醇脱氢酶在反胶束溶液中的催化动力学性质

以十六烷基三甲基溴化铵(CATB)-辛烷-己醇反胶束体系对醇脱氢酶(ADH)进行固定化,试验了含水量、酶液pH值、CTAB和己醇浓度对ADH固定化的影响。对游离酶和固定化酶的催化动力学性质研究表明：酶促反应的最适pH值分别为8.2和8.8,最适温度分别是31℃和20℃,对乙醇的米氏常数Km分别为12mmol/L和7.4mmol/L。在30℃时,游离酶存放150min后失活90%,固定化酶失活50%,表明反胶束固定化ADH有较好的热稳定性。     

反胶束固定化乳酸脱氢酶的催化动力学性质研究

以十六烷基三甲基溴化铵(CATB)-辛烷-己醇反胶束体系对乳酸脱氢酶(LDH)进行固定化,试验了含水量、CTAB和己醇浓度对LDH固定化的影响。对游离酶和固定化酶的催化动力学性质研究表明:酶促反应的最适pH值分别为9.2和9.5,最适温度分别是37℃和43℃,对乳酸的米氏常数Km分别为1.4 mmol/L和2.3mmol/L。30℃时,游离酶存放2 h,约失活50%,而固定化酶仅失活10%,表明反胶束固定化LDH具有较好的热稳定性。     

醇脱氢酶在反胶束溶液中的酶学性质研究

以十六烷基三甲基溴化铵(CATB)-辛烷-戊醇反胶束体系对醇脱氢酶(ADH)进行固定化,考察了pH、含水量、表面活性剂和助溶剂浓度对ADH固定化的影响。对游离酶和固定化酶的催化动力学性质研究表明:酶促反应的最适pH值均为9.0,最适温度分别是28℃和20℃,对乙醇的米氏常数分别为8.8mmol/L和5.5mmol/L。25℃时,游离酶存放120min约失活90%,而固定化酶仅失活30%,表明反胶束固定化ADH具有较好的热稳定性。     

青霉素酰化酶交联酶聚体的制备及热失活动力学

以0.53 g/mL硫酸铵为沉淀剂, 0.35%(体积分数)戊二醛为交联剂制得青霉素酰化酶交联酶聚体(CLEAs), 酶活收率30.1%, 其最适温度(57 ℃)比游离酶提高10 ℃, 最适pH(10.0)向碱性偏移1.7个单位. 对比游离酶及其CLEAs的热稳定性和热失活动力学模型发现, 游离青霉素酰化酶制成CLEAs后, 其热失活动力学模型由一步失活转变为连串失活, 失活反应活化能由248.8 kJ/mol增加至549.2 kJ/mol, 对CLEAs热稳定性大幅提高的原因进行了解释. CLEAs重复利用7次后, 酶活保留56%以上, 具有良好的重复利用性.     

反胶束固定化醇脱氢酶的制备及应用研究

研究十六烷基三甲基溴化铵(CTAB)-辛烷-己醇反胶束体系固定化醇脱氢酶(ADH)的制备及应用。考察了含水量、CTAB和己醇用量对于ADH固定化的影响。对游离酶和固定化酶的催化动力学性质研究表明:酶促反应的最适pH值分别为8.2和8.8,最适温度分别为31℃和20℃,米氏常数分别为12mmol/L和7mmol/L。30℃时,游离酶存放150min后失活90%,固定化酶失活50%,表明反胶束固定化ADH有较好的热稳定性。应用此体系测定了试样中乙醇的含量。     

双重敏感mPEG-PDPA-P(AAm-co-AN)聚合物自组装体的药物递送

设计合成了一种新型两亲性三嵌段ABC聚合物聚乙二醇单甲醚-聚甲基丙烯酸二异丙胺基乙酯-聚(丙烯酰胺-co-丙烯腈)(mPEG-PDPA-P(AAm-co-AN))。该聚合物具有pH敏感嵌段PDPA和温度敏感嵌段P(AAm-co-AN)，临界溶解温度(UCST)较高，且可以通过改变单体比例来调节UCST。在室温、中性环境下，该聚合物通过自组装形成刺激响应型胶束，可用于抗肿瘤药物的控释研究。温度升高诱导聚合物胶束向不对称囊泡结构转变，pH降低促使聚合物形成更加松散的胶束。在体外释药探究中，聚合物胶束对亲水药物阿霉素(DOX)和疏水药物槲皮素都具有良好的载药效果，在37℃、pH=7.4的条件下泄漏量低，随着温度升高和pH降低，胶束释放药物的速率和释放量明显增加。     

酶催化魔芋葡甘聚糖的可控降解

魔芋葡甘聚糖 (KGM)是一种来自植物的天然高分子 .它具有优异的可生物降解性和生物相容性 ,并具有许多独特的生理和药理功能 .本实验首先测定了 β 甘露糖酶在不同条件 (温度、pH值、介质 )下的活性 ,发现 β 甘露糖酶在 5 0℃左右 ,pH 9 4附近 ,乙醇含量低于 5 %的水介质中具有较高的活力 ;而在pH 7 0以下 ,或温度低于 3 0℃ ,或加入 2 0 %乙醇的条件下均基本上失活 .在此研究基础上 ,探讨了 β 甘露糖酶催化KGM降解反应的规律 ,通过调节反应条件制备了一系列分子量不同的降解样品 ,并确定了KGM的分子量与特性粘数之间的关系为 :[η]=5 0 6× 1 0 - 4M0 754w ,使得酶催化KGM的可控降解成为可能 ,从而为深入研究KGM及其衍生物的结构与性能 ,扩展其应用领域奠定了良好的理论和实验基础     

聚（异丙基丙烯酰胺）-b-聚（4-乙烯基吡啶）胶束负载铂纳米粒子的温度响应性催化

嵌段共聚物聚(N-异丙基丙烯酰胺)-b-聚(4-乙烯基吡啶)(PNPIAM-b-P4VP)在pH6.5的水溶液中自组装成,以聚(4-乙烯基吡啶)为胶束的核,以热响应聚(N-异丙基丙烯酰胺)为胶束壳的球形胶束.通过与4VP基络合作用,将氯铂酸(H2PtCl6)导入胶束的核中,原位还原获得胶束负载2~4nm的铂纳米粒子的温度敏感型催化体系.结果显示,最低临界溶解温度(LCST)为33℃,在LCST以下,催化反应速率会随着温度的升高而提高;在LCST以上,PNPIAM嵌段变成疏水而塌缩在催化剂表面,阻碍了反应物的扩散,因此胶束负载的铂纳米粒子的催化活性会随着温度的上升而下降.     

壳聚糖的酶法降解

用壳聚糖酶降解壳聚糖,探讨了壳聚糖降解过程中温度、pH值、底物浓度和金属离子对酶促反应的影响。结果表明:酶促反应进行到5 h左右时,即可得到聚合度小于10的壳寡糖。该酶促反应的最适温度为50℃,最适pH=5.5;最适底物浓度为0.02 g/mL;金属离子Ca2+和Mg2+对酶降解有一定的促进作用,而Zn2+、Cu2+对酶降解有较强的抑制作用。该酶促反应符合米氏动力学方程,米氏常数Km=7.80 g/L,最大反应速率Vmax=7.72 g/(min.L)。     

聚[(甲氧基乙氧基乙氧基)1.0(乙氧基吡咯烷酮)1.0]膦腈的合成及性能研究

用三氯化铝催化六氯三聚膦腈开环聚合制得线性聚二氯膦腈(PDCP), 通过PDCP磷原子上的亲核取代反应, 合成了新的水溶性高分子聚[(甲氧基乙氧基乙氧基)_1.0(乙氧基吡咯烷酮)_1.0]膦腈(P3), 用³¹P NMR, ¹H NMR, ¹³C NMR和IR对其结构进行了确证, 用DSC测定了其玻璃化转变温度T_g和熔融温度T_m, 用蒸汽压渗透法(VPO)测定了其数均分子量. 改进了聚二(乙氧基吡咯烷酮)膦腈(P2)的合成方法. 体外降解实验表明, P3具有和P2类似的pH响应性降解行为, 降解速率在pH=5.0时最快, 而在pH=7.4和8.0时较慢. P3在所测试的3个pH缓冲溶液中均比P2降解慢. 用³¹P NMR、薄层色谱(TLC)和滴定法对降解产物进行了检测, 初步推断了P3在不同pH介质中的水解机理, 其在pH=5.0的缓冲溶液中的降解, 除侧链断裂外, 聚膦腈的骨架也裂解; 而在pH=7.4和8.0时的降解仅为侧链的断裂. 用噻唑蓝(MTT)比色法进行的体外细胞毒性评价实验表明, P3及其在pH=5.0的缓冲溶液中降解49 d后的产物均对细胞表现出了很好的生物相容性, 而且其降解产物在浓度为800 μg/mL时还表现出一定的促进细胞增殖作用.     

pH/Temperature-responsive behavior of amphiphilic block copolymer micelles prepared using two different methods

The pH- and temperature-responsive behavior of amphiphilic block copolymer poly(L-lactide)-b-poly(2-(dimethylamino)ethyl methacrylate) (PLLA-b-PDMAEMA) in aqueous solutions is investigated using static and dynamic light scattering. Electrostatic force, hydrophobic interaction, and hydrogen bonding coexist in the system. Micelles with different structures are prepared using water addition (WA) and direct dissolution (DD) methods. The aggregation from loose micelles into large micellar clusters is observed above the transition temperature under basic conditions. Only micellar clusters from the DD method could disaggregate when temperature was decreased to 24.3 °C after heating. The behavior of the micelles prepared with the DD method indicates that only the outer parts of the PLLA-b-PDMAEMA chains in the corona are solvated.     

Fabrication of biofunctional complex micelles with tunable structure for application in controlled drug release

In acidic solution, complex micelles were formed by diblock copolymers of poly (ethylene glycol)-b-poly (ε-caprolactone) (PEG-b-PCL) and folate-poly (2-(dimethylamino) ethyl methylacrylate)-b-poly (ε-caprolactone) (Fol-PDMAEMA-b-PCL) with a PCL core, a mixed PEG/Fol-PDMAEMA shell. The surface charge of the complex micelles was positive at acidic surroundings for the protonated PDMAEMA. With increasing pH value to 7.4 (above pK _a of PDMAEMA), these micelles could convert into a core-shell-corona (CSC) structure composing a hydrophobic PCL core, a collapsed PDMAEMA shell, and a soluble PEG corona. Compared to core-shell micelles formed by PEG-b-PCL, micelles with CSC structure can prolong degradation by enzyme. Doxorubicin was physically loaded into the PCL core. The drug release rate was pH-dependent. At pH 5.5, complex micelles with core-shell structure showed faster drug release rate, while at pH 7.4, complex micelles gained CSC structure which control the drug release at a lower rate. The multifunctional complex micelles were prepared for enhanced tumor therapy.     

基于多级孔金属有机骨架构筑HRP固定化酶反应器及其染料降解应用

以不稳定的Cu-金属有机骨架(Cu-MOF)为模板剂, 利用自组装模板法制备多级孔Zr-MOF, 再通过物理吸附法在多级孔Zr-MOF的介孔孔道中负载辣根过氧化物酶(HRP)构筑了HRP@Zr-MOF固定化酶反应器. 通过改变孔径调节剂苯甲酸(HBC)的浓度调控孔径大小, 研究了孔径对固定化酶反应器催化活性的影响; 考察了固定化体系缓冲溶液pH值、 固定化时间及温度对固定效果的影响. 以HRP催化降解结晶紫染料为模型反应, 探讨了HRP@Zr-MOF的操作稳定性和重复使用性. 结果表明, pH=3.0、 固定化时间为60 min、 固定化温度为30 ℃是固定化HRP的最佳条件, 固载量最高可达61.6 mg/g. 与游离酶相比, HRP@Zr-MOF固定化酶反应器表现出更好的热稳定性、 酸碱稳定性、 H₂O₂稳定性和储存稳定性; 重复使用10次后, HRP@Zr-MOF的催化活性仍能保持62.3%. 将HRP@Zr-MOF应用于实际水样中结晶紫染料的催化降解, 在5 min内降解率高达90%以上, 表现出非常高效的催化效率.     

CONTROLLED RELEASE FROM PDMAEMA GELS PREPARED BY GAMMA RADIATION

Poly(N, N-dimethylaminoethyl methacrylate) (polyDMAEMA) hydrogels prepared by γ-irradiation showed obvioustemperature-sensitivity in a temperature range of 38-40℃ and pH-sensitivity at pH = 2.5. They also showed clectric responsebehavior although it was not typical. The hydrogels were used in controlled release at different pH, temperature, and electricvoltage. The release rates of methylene blue (MB) from the gels at 52℃ and pH = 1.24 were fatter than those at 20℃ and pH= 10.56, respectively. In addition, the release rate at a field voltage of 5.0 was also faster than that without electric field.     

嵌段共聚物聚(异丙基丙烯酰胺)-b-聚(双丙酮丙烯酰胺)制备及其对叶酸的载负和释放

以N-异丙基丙烯酰胺(NIPAm)和双丙酮丙烯酰胺(DAAM)为原料,采用可逆加成 断裂链转移(RAFT)可控聚合反应法合成了两亲性两嵌段共聚物 聚(异丙基丙烯酰胺)-b-聚(双丙酮丙烯酰胺)(PNIPAm-b-PDAAM),用红外光谱(FT-IR)、核磁共振(1H NMR)和凝胶渗透色谱(GPC)对其结构和组成进行了表征。 这种共聚物在水溶液中能够自组装成稳定的聚合物胶束,通过荧光探针测得其低临界胶束浓度(CMC)约为7.0 mg/L。 采用扫描电子显微镜(SEM)和动态激光光散射(DLS)测得,PNIPAm-b-PDAAM在水溶液中自组装成核壳结构的球形胶束,SEM测得其直径约150 nm,且分散性良好。 以其聚合物胶束为载体、叶酸(FA)为模型药物,模拟人体生理环境进行药物体外释放。 结果表明,叶酸的负载量及负载率分别为25%和74%。 在人体温度37℃、pH值分别为4.0、6.86、9.18磷酸缓冲溶液(PBS)中,FA在20 h内的释放均比25 ℃快,释放速率随pH值增加而增大,最大累积释放率分别为31%、67%和72%。     

Photochromic soft materials: flavylium compounds incorporated into pluronic F-127 hydrogel matrixes

The performance of flavylium-based photochromic systems is increased by their incorporation into Pluronic F-127 matrixes, which switch from polymeric solutions to micelles to gels with changes in temperature depending on copolymer concentration. Two flavylium compounds, 7,4'-dihydroxyflavylium and 7-(N,N-diethylamino)-4-hydroxyflavylium, both exhibiting a small thermal cis-trans isomerization barrier in water were investigated. In the first system the flavylium in the gel photoswitches from the colorless trans-chalcone (Ct) species to the yellow flavylium cation (AH+) with quantum yield Phi=0.04 (25 degrees C) at pH 2.2 or to the orange quinoidal base (A) with quantum yield Phi=0.015 (25 degrees C) at pH 5.2. The photoproducts revert back to their initial form by a thermal process characterized by first-order kinetics; the rate constants exhibit a bell shape variation with pH, with a maximum at pH 4.3 (lifetime 4.2 min). The second system, 7-(N,N-diethylamino)-4-hydroxyflavylium, does not exhibit photochemistry in water but, when incorporated into the Pluronic F-127 gel, switches from yellow to red with a quantum yield of Phi=0.01 at pH 4.9. The respective thermal back reaction takes place with a lifetime of 66.7 min1. The flavylium network of chemical reactions is a good sensor for the detection of not only the critical micelle temperature but also the gelation temperature of Pluronic and like solutions and, in some instances, the exposure to UV and visible radiation.     

吸附-纤维素覆膜联合固定化酶

以食品工业中常用的木瓜蛋白酶为模式酶, 建立了吸附-纤维素覆膜联合固定化酶方法. 通过对吸附载体类别、 纤维素种类及溶剂、 保护剂种类及其浓度、 干燥方式及时间等的优化, 得到最佳的吸附-纤维素覆膜联合固定化酶工艺. 以硅藻土或HPD-417(大孔树脂)作为吸附载体, 甲基纤维素(分子量40000~50000)丙酮溶液作为覆膜溶液, 加入6%(质量分数)的聚乙二醇或麦芽糖作为覆膜保护剂, 于4 ℃干燥9 h, 制得固定化木瓜蛋白酶, 硅藻土吸附-纤维素覆膜固定化酶酶活回收率达到96.50%, HPD-417吸附-纤维素覆膜固定化酶酶活回收率达到93.92%. 对吸附-纤维素覆膜固定化酶的性质进行了研究, 发现纤维素覆膜后固定化酶具有良好的热稳定性, 于80 ℃下保存12 h后, 固定化酶活残余率仍然能保持90%左右; 在pH=4.5~9.5的范围内, 固定化酶的稳定性较好; 连续使用9次后, 固定化酶活残余率仍能保持95%左右.     

Laccase immobilized on mesoporous SiO<Subscript>2</Subscript> and its use for degradation of chlorophenol pesticides

In this paper, mesoporous silica with large specific surface area was used to immobilize laccase by the glutaraldehyde cross-linking method, and after screening and optimization experiments, the best enzyme immobilization process conditions were found (25°C, pH 5.4, 4% glutaraldehyde and 0.2 g/L laccase, treatment time 6 h). After that, the removal and degradation ratio of 2,4-dichlorophenol (abbreviated as DCP) under different conditions were also studied. After the degradation process was performed for 6 h at 30°C, pH 5.4, and DCP initial concentration of 50 mg/L in the presence of 0.1 g of immobilized laccase, the removal ratio and the degradation ratio were 42.28 and 15.93%, respectively. Compared with free laccase, the reusability of immobilized laccase is significantly improved.     

Rod-sphere transition in polybutadiene-poly(L-lysine) block copolymer assemblies

This paper describes the synthesis and characterization of poly(butadiene)m-poly(L-lysine)n (m-n = 107-200, 107-100, and 60-50) block copolymers. The polymers are prepared in a two-step process whereby amine-terminated polybutadiene is used to initiate the ring-opening polymerization of the epsilon-benzyloxycarbonyl L-lysine N-carboxyanhydride. After deprotection, the self-assembly of the block copolymers in aqueous media were studied using dynamic light scattering, transmission electron microscopy, and circular dichroism spectroscopy. These block copolymers were found to form either spherical micelles or rod-like micelles at high pH depending on the composition of the block copolymer. As the pH is decreased, the micelles swell due to charge-charge repulsions between corona chains and from the helix-coil transition of the polypeptide block. The two systems that form rod-like micelles at high pH also exhibit a pH-induced rod-sphere transition at low pH. This transition was verified from Kratky analysis of the static light scattering data and via CONTIN analysis of the dynamic light scattering data, which shows a bimodal distribution in particle sizes.