离子液体溶解角蛋白过程及机理研究

发布时间：2018-03-22 18:39

本文选题：角蛋白　切入点：二硫键　出处：《中国科学院大学(中国科学院过程工程研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：角蛋白作为一种丰度高、来源广的可再生天然高分子,由于其良好的材料力学性能及生物相容性,在可降解材料、医用品及其他功能性材料方面具有广泛用途。利用角蛋白的前提是溶解角蛋白,然而角蛋白中复杂的二硫键交联结构导致其较难被传统溶剂溶解。离子液体作为一种绿色高效溶剂在溶解角蛋白等生物高分子方面的应用逐渐受到关注,其可用于溶解废弃羊毛、羽毛等提取角蛋白,或者以离子液体为溶解介质进一步制备角蛋白基复合功能材料。清晰认识离子液体溶解角蛋白机理,特别是离子液体对二硫键的影响是设计与筛选功能化离子液体溶解角蛋白的基础;此外,通过离子液体阴阳离子种类与溶解条件可调控角蛋白的溶解量及再生角蛋白结构与性能,获得这些变量对再生角蛋白二硫键含量等性质的影响规律可为优化离子液体溶解角蛋白工艺提供基础数据支持;最后,离子液体回收问题是其工业化应用的技术瓶颈之一,水常作为角蛋白再生的凝固浴,如何较大规模地从凝固浴中回收循环利用离子液体的问题也亟待解决。针对上述三个问题,围绕对羊毛角蛋白溶解具有重要影响的二硫键,本论文结合实验、谱学表征与模拟计算从不同尺度上研究获得离子液体与角蛋白的相互作用机制和构-效关系的共性关键科学问题,为设计高效离子液体溶解角蛋白以及离子液体溶解角蛋白的工业化应用提供科学基础。论文的创新性及主要研究成果如下:(1)采用含二硫键模型化合物氧化型谷胱甘肽,考察离子液体对二硫键影响。研究发现,模型化合物再生后特征峰消失,分子量降低,并检测到硫化氢生成,首次证明离子液体可以还原断裂二硫键。进一步使用14种离子液体,1-丁基-3-甲基咪唑卤盐([Bmim]Cl/[Bmim]Br)、1-乙基-3-甲基咪唑氯盐([Emim]Cl)、1-己基-3-甲基咪唑氯盐([Hmim]Cl)、1-丁基-3-甲基吡啶氯盐([Bpy]Cl)、1,2,3,4-四丁基季铵氯盐([N4444]Cl)、1,2,3,4-四丁基季磷氯盐([P4444]Cl)、1-烯丙基-3-甲基氯化咪唑([Amim]Cl)、1-丁基-3-甲基咪唑醋酸盐([Bmim]OAc)、1-乙基-3-甲基咪唑醋酸盐([Emim]OAc)、1-乙基-3-甲基咪唑磷酸二甲酯([Emim]DMP)、1-乙基-3-甲基咪唑磷酸二乙酯([Emim]DEP)、1-丁基-3-甲基咪唑磷酸二丁酯([Bmim]DBP)、1-丁基-3-甲基咪唑磷酸二氢盐([Bmim]H2PO4)),溶解羊毛角蛋白考察离子液体种类对再生角蛋白中二硫键含量及微观结构的影响,同样地,在溶解过程中检测到硫化氢生成,并且发现离子液体对角蛋白中二硫键具有差异化的破坏能力,咪唑醋酸类离子液体可断裂角蛋白中90%以上的二硫键,而季铵或季磷类离子液体对二硫键基本无破坏能力。并且利用13C-NMR分析再生角蛋白二级结构信息发现,离子液体的二硫键断裂能力越强,再生角蛋白中α-helix含量越低,β-sheet与无定型结构含量越高。通过分子模拟研究发现离子液体断裂二硫键能力越强,其与胱氨酸的相互作用能越强,离子液体在胱氨酸周围的分布密度越大。(2)在相同溶解条件下,对比离子液体阴阳离子种类对其破坏二硫键性能的影响。通过再生角蛋白二硫键含量表征发现,阴离子断裂二硫键的能力:[Emim]+系列[OAc]Cl-[DEP][DMP]-;[Bmim]+系列[OAc]Cl-Br-[DBP]-[H2PO4]-。阳离子断裂二硫键的能力为[Emim]+[Amim]+≈[Bmim]+[Hmim]+[BPy]+[P4444]+[N4444]+。此外,在离子液体阴离子相同,阳离子含有咪唑环的情况下,咪唑环上侧链长度对离子液体断裂二硫键能力的影响并不显著。进一步,分别考察溶解温度、时间及气氛对再生角蛋白中二硫键含量、胱氨酸含量、硫元素含量以及结晶度的影响。研究发现:随着溶解温度、时间的增加,再生角蛋白中二硫键含量、胱氨酸含量、硫元素含量均不断降低;在N2气氛下溶解角蛋白,可减少再生角蛋白中二硫键断裂量。升高溶解温度及延长溶解时间均会导致再生角蛋白结晶度下降,但温度的影响更加显著。(3)水分子与离子液体形成氢键作用,通过分子动力学模拟研究发现,随水含量增加,离子液体[Emim]DMP阴阳离子之间的相互作用被削弱。通过表征再生角蛋白二硫键含量,发现水含量增加导致离子液体二硫键断裂能力逐渐降低,溶解角蛋白所需时间逐渐延长。为保证离子液体对角蛋白具有较好溶解能力,水含量(摩尔比,H20/IL)应小于0.8。进一步设计开发了小试规模回收离子液体的降膜蒸发装置,经回收后离子液体水含量可低至4000 ppm左右,回收后仍能够实现对角蛋白的高效溶解。
[Abstract]:Keratin as a kind of high abundance, wide source of renewable natural polymer, because of its good biocompatibility and mechanical properties of biological materials, the biodegradable material, has been widely used in medical products and other functional materials. The premise of keratin is dissolved keratin, however two disulfide cross-linked keratin complex structure which is difficult to be dissolved. The traditional applications of ionic liquid as a solvent in the dissolution of green and efficient keratin and other aspects of the biopolymer has gradually attracted attention, which can be used to dissolve waste wool, feathers extracting keratin, or using ionic liquid as for further preparation of keratin composite functional materials. A clear understanding of the dissolution medium the ionic liquid dissolved keratin mechanism, especially the effect of ionic liquid on the two sulfur bond is the basis for the design and selection of functional ionic liquids dissolved keratin; in addition, by ion Liquid anion type and dissolution conditions can be dissolved and regeneration of keratin keratin structure and properties, obtain the influence of these variables on the properties of regenerated keratin two disulfide bond content can provide basic data support for the optimization of ionic liquid dissolved keratin process; the recovery of ionic liquid, the problem is one of the technical bottlenecks in industrial application, the water is often used as a coagulation bath keratin regeneration, to a larger scale from the bath in the recycling of ionic liquid problems are solved. To solve the above three problems, two disulfide bonds around has an important influence on the wool keratin solution, this paper combines the experiment, spectral characterization and simulation study on the interaction mechanism of ionic liquid and keratin from different scales and structure effect relationship of common key scientific problems, for the design of efficient ionic liquid dissolved keratin To provide scientific basis for the industrialization and application of ionic liquid dissolved keratin. The innovation and main achievements of this thesis are as follows: (1) with two disulfide model compounds of oxidized glutathione, the effects of ionic liquids on two disulfide bonds. The study found that the model compounds after regeneration characteristic peaks disappeared, lower molecular weight and detected the hydrogen sulfide formation, for the first time that ionic liquids can bebroken two disulfide bonds. The further use of 14 kinds of ionic liquids, 1- butyl -3- methylimidazolium halide salt ([Bmim]Cl/[Bmim]Br), 1- ethyl -3- methyl imidazole chloride ([Emim]Cl), 1- hexyl -3- methyl imidazole chloride ([Hmim]Cl), 1- butyl -3- methyl pyridine chloride ([Bpy]Cl) four, 1,2,3,4- Butyl Ammonium Chloride ([N4444]Cl), 1,2,3,4- four butyl phosphonium chloride ([P4444]Cl), 1- allyl -3- methyl imidazole chloride ([Amim]Cl), 1- butyl -3- methyl imidazole acetate ([Bmim]OAc), ethyl -3- methyl 1- Imidazole acetate ([Emim]OAc), 1- ethyl -3- methyl imidazole phosphoric acid methyl ester ([Emim]DMP), two 1- ethyl -3- methyl imidazole phosphoric acid ethyl ester two ([Emim]DEP), 1- butyl -3- methylimidazolium two butyl phosphate ([Bmim]DBP), 1- butyl -3- methylimidazolium dihydrogen phosphate ([Bmim]H2PO4), dissolved), wool keratin effects of ionic liquids on the content and microstructure of two disulfide bonds in regenerated keratin in the same, to generate hydrogen sulfide detection in the process of dissolution, and the damage ability of two sulfur ionic liquid keratin bond with the difference of the class, imidazole acetic acid ionic liquid can be more than 90% of the two disulfide bond fracture keratin, and quaternary ammonium or phosphonium ionic liquid on two disulfide bonds basically no damage ability. And the use of 13C-NMR information analysis of regenerated keratin two grade structure, two sulfur bond breaking ability of ionic liquids is stronger, then the content of -helix protein alpha male character Low beta, -sheet and amorphous structure. The higher the content of ionic liquid by molecular simulation study found that fracture of two disulfide bond stronger, its interaction with cystine to stronger ionic liquids in the distribution density of cystine around more. (2) in the same dissolving conditions, contrast ion liquid negative ion species to the destruction of the two disulfide bonds affect the performance. Through the regeneration of keratin two disulfide content characterization shows that the ability of two disulfide anion fracture: [Emim]+ series [Bmim]+ series [OAc]Cl-Br-[DBP]-[H2PO4]-. [OAc]Cl-[DEP][DMP]-; cationic fracture of two sulfur bond capacity of [Emim]+[Amim]+ is about [Bmim]+[Hmim]+[BPy]+[P4444]+[N4444]+. in addition, in the same ionic liquid anions, cations containing imidazole ring under the condition that the imidazole ring effect of side chain length of ionic liquid two disulfide bond fracture ability is not significant. Further, respectively. The effect of solution temperature, time The content of two disulfide bonds in regenerated keratin and atmosphere, cystine content, sulfur content and the effect of crystallization degree. It was found that with the increase of time, solution temperature, the content of two disulfide bonds in regenerated keratin, cystine content, sulfur content decreased continuously; in N2 atmosphere dissolved keratin, can reduce the two disulfide bond in regenerated keratin. High dissolving temperature and prolonging the dissolution time will cause the regenerated keratin crystallinity decreased, but the effect of temperature is more significant. (3) water molecule and the ionic liquid formed through hydrogen bonding interactions, molecular dynamics simulation study found that, with increasing the water content. The interaction between the ionic liquid [Emim]DMP ion is weakened. The characterization of regenerated keratin two disulfide bond content, found the water content increased ability to cause the ionic liquid two disulfide bond decreased dissolved keratin required to gradually extend. Ensure the ionic liquid keratin has good solubility, water content (molar ratio H20/IL) should be less than 0.8. and falling film evaporation device further design and development of small scale recovery of ionic liquid, the liquid water content after ion recovery can be as low as 4000 ppm or so, still can realize the efficient recovery of dissolved keratin.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ413.2;TQ936.2

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