COMPLEX SELF-SORTING SYSTEMS
Publication or External Link
Over the past century scientists have taken a reductionist approach towards much of the physical and biological sciences. More recently scientists have become interested in constructing complex systems from their components and thereby controlling their emerging behaviors. As supramolcular chemists we have been pursuing an approach to the creation of complex functional systems - systems chemistry - by preparation of self-sorting systems. Self-sorting system displays ability to efficiently distinguish between self- and non-self even within complex mixture. This dissertation is divided into four chapters that describe increasingly complex self-sorting systems.
Chapter 1 describes a literature review on self-sorting. First, we introduced the concept of self-sorting and then described the previously studied self-sorting phenomenon in the Isaacs group followed by a description of the examples of self-sorting systems in the literature.
Chapter 2 describes the synthesis and characterization of eleven C-shaped methylene bridged glycoluril dimers (II-1 - II-11) bearing H-bonding groups on their aromatic rings. Compounds II-1, II-2, (±)-II-4a, (±)-II-5, and II-7 form tightly associated homodimers in CDCl3 due to π - π and H-bonding interactions. Compounds II-2, (±)-II-5 and II-7, having disparate spatial distribution of their H-bonding groups show the ability to efficiently distinguish between self and non-self within three component mixtures in CDCl3. The effect of various structural modifications (e.g. chirality, side chain steric bulk, relative orientation, number and pattern of H-bonds) on the strength of self-assembly and the fidelity of self-sorting are presented.
Chapter 3 describes the stepwise construction of an 8-component self-sorted system (III-1 - III-8) by the sequential addition of components. This process occurs via a large number of states (28 = 256) and even a larger number of pathways (8! = 40320). A pathway (III-5, III-6, III-7, III-8, III-4, III-3, III-2, then III-1) that is self-sorted at every step along the way. Another pathway (III-1, III-8, III-3, III-5, III-4, III-7, III-2, then III-6) exhibits interesting shuttling of guest molecules among hosts. The majority of pathways - unlike the special ones described above - proceed through several non self-sorted states. We characterized the remainder of the 40320 pathways by simulation using GEPASI and describe the influence of concentration, mean binding constants and standard deviation on the fidelity of the self-sorting pathways.
Chapter 4 describes a method to control biological catalysis using synthetic self-sorting systems. We report the synthesis of IV-1 - IV-5 which contain both enzyme inhibitor and cucurbit[n]uril binding domains. The enzyme binding domains of IV-1 - IV-5 bind to the active sites of Bovine Carbonic Anhydrase or Acetylcholinesterase and inhibit their catalytic activities. Addition of CB catalyzes the dissociation of IV-1 and IV-2 from the active site of BCA and thereby regenerates the enzymatic activity. In contrast, addition of CB to AChE*IV-44 and AChE*IV-54 results in the formation of a ternary complex that does not regenerate the enzymatic activity.