined chemical and enzymatic manipulations of 1,6-anhydro-β-lactose as a key starting material. A key 1,6-anhydro-β-lactose derivative having two unprotected hydroxyl groups at C-3′ and C-6′ positions was prepared and employed for the chemical coupling reaction with a known 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl imidate to afford a tetrasaccharide derivative with two GlcNAc branches in 69% yield. Enzymatic galactosylation using UDP-Gal with a bovine milk β1,4-galactosyltransferase and subsequent sialylation with a recombinant α2,3-sialyltransferase in the presence of CMP-Neu5Ac proceeded smoothly and gave a desired model compound, a bivalent sialooctasaccharide (1), in 73% overall yield from the tetrasaccharide intermediate.     

点击功能化的叶酸受体靶向荧光纳米探针用于肿瘤细胞成像

采用点击化学偶联法对荧光二氧化硅纳米粒子表面进行叶酸功能化修饰,构建了一种叶酸受体靶向的荧光纳米探针,并成功用于肿瘤细胞的成像研究.首先通过St?ber法制备包裹钌联吡啶的荧光二氧化硅纳米粒子(RSiNPs),然后利用叠氮化硅烷偶联剂(Az-PTES)的水解反应在其表面引入叠氮基团,最后通过点击化学反应将炔丙基叶酸衍生物偶联到粒子表面.利用红外光谱对其偶联前后的叠氮基特征峰(2105 cm-1)进行表征,证实了叶酸功能化的荧光纳米探针(RSiNPs-Folate)已被成功制备.在生理pH条件下,以458 nm为激发波长,RSiNPs-Folate在601 nm处发射较强的红色荧光,且光稳定性较好.细胞成像结果表明,这种叶酸受体靶向的荧光纳米探针能够有效地标记叶酸受体呈阳性的人宫颈癌细胞(HeLa),而叶酸受体呈阴性的人肺癌细胞(A549)未观察到明显的荧光.叶酸竞争性结合实验证明了这种叶酸受体介导的肿瘤细胞成像机制.此探针能够实现混合细胞体系中HeLa细胞的选择性识别与荧光成像.与酰胺化反应偶联叶酸相比,这种点击功能化的纳米探针的合成方法简单、反应条件温和、产率高,可用于不同肿瘤细胞的荧光标记与成像.     

Effect of surface interaction of silica nanoparticles modified by silane coupling agents on viscosity of methylethylketone suspension

In order to control the viscosity of a dense silica methylethylketone (MEK) suspension, the surfaces of silica nanoparticles were modified by 3-glycidoxypropyltrimethoxysilane (GPS) or hexyltrimethoxysilane (C6S) in MEK with the addition of a small amount of pH-controlled water. First, the effect of water addition on the amount of chemisorbed coupling agent was investigated. pH-controlled water enhanced the reactivity of the coupling agent in MEK. The amount of chemisorbed coupling agent increased slightly with the addition of pH 3 water and increased remarkably with the addition of pH 12 water. Next, the effect of the organic functional groups of the coupling agent, pH of the additive water, and additive amount of coupling agent on surface interaction were determined by colloid probe AFM. The steric repulsive force between the silica nanoparticles increased due to water addition, particularly when the pH was maintained at 3. The viscosity of the silica MEK suspension reduced effectively when this repulsive force appeared; however, the optimum condition for reducing the suspension viscosity was dependent on the coupling agent species. The viscosity of the dense silica MEK suspension can be controlled by the addition of small amounts of pH-controlled water and the functional groups of the coupling agent.     

通过RAFT聚合制备SiO2/接枝共聚物纳米杂化粒子

以二氧化硅(SiO2)纳米粒子表面键接的二硫代苯甲酸酯作为可逆加成-断裂-链转移(RAFT)聚合反应的链转移剂, 在室温下引发苯乙烯和马来酸酐进行表面RAFT交替共聚反应, 制得了SiO2/苯乙烯-alt-马来酸酐杂化材料. 通过聚氧化乙烯(PEO)的羟基与马来酸酐的酯化反应, 将PEO接枝到SiO2纳米粒子的表面, 增加了硅粒子的生物相容性. 用FTIR, TGA和TEM对杂化材料的结构、组成和形貌进行了表征.     

Preparation of PDMS-ormosil and its application in miniemulsion polymerization

With the assistance of ultrasound, octamethylcyclotetrasiloxane (D4) and slight silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) were sufficiently mixed with silica sol, and the in situ ring-opening polymerization of D4 on the surface of silica nanoparticles, catalyzed by dodecylbenzene sulfonic acid (DBSA), was enhanced as well. Thus, polydimethylsiloxane (PDMS)-modified silica (PDMS-ormosil) mixture was obtained. A slight addition of silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) could significantly enhance the modified efficiency. The PDMS-ormosil mixtures were directly dispersed in the mixed monomer methyl methacrylate and butyl methacrylate. Then, miniemulsion polymerizations of acrylate monomers containing PDMS-ormosils were carried out, with free PDMS as hydrophobe and neutralized DBSA as emulsifier, both preexisted in the PDMS-ormosil mixture. Thus, the troubles of separation, purification, and redispersion in the traditional techniques can be omitted. Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscope, scanning electron microscope, and water contact angle tests were utilized to demonstrate that nanocomposite particles with a core–shell structure were synthesized; when the silica content was 3 wt% of the monomers, the average particle size was 97 nm, and the generated PDMS improved the hydrophobicity of the nanocomposite latex.     

Acrylic polymer/silica organic–inorganic hybrid emulsions for coating materials: Role of the silane coupling agent

Acrylic polymer/silica organic–inorganic hybrid emulsions were synthesized by a simple method, that is, a conventional emulsion polymerization and subsequent sol–gel process, to provide water‐based coating materials. The acrylic polymer emulsions contained a silane coupling agent monomer, such as methacryloxypropyltriethoxysilane, to form highly solvent‐resistant hybrid films. On the other hand, the hybrid films from the surface‐modified polymer emulsions, in which the silane coupling agent was located only on the surface of the polymer particles and the particle core was not crosslinked, did not exhibit high solvent resistance. A honeycomblike array structure, which was derived from the polymer particles (diameter ≈ 50 nm) and the silica domain, on the hybrid film surfaces was observed by atomic force microscopy. The crosslinked core part and silane coupling agent containing the shell part of the polymer particles played important roles in attaining high solvent resistance. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4736–4742, 2006     

Effect of pH on monolayer properties of colloidal silica particles at the air/water interface

Monodisperse colloidal silica particles were prepared by the St?ber method and hydrophobized by grafting a silane coupling agent, octadecyltrimethoxysilane. Two different types of silica particles, i.e., hydrophilic and hydrophobic silica particles were spread at the air/water interface to form the Langmuir monolayers. Monolayer properties of those particles were investigated by measuring surface pressure–area (π–A) isotherms at different subphase pH. At pH above the isoelectric point (IEP) of silica, as pH increased the π–A isotherms for the hydrophobic particles slightly shifted to larger surface area whereas those for the hydrophilic particles showed a reverse trend. At pH below the IEP, the π–A isotherms for both types of particles shifted to much larger surface area with different shapes. In order to analyze the π–A isotherm results further, the time dependence of π was examined. When pH is above the IEP, the π for the hydrophilic particles significantly decreased with increasing time and it did more at higher pH. On the other hand, the decrease in π for the hydrophobic particles was insignificant regardless of pH. For both types of silica particles, the decrease in π was minimal at pH below the IEP. These results were discussed in terms of particle desorption into the water subphase and interparticle electrostatic repulsion which is directly influenced by zeta potential.     

Novel polyester/SiO2 nanocomposite membranes: Synthesis,properties and morphological studies

In this paper, a new type of soluble polyester/silica (PE/SiO₂) hybrid was prepared by the ultrasonic irradiation process. The coupling agent γ-glycidyloxypropyltrimethoxysilane (GOTMS) was chosen to enhance the compatibility between the polyester (PE) and silica (SiO₂). Furthermore, the effects of the coupling agent on the morphologies and properties of the PE/SiO₂ hybrids were investigated using UV-vis and FT-IR spectroscopies and FE-SEM. The densities and solubilities of the PE/SiO₂ hybrids were also measured. The results show that the size of the silica particle was markedly reduced by the introduction of the coupling agent, which made the PE/SiO₂ hybrid films become transparent. Furthermore, thermal stability, residual solvent in the membrane film and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). The effects of SiO₂ nanoparticles on the glass transition temperature (T_g) of the prepared nanocomposites were studied by differential scanning calorimetry (DSC). Moreover, their mechanical properties were also characterized. It can be observed that the Young's moduli (E) of the hybrid films increase linearly with the silica content. The results obtained from gas permeation experiments with a constant pressure setup showed that adding SiO₂ nanoparticles to the polymeric membrane structure increased the permeability of the membranes.     

基于磁性微球的固定化金属亲和载体及其在蛋白质/多肽纯化中的应用

采用模板法制备的单分散磁性硅胶微球,经过表面修饰偶联上亚氨基二乙酸(IDA),与过渡金属离子Cu2 螯合,制成一种新型的磁性固定化金属亲和纯化载体。用牛血清白蛋白(BSA)作为模型进行磁性固定化金属亲和吸附蛋白的研究,结果表明,BSA在磁性亲和载体上的吸附可用Langmuir吸附方程描述,对BSA的饱和吸附量为90mg/g。将磁性亲和载体用于带有组氨酸标签的镇痛抗肿瘤多肽(analgesic-antitumorpeptide,AGAP)纯化,在未经过滤的细胞裂解液中可以将AGAP一步纯化,非特异性吸附低,操作简便,完全适用于含有组氨酸标记的重组多肽或蛋白的分离纯化。     

Synthesis and redox-active base-pairing properties of DNA incorporating mercapto C-nucleosides

Here, we describe the synthesis and incorporation of the nucleoside base analogue C-deoxyribonucleoside 3 carrying thiophenol into DNA. The 1′-β compound 3 was synthesized by Friedel-Crafts alkylation, followed by deprotection. The coupling reaction with 3,5-ditoluoyl-1-α/β-methoxy-2-deoxy-d-ribose and diphenyldisulfide in the presence of SnCl₄ afforded the α/β mixture 2 (β/α=2.8), and the β-form was separated by silica gel chromatography. After formation of the phosphoramidite derivative, the C-nucleoside 3 was incorporated into DNA. When the mercapto-bases were incorporated into complementary singled-stranded (ss) DNAs, the resulting duplex displayed high thermal stabilization on treatment with bubbling O₂ (T_m 73 °C), but was destabilized in the presence of mercaptoethanol (T_m 33 °C). CD spectra showed that the duplex had a right-handed double-stranded structure. Imino proton NMR studies of temperature stability suggested that the strength of hydrogen bonding around the mercapto C-nucleoside was larger when treated with bubbling O₂ than when in treated with reducing agent. Thus, formation of the base-to-base disulfide bond increased the stability of the duplex; correspondingly, reduction of the disulfide to two thiol bases destabilized the DNA reversibly. The duplex-forming disulfide base pair showed resistance to exonulease III. The present strategy could be used to introduce new functionalities into cells and novel biomaterials.