No description available.

No description available.

This thesis describes research based on synthetic protocols, methodologies, and applications of polymers containing side-chain molecular recognition elements. The use of molecular recognition, in lieu of covalent chemistry, potentially presents a path through the current limits of polymer science. The work described in this thesis is, at least in part, a testament to this proposal. The first two chapters presen a basic introduction of noncovalent interactions that are ubiquitous in the research of supramolecular polymers. Chapter 2 lays the foundation for the remaining chapters of this thesis by presenting several examples of prior work related specifically to the use of molecular recognition on the side-chains of polymers. The next two chapters present research focused on advancing the functionalization of polymers through molecular recognition. These chapters demonstrate that both architecturally controlled block copolymers and random terpolymers can accept a full load of different substrates without interference among distinct molecular recognition elements along the polymer backbone. Chapters 5 and 6 present a unique application of polymers containing molecular recognition elements, templated synthesis. Chapter 5 first discusses lessons learned from small molecule based templated synthesis in which a template and a substrate are held together by metal coordination and a subsequent bond forming reaction occurs. Chapter 6 discusses template polymerizations, in which a polymeric template was used, and a daughter monomer was polymerized while attached to the template. Another application of polymers containing molecular recognition elements is presented in Chapters 7 and 8. In these chapters, metal coordination is used to assemble polymer multilayer thin films that are both responsive to external stimuli, stable, and erasable. Finally, Chapter 9 summarizes the main conclusions of each chapter and presents a potential view of new projects that might result from the research presented in this thesis.

Submitted to the faculty of the Bioinformatics Graduate Program in partial fulfillment of the requirements for the degree Master of Science in the School of Informatics, Indiana University December 2005 / The last decade has witnessed numerous proteomic studies which have predicted and successfully confirmed the existence of extended structurally flexible regions in protein molecules. Parallel to these advancements, the last five years of structural bioinformatics has also experienced an explosion of results on molecular recognition and its importance in protein-protein interactions. This work provides an extension to past and ongoing research efforts by looking specifically at the “flexibility and disorder†found in protein sequences involved in molecular recognition processes and known as, Molecular Recognition Elements or Molecular Recognition Features (MoREs or MoRFs, as we call them). MoRFs are relatively short in length (10 – 70 residues length); loosely structured protein regions within longer sequences that are largely disordered in nature. Interestingly, upon binding to other proteins, these MoRFs are able to undergo disorder-to-order transition. Thus, in our interpretation, MoRFs could serve as potential binding sites, and that this binding to another protein lends a functional advantage to the whole protein complex by enabling interaction with their physiological partner. There are at least three basic types of MoRFs: those that form α-helical structures upon binding, those that form β-strands (in which the peptide forms a β-sheet with additional β-strands provided by the protein partner), and those that form irregular structures when bound. Our proposed names for these structures are α-MoRF (also known as α-MoRE, alpha helical molecular recognition feature/element), β-MoRF (beta sheet molecular recognition feature/element), and I-MoRF (Irregular molecular recognition feature/element), respectively. The results presented in this work suggest that functionally significant residual structure can exist in MoRF regions prior to the actual binding event. We also demonstrate profound conformational preferences within MoRF regions for α-helices. We believe that the results from this study would subsequently improve our understanding of protein-protein interactions especially those related to the molecular recognition, and may pave way for future work on the development of protein binding site predictions. We hope that via the conclusions of this work, we would have demonstrated that within only a few of years of its conception, intrinsic protein disorder has gained wide-scale importance in the field of protein-protein interactions and can be strongly associated with molecular recognition.

Doctor of Philosophy / Department of Chemistry / Christer B. Aakeröy / Co-crystallization allows the manipulation of physical properties of a given compound without affecting its chemical behavior. The ability to predict hydrogen bonding interactions, provides means to the rational design of supramolecular architectures. It also makes it possible to select with a degree of accuracy, a few co-formers that have a high probability of forming co-crystals with a compound of interest, instead of blindly screening against a large number of candidates. To study the effects of changing electronic environment on the ability to form co-crystals, five symmetric dioximes of different hydrogen bond donating ability were synthesized with different functional groups on the carbon α to the oxime moiety. It was shown that the supramolecular yield increase with the positive MEP value on the donor site. In order to further explore this relationship between calculated MEP values and supramolecular selectivity three asymmetric ditopic donors containing phenol carboxylic acid and aldoxime groups were screened against a series of asymmetric ditopic acceptors. Nine crystal structures show that the supramolecular outcome can be predicted according to Etter’s rules by ranking donors and acceptors according to calculated MEP values. To explore the possibility of using the same approach with other hydrogen bond donors, three asymmetric ditopic donor ligands containing cyanooxime groups were synthesized and screened against a series of asymmetric ditopic acceptors. Nine out of ten times the supramolecular outcome could be predicted by MEP calculations 1-deazapurine exists in two tautomeric forms (1H and 3H) in aqueous solution, which have very different hydrogen bonding environments. The 3H tautomer forms a self-complementary dimer involving a donor and an acceptor site leaving a second acceptor site vacant. In order to stabilize this tautomer the molecule was screened against a of series hydrogen and halogen bond donors. Four out of five structures obtained showed 3H tautomer. The 1H tautomer is the geometric complement of urea. Therefore the molecule was screened against a series of N,N-diphenylureas and all five structures showed the 1H tautomer.

Molecularly imprinted polymers (MIPs) are a novel, promising family of porous materials with potential applications ranging from separations, chemical sensing and catalysis to drug delivery and artificial immunoassays. The unique feature of these materials is their biomimetic molecular recognition functionality. Molecular recognition is the biological phenomenon of specific, selective and strong association between a substrate and a ligand. In man made MIPs this functionality is implemented via templated synthesis protocol. MIPs are synthesized in the presence of additional template molecules which form complexes with functional monomers in the pre‐polymerization mixture. After polymerization, the template is removed, leaving cavities in the structure which are complementary in shape and interaction patterns to the template molecules. These cavities act as mimics of biological receptors and are able to recognize and rebind template molecules. Although the imprinting concept is simple in principle, synthesis of MIPs with precisely controlled characteristics and performance remains a challenging task. Composition, polymerization conditions, template removal process and application conditions all affect the properties of MIPs. The material is affected at different scales, but crucially at the microscopic level, the number, fidelity and accessibility of binding sites are dependent on all the factors mentioned. The full potential of these materials can only be achieved if researchers can control and optimize the properties of MIPs through detailed understanding of adsorption and molecular recognition processes in these materials. The objective of this work is to, using computer simulations and statistical mechanics; develop a fundamental description of MIP formation and function, and to link morphological features of the model materials to their molecular recognition capabilities. In general, molecular simulations employed in this study should allow easier and more efficient exploration of a vast number of factors influencing the behaviour of MIPs. At the heart of the approach developed in this thesis is a computational strategy that imitates all the stages of MIP formation and function. First, the model simulates the pre‐polymerization mixture, allowing the formation of template‐functional monomer complexes. (This stage is implemented via canonical Monte Carlo simulation). Complexes can have different structures, depending on the chemical nature of template and functional monomer; therefore complexes can have a range of association constants. The distribution of template‐functional monomer complexes also translates into a distribution of binding sites of different specificity after template removal. In the second stage of the process, adsorption simulations (grand canonical Monte Carlo) are performed for a variety of model MIPs prepared to assess the role of various processing conditions such as composition, density and binding sites degeneration. This strategy was first applied to a simplified description of MIP species in order to identify the minimal model capable of molecular recognition and thus shed the light on the very nature of this phenomenon. In the developed model, the molecular species are constructed from hard spheres, featuring small interaction sites on their surfaces. The bond between two interaction sites has the strength and topological features of a typical hydrogen bond. The model exhibits molecular recognition, being able to preferentially adsorb template molecules. The associations between template and functional monomers were analyzed and classified to describe the distribution of binding sites and their heterogeneity. Using this model, several experimental trends typically observed in MIP studies could be explained, such as maximum in the selectivity as a function of monomer concentration. Using this model, we were also able to explore hypothetical, alternative protocols for MIP synthesis in order to improve their performance. These include the use of alternative templates and the post‐synthetic surface modifications of MIPs. The general strategy to modelling MIP, employed in this thesis, was then applied to a more detailed description of MIPs with realistic force field potentials for all the species involved. This more elaborate model is simulated with a combination of molecular dynamics (MD) and Monte Carlo techniques. This detailed model provided a wealth of information on various types of complexes observed in the pre‐polymerization mixture. Specifically, it revealed the relative weight of different interactions in the complex and their role in the binding energy of adsorbates. These simulations also provided the comparison of the relative contribution of different types of interactions (van der Waals, Coulombic) involved in a molecular recognition process. We believe the insights gained in this work will contribute to the development of rational MIP design strategies. In the discussion of the results of the thesis we speculate on how these models can be further developed in order to generate quantitative predictions and what type of systems it would be interesting and important to investigate in the future.

This thesis is concerned with the synthesis and study of novel anion templated rotaxanes and catenanes for electrochemical anion sensing, as well as interlocked structures that possess different anion binding properties, higher-order topologies and the ability to undergo molecular motion. Chapter One provides an introduction to anion recognition and the preparation of interlocked structures. A short summary of fundamental aspects of supramolecular chemistry is followed by detailed surveys of current approaches to anion binding and sensing, as well as the templated synthesis of rotaxanes and catenanes. Chapter Two describes the preparation of rotaxanes and catenanes appended with ferrocene to allow for electrochemical anion sensing. The anion recognition properties of a [2]rotaxane and a [2]catenane, as investigated by ¹H NMR spectroscopy and electrochemical methods, are presented. The utilization of a ferrocene-appended macrocycle in the construction of surface confined anion templated rotaxanes and catenanes is also discussed. Chapter Three reports the work carried out to achieve electrochemical anion sensing by the incorporation of redox-active groups into the integral structures of interlocked structures. The syntheses of a bis-stoppered 1, 2, 3, 4, 5-pentaphenylferrocene [2]rotaxane and a ferrocene containing [3]rotaxane are presented, along with their subsequent anion recognition studies. In addition, attempts to incorporate ferrocene into the macrocyclic components of rotaxanes and catenanes are outlined. Chapter Four details further investigations into the use of interlocked structures to achieve anion recognition. Doubly-charged [2]catenanes able to bind anions in aqueous solvent media, as well as the incorporation of alternative anion binding motifs into interlocked architectures are reported. The exploitation of anion templated synthesis to allow for the construction of higher order structures (including [3]catenanes, a “handcuff” catenane and a Janus [2]rotaxane), as well as a [2]catenane system with anion controlled molecular motion is also described. Chapter Five presents the experimental procedures and characterization data relating to the compounds prepared in Chapters Two, Three and Four. Chapter Six summarizes the main conclusions of the work contained within this thesis. Supplementary experimental information relating to titration protocols, investigations into self-assembled monolayers (SAMs) and crystallographic data are provided in Appendices I, II and III.

Nanotechnology is a term used to describe nanometer scaled systems. This thesis presents various nanomaterials and systems for the investigation of biologically relevant analytes in general, and in particular for their detection, decontamination, or destruction. The validation of short peptide fragments as models for protein aggregation is initially discussed through applying spectroscopic and microscopic techniques to Langmuir monolayer surface chemistry. Following this validation, the use of nanogold as a photoablative material for the destruction of aggregated protein is investigated. Subsequently, the versatility of nanotechnology is shown by investigating a different form of nanogold; namely, gold quantum dots and the interesting phenomenon that arise when dealing with materials on a nanoscale. Experiments involving a complex between these gold quantum dots and an antibody are performed for the detection of an immunoglobulin in solution. The power of this analytical technique is highlighted by the capability of detecting the analyte at nanomolar concentrations. Finally, a limitation-the multiple synthetic steps necessary for imparting biological activity-- of quantum dots is addressed: a single step reaction is studied that allows for direct stabilization and conjugation of quantum dots with proteins and enzymes. As a representative application of the above mentioned procedure, the detection and decontamination of an organophosphorus compound is explored. In general, methods for overcoming limitations of nanoparticles and nanocrystals are discussed.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 119-136).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.