介孔泡沫对芥子气降解酶DhaA的吸附研究

doi:10.15541/jim20180061

摘要/Abstract

摘要：

以聚乙二醇-聚丙二醇-聚乙二醇三嵌段共聚物(P123)为模板剂, 1,3,5-三甲苯(TMB)为扩孔剂, 正硅酸乙酯(TEOS)为硅源, 采用水热合成法制备了三维连通笼状介孔泡沫(MCF)。N₂吸脱附等温实验发现MCF最大孔径尺寸17.3 nm, 窗口尺寸8.2 nm, 比表面积770.3 m²/g, 孔容可达2.3 cm³/g。以MCF为载体, 考察了MCF对芥子气降解酶DhaA的吸附作用, 发现pH为6.5时, DhaA在MCF上的饱和吸附量最大, 吸附动力学满足Elovich动力学模型, DhaA在MCF孔道中的内扩散过程是吸附的限速步骤, 吸附等温线符合Sips模型。MCF吸附后DhaA的活性和构象均发生明显改变, DhaA酶活残留12.4%, 本征荧光光谱发生红移。研究结果表明：大孔径、大孔容和三维笼状孔道等结构特征使MCF有利于吸附DhaA, 静电排斥作用影响吸附过程, DhaA构象改变是造成DhaA催化活性降低的主要因素。

关键词: 介孔泡沫, 芥子气降解酶, 吸附, 构象

Abstract:

With polyoxyethylene-polyoxypropylene-polyoxyethylene (P123) as template, 1,3,5-trimethylbenzene (TMB) as swelling agent and tetramethoxysilane (TEOS) as silica source, mesocellular foam (MCF) with three dimensional (3D) cage-like mesopores linked by windows was successfully synthesized by hydrothermal method. N₂ isothermal adsorption characterization indicated that the largest pore size was 17.3 nm, and the other structural parameters as window size, specific surface area and pore volume were 8.2 nm, 770.3 m²/g, 2.3 cm³/g, respectively. MCF was employed as carrier for adsorption of DhaA which is an enzyme for sulfur mustard decontamination. The effect of pH to saturated adsorption capacity of DhaA in MCF was studied and the results showed that the largest loading amount of DhaA was achieved at pH 6.5. The adsorption kinetics followed Elovich kinetic model very well, and rate-determining step of this adsorption process was intraparticle diffusion. Adsorption isotherm curve of DhaA matched Sips model. The catalytic activity and conformation of DhaA changed obviously after being adsorbed in MCF. The residual activity of DhaA was 12.4% after being adsorbed, and the intrinsic fluorescence spectrum was found red shift. From the experimental results it can be observed that the big pore size, large specific surface area, and 3D cage-like structure of MCF facilitated the adsorption of DhaA, The electrostatic repulsion between DhaA and MCF influenced the adsorption process, and the conformation change of DhaA was the major factor of the decreased catalytic activity.

Key words: mesocellular foam, enzyme for sulfur mustard decontamination, adsorption, conformation

中图分类号:

TQ174

郑禾, 钟近艺, 刘景全, 张哲, 崔燕, 郑永超. 介孔泡沫对芥子气降解酶DhaA的吸附研究[J]. 无机材料学报, 2018, 33(11): 1201-1207.

ZHENG He, ZHONG Jin-Yi, LIU Jing-Quan, ZHANG Zhe, CUI Yan, ZHENG Yong-Chao. Adsorption of Enzyme for Sulfur Mustard Decontamination by Mesocellular Foam[J]. Journal of Inorganic Materials, 2018, 33(11): 1201-1207.

图/表 10

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Sample	BET surface area/(m²•g^-1)	Pore size /nm	Window size/nm	Pore volume /(cm³•g^-1)
MCF0	858.2	6.8	6.6	1.2
MCF1	538.4	8.5	6.8	0.9
MCF2	544.3	11.0	6.0	1.1
MCF3	507.3	12.9	4.9	1.3
MCF4	606.7	16.6	7.7	1.8
MCF5	770.3	17.3	8.2	2.3
MCF6	779.5	14.1	8.4	2.1

Sample	BET surface area/(m²•g^-1)	Pore size /nm	Window size/nm	Pore volume /(cm³•g^-1)
MCF0	858.2	6.8	6.6	1.2
MCF1	538.4	8.5	6.8	0.9
MCF2	544.3	11.0	6.0	1.1
MCF3	507.3	12.9	4.9	1.3
MCF4	606.7	16.6	7.7	1.8
MCF5	770.3	17.3	8.2	2.3
MCF6	779.5	14.1	8.4	2.1

Kinetic model		Parameters
Pseudo- first-order	\(\ln ({{q}_{e}}-{{q}_{t}})=ln({{q}_{e}})-{{k}_{1}}t\)	q_e=79.58(mg•g^-1), k₁=0.25(min^-1), R²=0.9300, RMSE=7.38
Pseudo- second-order	\(\frac{t}{{{q}_{t}}}=\frac{1}{{{k}_{2}}q_{e}^{2}}+\frac{t}{{{q}_{e}}}\)	q_e=83.41(mg•g^-1), k₂=0.01(mg•g^-1•min^-1), R²=0.9773, RMSE=4.10
Elovich	\({{q}_{t}}=\frac{\ln (\alpha \beta )}{\beta }+\frac{\ln t}{\beta }\)	α=33.52(mg•g^-1•min^-1), β=9.99(mg•g^-1), R²=0.9860, RMSE=3.18

Kinetic model		Parameters
Pseudo- first-order	\(\ln ({{q}_{e}}-{{q}_{t}})=ln({{q}_{e}})-{{k}_{1}}t\)	q_e=79.58(mg•g^-1), k₁=0.25(min^-1), R²=0.9300, RMSE=7.38
Pseudo- second-order	\(\frac{t}{{{q}_{t}}}=\frac{1}{{{k}_{2}}q_{e}^{2}}+\frac{t}{{{q}_{e}}}\)	q_e=83.41(mg•g^-1), k₂=0.01(mg•g^-1•min^-1), R²=0.9773, RMSE=4.10
Elovich	\({{q}_{t}}=\frac{\ln (\alpha \beta )}{\beta }+\frac{\ln t}{\beta }\)	α=33.52(mg•g^-1•min^-1), β=9.99(mg•g^-1), R²=0.9860, RMSE=3.18

Isotherm model	Equation	Parameters
Langmuir	\({{q}_{e}}=\frac{{{q}_{\max }}\times {{C}_{e}}}{{{K}_{\text{l}}}+{{C}_{e}}}\)	q_max=91.49(mg•g^-1), K_l=0.01(mL•mg^-1), R²=0.9800, RMSE=4.68
Freundlich	\({{q}_{e}}={{K}_{\text{f}}}\times C_{e}^{1/n}\)	K_f=102.58(mg•g^-1), n=0.11, R²=0.9436, RMSE=10.94
Tempkin	\({{q}_{e}}\text{=}\frac{RT}{{{b}_{T}}}\times \ln ({{A}_{\text{T}}}\times {{C}_{e}})\)	A_T=175388.80 (mL•mg^-1), b_T=295.93 (J•mol^-1), R²=0.9119, RMSE=9.8
Sips	\({{q}_{e}}=\frac{{{K}_{\text{s}}}C_{e}^{{{\beta }_{s}}}}{1+{{\alpha }_{\text{s}}}\times C_{e}^{{{\beta }_{s}}}}\)	K_s=236338.20(mL•mg^-1), β_s=1.26, α_s=2612.06, R²=0.9844, RMSE=4.13
Redlich- Peterson	\({{q}_{e}}=\frac{{{K}_{\text{R}}}\times {{C}_{e}}}{1+{{\alpha }_{\text{R}}}\times C_{e}^{g}}\)	K_R=39323.82(mL•mg^-1), α_R=449.02(mg^-1), g=1.03, R²=0.9832, RMSE=4.28