타이로신을 함유한 나선형 펩타이드의 2차원 대면적 자기조립과 타이로신-망간 산화물 하이브리드 박막의 수소이온전도에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2018. 8. 남기태.One of the important challenges in the development of protein-mimetic materials is to understand the sequence specific assembly behavior and the dynamic folding change. The discovery of laterally extended, untwisted, two-dimensional assembled structures in pure water is fundamentally challenging in peptide-based systems. Until now, most of the previous approaches for preparing 2D peptide assembled structures have been based on beta-sheet-like assembly or fibril-aggregated structures. In this study we present the assembly of a designed tyrosine-rich 5-mer peptide at the air/water interface, displaying facet formation of a water droplet. The identified peptides had a strong driving force to flatten the rounded top of droplet into a plane with a macroscopic 2D structure. The facet formation is driven by interactions of tyrosine and cross-linked stabilization by cysteine. We revealed the helical conformation of the peptide was stabilized by a disulfide bond, which was confirmed by circular dichroism and 2D-nuclear magnetic resonance spectroscopy. Futhermore, we created giant nanosheets decorated with gold nanoparticles at the air/water interface by introducing gold ion into the peptide. Due to the gold ions as an oxidant to rapidly induce a disulfide bridge between cysteines, the peptide assembled into the nanosheet and Au3+ were reduced to gold nanoparticles on the peptide sheet in the absence of other reducing agents simultaneously. In an effort to investigate the potential of tyrosine-rich peptide with redox active functions, we examine proton conductivity of the peptide films hybridized with manganese oxides. Proton conduction in biological systems has been an important issue for a better understanding of fundamental life mechanism. To understand and manipulate proton conduction in bio-system, several studies have investigated bulk proton conduction of biomaterials. However, little is known about the bulk proton conductivity of short peptides and their sequence-dependent behavior. We focus on tyrosine-rich peptide which has redox-active and crosslinkable phenol. Tyrosine has been known to play a critical role in PCET interplaying with a Ca-Mn cluster in the photosystem II. Moreover, it can be polymerized into cross-linked polymers, melanin, possessing a semiconductor-like behavior dependent on hydration. Inspired from this, we made proton conductor with tyrosine containing 2D peptide material by hybridization with manganese oxide (MnOx) via the tyrosine oxidation reaction. The peptide/MnOx hybrid films can efficiently transport proton and proton conductivity was 18.6 mS cm-1. The value is much higher than that of biomaterials and comparable with synthetic materials. These results suggest that peptide-based hybrid material can be a promising new class of proton conductor. In perspective of bioelectronics and further applications, it would be a good example for designing versatile platforms for bio-functionalized devices with biocompatible materials.Abstract.……………………………………………………………………………………ii Contents.……………………………………………………………………………………v List of Tables.………………………………………………………………………………ix List of Figures.………………………………………………………………………………x Chapter 1. Introduction…………………………………………………………………1 1.1 Bio-inspired peptide-based nanomaterials……………………………………1 1.2 The role of tyrosine in natural system…………………………………………5 1.3 Molecular tyrosine as a redox-active link……………………………………15 1.4 Biomaterials developed by dityrosine cross-linking…………………………23 1.5 Self-assembly of tyrosine-rich short peptide…………………………………29 1.6 Tyrosine-rich peptide-based hybrid functional materials…………………39 1.7 Objective of the thesis……………………………………………………………44 1.8 References……………………………………………………………………………48 Chapter 2. Macroscale 2D self-assembly of tyrosine-containing helical peptide……………………………………………………………………………………62 2.1 Introduction …………………………………………………………………………62 2.2 Experimental Procedure…………………………………………………………68 2.2.1 Chemicals …………………………………………………………………………68 2.2.2 Peptide dimerization and facet formation…………………………………68 2.2.3 Facet formation time measurement…………………………………………69 2.2.4 Characterization…………………………………………………………………70 2.2.3.1 Atomic force microscopy (AFM) analysis………………………………70 2.2.3.2 Scanning electron microscopy (SEM) analysis…………………………71 2.2.3.3 Transmission electron microscopy (TEM) analysis……………………71 2.2.3.4 High-performance liquid chromatography (HPLC)……………………71 2.2.3.5 Electrospray ionization mass spectrometer (ESI-MS)…………………73 2.2.3.6 Fourier transform infrared spectroscopy (FT-IR)………………………74 2.2.3.7 Raman spectroscopy analysis………………………………………………74 2.2.3.8 Circular dichroism (CD) spectroscopy……………………………………75 2.2.3.9 2-dimensional nuclear magnetic resonance spectroscopy…………76 2.3 Results and Discussions…………………………………………………………77 2.3.1 Self-assembly of YFCFY peptide ……………………………………………77 2.3.2 Facet formation kinetics………………………………………………………84 2.3.3 Building block of 2D self-assembly…………………………………………88 2.3.4 Molecular conformation of YFCFY peptide………………………………91 2.3.5 Hybrid 2D self-assembly of YYCYY peptide using gold ion…………101 2.3.6 Chemical structure of YYCYY after reaction with gold ion…………109 2.3.7 Molecular conformation of YYCYY peptide……………………………112 2.4 Conclusion…………………………………………………………………………117 2.5 References…………………………………………………………………………119 Chapter 3. Proton conduction in a tyrosine-rich peptide/manganese oxide hybrid nanofilm……………131 3.1 Introduction ………………………………………………………………………131 3.2 Experimental Procedure………………………………………………………136 3.2.1 Chemicals………………………………………………………………………136 3.2.2 Fabrication of peptide/MnOx hybrid nanofilm devices………………136 3.2.3 Characterization………………………………………………………………138 3.2.3.1 Electrical Characterization ………………………………………………138 3.2.3.2 Atomic force microscopy (AFM) analysis……………………………138 3.2.3.3 Transmission electron microscopy (TEM) analysis…………………139 3.2.3.4 X-ray photoelectron spectroscopy (XPS)………………………………139 3.2.3.5 Inductively coupled plasma mass spectroscopy (ICP-ms)…………139 3.2.3.6 X-ray absorption near edge structure (XANES) analysis…………140 3.2.3.7 Fourier transform infrared spectroscopy (FT-IR) analysis…………141 3.2.3.8 Thermal gravimetric analysis (TGA) ……………………………………141 3.3 Results and Discussions…………………………………………………………142 3.3.1 Morphology and structural analysis of the hybrid film………………142 3.3.2 Characterizations of manganese oxides…………………………………147 3.3.3 Characterizations of peptide in hybrid films……………………………155 3.3.4 Electrical property of hybrid films depending on humidity…………159 3.3.5 Electrochemical impedance spectroscopy analysis……………………163 3.3.6 Deuterium kinetic isotope effect on conductivity………………………168 3.3.7 Transient current measurements …………………………………………170 3.3.8 Synergistic effect on proton conduction of peptide and manganese oxides……………………………………………………………………………………174 3.4 Conclusion………………………………………………………………………182 3.5 References………………………………………………………………………185 Chapter 4. Concluding remarks……………………………………………………197 국문 초록…………………………………………………………………………………201Docto