以類澱粉樣胜肽模板調控礦化過程

Mineralization controlled by templates of amyloidogenic peptides

趙語柔(Yu-Jo Chao)

指導教授 ： 陳振中

國立臺灣大學/理學院/化學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601631

摘要

生物礦化為生物體生成礦物之過程，形成各式具有特殊形貌、結構與性質的組織，而有機物如多肽、蛋白質在礦化過程中被認為是扮演模板的角色，去調控與引導無機物長晶。因此我們利用仿生的概念，設計一可自組裝形成類澱粉樣纖維結構的胜肽序列(EGAGAAAAGAGE)，其高度重複的β-sheet結構可作為成礦模板，序列中AGAAAAGA來自倉鼠普恩蛋白(hamster prion)疏水片段113−120，已知為形成類澱粉樣纖維結構的主要序列，我們於序列N端與C端對稱性加上穀胺酸作為成核點以誘使無機礦物成核長晶。實驗中我們研究設計胜肽的自組裝性質，由圓二色光譜儀及固態核磁共振儀發現在鹼性條件培養下的胜肽溶液於基材上自然乾燥過程中會由無序結構轉變為β-sheet，且結構稍異於酸性條件培養之類澱粉樣纖維，而經碳酸氫鈉溶液透析後則會於基材上產生碎形堆積形貌。我們藉由氣體擴散礦化實驗，使用穿透式電子顯微鏡與選區電子繞射鑑定，可觀察到大量銨鹽晶體沿著胜肽模板纖維軸生長，且硝酸銨晶體以特定晶面生長並具有特定的排列位向。我們建立了一個平台去研究有機物與無機物間之作用力、介面能量，與其調控礦物生長之機制。

關鍵字

生物礦化 ； 類澱粉樣纖維 ； 模板成礦

並列摘要

Nature uses organic matrices to control the formation of minerals, which have complex structures and exquisite morphologies. These organic molecules provide nucleation sites and dictate crystal orientation and morphologies. We have designed a 12-residue peptide (EGAGAAAAGAGE) that can self-assemble into beta-sheet conformation. The central region of the peptide, AGAAAAGA, is a hydrophobic fragment of prion protein which is highly amyloidogenic. The glutamic acids added at both the N- and C-termini might provide binding sites for the nucleation minerals. We studied the fibril structure of the peptides and the associated self-assembly propensity. Interestingly, our designed peptide forms hierarchical fractal growth pattern on substrates after dialysis against sodium bicarbonate solution. CD spectra and solid state NMR results show that the peptide transformed from random coils to beta-sheet structure after air drying on substrate. Under the atmosphere of ammonia and carbon dioxide, crystallites of ammonium salt were formed along the long axis of the peptide aggregates. By TEM and SAED, we demonstrated that the peptide served as selective templates for the formation of minerals. In this work, we have designed and synthesized a novel peptide sequence which can serve as a good model system for the study of organic-inorganic interfacial interaction and crystal growth mechanism.

並列關鍵字

biomineralization ； amyloid peptide ； organic template

參考文獻

(66) Volkmer, D.; Fricke, M.; Huber, T.; Sewald, N. Acidic Peptides Acting as Growth Modifiers of Calcite Crystals. Chem. Commun. 2004, No. 16, 1872–1873.

(1) Weiner, S.; Dove, P. M. An Overview of Biomineralization Processes and the Problem of the Vital Effect. Rev. Mineral. Geochem. 2003, 54 (1), 1–29.

(2) Nudelman, F.; Sommerdijk, N. A. J. M. Biomineralization as an Inspiration for Materials Chemistry. Angew. Chem. Int. Ed Engl. 2012, 51 (27), 6582–6596.

(3) Marin, F.; Roy, N. L.; Marie, B. The Formation and Mineralization of Mollusk Shell. Front. Biosci. Sch. Ed. 2012, 4 (3), 1099–1125.

(4) Weber, J.; Greer, R.; Voight, B.; White, E.; Roy, R. Unusual Strength Properties of Echinoderm Calcite Related to Structure. J. Ultrastruct. Res. 1969, 26 (5), 355–366.