胜肽與硝醯配位之雙亞硝基鐵錯合物

Peptide- and Nitroxyl-Bound Dinitrosyl Iron Complexes (DNICs)

林宗憲(Zong-Sian Lin)

指導教授 ： 廖文峯

國立清華大學/理學院/化學系/博士(2013年)

摘要

本研究中，利用小分子DNICs與新設計胜肽的反應，來探討胜肽鍵DNICs/RREs的結構、穩定度與反應性。在文獻中，已報導可用EPR、XAS與NRVS來鑑定DNICs/RREs的生成，在本研究中，證實結合水相FTIR與UV-vis光譜是一種有效的工具，鑑定及區別在水相中生成的胜肽鍵DNICs/RREs。同時，合成出新設計含有螯合半胱氨酸的胜肽鍵DNICs (CnA-DNIC)與具有單牙半胱氨酸的胜肽鍵RREs (KCAAK-RRE/KCAAHK-RRE)，並以水相FTIR、UV-vis、EPR、CD、XAS和ESI-MS來做為鑑定。在反應性中，相對於含螯合半胱氨酸DNIC CnA-DNIC與單牙半胱氨酸胜肽KCAAK/KCAAHK的不反應，KCAAK- RRE/KCAAHK-RRE會由CnA觸發，而轉變為CnA-DNIC，加上CnA-DNIC和CnA-RRE之間可經由{Fe(NO)2}9-{Fe(NO)2}10還原態RREs而互相轉換，來證明DNICs對於配位上螯合半胱氨酸胜肽的穩定度是大於單牙半胱氨酸胜肽。另外，本研究中，也說明了鐵硫簇中所處的蛋白質環境以及所含金屬Fe的氧化態，會調控當鐵硫簇產生亞硝基化反應時，所生成的產物(protein-bound RREs, reduced protein-bound RREs 或 protein-bound DNICs)。
在生物擬態化學中，將具有硫醇基螯合的DNIC亞硝基化，會產生含有四個一氧化氮配位的錯合物([Fe(NO)4]−)，從晶體圖上來看，具有較長鍵長的N(3)− O(3)/N(4)−O(4)和Fe(1)−N(3)/Fe(1)−N(4)與較彎鍵角的Fe(1)−N(3)− O(3)/Fe(1)−N(4)−O(4)，來證實在錯合物[Fe(NO)4]−中，N(3)−O(3)和N(4)−O(4)可形容作為硝醯配位基，再結合理論計算，得知，最好描述錯合物[Fe(NO)4]−的電子結構為帶正一價的{Fe(NO)2}9核心，配位上兩個亞硝醯基與兩個硝醯基。

關鍵字

胜肽 ； 硝醯 ； 雙亞硝基鐵錯合物

並列摘要

This study describes the interaction of low-molecular-weight DNICs with short peptides designed to explore the stability and structure of peptide-DNIC/peptide-RRE constructs. Although characterization of DNICs is possible via EPR, XAS and NRVS, combination of aqueous IR νNO and UV-vis spectra can serve as an efficient tool to characterize and discriminate the peptide-bound DNICs/RREs. The de novo chelate-cysteine-containing peptides KC(A)nCK-bound DNICs CnA-DNIC and monodentate-cysteine-containing peptides KCAAK-/KCAAHK-bound Roussin’s red esters KCAAK-RRE/ KCAAHK-RRE were synthesized and characterized by aqueous IR, UV-vis, EPR, CD, XAS and ESI-MS. In contrast to the inertness of chelate-cysteine-containing peptide-bound DNICs toward KCAAK/KCAAHK, transformation of KCAAK-RRE/KCAAHK-RRE into CnA-DNIC triggered by CnA and the reversible transformation between CnA-DNIC and CnA-RRE via the {Fe(NO)2}9-{Fe(NO)2}10 reduced-form peptide-bound RREs demonstrate that {Fe(NO)2}9 motif displays a preference for chelate-cysteine-containing peptides over monodentate-cysteine-containing peptides. Also, this study may signify that nitrosylation of [Fe-S] proteins generating protein-bound RREs, reduced protein-bound RREs or protein-bound DNICs are modulated by both the oxidation state of Fe and chelating effect of the bound proteins of [Fe-S] clusters.
Nitrosylation of the chelate-thiolate-containing DNIC triggers NO activation to generate the homoleptic nitrosyl DNIC [Fe(NO)4]− made up of two nitroxyls attached to a delocalized {Fe(NO)2}9 motif. The significantly longer N(3)−O(3)/N(4)−O(4) and Fe(1)−N(3)/Fe(1)−N(4) bond distances (bent Fe(1)−N(3)−O(3)/Fe(1)−N(4)−O(4) bond angel) reflect that N(3)−O(3) and N(4)−O(4) of [Fe(NO)4]− may act as nitroxyl- coordinated ligands. That is, the electronic structure of the [Fe(NO)4]− is best described as a {Fe(NO)2}9 motif coordinated by two nitroxyl (NO−) ligands.

並列關鍵字

Peptide ； Nitroxyl ； Dinitrosyl Iron Complexes

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