Adaptable Porous Materials

多孔材料在存储、分离和催化技术中有着广泛的应用。客体分子被刚性多孔材料（如沸石或活性炭）吸附是由固定的孔的大小和形状控制的。大自然催化化学过程并使用蛋白质操纵分子。蛋白质的特征在于对其环境的适应性响应，其通过从能量低和动力学可接近状态的大集合中构象选择适当的功能结构（例如，用于酶催化，或离子通道中小电导的机械敏感通道的孔打开）而产生。这是通过多肽链的多种扭曲实现的，其允许折叠成所需的结构。项目团队最近（Rabone等人Science 2010）使用简单的二肽接头通过金属结合组装结晶多孔框架。所得材料将预形成的孔与构象选择所需的肽接头的自由度结合。这种基于肽的开放框架显示出适应性的孔隙率，其响应于客体内容而从开放连续地演变为部分无序的封闭结构。的功能多孔行为是非常规的，显示协同反馈特性的合作相互作用的孔形貌的变化，响应于客人占据的主机的孔体积的数量。基于肽的材料显示出可适应的孔隙率。它经历了动态的结构变化的客人加载，因为有许多可访问的吸附状态与它们之间的低能量障碍。这种能量景观的出现是因为肽连接体结构的扭转变化所需的能量较低。这为设计适应性多孔材料提供了可能性，这些材料以类似于生物分子经历构象选择的方式对客人做出反应，通过多个氨基酸残基围绕几个金属中心的模块化组装来获得大的功能多样的单位细胞。这一愿景目前还无法实现，因为这些材料中有大量潜在的化学成分，而且缺乏计算工具来理解和预测它们对客人的反应。这种材料虽然是前所未有的，并提供新的和潜在的有用的吸附和催化functional.The拟议的研究旨在开发的工具，允许通过专注于从化学上简单的二肽和三肽接头分别含有两个和三个氨基酸残基衍生的适应性多孔材料的此类材料的分离。我们将确定两个单独的肽接头和基于金属的单位，使适应多孔行为的特点。这将允许开发第二代系统，其中使用多个肽和金属单元，使得在功能性多孔固体中展示模块化氨基酸残基组装的关键进展。刚性接头将与肽一起引入以产生其中刚性亚单元被柔性肽基单元重新定位的结构，其方式类似于蛋白质折叠中刚性螺旋和片层单元的重新定位。将开发包括机器学习在内的基于计算机的计算方法，作为第二次世界大战期间选择合成目标的补充方法。自适应多孔材料对客体的响应不遵循经典模型，并且将从实验吸附、动力学和结构数据与适合于客体周围的自适应多孔主体的动态重构的计算模型耦合来评估，以超越合成多孔材料中的主体-客体相互作用的当前静态观点。

Porous materials find widespread application in storage, separation and catalytic technologies. The sorption of a guest molecule by a rigid porous material such as a zeolite or active carbon is controlled by the fixed size and shape of the pores.Nature catalyses chemical processes and manipulates molecules using proteins. Proteins are characterised by an adaptable response to their environment, produced by conformational selection of an appropriate functional structure (e.g. for enzyme catalysis, or pore opening of the mechanosensitive channel of small conductance in an ion channel) from a large ensemble of energetically low-lying and kinetically accessible states. This is enabled by the manifold torsions available to polypeptide chains, which allow folding into the required structures.The project team have recently (Rabone et al Science 2010) used a simple dipeptide linker to assemble a crystalline porous framework through metal-binding. The resulting material combines pre-formed pores with the degrees of freedom from a peptide linker required for conformational selection. This peptide-based open framework displays adaptable porosity that evolves continuously from an open to a partially disordered closed structure in response to the guest content. The functional porous behavior is unconventional, displaying cooperative feedback characteristic of cooperative interactions as the pore topography changes in response to the number of guests occupying the pore volume of the host. The peptide-based material displays adaptable porosity. It undergoes dynamical structural changes on guest loading because there are many accessible sorption states with low energy barriers between them. This energy landscape arises because of the low energies required for torsional changes to the structure of the peptide linker.This opens up the possibility of designed adaptable porous materials which respond to guests in a manner analogous to that of a biomolecule undergoing conformational selection, produced by the modular assembly of multiple amino acid residues around several metal centres to access large and functionally diverse unit cells. This vision cannot be presently realized due to the large numbers of potential chemical constituents of such materials and the absence of computational tools to understand and predict how they would respond to guests. Such materials would though be unprecedented and offer new and potentially useful sorption and catalysis functionality.The proposed research aims to develop the tools to allow the isolation of such materials by focussing on adaptable porous materials derived from chemically simple di- and tripeptide linkers containing two and three amino acid residues respectively. We will identify the characteristics of both individual peptide linkers and metal-based units which give adaptable porous behaviour. This will allow the development of second-generation systems in which multiple peptide and metal units are used, making the key advance of demonstrating modular amino acid residue assembly in a functional porous solid. Rigid linkers will be introduced together with the peptides to produce structures where rigid sub-units are repositioned by the flexible peptide-based units, in a manner analogous to the repositioning of rigid helix and sheet units in protein folding.Given the diversity of possible peptide components, descriptor-based computational methods including machine-learning will be developed as a complementary approach to the selection of synthetic targets in the second- and third-generation families.The response of adaptable porous materials to guests does not follow classical models, and will be evaluated from experimental sorption, dynamics and structural data coupled with computational models appropriate to the dynamical restructuring of the adaptable porous host around a guest, to move beyond the current static view of host-guest interactions in synthetic porous materials.