CAS OpenIR
基于光-酶偶联模型的人工光合作用体系仿生构建
姬晓元
Thesis Advisor张松平
2017-01
Degree Grantor中国科学院研究生院
Degree Name博士
Degree Discipline生物化工
Keyword人工光合作用,中空纳米纤维,Tas2纳米片,仿生叶绿体,仿生绿小体
Abstract

构建光-酶偶联人工光合作用体系,即将光化学辅酶再生与氧化还原酶催化过程相偶联,利用太阳能在温和的条件下,合成人类所需要的各种燃料或化学品,对于解决能源、环境危机具有重要的意义。这一过程最大的难点是构建有效的光催化—酶催化界面,提高光激发电子在光敏剂、电子媒介、辅酶和氧化还原酶之间的传递效率。 受自然界光合反应过程的启发,本论文的从如下三个方面入手,仿生设计并构建基于光-酶偶联模型的人工光合作用体系,并用于CO2合成甲醇:首先制备并利用杂化中空纳米纤维对人工光合作用体系各要素进行精确排列与集成组装,通过各要素宏观距离上的缩短来提高激发电子的传递速率;其次借助二维半导体材料优越的光电以及负载组装性能,实现TaS2纳米片二维尺度上的激发电子高速传递;最后采用“bottom-up”自下而上化学合成法构建单分子尺度上高效的电子激发与传递。具体包括以下研究内容: (1)聚合电解质掺杂的中空纳米纤维的制备、表征与多酶定位组装。将同轴共纺静电纺丝技术与分子组装相结合,在内相电纺液中添加离子型长链聚合电解质(PAH),使中空纳米纤维的壳层的内、外表面布满正电荷的离子化基团,通过带负电荷辅酶与PAH之间静电相互作用实现其在中空纳米纤维腔室内的有效截留,解决了辅酶截留与重复使用的难题,同时实现CO2转化甲醇的含辅酶再生的多酶体系在纤维腔室、外表面的定位组装,甲醇的转化率高达103.2%。此外,发现并利用中空纳米纤维具有自发地分布到油/水两相界面上这一特性,将葡萄糖氧化酶(GOD)和脂肪酶(CALB)定位组装到中空纳米纤维上,通过级联反应在油水两相界面催化油酸环氧化反应,最高速率较游离体系提高约115倍。 (2)基于聚合电解质掺杂的中空纳米纤维的光-酶偶联人工光合作用体系。借鉴自然界绿色植物叶绿体的结构,以掺杂有PAH和氧化石墨烯(GO)的中空纳米纤维为载体材料,将用于催化CO2还原合成甲醇的三种脱氢酶和辅酶NAD(H)原位包埋在材料的中空腔室内;结合层层自组装的技术原理,依次将电子媒介和光敏剂分子通过与材料外壁上聚合电解质之间的静电力以及GO之间的π-π作用力,精确组装到中空纳米纤维的外表面,构建GO介导电子传递的整合人工光合作用体系,甲醇得率比游离体系提高了10倍。 (3)基于TaS2纳米片的光-酶偶联人工光合作用体系。通过探针超声制备TaS2纳米片,然后表面修饰LA-PEG提高其水溶液分散性,表面组装石墨烯GR,最后将电子媒介M组装到GR表面,制备整合电子媒介与光敏剂的整合人工光合作用。TaS2纳米片表面组装电子媒介使得激发电子在二维尺度上高速传递, NADH再生率高达83.9%,CO2转化甲酸的转化率高达101.4 mM (5 h)。(4)仿绿色植物叶绿体单分子人工光合作用体系:通过化学合成分别制备光敏剂TCPP和电子媒介M修饰的硅烷,结合溶胶-凝胶化反应形成同时负载有光敏剂和电子媒介的TCPP/SiO2/Rh HNPs复合纳米颗粒,实现电子在单分子内的激发与传导;进一步通过静电引力作用,将甲酸脱氢酶与辅酶NAD+分子组装到HNPs的外表面,降低了整个体系的电子传递距离。这种模拟叶绿体结构的TCPP/SiO2/Rh HNPs整合人工光合作用体系光催化NADH的再生效率达到了75%,甲酸得率从游离体系的15 mM提高到了100 mM。(5)仿光合细菌绿小体的单分子人工光合作用体系:以光敏剂TCPP为母核,首先进行有机染料EY敏化修饰来提高TCPP捕获太阳能可见光的能力,再将电子媒介配体通过共价键修饰到TCPP剩余的配基上构建TCPP/EYx/Rh8-x复合物。利用TCPP/EYx/Rh8-x复合物相互之间氢键以及静电引力作用在水溶液中自发组装成为类似光合细菌绿小体结构的纳米组装体。TCPP/EYx/Rh8-x超分子组装体不仅在单分子尺度上实现光敏剂敏化以及电子传递链的构建,而且通过自组装还形成了众多分子间的电子传递链,将目前人工光合系统中“分子间”或“材料间”的电子传递界面,变为“分子内”的传递,有望从根本上解决现有人工光合作用体系电子传递效率和速率低的难题。催化NADH的再生率高达91%,偶联酶体系催化甲醇的转化率高达38 uM (2 h);Construction of artificial photosynthesis system by incorporating the solar energy driven photochemical regeneration of coeznyem NADH with the redox enzymatic process to produce various fuels or chemicals has an important significance for solving energy and environmental crisis. However, how to create a direct photocatalytic and enzymatic interface to facilitate the transfer of the photo-excited electrons in photosensitizer, electronic mediator, cofactor and oxidoreductase still remains a big challenge.Inspired by the structure and mechanism of natural photosynthesis system, this thesis was aimed at biomimetic design of artificial photosynthesis system based on photo-enzymatic coupling model for conversion methanol from CO2. This thesis mainly includes the following three aspects: firstly, hybrid hollow nanofibers were prepared and used as a scaffold for accurately assembling elements of artificial photosynthesis. The transfer efficiency of excited electrons could be improved by shortening the distance of the electron transfer chain. Secondly, based on the predominant optoelectronic and assembly load capacity, we constructed two-dimensional TaS2 nanosheets-based electrons transfer chain with enhanced efficiency. Thirdly, we constructed efficient electrons excitation and transfer system based on single molecular by bottom-up chemical synthesis method. The specific research contents include the following:(1) Preparation, characterization and application of polyelectrolyte doped hollow nanofibers: polyelectrolyte (PAH) doped hollow nanofibers with positively charged ionogen groups distributing on their inner and outer surface were prepared by combination of coaxial electrospinning technology and self-assembly technology. The retention and reuse of cofactors, and positional assembly multienzyme system for conversion methanol from CO2 on nanofibers surface or in their hollow chambers were realized based on the ion-exchange interactions between oppositely charged enzymes/NAD(H) and PAH that was doped in hollow nanofibers. And the yield of methanol reached to 103.2%. Besides, the polyelectrolyte doped hollow nanofibers membrane was found to float spontaneously at the O/W interface, thus providing opportunity to develop novel interfacial active biocatalyst. When an hollow nanofibers-based interfacial cascade bienzyme systems lincluding glucose oxidase (GOD) and CALB lipse were prepared and used for epoxy stearate synthesis in an oil-aqueous biphasic system, the highest reaction rate was attained by lumen (GOD)-surface (CALB), corresponding to 114.45 times enhancement as compared to that of the free bienzyme system.(2) Integrated artificial photosynthesis based on polyelectrolyte-doped hollow nanofibers: inspired by the structure of green plant chloroplasts, the biocatalysis part including multiple oxidoreductases and coenzymes NAD(H) was in situ encapsulated inside the lumen GO and PAH doped hollow nanofibers fabricated via co-axial electrospinning; while the precise and spatial arrangement of the photocatalysis part, including electron mediator and photosensitizer for photo-regeneration of the coenzyme, was achieved by ion-exchange and p-p interaction-driven LbL self-assembly. The highly integrated artificial photosynthesis with GO mediated electron transfer was realized. Compared to solution-based systems, the methanol yield increased 10 times using the integrated artificial photosynthesis.(3) Artificial photosynthesis based on TaS2 nanosheets: the integration of M to TaS2 nanosheets was realized through sequential functionalization by probe sonication, pegylation with lipoic acid conjugated PEG (LA–PEG), surface assembly of graphene (GR), and final integration of M. Two-dimensional TaS2 nanosheets with assembling M, made electrons transfer in two dimensional scale with enhanced efficiency. The integrated photocatalyst termed as TaS2–PEG–GR–M exhibited significantly improved efficiency with a NADH regeneration yield up to 83.9% and the formic acid converted from CO2 reached 101.4 mM in 5 hours.(4) Chloroplast mimicking artificial photosynthesis: the TCPP/SiO2/Rh HNPs are fabricated via sol-gel reaction of silica precursors functionalized with photosensitizer (porphyrin, TCPP) and electron mediator (Cp*Rh(bpy)Cl, M); while the integrating of enzyme and NAD(H) on the outer surface of the HNPs were achieved through electrostatic interactions driven assembling under the entanglement of a negatively charged polyelectrolyte. The chloroplast-mimicking, highly integrated APS exhibits remarkably superior performance over free system, such that the regeneration of NADH is improved from 11% to 75%, and the synthesis of formic acid from CO2 increased from 15 mM to 100 mM in 4 hours. (5)Chlorosome mimicking artificial photosynthesis: TCPP/EYx/Rh8-x macromolecules, synthesized through sequential amidation reaction between TCPP, EY, and [Cp*RhCl2]2, was found to self-assembled into chlorosome-mimicking supramolecular assemblies through hydrogen bonding and ion-exchange interactions. TCPP/EYx/Rh8-x supramolecular assembly not only realized photosensitizer sensitized and electron transfer chain construction on single molecular scale, but also evolved intramolecular electron transfer to intramolecular electron, which was expected to fundamentally solve the low electron transfer efficiency of artificial photosynthesis. The yield of NADH photo-regeneration using TCPP/EYx/Rh8-x supramolecular assembly was improved 91%, and the conversion of methanol from CO2 increased to 38 uM coupling with biocatalyzed system in 2 hours.

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26824
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
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姬晓元. 基于光-酶偶联模型的人工光合作用体系仿生构建[D]. 中国科学院研究生院,2017.
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