Synthesis of side‐chain liquid‐crystalline homopolymers and triblock copolymers with p‐methoxyazobenzene moieties and poly(ethylene glycol) as coil segments by atom transfer radical polymerization and their thermotropic phase behavior

A series of side‐chain liquid‐crystalline (LC) homopolymers of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with different degrees of polymerization were synthesized by atom transfer radical polymerization (ATRP), which were prepared with a wide range of number‐average molecular weights from 5.1 × 10³ to 20.6 × 10³ with narrow polydispersities of around 1.17. Thermal investigation showed that the homopolymers exhibit two mesophases, a smectic phase, and a nematic phase, and the phase‐transition temperatures of the homopolymers increase clearly with increasing molecular weights. A series of novel LC coil triblock copolymers with narrow polydispersities was synthesized by ATRP, and their thermotropic phase behavior was investigated with differential scanning calorimetry and polarized optical microscopy. The LC coil triblocks were designed to have an LC conformation of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with a wide range of molecular weights from 3.5 × 10³ to 1.7 × 10⁴ and the coil conformation of poly(ethylene glycol) (PEG) (number‐average molecular weight: 6000 or 12,000) segment. Their characterization was investigated with ¹H NMR, Fourier transform infrared spectra, and gel permeation chromatography. Triblock copolymers exhibited a crystalline phase, a smectic phase, and a nematic phase. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased, and the crystallization of PEG depressed with increasing molecular weight of the LC block. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2854–2864, 2003     

A ONE-STEP SURFACE MODIFICATION PROCEDURE TO PEG-GRAFTED NANO-TITANIA

PEG （Polyethylene Glycol）-grafted nano-titania has been obtained in a one-step procedure using hexamethylene diisocyanate as the coupling agent and dibutyltin dilaurate as the catalyst in toluene at 80℃ and characterized qualitatively by FTIR and quantitatively by elemental analysis and thermogravimetric analysis. A comparison of nano-titania with two other commonly used inorganic nanoparticles, nano-silica and nano-alumina, is made, revealing that reactivity order is nano- silica 〉 nano-alumina 〉 nano-titania in view of PEG grafting. Possible mechanism of PEG grafting is also discussed.     

人血清中地尔硫高效液相色谱法测定及药代动力学参数

建立了反相高效液相色谱法监测人口服地尔硫艹卓缓释片后血药浓度。血样用正己烷－氯仿－异丙醇混合溶剂（６０４０５）提取后，以Ｃ１８化学键合硅胶为固定相，甲醇－水－三乙胺为流动相，安定为内标，在２３９ｎｍ波长处定量检测。血药浓度在１５～３００μｇ／Ｌ范围内线性关系良好，最低检测浓度为３μｇ／Ｌ。批内（ｎ＝７）及批间（ｎ＝５）测定相对标准偏差分别小于６．８％和８．４％，回收率为９１％～１０４％。监测了８名健康人口服盐酸地尔硫艹卓缓释片后的不同时间的血药浓度变化，计算了有关的药代动力学参数。     

蒿甲醚在模拟体内酸碱环境中的代谢动力学研究

 利用高效液相法对蒿甲醚进行了模拟体内酸碱环境的代谢动力学研究 ,测定了蒿甲醚及其代谢产物双氢青蒿素、蒿甲醚呋喃酯的代谢曲线。结果表明 ,蒿甲醚在模拟体内肠道和血液的弱碱性环境条件下半衰期为2 87 2min(计算值 ) ;在模拟体内胃液的酸性环境条件下半衰期为 74 6min ;在两种条件下的主要代谢产物均为双氢青蒿素和蒿甲醚呋喃酯。该方法克服了以往文献所报道方法的一些缺点 ,不仅简化了样品制备方法 ,也提高了检测结果的准确性。     

Synthesis of Thiourea Derivatives on Soluble Polymeric Support

A modified poly(ethylene glycol) (PEG) has been developed as the soluble polymeric supports for liquid phase synthesis of novel thiourea derivatives.In each step of the sequence,the PEG-bound products were precipitated in cold Et2O and the unreacted materials and by-products were removed by simple filtration.The progress of reaction,purity of the isolation and the structure of the PEG-bound products were easily monitored by TLC,IR and ^1H NMR spectra.Representative thiourea derivatives were obtained in moderate yields with excellent purity from this modified PEG-bound product by the cleavage with 50% TFA/H2O.     

Determination of clindamycin in animal plasma by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

A method for the quantification of clindamycin in animal plasma using high-performance liquid chromatography combined with electrospray ionization mass spectrometry (LC/ESI-MS/MS) is presented. Lincomycin is used as the internal standard. The sample preparation includes a simple deproteinization step with trichloroacetic acid. Chromatographic separation is achieved on an RP-18 Hypersil column using gradient elution with 0.01 M ammonium acetate and acetonitrile as mobile phase. Good linearity was observed in the range 0-10 microg ml(-1). The limit of quantification of the method is 50 ng ml(-1) and the limit of detection is 1.3 ng ml(-1). The method was shown out to be of use for pharmacokinetic studies of clindamycin formulations in dogs.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

Controllable and flexible cellular network for virus cell-to-cell spread

Cellular networks were constructed based on PEG modification and soft lithography, in which cell numbers and spatial distributions can be controlled. A micro-injector was combined with cellular networks to fix virus induced plaque and virus spread direction, by which virus cell-to-cell spread can be distinguished from cell-free spread.     

Volume and compressibility changes on mixing aqueous solutions of the amino acid and poly(ethylene glycol)

The volume and compressibility changes on mixing aqueous solutions of the amino acid and poly(ethylene glycol) were measured with a vibration densimeter and a sing-around velocimeter at 298.15 K. For the system of alanine-PEG-H₂O, the additivity rule for the mean apparent molal volume and compressibility at infinite dilution held, and the excess volume and compressibility changes on mixing were obtained. For the system of glycine-PEG-H₂O, the additivity rule for the mean apparent molal compressibility at infinite dilution did not hold. While the mean apparent molal volume and compressibility changes were negative and positive for the systems of another amino acid-PEG-H₂O, respectively, where amino acids were valine, isoleucine, leucine, phenylalanine, and tryptophan. These results suggest that glycine and alanine are excluded from the hydration layer around PEG chain and the amino acids with a larger side chain than alanine are bound to the PEG chain due to the hydrophobic interaction. The hydration number per monomer around PEG chain was estimated to be 3.9.     

Synthesis of protected peptides from the human IgG1 hinge region on PEG support using disulfide bond synthons and alkaline or enzymatic detachment

Peptides from the hinge region of human IgG1 are potential defined carriers of synthetic immunogens. Their synthesis was carried out on the soluble support—PEG-OMe 2000 using disulfide bond synthons. The loading capacity of the polymer was increased twofold by anchoring the lysine as a simple branching unit. The amino acid leucine was used as an enzymatically cleavable linker. Peptide detachment from the polymer was performed either by classical ester bond saponification or newly by peptide bond cleavage catalyzed by thermolysin in water.