Random, blocky and alternating ordering in supramolecular polymers of chemically bidisperse monomers

As a first step to understanding the role of molecular or chemical polydispersity in self-assembly, we put forward a coarse-grained model that describes the spontaneous formation of quasi-linear polymers in solutions containing two self-assembling species. Our theoretical framework is based on a two-component self-assembled Ising model in which the bidispersity is parameterized in terms of the strengths of the binding free energies that depend on the monomer species involved in the pairing interaction. Depending upon the relative values of the binding free energies involved, different morphologies of assemblies that include both components are formed, exhibiting paramagnetic-, ferromagnetic- or anti ferromagnetic-like order,i.e., random, blocky or alternating ordering of the two components in the assemblies. Analyzing the model for the case of ferromagnetic ordering, which is of most practical interest, we find that the transition from conditions of minimal assembly to those characterized by strong polymerization can be described by a critical concentration that depends on the concentration ratio of the two species. Interestingly, the distribution of monomers in the assemblies is different from that in the original distribution, i.e., the ratio of the concentrations of the two components put into the system. The monomers with a smaller binding free energy are more abundant in short assemblies and monomers with a larger binding affinity are more abundant in longer assemblies. Under certain conditions the two components congregate into separate supramolecular polymeric species and in that sense phase separate. We find strong deviations from the expected growth law for supramolecular polymers even for modest amounts of a second component, provided it is chemically sufficiently distinct from the main one.Comment: Submitted to Macromolecules, 6 figures. arXiv admin note: substantial text overlap with arXiv:1111.176

Self-assembly in solution of a reversible comb-shaped supramolecular polymer

We report a single step synthesis of a polyisobutene with a bis-urea moiety in the middle of the chain. In low polarity solvents, this polymer self-assembles by hydrogen bonding to form a combshaped polymer with a central hydrogen bonded backbone and polyisobutene arms. The comb backbone can be reversibly broken, and consequently, its length can be tuned by changing the solvent, the concentration or the temperature. Moreover, we have proved that the bulkiness of the side-chains have a strong influence on both the self-assembly pattern and the length of the backbone. Finally, the density of arms can be reduced, by simply mixing with a low molar mass bis-urea

Selectivity via Cooperativity: Preferential Stabilization of the p65/14-3-3 Interaction with Semisynthetic Natural Products

Natural compounds are an important class of potent drug molecules including some retrospectively found to act as stabilizers of protein–protein interactions (PPIs). However, the design of synthetic PPI stabilizers remains an understudied approach. To date, there are limited examples where cooperativity has been utilized to guide the optimization of a PPI stabilizer. The 14-3-3 scaffold proteins provide an excellent platform to explore PPI stabilization because these proteins mediate several hundred PPIs, and a class of natural compounds, the fusicoccanes, are known to stabilize a subset of 14-3-3 protein interactions. 14-3-3 has been reported to negatively regulate the p65 subunit of the NF-κB transcription factor, which qualifies this protein complex as a potential target for drug discovery to control cell proliferation. Here, we report the high-resolution crystal structures of two 14-3-3 binding motifs of p65 in complex with 14-3-3. A semisynthetic natural product derivative, DP-005, binds to an interface pocket of the p65/14-3-3 complex and concomitantly stabilizes it. Cooperativity analyses of this interaction, and other disease relevant 14-3-3-PPIs, demonstrated selectivity of DP-005 for the p65/14-3-3 complex. The adaptation of a cooperative binding model provided a general approach to characterize stabilization and to assay for selectivity of PPI stabilizers

Supramolecular approach to new inkjet printing inks

Electronically complementary, low molecular weight polymers that self-assemble through tunable π−π stacking interactions to form extended supramolecular polymer networks have been developed for inkjet printing applications and successfully deposited using three different printing techniques. Sequential overprinting of the complementary components results in supramolecular network formation through complexation of π-electron rich pyrenyl or perylenyl chain-ends in one component with π-electron deficient naphthalene diimide residues in a chain-folding polyimide. The complementary π−π stacked polymer blends generate strongly colored materials as a result of charge-transfer absorption bands in the visible spectrum, potentially negating the need for pigments or dyes in the ink formulation. Indeed, the final color of the deposited material can be tailored by varying the end-groups of the π-electron rich polymer component. Piezoelectric printing techniques were employed in a proof of concept study to allow characterization of the materials deposited, and a thermal inkjet printer adapted with imaging software enabled in situ analysis of the ink drops as they formed and of their physical properties. Finally, continuous inkjet printing allowed greater volumes of material to be deposited, on a variety of different substrate surfaces, and demonstrated the utility and versatility of this novel type of ink for industrial applications

The Many Face of Religious Truth : Developing Hilary Putnam's Pragmatic Pluralism into an Alternative for Religious Realism and Antirealism

The question this study addresses is whether, on a conceptual level, religious propositions can have truth-value. It reflects on this question from a philosophy of religion perspective that stands in philosophy of language and mind. It analyzes paradigmatic religious realist and antirealist perspectives on this question, and establishes that their underlying notions of truth and experience have significant limitations. It develops an alternative perspective on the basis of a critical analysis of contemporary pragmatist and (post-) analytic philosopher Hilary Putnam’s notions of truth and experience. The analysis of Putnam’s notion of truth and experience shows that he manages to evade fundamental difficulties of both the realist and antirealist view. In his pragmatic pluralist perspective, truth is an interactional notion. It is akin to a realist view because truth ultimately depends on reality, but it holds that what the notion of truth comes down to depends on the practice of which a particular proposition is part. Conceptual and practical abilities are interdependent. Furthermore, experience is a transactional notion: experiences (i.e., those of which we are aware) are direct and simultaneously conceptualized. This allows them to play a cognitive role, and for us to come to true propositions on the basis of them. Putnam’s perspective evades important difficulties of the realist and antirealist views, but it has its own limitations too. It runs the risk of taking the truth of at least some propositions to be relative to a particular community (relativism), and of presuming on beforehand that some experiences cannot be real (reductionism). In developing a religious pragmatic pluralist perspective, then, the research goes in against some of Putnam’s own viewpoints on the truth-value of moral and religious propositions by amending his views on the basis of a Jamesian understanding of religious experiences as pertaining to religious aspects of reality which are irreducible to other, non-religious aspects of reality. This amends Putnam’s pragmatic pluralist perspective on truth-value so that it evades the risks of relativism and reductionism. Religious pragmatic pluralism takes Putnam’s views that truth is interactional and that experience is transactional to be applicable to all areas of human reasoning. This means that (meaningful) religious propositions too have truth-value. The truth of religious propositions ultimately depends on the way the world is, because our religious practices are interactions with reality. Religious and non-religious propositions can and do conflict, since similar notions of truth-value can be at play in between the various practices, and since the various practices all pertain to reality. As immediate and conceptualized transactions between ourselves and our environment, religious experiences are potentially veridical, and can therefore in principle serve as bases for true religious propositions. The religious pragmatic pluralist perspective on the truth-value of religious propositions does justice to the diversity of religious practices as well as to the notion that religious propositions do not rest on mere conventional beliefs but ultimately depend for their truth-value on reality. As such, it provides a promising answer to the question of the truth-value of religious propositions

The Many Face of Religious Truth : Developing Hilary Putnam's Pragmatic Pluralism into an Alternative for Religious Realism and Antirealism

The question this study addresses is whether, on a conceptual level, religious propositions can have truth-value. It reflects on this question from a philosophy of religion perspective that stands in philosophy of language and mind. It analyzes paradigmatic religious realist and antirealist perspectives on this question, and establishes that their underlying notions of truth and experience have significant limitations. It develops an alternative perspective on the basis of a critical analysis of contemporary pragmatist and (post-) analytic philosopher Hilary Putnam’s notions of truth and experience. The analysis of Putnam’s notion of truth and experience shows that he manages to evade fundamental difficulties of both the realist and antirealist view. In his pragmatic pluralist perspective, truth is an interactional notion. It is akin to a realist view because truth ultimately depends on reality, but it holds that what the notion of truth comes down to depends on the practice of which a particular proposition is part. Conceptual and practical abilities are interdependent. Furthermore, experience is a transactional notion: experiences (i.e., those of which we are aware) are direct and simultaneously conceptualized. This allows them to play a cognitive role, and for us to come to true propositions on the basis of them. Putnam’s perspective evades important difficulties of the realist and antirealist views, but it has its own limitations too. It runs the risk of taking the truth of at least some propositions to be relative to a particular community (relativism), and of presuming on beforehand that some experiences cannot be real (reductionism). In developing a religious pragmatic pluralist perspective, then, the research goes in against some of Putnam’s own viewpoints on the truth-value of moral and religious propositions by amending his views on the basis of a Jamesian understanding of religious experiences as pertaining to religious aspects of reality which are irreducible to other, non-religious aspects of reality. This amends Putnam’s pragmatic pluralist perspective on truth-value so that it evades the risks of relativism and reductionism. Religious pragmatic pluralism takes Putnam’s views that truth is interactional and that experience is transactional to be applicable to all areas of human reasoning. This means that (meaningful) religious propositions too have truth-value. The truth of religious propositions ultimately depends on the way the world is, because our religious practices are interactions with reality. Religious and non-religious propositions can and do conflict, since similar notions of truth-value can be at play in between the various practices, and since the various practices all pertain to reality. As immediate and conceptualized transactions between ourselves and our environment, religious experiences are potentially veridical, and can therefore in principle serve as bases for true religious propositions. The religious pragmatic pluralist perspective on the truth-value of religious propositions does justice to the diversity of religious practices as well as to the notion that religious propositions do not rest on mere conventional beliefs but ultimately depend for their truth-value on reality. As such, it provides a promising answer to the question of the truth-value of religious propositions