Role of Dynamics in Self-Organisation of Amino Acids on Coinage Metal Surfaces

生物分子在其化学中表现出许多微妙之处，这些微妙之处对它们在生命系统中所扮演的角色产生了深远的影响。其中最重要的是它们倾向于形成特殊类型的化学键（称为“氢键”），以及它们倾向于以两种互补的镜像（“手性”）形式存在。手性在许多生物学情况下是至关重要的，因为分子的左手和右手形式在与其他手性分子相互作用时可能表现得非常不同。另一方面，氢键很重要，因为它们的强度足以在室温下保持稳定，但不会强到在生物过程中必要时无法切断。因此，氢键和手性现象在分子生物学中得到了广泛的研究。然而，就在最近，生物分子在表面的行为受到了大量的关注，特别是关注氨基酸-根据DNA蓝图构建复杂蛋白质的简单构件。这种兴趣的驱动力包括开发新的生物相容性材料用于医疗用途，生物传感器（特别是手性敏感的生物传感器，能够区分其他相同分子的左手和右手版本）和药物前体的手性合成路线（根据需要专门生产左手或右手版本的分子）。在这些努力中，氢键在决定分子如何在表面排列方面的作用已成为关注的焦点，并且似乎与分子手性在扩展分子网络的几何结构中表现的方式密切相关。然而，以前的研究通常仅限于报告可以产生的网络类型，但相对较少地阐明它们如何以及为什么以这种方式形成。我们的项目旨在通过扫描探针显微镜、电子衍射、氦原子散射、红外光谱和理论建模的结合，精确地揭示后一种类型的信息。此外，我们的目标是了解如何通过与氢的相互作用来调节手性分子网络的性质（模拟溶液化学中酸度变化的影响）来改变化学反应性，以期最终控制表面的手性化学反应。我们最初的大部分注意力将集中在铜表面上氨基酸形成的结构上，我们和其他人已经取得了一些进展。我们强调的动态和动力学过程，这些结构的形成设置这项工作除了以前的研究，但是，此外，我们将纳入其他金属，如银和金，这已经收到了远未通知在文献中。该项目的这一阶段将大大推进我们对单个分子的短程手性与它们自组装成的表面网络所表现出的长程手性之间联系的理解。随后，我们将致力于了解表面氢在修饰氨基酸性质中的作用。在活细胞中，生物分子存在于水溶液中，水环境的pH值可能对可能发生的反应产生深远的影响。在表面，我们预计不同浓度的氢可能会模拟溶液中如此重要的酸度变化。最后，我们的目标是联合收割机结合我们的理解，在表面的手性表现与我们的研究结果的反应性的调整，以进行手性表面化学。目标反应包括通过与（例如）脲反应将非手性甜菜碱酸转化为手性丙氨酸，或通过与氢反应将非手性甜菜碱酸转化为手性乳酸。

Biomolecules exhibit a number of subtleties in their chemistry that have profound impacts upon the roles they play in living systems. Amongst the most important are their propensity to form special kinds of chemical bonds (known as "hydrogen bonds") and their tendency to exist in two complementary mirror image ("chiral") forms. Chirality is crucial in many biological situations because left- and right-handed forms of a molecule may behave very differently when interacting with other chiral molecules. Hydrogen bonds, on the other hand, are important because they are just strong enough to be stable at room temperature, but not so strong that they cannot be severed when necessary during biological processes. Both hydrogen bonds and the phenomenon of chirality have consequently been much studied in the context of molecular biology.Just recently, however, the behaviour of biomolecules at surfaces has received a great deal of attention, in particular focusing upon amino acids - the simple building blocks from which complex proteins are constructed according to the blueprint of DNA. Drivers for this interest include development of new biocompatible materials for medical use, biosensors (especially chirally sensitive biosensors, capable of discerning between left- and right-handed versions of otherwise identical molecules) and routes towards chiral synthesis of drug precursors (producing exclusively the left- or the right-handed version of a molecule, as required). In these efforts, the role of hydrogen bonds in dictating how molecules arrange themselves at the surface has become a key focus of attention, and appears to be strongly related to the way in which molecular chirality is manifest in the geometry of extended molecular networks. Previous studies, however, have generally been limited to reporting on the kinds of network that can be produced, but shed relatively little light on how and why they form in the way that they do. Our project aims to uncover precisely this latter type of information, through a combination of scanning probe microscopy, electron diffraction, helium atom scattering, infra-red spectroscopy and theoretical modelling. Furthermore, we aim to learn how the properties of chiral molecular networks may be tuned by interaction with hydrogen (mimicking the effects of acidity variation in solution chemistry) to alter chemical reactivity, with a view towards ultimately controlling chiral chemical reactions at surfaces.Much of our initial attention will focus upon the structures formed by amino acids on copper surfaces, where some progress has already been made by ourselves and others. Our emphasis on the dynamic and kinetic processes by which these structures are formed sets this work apart from prior studies, however, and in addition we will incorporate work on other metals such as silver and gold, which have received far less notice in the literature to date. This phase of the project will greatly advance our understanding of the link between the short-range chirality of individual molecules and the long-range chirality exhibited by the surface networks into which they self-assemble. Subsequently, we will devote considerable efforts toward understanding the role of surface hydrogen in modifying the properties of amino acids. In living cells, biological molecules exist in aqueous solution, and the pH of the water environment can have profound effects upon the reactions that may occur. At the surface, we anticipate that varying concentrations of hydrogen may mimic variations in the acidity that are so important in solution. Finally, we aim to combine our understanding of the manifestation of chirality at surfaces with our findings on the tuning of reactivity, in order to conduct chiral surface chemistry. Target reactions include transformation of non-chiral pyruvic acid into chiral alanine by reaction with (for example) urea, or into chiral lactic acid by reaction with hydrogen.