物理化学学报 >> 2021, Vol. 37 >> Issue (3): 1912050.doi: 10.3866/PKU.WHXB201912050

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氯化血红素分子对牛血清白蛋白电子传输能级的调控

吴传丽1, 梁文慧1, 樊晶晶1, 曹钰贤2, 吴萍1, 蔡称心1,*()   

  1. 1 南京师范大学化学与材料科学学院,江苏省新型动力电池重点实验室,江苏省生物医药功能材料协同创新中心,南京 210023
    2 南京师范大学教师教育学院,南京 210023
  • 收稿日期:2019-12-23 录用日期:2020-01-24 发布日期:2020-03-03
  • 通讯作者: 蔡称心 E-mail:cxcai@njnu.edu.cn
  • 基金资助:
    国家自然科学基金(21335004);国家自然科学基金(21675088);江苏省自然科学基金(BK20181382);江苏省自然科学基金(BK20181383);江苏省高等学校特色优势学科建设项目

Regulating Electron Transport Band Gaps of Bovine Serum Albumin by Binding Hemin

Chuanli Wu1, Wenhui Liang1, Jingjing Fan1, Yuxian Cao2, Ping Wu1, Chenxin Cai1,*()   

  1. 1 Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China
    2 College of Education, Nanjing Normal University, Nanjing 210023, China
  • Received:2019-12-23 Accepted:2020-01-24 Published:2020-03-03
  • Contact: Chenxin Cai E-mail:cxcai@njnu.edu.cn
  • About author:Chenxin Cai, Email: cxcai@njnu.edu.cn; Tel.: +86-25-85891780
  • Supported by:
    the National Natural Science Foundation of China(21335004);the National Natural Science Foundation of China(21675088);the Natural Science Foundation of Jiangsu Province, China(BK20181382);the Natural Science Foundation of Jiangsu Province, China(BK20181383);the Priority Academic Program Development of the Jiangsu Higher Education Institutions, China

摘要:

蛋白质分子的电子传输(ETp)性能,即导带(CB)和价带(VB)的能量差(带隙)是影响蛋白质电子器件性能的主要因素之一。因此,调控蛋白质ETp带隙是提高这些电子器件性能并扩展其应用领域的重要途径。本文报道一种通过外部分子结合调控蛋白质ETp带隙的方法。以氯化血红素(hemin)与牛血清白蛋白(BSA)结合为例,首先运用分子对接方法从理论上确定hemin分子能结合到BSA分子IIA域的疏水口袋中,位于Tpr213附近;然后实验(荧光光谱和吸收光谱)证实hemin与BSA结合后,能形成hemin-BSA复合物,并且没有改变BSA的原有结构;最后将hemin-BSA通过BSA分子表面Cys34的―SH固定在金电极表面,形成有序的分子层,研究其ETp性能;IV结果表明,BSA表现出半导体的ETp特征,并且hemin的结合能使BSA的带隙由原来的~1.50 ± 0.05 eV降低到~0.93 ± 0.05 eV。本文的结果为调控蛋白质分子的ETp带隙提供了一种简单有效的方法,通过选择不同的结合分子能使蛋白质分子的带隙调控至所需要的范围,并且形成的蛋白质复合物还能用于各种电子器件的制作。

关键词: 蛋白质电子传输, 蛋白质电子器件, 牛血清白蛋白, 氯化血红素

Abstract:

The small size (nanoscale) of proteins and their favorable electron transport (ETp) properties make them suitable for various types of bioelectronic devices and offer a solution for miniaturizing these devices to nanoscale dimensions. The performance of protein-based devices is predominantly affected by the ETp property of the proteins, which is largely determined by the band gaps of the proteins, i.e., the energy difference between the conduction band (CB) and valence band (VB). Regulating the protein ETp band gaps to appropriate values is experimentally demanding and hence remains a significant challenge. This study reports a facile method for modulating the ETp band gaps of bovine serum albumin (BSA), via its binding with a foreign molecule, hemin. The formation of the hemin-BSA complex was initially confirmed by theoretical simulation (molecular docking) and experimental characterization (fluorescence and absorption spectra), which indicated that the hemin is positioned inside a hydrophobic cavity formed by hydrophobic amino acid residues and near Trp213, at subdomain IIA of BSA, with no significant effects on the structure of BSA. Circular dichroism (CD) spectra indicated that the BSA conformation remains essentially unaltered following the formation of the hemin-BSA complex, as the helicities of the free BSA (non-binding) and the hemin-BSA complex were estimated to be 66% and 65%, respectively. Moreover, this structural conformation remains preserved after the hemin-BSA complex is immobilized on the Au substrate surface. The hemin-BSA complex is immobilized onto the Au substrate surface along a single orientation, via the ―SH group of Cys34 on the protein surface. Atomic force microscopy (AFM) images indicate that hemin-BSA forms a dense layer on the surface of the Au substrate with a lateral size of ~3.2‒3.7 nm, which is equivalent to the actual size of BSA, ~4.0 nm × 4.0 nm × 14.0 nm. The current-voltage (I-V) responses were measured using eutectic gallium-indium (EGaIn) as the top electrode and an Au film as the substrate electrode, revealing that the ETp processes of BSA and hemin-BSA on the Au surface have distinct semiconducting characteristics. The CB and VB were estimated by analysis of the differential conductance spectra, and for the free BSA, they were ~0.75 ± 0.04 and ~ −0.75 ± 0.08 eV, respectively, being equally distributed around the Fermi level (0 eV), with a band gap of ~1.50 ± 0.05 eV. Following hemin binding, the CB (~0.64 ± 0.06 eV) and VB (~ −0.29 ± 0.07 eV) of the protein were closer to the Fermi level, resulting in a band gap of ~0.93 ± 0.05 eV. These results demonstrated that hemin molecules can effectively regulate ETp characteristics and the transport band gap of BSA. This methodology may provide a general approach for tuning protein ETp band gaps, enabling broad variability by the preselection of binding molecules. The protein and foreign molecule complex may further serve as a suitable material for configuring nanoscale solid-state bioelectronic devices.

Key words: Protein electron transport, Protein-based electronic device, Bovine serum albumin, Hemin

MSC2000: 

  • O646