流通池光度滴定法应用—络合反应中的质子释放数测定

用具有流通池的分光光度计作测定装置,建立了由平衡移动法测定络合反应中质子释放数的新方法。方法简单、快速,仅用一个标准溶液,适于在变更pH值范围内金属离子不发生水解和没有其他副反应的体系。     

Theoretical study of structure and stability of fullerene derivative: C50O

A total of eight possible isomers of C₅₀O, an oxide of fullerene C₅₀ (D_5h), have been investigated by B3LYP/3‐21G calculations. The isomer, which has an annulene‐like structure with oxygen bridging across a [5,6] type C? C bond at the site between the pole and the equatorial belt, is found being the ground state of C₅₀O. Four isomers are relatively more stable and the energy differences between them are not large. This result indicates that more than one C₅₀O isomer will coexist once C₅₀O is synthesized. The relative stabilities of the C₅₀O isomers may be determined mainly by the strain release and by the formation of the cyclic phenylene substructure at the equatorial belt of the cage. The calculated nucleus independent chemical shifts (NICS) of the C₅₀O isomers will be useful because from them one can expect outstanding NMR properties that can lead to their identification and characterization. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Silicone-modified starch/protein microparticles: protecting biopolymers with a hydrophobic coating

Silicone-coated starch/protein (human serum albumin, HSA) microparticles were prepared by precipitation of a starch/HSA/DMSO/water (water-in-oil) emulsion into acetone containing a silicone: the silicone polymer was either unfunctionalized (SiMe₃ terminated, PDMS) or functionalized at its termini with Si(OEt)₃ groups (TES-PDMS). The microparticles of approximate diameter 2–7 μm were highly hydrophobic with advancing contact angles 115°. Over several minutes, however, the contact angle decreased to ca. 40–70°. Soxhlet extraction with water led to degradation of the microparticles, irrespective of the nature of their silicone coating, as evidenced by release of the protein from them. Intraperitoneal (IP) or gastric administration of the two different particles to mice, however, showed a clear difference between the two silicones. The microparticles coated with either PDMS or TES-PDMS led to very different immune responses. Oral administration of the microparticles prepared with functionalized silicone elicited a significant production of antibodies, whereas the particles prepared with the unfunctionalized silicone (PDMS) were only weakly active. By contrast, the IP results demonstrated that particles coated with PDMS elicited an immune response that was established much more rapidly than with the particles modified with TES-PDMS. It is proposed that the TES-PDMS forms a physically adhering film or covalent bond to the protein molecules, which serves to protect the microparticle from biological degradation in the gut and/or facilitates the microparticle/protein interaction with the immune system.     

Nucleophilic Addition of Thiaproline to Electrochemically Derived o‐Quinone,Application to the Sensitive Voltammetric Detection of Thiaproline

The mechanism of electrochemical behavior of catechol in the presence of thiaproline is investigated by cyclic voltammetry, controlled‐potential coulometry and spectrophotometric tracing of the reaction coordinate. The results indicate that thiaproline participate in with an ECEC mechanism in a nucleophilic (Michael) addition to o‐quinone. Effect of pH of buffer solution on reaction pathway is studied and showed that addition of thiaproline to the o‐quinone is performed only in solutions with pHs higher than 5. These results indicate that the addition of thiaproline is occurred first from amine functional group. In the second step, the addition of carboxylate group of thiaproline to C‐5 of catechol results the final product with a lactone ring in its structure. Observation of two isosbestic point in absorption spectrum during the progress of the electrolysis together with the FT‐IR results for final product can be presented as evidence for two step addition of thiaproline to catechol. Final product, due to the electron donor property of thiaproline, more easily oxidized respect to the former catechol and as a result, a new redox couple is obtained for this compound in lower potentials. The easier anodic oxidation of addition product (relative to catechol) caused to an increase in anodic current for catechol, which is proportional to the thiaproline concentration. The differential pulse voltammetry (DPV) is applied as a sensitive voltammetric method for the detection of thiaproline. A linear range from 5×10^?8 to 5×10^?6 M with a detection limit of 1×10^?8 M is resulted for thiaproline. With respect to the reversibility of the electrochemical reactions in the mechanism, and also more facile oxidation of the addition products, the square‐wave voltammetry is presented as a method with considerably more sensitivity for the detection of sub‐micromolar amounts of thiaproline. The advantageous properties of the voltammetric method for thiaproline detection lie in its excellent catalytic activity, sensitivity and simplicity.     

药用缓释辅料——羟丙基甲基纤维素的合成及其缓释性能的研究

本文研究了药物缓释材料HPMC的合成方法,探讨了碱纤维素制备,醚化剂浓度,混合醚化剂配经以及产品后处理对高粘度HPMC的影响。本文还初步对KCl,氨茶碱,硝酸异山梨醇酯等药物采用合成的HPMC作辅料,进行了缓释制剂的研究,结果表明合成的HPMC具有满意的缓释性能。     

乌江流域沉积岩风化过程中稀土元素的富集与释放

以乌江流域石灰岩、白云质灰岩、白云岩、硅质岩、页岩和砂岩等沉积岩的13条风化剖面为对象，运用R型分层聚类分析和质量平衡计算方法，研究了这些岩石风化过程中稀土元素（REE）的富集与释放及其对植物生长和河水REE分布的影响，目的是为河水物质来源研究和为农业生产提供依据。结果表明：（1）乌江流域石灰土中REE的富集程度显著高于各自母岩、黄壤、上陆壳（UCC）、中国土壤（CS）和世界土壤（WS）；（2）沉积岩风化过程中REE的富集特征和机制可能与母岩中REE分布特征以及风化剖面中有机质、铁（氢）氧化物和粘土矿物的吸附有关；（3）沉积岩风化过程中释放的REE可为植物吸收利用；（4）石灰岩等沉积岩风化过程中REE和F。等元素的释放对河水溶解态REE的分布有重要影响。     

Controlled/“Living “Radical Polymerization of(-)-Menthyl Methacrylate

The atom transfer radical polymerization(ARP)of (-)-menthyl methacrylatc((-)-MnMA) mediated by CuCl/bipyridine and ethy1 2-bromopropionate or 1-phenylethyl bromide in THF system has been studied.The dependence of the specific rotation on molecular weight and the CD of Poly((-)-MnMA) thus obatined was investigated.     

Solvent release upon ion association from entropy data

The translational entropy loss on the association of two ions to form an ion pair or 11 complex is overcompensated by a rotational entropy gain, an electrostatic entropy gain, and an entropy gain due to solvent release from translational immobilization. The first three effects can be calculated, leaving the fourth as a difference from the experimental entropy change on association. The ratio of the solvent release entropy gain to the entropy change on melting of the solvent indicates the number of solvent molecules released on the association. A similar value is obtained from data for the volume change on association.Presented as a poster at the 10th International Conference on Non-Aqueous Solvents (ICNAS) at Leuven, Belgium, August 1986, and at the 24th International Congress on Coordination Chemistry (ICCC) at Athens, Greece, August 1986.     

A new poly(2-hydroxy-3-phenoxypropylacrylate, 4-hydroxybutyl acrylate, diethyl maleate) membrane controlled clonidine linear release in the transdermal drug delivery system

Oral clonidine, used as an antihypertensive, can result in some side effects such as dry mouth, drowsiness, dizziness and sedation; thus, clonidine transdermal drug delivery (TDD) was considered. Use of the controlled release membrane was one of the methods in TDD systems to regulate the permeation properties. A new type of copolymer membrane that controlled clonidine linear release in TDD system was synthesized by UV radiation. This membrane consisted of three monomers: 2-hydroxy-3-phenoxypropylacrylate, 4-hydroxybutyl acrylate and diethyl maleate. The membrane had both fine permeation properties and perfect physical properties when three monomers were in the weight ratio of 4:4:2; this type of membrane was chosen as an optimized membrane. It was found that the membrane controlled clonidine zero-order release, the permeation rates decreased with the thicknesses of membranes increasing, and the permeation rates were linearly dependent on the square root of the concentration of clonidine. Furthermore, the optimized membranes were characterized by FTIR, DSC and SEM.     

Polyelectrolyte microcapsules templated on poly(styrene sulfonate)-doped CaCO3 particles for loading and sustained release of daunorubicin and doxorubicin

A strategy to incorporate and release anti-cancer drugs of daunorubicin (DNR) and doxorubicin (DOX) in preformed microcapsules is introduced, which is based on charge interaction mechanism. Oppositely charged poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) were assembled onto PSS doped-CaCO₃ colloidal particles in a layer-by-layer manner to yield core-shell particles. After removal of the carbonate cores, hollow microcapsules with entrapped PSS were fabricated, which showed spontaneous loading ability of positively charged DNR and DOX. The drug loading was confirmed quantitatively by observations under confocal laser scanning microscopy, transmission electron microscopy and scanning force microscopy. Quantification of the drug loading was performed under different conditions, revealing that a larger amount of drugs could be incorporated at higher drug feeding concentrations and higher salt concentrations. However, putting additional polyelectrolyte layers on the microcapsules after core removal resulted in weaker drug loading efficiency. The drug release behaviors from the microcapsules with different layer numbers were studied too, revealing a diffusion controlled release mechanism at the initial stage (4 h).