纤维素酯类手性固定相的最新研究进展

微晶纤维素是天然的光学活性线性高聚物,对其衍生化可以得到一系列新的衍生物。由于纤维素衍生物的耐压性较差,不能直接用作液相色谱的固定相,常需要将其固定于硅胶载体上。文章从纤维素酯类手性固定相的种类及合成方法、固定于硅胶载体的方法及其分离性能方面进行详细的综述。     

离子液体与水混合溶剂应用于微晶纤维素溶剂液化研究

将离子液体氯化1-丁基-3-甲基咪唑（[BMIM]C1）、水、固体酸催化剂组成的混合溶剂应用于微晶纤维素的预处理过程中,并尝试把经过预处理的微晶纤维素应用于随后的溶剂液化的研究中,对经过混合溶剂处理后的微晶纤维素进行表征分析。通过测定纤维素的聚合度、官能团基变化、热重分析、结晶结构和表面结构等对微晶纤维素结构进行比较分析。通过对苯酚溶剂液化的基本表征、残渣物的结晶结构以及生成物相对分子质量的变化了解了混合溶剂对微晶纤维素的处理效果。结果表明,通过混合离子液体[BMIM]C1和水并且添加固体酸催化剂形成新的混合溶剂体系对微晶纤维素进行预处理,发现溶剂在保留纤维素主要葡萄糖单元的同时能够有效地降低聚合度。聚合度从未处理时的190降到样品[B]C1（10）的165和样品[B]C1（10）＋NR50的151。混合溶剂对非结晶或低结晶物质具有一定的溶解能力,并且对高结晶性纤维素部分的氢键结构起到破坏作用和造成整体结晶结构的歪曲。在随后的液化过程中,处理后的纤维素液化效率有所提高,在反应2min时,固体酸加混合溶剂处理的微晶纤维素液化残渣率为19％,而未处理的液化残渣率29％。表明使用了混合溶剂添加固体酸的溶剂体系对加速液化的效果更佳,预处理对最终液化生成物的性质影响不大。     

微晶纤维素的合成

作为天然植物纤维原料制品,微晶纤维素在医药食品工业中具有先天的优势和独特的性质,是多功能的辅料[1]。国外微晶纤维素产品主要是以特殊等级的高α-纤维素含量的纯木材纤维素为原料,而国内传统采用棉为原料,其中棉短绒中纤维素含量较高,约在90%以上,是制备微晶纤维素的良好原料[2]。本实验主要探讨由棉短绒制备微晶纤维素的条件。实验发现脱脂过程中氢氧化钠浓度和脱脂时间有较大影响,最佳条件为20%氢氧化钠溶液室温下浸泡72 h,然后在90~95℃水浴温度下搅拌约220 min。脱脂后的棉短绒经过氧化氢漂白后直接用盐酸催化水解,水解过程中盐酸浓度、时间和温度对最终产物影响较大,结晶最好的条件为10%盐酸、90℃搅拌水解145 min。测试了产物的XRD,证明所得的产物有较好的结晶度。     

富铁亚硝基猪血红素肽的制备

目的制备富铁亚硝基猪血红素肽。方法以新鲜猪血为原料制备血红蛋白,分别取胰蛋白酶、木瓜蛋白酶、风味蛋白酶及碱性蛋白酶,在各自最适温度和p H条件下水解,有限酶解成较长的多肽链,分析水解效果,选择最适酶进行酶解条件确定试验。取酶解后的产物,合成富铁亚硝基血红素肽,定性检测合成肽产物。结果综合螯合物颜色和铁螯合活性,确定最佳酶解用酶为胰蛋白酶。最佳酶解条件为:底物浓度10%,加酶量5 000 U/g,反应时间4 h,在此条件下,水解产物与亚硝酸钠反应生成亚硝基血红素肽,且螯合铁的效果最好。定性检测显示,产物中生成了亚铁血红素肽及亚硝基血红素肽。结论成功制备了富铁亚硝基猪血红素肽。     

无定形介孔磷酸锆固定葡萄糖氧化酶的直接电化学

利用无定形介孔磷酸锆(ZrP)为载体,通过吸附法固定葡萄糖氧化酶(GOD),修饰玻碳(GC)电极得到GOD/ZrP/GC电极。在0.1 mol·L^-1磷酸盐缓冲溶液中,利用循环伏安法研究了GOD/ZrP/GC电极的直接电化学行为和对葡萄糖的催化性能。结果表明,无定形磷酸锆ZrP为载体修饰的电极GOD/ZrP/GC其电化学反应电子转移速率快、表观覆盖量大;对葡萄糖的检测表现出较快的电流响应和较高的灵敏度,说明无定形磷酸锆更有利于GOD的固定和酶电极的直接电化学。     

Clostridium acetobutylicum细胞的无机载体吸附固定化及其应用研究

为避免渗透汽化膜原位分离过程中丁醇生产菌对膜的污染,对无机载体吸附固定Clostridium acetobutylicum XY16进行了研究,考察了多种无机载体对菌体的固定效率及其发酵产丁醇性能的影响.研究发现:在静电引力的作用下,携带正电荷的沸石对荷负电的菌体具有良好的吸附作用.在此基础上,对沸石载体进行负载阳离子改性,沸石负载铁离子改变了载体表面Zeta电位,可增强对菌体的固定效率,并提高发酵性能.当培养基中葡萄糖浓度为60 g?L?1时,添加Fe3+-沸石18%(W/V)进行批式发酵,总溶剂的转化率为0.31 g?g?1,对菌体的固定效率达到87%,比未改性沸石提高了22%,丁醇产量为13.5 g?L?1,总溶剂可达20 g?L?1,比沸石改性前分别提高了8%和11.1%.对该材料固载的细胞进行4次重复批式发酵,总溶剂的基质得率与游离细胞批式发酵结果类似.以上研究结果表明Fe3+-沸石对Clostridium acetobutylicum XY16具有较好的细胞固定效率,并对其生产性能具有一定的促进作用,适宜作为丁醇生产菌的吸附载体.     

离子液体中采用AGET ATRP法制备MCC-g-PGMA

在氯化1-烯丙基-3-甲基咪唑([AMIM]Cl)离子液体中, 采用AGET ATRP技术, 以VC为还原剂、CuBr₂/乙二胺为催化体系, 成功制备了微晶纤维素接枝聚甲基丙烯酸缩水甘油酯(MCC-g-PGMA)分子。研究表明:[AMIM]Cl对微晶纤维素有较好的溶解性, 最佳反应条件为GMA/乙二胺/CuBr₂/VC摩尔比为100:4:1:1, 反应温度25℃, 反应时间4 h, 接枝效率可达54.56%, 分子量分布较窄为1.48。通过FT-IR、TEM和SEM测试表明:成功合成了MCC-g-PGMA接枝共聚物分子, PGMA接枝微晶纤维素后表面形态变得粗糙, 接枝共聚物在丙酮溶液中可自组装成150～200 nm的球形结构, 在药物载体领域具有良好的应用潜能。     

酸碱结合预处理对水稻秸秆纤维素乙醇转化率的影响

以水稻秸秆为原料．在常温常压条件下分别用乙酸、过氧化氢、乙酸-过氧化氢（PPA）、氢氧化钠-PAA进行预处理,然后加入纤维素酶和酵母进行异步发酵产乙醇。结果表明,酸碱结合（氢氧化钠～PPA）处理后的固体得率显著低于乙酸或过氧化氢的单独处理,固体得率和纤维素水解后产生的葡萄糖浓度呈负相关;氢氧化钠-PAA处理能有效去除水稻秸秆中的木质素．大幅提高纤维素水解率和乙醇转化率;用10％氢氧化钠-PAA室温浸泡处理水稻秸秆48h与用5％氢氧化钠-PAA90℃处理水稻秸秆1．5h具有同样的效果。     

HIV-1 GP120主要抗原性片段的制备及其在HIV诊断中的应用

目的研制HIV中国流行株RL42GP120主要抗原性片段,以便进一步开发HIV抗体检测试剂。方法克隆RL42毒株GP120蛋白C-端250个氨基酸的编码序列,克隆入大肠杆菌表达载体pBV220进行表达。通过包涵体处理和离子交换层析纯化目的蛋白。将纯化后的蛋白用狭缝电转技术转印硝酸纤维素膜,利用HIV参考品血清检测其灵敏度和特异性。结果目的蛋白的表达量占菌体总蛋白的10%左右。纯化后其纯度高于95%,HIV参考品血清检测显示出良好的灵敏度和特异性,检测8份阳性临床标本无一漏检,而7份阴性临床标本无交叉反应。结论已研制出具有良好灵敏度和特异性的HIV-1GP120主要抗原性片段。为开发HIV抗体检测试剂创造了条件。     

过氧化氢酶活性检测罗丹明B褪色光度法的建立

目的建立检测过氧化氢酶活力的罗丹明B褪色光度法。方法在硫酸介质中,加入过氧化氢氧化罗丹明B褪色,再加入Fe3+加速反应进程,根据酶促反应前后吸光度变化值△A确定过氧化氢酶活性。对建立的方法中的罗丹明B褪色反应条件(褪色反应催化剂、罗丹明B用量、褪色反应时间、褪色反应温度、硫酸用量)及酶促反应条件(过氧化氢体积、酶促反应时间)进行优化;确定该方法的线性范围;加入浓度小于过氧化氢基底液1/2的共存还原性物质(葡萄糖、果糖、乳糖、半乳糖)进行干扰试验。用建立的方法检测鱼肝脏中过氧化氢酶活性。结果以1 mL Fe~(3+)作为催化剂,5 mL罗丹明B作为底液时,体系吸光度控制在0. 8以内;在2 mmol/L硫酸介质中,40℃条件下反应60 min,罗丹明B褪色程度趋于最大;取过氧化氢基质液1. 00 mL,在15 min内,酶促反应达到完全。在最佳条件下,过氧化氢酶活性在0. 02～0. 3 U/mL范围内与△A具有良好的线性关系,r=0. 999 2,检测限为0. 011 U/mL。建立的方法可检测鱼肝脏中过氧化氢酶活性。结论建立的罗丹明B褪色光度法具有较好的选择性和较高的灵敏度,仪器设备简单,操作简便,适用于生物样品微量过氧化氢酶活性分析。     

Preparation of hemin polymer monolithic column and its application in the separation of proteins and small molecules

A poly(hemin-co-C16-co-TEGDA) monolith was prepared using hemin and 1-hexadecene (C16) as monomers; triethylene glycol dimethacrylate (TEGDA) as crosslinking agent; N,N-dimethylformamide and isopropyl alcohol as porogens; and dibenzoyl peroxide and N,N-dimethyl aniline as initiators in 50?×?4.6?mm i.d. stainless steel column. The morphology and structure of the monolith were characterized by scanning electron microscopy and nitrogen adsorption/desorption isotherm measurement, respectively. Compared with poly(C16-co-TEGDA) monolith, poly(hemin-co-C16-co-TEGDA) monolith had better mechanical properties, higher permeability, and better separation ability. The prepared monolith was used to separate not only proteins but also small molecules.     

Graft copolymerization to cellulose. Effect of sodium thiosulfate on hydrogen peroxide initiator system

The effect of sodium thiosulfate on the graft copolymerization of methyl methacrylate to cellulose in the hydrogen peroxide initiator system was investigated. The addition of sodium thiosulfate in general was effective for decreasing the per cent grafting and the average molecular weight of grafts and increasing the formation of homopolymer, and the effects became pronounced with increasing hydrogen peroxide concentration. Moreover, the addition of sodium thiosulfate slightly suppressed the formation of grafts at a hydrogen peroxide concentration of 3 mmole/l., but greatly promoted it at 20 mmole/l. Traces of metallic ions present in cellulose could not be eliminated sufficiently by treatment with 3N hydrochloric acid. Such ions were found to interact with hydrogen peroxide and thus participate directly in the initiation and termination of the polymerization reaction. EDTA, the chelating agent, was highly effective for suppressing such participation of metallic ions. In the hydrogen peroxide initiator system applied to the EDTA-treated samples, sodium thiosulfate caused an effective initiation of graft formation.     

Studies of the initiation mechanism of ferric ion–hydrogen peroxide systems in graft copolymerization on cellulose

The decomposition of hydrogen peroxide by ferric ion adsorbed on cellulose, the lowering of the degree of polymerization of cellulose, and the graft copolymerization in the systems containing methyl methacrylate were studied. As the amount of ferric ion adsorbed on cellulose and the concentration of hydrogen peroxide became higher, the amount of decomposition of hydrogen peroxide and the number of scissions of cellulose chains with higher rates at the initial stage of reaction were both observed to increase. It was recognized that the graft copolymerization was hardly initiated, while such initial reactions were proceeding. Assuming that the hydrogen peroxide decomposed with a higher rate was indifferent to the initiation reaction, a certain relationship was found between the amount of ferric ion adsorbed on cellulose ànd the initiation efficiency of hydrogen peroxide in graft copolymerization.     

基于硫胺素荧光增强的可更新液滴荧光法用于痕量过氧化氢的测定

硫胺素在碱性条件下能被过氧化氢氧化成具有较强荧光的硫胺荧。基于此基本原理,利用连续动态液滴荧光法测定溶液中的痕量过氧化氢。连续产生与滴落的液滴可充当无光窗光池。在优化的实验条件下,传感器对2.5×10-5 mol/L～1.9×10-4 mol/L浓度范围内的过氧化氢具有良好的线性响应,检测限为4.88×10-6 mol/L。方法灵敏度高,选择性好,操作简单,试剂用量少。将其用于雨水中痕量过氧化氢的测定,结果满意。     

游离态和吸附态铁催化分解过氧化氢

通过制备差异态铁,研究了差异态铁对碱性过氧化氢的催化分解行为,考察了硫酸镁、硅酸钠及DTPA在差异态铁存在下的功能效果.研究发现,游离态铁以Fe₂O₃晶体颗粒形式存在,通过吸附在纤维表面或者填充在纤维“孔腔”内形成纤维素吸附态铁;游离态铁减弱了过氧化氢碱性分解,吸附态铁强化了过氧化氢碱性分解.DTPA、硫酸镁显著抑制游离态铁催化分解碱性过氧化氢,将过氧化氢分解率分别降至25%,50%.DTPA、硫酸镁对抑制纤维素吸附态铁的催化分解无效,1 h内碱性过氧化氢分解率达到80%以上.     

氯化血红素钠的制备

氯化血红素Hemin用于治疗缺铁性贫血已逐渐得到人们的重视。探讨了从新鲜猪血中分离制备氯化血红素的工艺过程,其优化的条件是血红蛋白与冰醋酸比例1∶4,加NaCl40g,反应温度为100～106°C,反应时间为15min,此工艺操作简单,成本低,收率高。将其制成钠盐,易溶于水,便于制成口服制剂,服用方便。     

Cellulose peroxides derived from carbonylated cellulose and hydrogen peroxide

Cellulose peroxides derived from hydrogen peroxide and cellulose derivative into which a ketone group is introduced by reaction with methyl vinyl ketone were investigated. The amount of peroxide formed on the cellulose substrate increased linearly with increasing carbonyl content of the sample, and sulfuric acid activated the formation of peroxide. The cellulose peroxide was gradually decomposed at 60°C in aqueous medium, and the decomposition was accelerated by addition of ferrous salt or irradiation with light of λ > 300nm. Grafting was initiated by adding methyl methacrylate to the thermal decomposition system under nitrogen. The formation, stability, thermal decomposition, and structure of the cellulose peroxide were discussed in comparison with one derived from aldehyde cellulose and hydrogen peroxide.     

Reactivity of glycidyl-methacrylate-grafted cellulose prepared by means of photografting

Photografting was applied to functionalize cellulose, that is, epoxy groups were introduced into the cellulose substrate by photografting of glycidyl methacrylate (GMA) using hydrogen peroxide as a photoinitiator. Dissolving pulp from softwoods was used as the cellulose sample. The GMA-grafted cellulose (G-Cell) was subjected to the following examinations in comparision with epoxy-activated cellulose (E-Cell) prepared by reaction with epichlorohydrin: (1) reactivity of G-Cell towards amines such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine; (2) ability of the aminated celluloses obtained by examination (1) to adsorb cupric ion; and (3) catalytic activity of the aminated cellulose–cupric ion complexes prepared by examination (2) for decomposition of hydrogen peroxide. The amount of amine residue introduced into the substrate was higher for E-Cell than G-Cell, showing the existence of epoxy groups in G-Cell which cannot contribute to the reaction. The ability of the aminated celluloses to adsorb cupric ion was nearly equal for G-Cell and E-Cell though tetramethylenediamine and hexamethylenediamine-introduced samples did not show the ability. It was found that all complexes prepared by reaction of the aminated cellulose with cupric ion exhibited catalytic activity for decomposition of hydrogen peroxide. © 1995 John Wiley & Sons, Inc.     

氨肟化反应中双氧水分解的影响因素探讨

在实验装置上对环己酮氨肟化反应体系中引发双氧水分解的因素进行了分析,将实验结果应用于工业化生产。结果表明:在氨肟化反应体系中,氨过量导致的碱性环境、双氧水过量加入或氨肟化反应不完全是双氧水分解的主要原因;反应温度、反应时间等反应条件的变化可改变双氧水的分解速度;微量的铜、铁、铬等金属离子的存在会加速双氧水的分解;适当控制氨浓度、环己酮∶双氧水摩尔比、反应条件及降低金属离子含量有利于提高双氧水的有效利用率;在工业生产装置中,控制反应液中氨质量分数2.0%～2.8%,环己酮∶双氧水摩尔比为1∶(1.05～1.10),反应温度78～81℃,催化剂(相对于环己酮)质量分数小于4%,双氧水利用率提高了3.7%。     

氨肟化反应中影响双氧水分解因素浅析

本文对环己酮氨肟化反应体系中引发H2O2分解的因素进行了研究,针对各种影响因素提出控制H2O2分解的优化措施。结果表明：在氨肟化反应体系中,NH3过量导致的碱性环境、H2O2过量加入或H2O2浓度过高以及氨肟化反应不完全,是引起H2O2分解的主要原因;反应温度、反应压力等操作条件的变化也可改变H2O2的分解速度;微量的锰、锌、铜、铁、镍等金属离子的存在,也会大大加速H2O2的分解。控制适当的NH3浓度及酮/H2O2摩尔比、反应条件以及降低金属离子含量有利于提高H2O2的有效利用率,这些结果可以为优化氨肟化反应工艺、降低H2O2消耗提供依据。