Home About us Contact
|
Home About us Contact | ||
|
|
||
Synthetic Receptors (synthetic + receptor)
Selected AbstractsExploring the Relation between Amplification and Binding in Dynamic Combinatorial Libraries of Macrocyclic Synthetic Receptors in WaterCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2008Peter Abstract Herein we describe an extensive study of the response of a set of closely related dynamic combinatorial libraries (DCLs) of macrocyclic receptors to the introduction of a focused range of guest molecules. We have determined the amplification of two sets of diastereomeric receptors induced by a series of neutral and cationic guests, including biologically relevant compounds such as acetylcholine and morphine. The host,guest binding affinities were investigated using isothermal titration calorimetry. The resulting dataset enabled a detailed analysis of the relationship between the amplification of selected receptors and host,guest Gibbs binding energies, giving insight into the factors affecting the design, simulation and interpretation of DCL experiments. In particular, two questions were addressed: Is amplification by a given guest selective for the best receptor? And does the best guest induce the largest amplification of a given receptor? Our experimental results and computer simulations showed that the relative levels of amplification of hosts by a guest are well-correlated with their relative affinities, and simulations have confirmed previous observations that amplification can be selective for the best receptor when only modest amounts of guest are used. In contrast, the correlation between guest binding and the extent of amplification of a given receptor across a wide range of guests tends to be poorer, because every guest has its own unique set of affinities for competing receptors in the DCL. This implies that the results of screening a DCL for selective receptors by comparing the response of the mixture to two different guests should be interpreted with caution. DCLs are complex mixtures in which all compounds are connected through a set of equilibria. Obtaining quantitative information about all host,guest binding constants from such systems will require the explicit and simultaneous consideration of all of the main equilibria within a DCL. [source] Water Accessibility to the Binding Cleft as a Major Switching Factor from Entropy-Driven to Enthalpy-Driven Binding of an Alkyl Group by Synthetic ReceptorsCHEMISTRY - AN ASIAN JOURNAL, Issue 5 2010Sayaka Matsumoto Abstract Free energy, enthalpy, and entropy changes in the binding of alkyl pyridines to water-soluble zinc porphyrin receptors with varying accessibility of water to the binding cleft were determined to explain why the driving force of hydrophobic effects is enthalpic in some occasions and entropic in others. Zinc porphyrins bearing four alkyl pillars with terminal solubilizing poly(oxyethylene) (POE) chains of molecular weight of 750 (1), with eight alkyl pillars with terminal solubilizing POE chains of molecular weight of 350 (3), and with eight alkyl pillars with POE of molecular weight of 750 (4) had a binding cleft with decreasing water accessibility in this order as revealed by binding selectivity of imidazole/pyridine. Although all these porphyrins showed that the free energy of binding (,,Go) increases linearly as the alkyl group of the guest is lengthened (,,Go per CH2 was 2.6, 2.8, and 2.6,kJ,mol,1 for 1, 3, and 4, respectively), the origin of the free energy gain was much different. Receptor 1 with the most hydrophilic binding site bound the alkyl group by an enthalpic driving force (4-pentylpyridine favored over 4-methylpyridine by ,,Ho=,16.4,kJ,mol,1), while receptor 4 with the most hydrophobic binding site by an entropic driving force (4-pentylpyridine favored over 4-methylpyridine by ,,So=39.6,J,K,1,mol,1). Receptor 3 showed intermediate behavior: both enthalpic and entropic terms drove the binding of the alkyl group with the enthalpic driving force being dominant. The binding site of the four-pillared receptor (1) is open and accessible to water molecules, and is more hydrophilic than that of the eight-pillared receptor (4). We propose that the alkyl chains of 1 are exposed to water to produce a room to accommodate the guest to result in enthalpy-driven hydrophobic binding, whereas 4 can accommodate the guest without such structural changes to lead to entropy-driven hydrophobic binding. Therefore, accessibility of water or exposure of the binding site to the water phase switches the driving force of hydrophobic effects from an entropic force to an enthalpic force. [source] Synthesis and Modulation of Bis(triazine) Hydrogen-Bonding ReceptorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2006Pamela V. Mason Abstract The synthesis of bis(triazine) molecules capable of acting as synthetic receptors for barbiturate guest molecules is described. The binding properties are also reported illustrating the modulation of the binding properties of these species by the modification of the hydrogen-bonding patterns of the receptor molecule, namely 1,3- N,N, -bis[4-(dibenzylamino)-6-(butylamino)-1,3,5-triazin-2-yl]xylylenediamine (1). Thus 1,3- O,O, -bis[4-(dibenzylamino)-6-(butylamino)-1,3,5-triazin-2-yl]benzenedimethanol (3) and 1,3- O,O, -bis[4-(dibenzylamino)-6-(diethylamino)-1,3,5-triazin-2-yl]benzenedimethanol (5) have been prepared, and their binding constants compared to those observed for 1. In the case of compounds 3 and 5 the hydrogen-bonding secondary amines at the apex of the receptor 1 are substituted by non-hydrogen-bonding ether links. The hydrogen-bonding ability is further modified in the case of 5 by the removal of all hydrogen-bond donors from the receptor site, replacing secondary amines by tertiary amines. NMR binding studies illustrate how these simple modifications of the hydrogen-bonding patterns of these receptors influences the overall strength of binding demonstrating a simple mechanism for controlling host-guest complex formation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Engineering functional materials by halogen bondingJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2007Pierangelo Metrangolo Abstract Engineering functional materials endowed with unprecedented properties require the exploitation of new intermolecular interactions, which can determine the characteristics of the bulk materials. The great potential of Halogen Bonding (XB), namely any noncovalent interaction involving halogens as electron acceptors, in the design of new and high-value functional materials is now emerging clearly. This Highlight will give a detailed overview on the energetic and geometric features of XB, showing how some of them are quite constant in most of the formed supramolecular complexes (e.g., the angle formed by the covalent and the noncovalent bonds around the halogen atom), while some others depend strictly on the nature of the interacting partners. Then, several specific examples of halogen-bonded supramolecular architectures, whose structural aspects as well as applications in fields as diverse as enantiomers' separation, crystal engineering, liquid crystals, natural, and synthetic receptors, will be fully described. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: PolymChem 45: 1,15, 2007 [source] | ||||||||||