Low molecular weight polyethylenimines linked by beta-cyclodextrin for gene transfer into the nervous system

BACKGROUND: Polyethylenimines (PEIs) with high molecular weights are effective nonviral gene delivery vectors. However, the in vivo use of these PEIs can be hampered by their cellular toxicity. In the present study we developed and tested a new PEI polymer synthesized by linking less toxic, low molecular weight (MW) PEIs with a commonly used, biocompatible drug carrier, beta-cyclodextrin (CyD). METHODS AND RESULTS: The terminal CyD hydroxyl groups were activated by 1,1'-carbonyldiimidazole. Each activated CyD then linked two branched PEI molecules with MW of 600 Da to form a CyD-containing polymer with MW of 61 kDa, in which CyD served as a part of the backbone. The PEI-CyD polymer developed was soluble in water and biodegradable. In cell viability assays with sensitive neurons, the polymer performed similarly to low-MW PEIs and displayed much lower cellular cytotoxicity compared to PEI 25 kDa. The gene delivery efficiency of the polymer was comparable to, and at higher polymer/DNA ratios even higher than, that offered by PEI 25 kDa in neural cells. Attractively, intrathecal injection of plasmid DNA complexed by the polymer into the rat spinal cord provided levels of gene expression close to that offered by PEI 25 kDa. CONCLUSIONS: The polymer reported in the current study displayed improved biocompatibility over non-degradable PEI 25 kDa and mediated gene transfection in cultured neurons and in the central nervous system effectively. The new polymer would be worth exploring further as an in vivo delivery system of therapeutic genetic materials for gene therapy of neurological disorders.     

In vitro chiral nematic ordering of chitin crystallites

Microfibrillar fragments of purified crab and shrimp chitin were prepared by hydrolysis in 3 HCl at its boiling point (104°C). After removal of the acid by centrifugal washing and dialysis, an ultrasound treatment converts the residual product to a colloidal suspension stabilized by NH₃⁺ charges. When dewatered to a critical concentration, spontaneous formation of a two-phase equilibrium system occurs. The upper phase (lower concentration) is isotropic and the lower phase is anisotropic. The latter displays chiral nematic order and dries to a solid film which mimics the helicoid organization characteristic of the chitin microfibrils in the cuticle of arthropods.     

Catalytic properties of β-cyclodextrin glucanotransferase from alkalophilic<Emphasis Type="Italic">Bacillus</Emphasis> sp. BL-12 and intermolecular transglycosylation of stevioside

The catalytic properties of β-cyclodextrin glucanotransferase (β-CGTase) from alkalophilicBacillus sp. BL-12 specific for the intermolecular transglycosylation of stevioside were investigated. The molecular mass of purified β-CGTase by ultra-filtration and β-cyclodextrin polymer affinity chromatography was estimated to be 90 kDa, which is high compared to other known bacterial CGTases. The optimal pH and temperature were 9.0 and 50°C, respectively, and thermal stability at 40°C was elevated 10-fold in the presence of 1% maltodextrin. The kinetic parameters of the new β-CGTase from alkalophilicBacillus sp. BL-12 indicate that it is more suitable for transglycosylation than the cyclization reaction. Maltodextrin was the most suitable glycosyl donor for transglycosylation of stevioside. The transglycosylation of stevioside was carried out using 60 units of CGTase per gram of maltodextrin, 20 g/L stevioside as the glycosyl acceptor, and 50 g/L maltodextrin as the gycosyl donor at 40°C for 6 h, and a conversion yield of stevioside as high as 76% was obtained.     

地尔硫卓手性中间体合成进展

地尔硫卓是重要的心血管药物,在其分子结构中含有2个手性中心,可产生4个立体异构体,其中只有（2s,3s）-异构体具有药理活性,因此其立体选择性合成具有很大的挑战性。研究人员采用多种方法合成单一构型的地尔硫卓手性中间体,其中包括化学拆分、化学不对称合成以及化学-酶法合成等方法。对地尔硫卓手性中间体的制备方法进行了综述。     

化学药物杂质研究进展

药物杂质的分析和控制是用药安全有效的基础。从杂质谱分析、杂质检测、杂质限度的制定等方面综述了近年来国内外化学药 物杂质研究进展,旨在为化学药物杂质的研究提供有效思路和方法。     

S-亚胺还原酶和葡萄糖脱氢酶共表达系统的构建及手性胺的合成

旨在构建S-亚胺还原酶(S-IRED)和葡萄糖脱氢酶(GDH)在大肠杆菌中的一菌双酶共表达系统,实现辅酶NADPH的再生,高效合成手性仲胺。利用无缝克隆的手段设计构建一种单质粒双启动子共表达系统,以全细胞为催化剂催化手性仲胺S-2-甲基吡咯烷(S-2MP)的合成,并研究温度、pH及有机溶剂对双酶反应的影响。成功构建了S-IRED和GDH的重组共表达质粒,实现了S-IRED与GDH在大肠杆菌中的胞内共表达,以亚胺2-甲基吡咯啉(2MPN)为模式底物,以工程菌全细胞催化手性仲胺S-2MP的合成,在低辅酶添加时催化手性胺的产率和光学纯度均高于95%。该双酶共表达体系的最适温度和pH分别为37℃和pH 8,10%以下的甲醇对双酶反应有正向促进作用。大肠杆菌胞内双酶共表达系统的构建实现了辅酶NADPH的原位再生,降低了亚胺还原酶催化合成手性胺的成本,为手性胺的规模制备奠定了基础。     

Synthesis of enantiopure trans-N-Boc-3-aminobicyclo[2.2.2]octane-2-carboxylic acids and their bicyclic 1,3-amino alcohol derivatives via the [4+2] cycloaddition of 1,3-cyclohexadiene to a chiral β-nitroacrylate

The chiral β-nitroacrylate 2 derived from the (R)- or (S)-4-(3-hydroxy-4,4-dimethyl-2-oxopyrrolidin-1-yl) benzoic acid 1 acts as a reactive dienophile in a diastereoselective Diels-Alder reaction with 1,3-cyclohexadiene. The major cycloadducts have been isolated and transformed into enantiopure trans(2S,3S)- or (2R,3R)-N-Boc-3-aminobicyclic[2,2,2]octane-2-carboxylic acids 5. The trans-(2S,3S)- or (2R,3R)-N-Boc 3-(hydoxymethyl)-2-aminobicyclic[2,2,2]octane 6 derivatives were also obtained.     

Immobilization of Escherichia coli containing ω-transaminase activity in LentiKats®

Whole Escherichia coli cells overexpressing ω‐transaminase (ω‐TA) and immobilized cells entrapped in LentiKats® were used as biocatalysts in the asymmetric synthesis of the aromatic chiral amines 1‐phenylethylamine (PEA) and 3‐amino‐1‐phenylbutane (APB). Whole cells were permeabilized with different concentrations of cetrimonium bromide (CTAB) and ethanol; the best results were obtained with CTAB 0.1% which resulted in an increase in reaction rate by 40% compared to the whole cells. The synthesis of PEA was carried out using isopropyl amine (IPA) and L ‐alanine (Ala) as amino donors. Using whole cell biocatalysis, the reaction with IPA was one order of magnitude faster than with Ala. No reaction was detected when permeabilized E. coli cells containing ω‐TA were employed using Ala as the amino donor. Additionally, the synthesis of APB from 4‐phenyl‐2‐butanone and IPA was studied. Whole and permeabilized cells containing ω‐TA and their immobilized LentiKats® counterparts showed similar initial reactions rates and yields in the reaction systems, indicating 100% of immobilization efficiency (observed activity/activity immobilized) and absence of diffusional limitations (due to the immobilization). Immobilization of whole and permeabilized cells containing ω‐TA in LentiKats® allowed improved stability as the biocatalyst was shown to be efficiently reused for five reaction cycles, retaining around 80% of original activity. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012     

Alkali Protease and Alcohol Dehydrogenase Immobilized to Weakly Basic Anion Exchange Resins Using 2-Car-boxymethylamino-4,6-dichloro-s-triazine

Alkali protease partially purified from a strain of Bacillus subtilis and yeast alcohol dehydrogenase were immobilized to weakly basic anion exchange resins using a bifunctional reagent, 2-carboxymethyIamino-4,6-dichloro-s-triazine.

Properties of these immobilized enzymes were studied both in batchwise operation and in packed bed reactor systems.     

Liquid chromatographic separation of chiral diarylcarbinols

The direct HPLC separation of three chiral carbinols of general formula Mesityl-CH(OH)-Aryl has been achieved using Pirkle (R)-DNBPG ionic or covalent columns and, for Aryl = o-tolyl, on a Chiralpak OP(+) phase. It is apparent that steric hindrance and hydrogen bonding play important roles in chiral recognition. Two compounds structurally very similar but lacking the hydroxyl group were not resolved in their enantiomeric pairs. © 1992 Wiley-Liss, Inc.