Through allosteric-regulation, biological molecules are able to relay the effect of binding at one site to another, often distal, functional site in order to regulate protein function. This often occurs when a binding event causes a conformational change that affects activity at the remote functional site. Allostery serves to attenuate or promote protein function in the biological environment, and is integral to maintaining cellular homeostasis. Such processes are essential for life to function, as they form the basis for processes such as neural communication, protein folding, and gas exchange. While many such processes rely on changes in tertiary structure that occur over length scales of nanometers, many occur due to subtle geometric changes caused by effector binding proximal to the functional site. By adapting these aspects of allosteric regulation in biology, synthetic systems have been developed that mimic, complement, and even surpass the ability of their natural counterparts. The majority of effort in the area of functional allosteric protein mimics has been focused towards developing addressable organometallic complexes (effector sites) that allow for the regulation of pendant catalytic or binding sites (functional sites) largely by controlling steric access to the site of interest. In the Mirkin Group, this approach has been applied to metallo-porphyrins and salens in homoligated “macrocycles” and heteroligated “triple-decker” Weak-Link Approach (WLA) systems, whereby regulation occurs upon the introduction or removal of a coordinating moiety that alters the geometry at the addressable metal center. Although significant progress has been made in regard to controlling catalytic activity, little focus has been placed on the arguably more difficult and attractive tasks of allosterically regulating selective molecular encapsulation, transport, and co-localization commonly found in biological systems. This limited progress is perhaps due to the fact that the purview of host-guest chemistry has been primarily limited to static/rigid structures. Ideally, such systems would be addressable at nodes that also aid in the assembly of complex and well-defined three-dimensional pockets. To this end, the hemilabile ligand coordination inherent to the WLA can be exploited to assemble and control the host-guest properties of these heteroligated capsules and cages, by tuning size, shape, charge and recognition ability. We aim to acquire fundamental insight into: (i) controlling the chemistry underlying the assembly of heterodimeric capsules and cages; and (ii) the principles behind achieving advanced recognition in heterodimeric capsules, in particular how orthogonal yet complementary recognition units can be brought together for enhanced recognition and specificity. Ultimately, the goal of this proposed research is to develop the design rules for developing synthetic receptors capable of selective binding. Questions that we will seek to answer in developing these rules include: (i) How close in proximity do complementary interactions have to be? (ii) Can the control over rigidity be used to enhance state-dependent selectivity by toggling between highly preorganized and highly flexible structures? (iii) How can electrostatic charge on the metal center enhance state-dependent selectivity with polar substrates? and (iv) How many additional secondary interactions are required to achieve enantioselective binding in chiral cavitands such as cyclodextrins? In order to accomplish these goals, we will build upon extensive experience developing WLA
|Effective start/end date||8/1/17 → 7/31/22|
- National Science Foundation (CHE-1709888-001)
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