【作者】 沈江珊；

【导师】 江云宝；

【作者基本信息】 厦门大学 ， 分析化学， 2009， 博士

【摘要】 半胱氨酸（Cys）在人体内发挥极其重要的作用，且其对映体所扮演的角色亦不同。例如，L-Cys的缺失将导致人体出现AIDS、肝损伤和皮肤损害等严重疾病，而D-Cys则能和细胞内诸多靶标作用并且妨碍细胞生长。尽管目前已有不少Cys的识别方法，但极少研究涉及到Cys对映体识别。因此，发展可靠且高选择性的Cys对映体识别与传感方法对正确认识和理解Cys对映体和相关疾病之间的关系十分重要，是目前一项富有挑战性的研究。传统的光谱学传感研究中颜色或荧光的背景对光谱信号的干拢，成为一个棘手的问题。基于金属-金属相互作用的超分子化学以及金属纳米结构材料研究的良好发展，拟通过特定的相互作用操纵和调控此类弱的非价键作用以期“精明”地控制这些超分子结构材料和金属纳米结构材料，为分子识别与传感研究开辟新的领域。本论文在前述认识的基础上，主要概念性地提出利用并操纵金属．金属相互作用，构建新型的分子识别和传感体系，为解决上述两个问题提供有益的启示。论文共分五章，包括如下内容：第一章为前言。首先概述了币族金属-金属相互作用，简要介绍了超分子化学中币族金属-金属相互作用的研究及应用，同时探讨了此类弱相互作用在金属纳米结构材料领域中的研究现状和发展前景。最后，综述了Ⅱ-Ⅵ族半导体发光纳米晶（NCs）的基本光物理性质和合成方法。第二章介绍了基于Ag（I）和Cys原位形成Ag（I）-Ag（I）相互作用促进的Ag（I）-Cys金属配位聚合物，构建可靠且高选择性Cys对映体识别与传感体系。系统研究了导致该体系产生特征吸收和CD光谱报告信号的原因，认为这些光谱信号系来源于伴随着Ag（I）-Ag（I）相互作用的从Cys到Ag（I）的电荷转移（LMMCT）跃迁。实验发现，pH可调控聚合物骨架上的Ag（I）-Ag（I）相互作用。该pH调控行为不仅起到提高传感体系选择性的作用，而且为Ag（I）-Cys体系中存在Ag（I）-Ag（I）相互作用提供有力支持。本识别体系对Cys对映体的检测限均达到1pM水平；基于摩尔吸光系数值考虑，具有信号放大作用。研究展示了一个概念性的识别新策略，即操纵Ag（I）-Ag（I）相互作用可选择性地识别具有重要意义的目标分子。在Ag（I）-Cys和Ag（I）-谷胱甘肽（GSH）体系的研究之基础上，受启于其中金属配位聚合物的超分子结构，概念性地提出并构建了阴离子诱导Ag（I）-GSH金属配位聚合物超分子水凝胶Gel-Sol态转换的体系且成功地用于I^-的识别，具体内容于第三章详述。本例为首次获得的高选择性阴离子响应的超分子水凝胶体系。本超分子水凝胶体系高选择性响应I^-可归因于AgI和AgXs（X=F^-、Cl^-、Br^-、H₂PO₄^-和-SR）的稳定常数间存在较大的差异而导致仅I^-能使Ag（I）-GSH配位聚合物解聚。I^-诱导Gel-Sol态转换所释放的水分子实际上为本体系的“信号报告基团”。本体系不仅可实现可视化识别，且能实施定量分析。与传统的重量法不同的是，所释放的水的重量大约为所引入I^-的660倍，表明本识别体系具有“信号放大”作用。原则上，本策略可以通过设计新型超分子水凝胶以实现“精明”的Gel-Sol态转换而使之拓展至其它体系。基于前述对Ag（I）-Cys和Ag（I）-GSH体系的认识，我们进一步对目前备受关注的Ⅱ-Ⅵ族半导体发光NCs开展了下列研究。研究了Ⅱ-Ⅵ族半导体发光NCs与电子受体亚甲基蓝（MB）之间发生的光诱导电子转移（PET）过程，旨在发展简单且可靠的策略以构建基于PET机理的Ⅱ-Ⅵ族半导体发光NCs型的分子识别与传感体系。第四章描述了稳态和时间分辨发光实验、热力学能量分析以及电子顺磁共振（EPR）实验，结果支持了激发态NCs到基态MB的PET系NCs发光猝灭原因的结论。双链DNA（ds-DNA）能使NCs-MB体系的发光恢复，这是因为MB籍与DNA双链的嵌入作用和静电作用而脱离NCs的表面，NCs与MB间的PET受到抑制。单链DNA（ss-DNA）亦可使NCs-MB体系的发光恢复，但恢复程度小于ds-DNA的，可能是因为MB与ss-DNA之间仅存在静电作用的缘故。所观察到的发光恢复程度的差异使本体系可用于DNA的选择性识别和传感。此研究为构建新一类的分子识别与传感体系提供了有益的启示，可望拓展至其它类型目标分子。第五章叙述了基于对Ag（I）-Cys／GSH体系的研究，使用Cys作为表面配体、水溶液相法合成手性D-／L-Cys-CdS NCs对映体，为进一步认识和理解发光Ⅱ-Ⅵ族半导体手性NCs的手性起源提供实验基础。更多还原

【Abstract】 Cysteine （Cys） is vital naturally occurringα-amino acid in human body and its twoenantiomers actually play different roles. For example, the deficiency of L-Cys wouldlead to a series of serious diseases including AIDS, liver damage, and skin lesions.However, D-Cys is considered to interfere with many targets inside cells and furtherimpair cell growth. Although numerous recognition methods for L-Cys have beenreported, few involved Cys enantiomeric signaling. In order to understand the linksbetween enantiomeric Cys and related diseases, developing feasible while highlyselective and sensitive enantiomeric discrimination strategies for D- and L-Cys istherefore undoubtedly crucial. Traditional spectrophotometric methods employed assignaling means in molecular recognition and sensing fields often suffer from seriousspectral interferences in colored and/or fluorescent background. Therefore, it alsoremains a challenge to overcome this drawback. Development in supramolecularchemistry and metal nanostructure materials based on metal-metal interactions offer achance to manipulate metallophilicity via a specific interaction event, which wouldnot only allow a smart control of these supramolecular and metal nanostructurematerials, but also open a new field of research in molecular recognition and sensing.Based on these understandings, we intended to manipulate metal-metal interaction toconstruct novel molecular recognition and sensing platforms.The dissertation consists of five chapters.Chapter 1 introduces in general the coinage metal-metal interaction, reviews anddiscusses the development and applications of the metal-metal interaction insupramolecular chemistry and metal nanostructure materials. Fundamentalphotophysical properties and synthesis ofⅡ-Ⅵgroup semiconductorphotoluminescent nanocrystals are also described.Chapter 2 reports an enantiomeric discriminating strategy for Cys based on thein-situ formed Ag（I）-Cys coordination polymers facilitated by argentophilicity. Detailed investigations were conducted to clarify the origin of characteristicabsorption and CD signals. It was shown that these characteristic spectral signalsoriginate from ligand-to-metal charge transfer transition accompanied by metal-metalinteraction （LMMCT）. Solution pH was found to be able to modulate themetallophilicity in the polymeric backbone composed of Ag（I）-Cys repeating unit.Such pH switching character not only allows to improve the selectivity of thissignaling strategy, but also offers a strong support of metallophilicity in Ag（I）-Cyspolymers. Limit of detection of this signaling platform for D- or L-Cys was calculatedto be down to 1μM level. On the basis of the molar extinction coefficient, a signalamplification was indicated in this strategy. It is expected that the present system canin principle serve as a signaling platform following the concept of manipulatingmetallophilicity for extended applications.Chapter 3 describes a highly selective anion-responsive reversible gel-sol statetransition in a supramolecular hydrogel of Ag（I）-glutathione （GSH） coordinationpolymers. To the best of our knowledge, this is the first example for highly selectiveanion-responsive reversible gel-sol state transition in supramolecular hydrogels. Largedifference of the stability constant of AgI from those of the other AgXs （X= F^-, Cl^-,Br^-, H₂PO₄^- and -SR） is considered responsible for the high selectivity towards I- thatresults in the depolymerization of Ag（I）-GSH supramolecular hydrogels. This allowsfor a visual semiquantitative assay for I^- by naked eyes. The released water moleculesin the gel-sol state transition process actually acted as the signal reporter whichoffered a signal amplification, since the weight of released water is ca. 660 times thatof the introduced I^- in case of 0.5% Ag（I）-GSH hydrogel. This strategy is expected inprinciple to be applicable to other species by following the smart gel-sol statetransition in designed supramolecular hydrogels.Ⅱ-Ⅵgroup semiconductor photoluminescent nanocrystals following theunderstanding of Ag（I）-Cys（GSH） systems were then carried out that will bedescribed later.Chapter 4 presents a signaling system that operates under the photo-induced electron transfer （PET） mechanism usingⅡ-Ⅵgroup semiconductorphotoluminescent nanocrystals. Steady-state and time-resolved photoluminescent （PL）spectroscopy, thermodynamic energetic analysis, and electron paramagnetic resonance（EPR） experiments support for the PET quenching mechanism that the electrontransfers from conduction band （CB） of excited NCs to the ground state of MB. PL ofNCs could be restored by double stranded DNA （ds-DNA） by inhibiting this electrontransfer process via taking MB away through intercalation into and electrostaticinteractions with the DNA strands. Single stranded DNA （ss-DNA） could also restorethe PL of this nanohybrid but to a lower extent since only electrostatic interactionexists between MB and ss-DNA. This distinct difference therefore allows for aselective sensing of ds-DNA and ss-DNA and for probing DNA hybridization. Thenanohybrid strategy is expected to be of general applicability subject to a suitablechoice of an electron acceptor for theⅡ-Ⅵgroup semiconductor photoluminescentNCs and for interaction with a target species.Chapter 5 reports an aqueous phase synthetic route to D- and L-Cys-CdS NCsenantiomers using chiral Cys as a surface ligand based on the investigation ofAg（I）-Cys（GSH）. It offers a new entry to understand the origin of optical activity ofⅡ-Ⅵgroup semiconductor chiral NCs.更多还原