特种纤维素酶催化水解壳聚糖及壳寡糖的制备研究

用凝胶渗透色谱法研究了特种纤维素酶催化水解过程中的分子量及其分布,制备了不同低分子量的壳聚糖和壳寡糖,详细研究了水解温度、pH值、时间和酶的用量等因素对酶催化水解产物的分子量及其分布的影响,制备壳寡糖的反应条件为壳聚糖质量分数w=0．01,水解温度58℃,pH=5．3,特种纤维素酶w=0．10,反应时间3h。     

琼脂固定化过氧化氢酶的催化活性

采用琼脂包埋法对过氧化氢酶进行固定化,考察了固定化过氧化氢酶催化过氧化氢降解的活性,确定了最佳催化反应条件.结果表明,经琼脂包埋法固定化后,过氧化氢酶仍保留较高的催化活性,其催化过氧化氢分解反应的最佳条件为温度35℃、pH 9.0.与此同时,固定化过氧化氢酶具有更强的温度适应能力和更宽的pH作用范围,并具有一定的重复使用性能.     

催化酯化升级生物质油

以稻壳热解油为原料,采用减压蒸馏法将生物质油轻组分和重组分分离.由生物质油重组分通过催化酯化反应制备了乙醇生物质油,对催化剂硫酸采用纳米碳酸钙沉淀法进行分离,从而实现生物质油的品质升级.以生物质油的pH值作为评价升级反应的指标,考察了催化酯化反应条件和后处理条件的影响.采用气相色谱-质谱联用(GC/MS)和凝胶色谱(GPC)研究了稻壳热解油和乙醇生物质油的组成和分子量的变化.实验结果表明,在催化酯化过程中,当反应温度为120℃,反应时间为3 h,硫酸用量为4 g,溶剂为无水乙醇时,乙醇生物质油的pH值可达5. 86.在催化剂中和过程中,中和剂对乙醇生物质油pH值的影响顺序为BaO≈BaCO_3CaCO_3nano-CaCO_3CaO.经过催化酯化升级过程,不仅乙醇生物质油中的酯类物质增加了26. 1%,酸类物质和酚类物质分别减少了15. 9%和12. 8%,而且乙醇生物质油的分子量也降低了90%.     

高取代度魔芋葡甘聚糖醋酸酯的制备及其热塑性和流变性研究

以魔芋葡甘聚糖(KGM)为原料,浓硫酸为催化剂,乙酸酐为改性剂,制备了KGM醋酸酯.研究了反应条件对KGM醋酸酯取代度(DS)的影响,KGM醋酸酯制备的最佳反应条件是乙醇∶水量比5∶5,反应时间2h,反应温度75℃,催化剂浓硫酸的浓度0.1mol/L,KGM与乙酸酐的量比5∶40(g/mL),取代度高达2.93,其分子量与KGM相比,则明显降低.运用傅立叶红外光谱仪(FTIR)、X射线衍射仪(XRD)、扫描电镜(SEM)、热重分析仪(TGA)、示差扫描量热仪(DSC)和旋转流变仪对KGM和高取代度KGM醋酸酯进行了表征.结果表明,KGM醋酸酯的羰基(CO)特征吸收峰较KGM明显增强,其表观形貌大部分为疏松絮状,KGM及其醋酸酯均为非晶态结构.与KGM相比,KGM醋酸酯的热稳定性下降,分解温度(Td)由KGM的261.10℃降低至KGM醋酸酯的204.56℃,KGM醋酸酯出现了明显的玻璃化转变,其玻璃化转变温度(Tg)为128.49℃.KGM醋酸酯是典型的黏弹性材料,其弹性比率占21.27%,其剪切黏度η对温度变化非常敏感,可通过温度的改变来调节KGM醋酸酯的加工流动性.KGM醋酸酯具有较好的热塑性.     

真菌漆酶及其催化对苯基苯酚聚合条件的研究

白腐菌Panus conchatus在液体培养条件下产生了漆酶,经纯化分离后用于对苯基苯酚的催化聚合,探讨了反应温度、缓冲溶液pH以及反应体系中溶剂二氧六环的含量对漆酶催化对苯基苯酚聚合的影响。结果表明,漆酶催化对苯基苯酚聚合反应的最佳反应条件为：温度为40℃,混合溶剂中二氧六环的体积百分数为85％。缓冲溶液为pH=4的0．2mol／L HAc-NaAc溶液。在此条件下用漆酶催化对苯基苯酚聚合,得到了重均分子量Mw=80533的聚酚产物。得率为75.5％。     

分子量及酰基供体对酶促魔芋葡甘聚糖酰化反应的影响

研究了在有机介质叔丁醇中魔芋葡甘聚糖(KGM)的分子量及酰基供体对固定化脂肪酶Novozym 435催化KGM乙酰化反应的影响.KGM的分子量对酶促其酰化反应的活性及产物取代度有显著影响.随着KGM分子量的增大,酶催化反应的速率逐渐下降,产物的取代度逐渐减小.KGM分子量对该反应的影响与不同分子量KGM的溶解度、体系粘度、空间位阻及颗粒形态等因素有关.以不同链长的脂肪酸乙烯酯为酰基供体时,随着酰基供体中脂肪酸碳链的增长,酶促KGM酰化反应速率逐渐下降,产物的取代度逐渐减小,且该酰化反应具有高度的区域选择性,反应均发生在C6-OH上.     

多酚氧化酶在非水相中催化对氯苯酚氧化反应的动力学研究

用丙酮沉淀法从蘑菇中提取多酚氧化酶 ,以多孔玻璃粉为载体 ,用吸附沉积法将酶固定法 ,研究了该酶在氯仿介质中催化对氯苯酚氧化反应的机理遵循米氏 ( Michaelis- Menten)动力学方程 ;而且 ,在有机介质中含水率大小直接影响酶的催化活性。实验测得反应的最佳条件为 p H=7.0 ,温度为 2 5℃ ,含水率为 0 .5 % ( v/v) ;表面活化能 Ea= 2 9.5 4KJ· mol- 1 ,米氏常数 Km=1 .0 5 8mol· dm- 3,最大反应速率 rmax=90 .74× 1 0 - 3min- 1 。     

H2O2氧化降解海藻酸钠

研究了清洁高效的氧化剂H2O2对海藻酸钠的降解,探讨了溶液pH值、反应温度、H2O2用量及金属离子浓度对降解速度的影响. 结果表明,随着溶液pH值的降低、反应温度的升高及H2O2用量的增加,降解速度加快. 当反应pH=5.3、反应温度50 ℃、H2O2用量0.5%时,反应2 h即可降低海藻酸钠的分子量. 4 mg/L的Cu2+或Fe2+可明显加快降解速度,反应30 min的粘度变化相当于不加Cu2+或Fe2+时300 min的变化. GPC结果表明,海藻酸钠被氧化降解后,分子量下降,分布变宽;FTIR显示降解前后海藻酸钠的糖环结构没有改变,主要是糖苷键的断裂.     

非专一性酶催化壳聚糖水解反应的特性

某些非专一性酶对壳聚糖具有一定的降解作用，具有普遍的壳聚糖酶的活性。α-淀粉酶对壳聚糖的降解作用受温度、底物浓度、酶浓度、反应时间、pH等因素的影响，其最佳反应条件为壳聚糖浓度20g/L，酶浓度4g/L,pH值6.0，反应温度50℃。降解反应初期是以内切的方式进行，所得到的壳寡糖具有较低的分散度。     

可生物降解的聚磷酸异山梨醇酯的合成与表征

由异山梨醇和苯膦酰二氯经本体聚合法和溶液聚合法得到了不同分子量的新型聚磷酸酯(PPI),采用傅立叶变换红外(FTIR),核磁共振氢谱(~1H-NMR)和凝胶渗透色谱(GPC)对聚酯的组成和分子量进行表征,结果表明产物为聚磷酸酯结构.聚合物在水溶液和酶溶液中的降解和溶胀实验表明,当PPI的分子量(M_w)低于5×10~4时,聚合物具有很好的降解性能和溶胀性能,25天后其降解率达到80%,溶胀率达到150%.当M_w高于5×10~4时,其降解速率和吸水率明显下降,25天后降解率和溶胀率分别仅为25%和40%.研究了PPI的玻璃化转变温度(T_g)和分子量的关系,PPI具有较高的Tg,且随着分子量的增加,聚合物的T_g显著增加.当PPI的分子量为6×10~4时,其玻璃化转变温度达到176℃.同时研究了聚合物分子量对其热稳定性的影响,当重均分子量由2×10~4增加到6×10~4时,PPI的起始分解温度从260℃提高到315℃.结果表明提高分子量有助于提高PPI的热分解温度.     

Rheological study of physical cross-linked quaternized cellulose hydrogels induced by β-glycerophosphate

As a weak base, β-glycerophosphate (β-GP) was used to spontaneously initiate gelation of quaternized cellulose (QC) solutions at body temperature. The QC/β-GP solutions are flowable below or at room temperature but gel rapidly under physiological conditions. In order to clarify the sol-gel transition process of the QC/β-GP systems, the complex was investigated by dynamic viscoelastic measurements. The shear storage modulus (G') and loss modulus (G″) as a function of (1) concentration of β-GP (c(β-GP)), (2) concentration of QC (c(QC)), (3) degree of substitution (DS; i.e., the average number of substituted hydroxyl groups in the anhydroglucose unit) of QC, (4) viscosity-average molecular weight (M(η)) of QC, and (5) solvent medium were studied by the oscillatory rheology. The sol-gel transition temperature of QC/β-GP solutions decreased with an increase of c(QC) and c(β-GP), the M(η) of QC, and a decrease of the DS of QC and pH of the solvent. The sol-gel transition temperature and time could be easily controlled by adjusting the concentrations of QC and β-GP, M(η) and DS of QC, and the solvent medium. Gels formed after heating were irreversible; i.e., after cooling to lower temperature they could not be dissolved to become liquid again. The aggregation and entanglement of QC chains, electrostatic interaction, and hydrogen bonding between QC and β-GP were the main factors responsible for the irreversible sol-gel transition behavior of QC/β-GP systems.     

Synthesis and Properties of IPN Hydrogels Based on Konjac Glucomannan and Poly（acrylic acid）

As a random copolymer of β-(1,4) linked D-mannose and D-glucose, konjac gluco- mannan (KGM) is a naturally occurring water-soluble polysaccharide, and has been paid attention in the field of drug controlled release carriers potentially used in colon1,2. …     

生物相容性嵌段型聚电解质胶束在水溶液中的酶降解行为

采用激光光散射仪和原子力显微镜研究了生物相容性嵌段型聚电解质聚左旋乳酸-b-聚甲基丙烯酸二甲氨基乙酯(PLLA-b-PDMAEMA)胶束在水溶液中2个温度(室温25.0℃和人体温度36.8℃)和2个pH值(肿瘤pH=4.9和正常组织pH=7.4)条件下的酶降解行为. 酶降解过程中存在一个失活时间, 在此之前, 胶束的酶降解遵循逐个降解机理. 失活时间之后, 出现裂纹或是通道的胶束核为降低其在溶剂中的表面积, 从而降低体系自由能, 胶束之间发生了聚集. 升高温度后, 酶的活性提高, 初始降解速率加快. 由于pH=4.9时胶束壳层因静电斥力作用而较为伸展, 使得胶束降解更快.     

Synthesis and Characterization of Phosphated Konjac Glucomannan Hydrogels

Konjac glucomannan （KGM） was crosslinked with sodium tripolyphosphate （STPP） to synthesize hydrogels. The crosslinking reaction was confirmed by FT-IR. The results of degradation test show that the hydrogels retain the enzymatic degradation character of KGM and can be degraded for 74.45% in 5 days by cellulase E0240.     

NO-NH_3-O_2 reaction catalyzed by V_2O_5/AC at low temperatures——Effects of SO_2, V_2O_5 loading and reaction temperature

The effects of SO2, V2O5 loading and reaction temperature on the activity of activated carbon supported vanadium oxide catalyst have been studied for the reduction of NO with NH3 at low temperatures (150-250℃). It is found that SO2 significantly promotes the catalyst activity. Both V2O5 loading and reaction temperature are vital to the promoting effect of SO2. The catalysts with V2O5 loadings of 1 -5 weight percent have a positive effect on the promotion of SO2, while the catalysts with V2O5 loadings of above 7 weight percent have not such an effect or show a negative effect. At lower temperatures (<180℃) SO2 poisons the catalyst but at higher temperatures promotes it. The reason of the SO2 promotion was also discussed; it may results from the formation of SO42- on the catalyst surface, which increases the surface acidity and hence the catalytic activity.     

〔NEt_4〕〔CoCl_3(PPh_3)〕的合成和晶体结构

标题化合物是反应体系 (NH4) 3VS4/CoCl2 (PPh3) 2 /NEt4Cl在CH2 Cl2 中反应而得到的 ,单晶X射线结构分析表明 :其晶体属于立方晶系 ,化学式为C2 6 H35 NCl3CoP ,空间群为Pa3 ,Mr=5 5 7.84,a =17.80 7(5 ) ,V =5 6 46 .4 3,Z =8,Dc=1.31g/cm3,F(0 0 0 ) =2 32 8,μ(MoKα) =9.6cm- 1 ,R =0 .0 6 2 ,Rw =0 .0 6 7。标题化合物分子结构具有结晶学三次轴对称性 ,Co(II)原子为四面体配位 ,键角Cl-Co -Cl(113 .4(2 )°)大于键角Cl-Co -P(10 5 .2 (2 )°)。同时也讨论了标题化合物的电子光谱和变温磁化率     

Synthesis and characterization of novel poly（aryl ether sulfone ketone）s containing phthalazinone and biphenyl moieties

A novel series of poly（aryl ether sulfone ketone）s （PPESKs） containing phthalazinone and biphenyl moieties were prepared by two-step nucleophilic polycondensation reaction. The ^-Mw values of these copolymers were between 38,330 and 67,900. The glass transition temperatures （Tg） and 5% decomposition temperatures were ranged in 253-269 ℃ and 488-500 ℃, respectively, The structures of these copolymers were confirmed by FT-IR and ^1H NMR. Moreover, all the resultant copolymers were amorphous determined by wide angle X-ray diffraction （WAXD）.     

Hierarchically‐ordered electroactive silica‐polyaniline nanohybrid: A novel material with versatile properties

Poly(trimethoxy silylpropylaniline), a nanoporous (pore diameter of 2.4 nm), electroactive (stable reversible redox characteristics), electrochromic (yellow at ?0.10 V, blue green at +0.50 V, and dark green at +0.70 V), and pH‐sensitive, silica–polyaniline (PANI) hybrid material (designated as KGM‐1) has been synthesized in powder form by a simple one‐pot chemical synthesis as well as a “thin nanolayered film” by cyclic voltammetry. High‐resolution transmission image of KGM‐1 informs that the particles are spherical, with diameters in the range of 0.5–1.5 μm. X‐ray diffraction pattern of pristine KGM‐1 confirms the combined presence of ordered silica network and PANI chains. The surface area of calcined KGM‐1 is 40 m²/g (～15 times higher than KGM‐1), and the average pore size is 2.4 nm. The N₂ adsorption features also inform that PANI is present as a uniform layer within the pores of silica and because of that the silica pores are not completely blocked. The reversible redox transitions in PANI units and nanoporosity of KGM‐1 are effectively used for the electro‐driven loading/release of DNA or adenosine 5′‐triphosphate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010