International Journal of Molecular Sciences

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15 pages, 2480 KiB

Open AccessArticle

Simultaneous Disulfide and Boronic Acid Ester Exchange in Dynamic Combinatorial Libraries

by Sanna L. Diemer, Morten Kristensen, Brian Rasmussen, Sophie R. Beeren and Michael Pittelkow

Int. J. Mol. Sci. 2015, 16(9), 21858-21872; https://doi.org/10.3390/ijms160921858 - 10 Sep 2015

Cited by 26 | Viewed by 10716

Abstract

Dynamic combinatorial chemistry has emerged as a promising tool for the discovery of complex receptors in supramolecular chemistry. At the heart of dynamic combinatorial chemistry are the reversible reactions that enable the exchange of building blocks between library members in dynamic combinatorial libraries [...] Read more.

Dynamic combinatorial chemistry has emerged as a promising tool for the discovery of complex receptors in supramolecular chemistry. At the heart of dynamic combinatorial chemistry are the reversible reactions that enable the exchange of building blocks between library members in dynamic combinatorial libraries (DCLs) ensuring thermodynamic control over the system. If more than one reversible reaction operates in a single dynamic combinatorial library, the complexity of the system increases dramatically, and so does its possible applications. One can imagine two reversible reactions that operate simultaneously or two reversible reactions that operate independently. Both these scenarios have advantages and disadvantages. In this contribution, we show how disulfide exchange and boronic ester transesterification can function simultaneous in dynamic combinatorial libraries under appropriate conditions. We describe the detailed studies necessary to establish suitable reaction conditions and highlight the analytical techniques appropriate to study this type of system. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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16 pages, 2370 KiB

Open AccessArticle

NMR Studies on Li⁺, Na⁺ and K⁺ Complexes of Orthoester Cryptand o-Me₂-1.1.1

by René-Chris Brachvogel, Harald Maid and Max Von Delius

Int. J. Mol. Sci. 2015, 16(9), 20641-20656; https://doi.org/10.3390/ijms160920641 - 31 Aug 2015

Cited by 24 | Viewed by 11774

Abstract

Cryptands, a class of three-dimensional macrobicyclic hosts ideally suited for accommodating small guest ions, have played an important role in the early development of supramolecular chemistry. In contrast to related two-dimensional crown ethers, cryptands have so far only found limited applications, owing in [...] Read more.

Cryptands, a class of three-dimensional macrobicyclic hosts ideally suited for accommodating small guest ions, have played an important role in the early development of supramolecular chemistry. In contrast to related two-dimensional crown ethers, cryptands have so far only found limited applications, owing in large part to their relatively inefficient multistep synthesis. We have recently described a convenient one-pot, template synthesis of cryptands based on O,O,O-orthoesters acting as bridgeheads. Here we report variable-temperature, ¹H-1D EXSY and titration NMR studies on lithium, sodium, and potassium complexes of one such cryptand (o-Me₂-1.1.1). Our results indicate that lithium and sodium ions fit into the central cavity of the cryptand, resulting in a comparably high binding affinity and slow exchange with the bulk. The potassium ion binds instead in an exo fashion, resulting in relatively weak binding, associated with fast exchange kinetics. Collectively, these results indicate that orthoester cryptands such as o-Me₂-1.1.1 exhibit thermodynamic and kinetic properties in between those typically found for classical crown ethers and cryptands and that future efforts should be directed towards increasing the binding constants. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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12 pages, 1265 KiB

Open AccessCommunication

Supracolloidal Assemblies as Sacrificial Templates for Porous Silk-Based Biomaterials

by John G. Hardy, Chiara E. Ghezzi, Richard J. Saballos, David L. Kaplan and Christine E. Schmidt

Int. J. Mol. Sci. 2015, 16(9), 20511-20522; https://doi.org/10.3390/ijms160920511 - 28 Aug 2015

Cited by 6 | Viewed by 6780

Abstract

Tissues in the body are hierarchically structured composite materials with tissue-specific properties. Urea self-assembles via hydrogen bonding interactions into crystalline supracolloidal assemblies that can be used to impart macroscopic pores to polymer-based tissue scaffolds. In this communication, we explain the solvent interactions governing [...] Read more.

Tissues in the body are hierarchically structured composite materials with tissue-specific properties. Urea self-assembles via hydrogen bonding interactions into crystalline supracolloidal assemblies that can be used to impart macroscopic pores to polymer-based tissue scaffolds. In this communication, we explain the solvent interactions governing the solubility of urea and thereby the scope of compatible polymers. We also highlight the role of solvent interactions on the morphology of the resulting supracolloidal crystals. We elucidate the role of polymer-urea interactions on the morphology of the pores in the resulting biomaterials. Finally, we demonstrate that it is possible to use our urea templating methodology to prepare Bombyx mori silk protein-based biomaterials with pores that human dermal fibroblasts respond to by aligning with the long axis of the pores. This methodology has potential for application in a variety of different tissue engineering niches in which cell alignment is observed, including skin, bone, muscle and nerve. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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12 pages, 2494 KiB

Open AccessArticle

Perfluoroalkyl-Functionalized Hyperbranched Polyglycerol as Pore Forming Agents and Supramolecular Hosts in Polymer Microspheres

by Olaf Wagner, Maximilian Zieringer, Wynter J. Duncanson, David A. Weitz and Rainer Haag

Int. J. Mol. Sci. 2015, 16(9), 20183-20194; https://doi.org/10.3390/ijms160920183 - 26 Aug 2015

Cited by 7 | Viewed by 7131

Abstract

Perfluoroalkyl-functionalized, hyperbranched polyglycerols that produce stable microbubbles are integrated into a microfluidic emulsion to create porous microspheres. In a previously-presented work a dendrimer with a perfluorinated shell was used. By replacing this dendrimer core with a hyperbranched core and evaluating different core sizes [...] Read more.

Perfluoroalkyl-functionalized, hyperbranched polyglycerols that produce stable microbubbles are integrated into a microfluidic emulsion to create porous microspheres. In a previously-presented work a dendrimer with a perfluorinated shell was used. By replacing this dendrimer core with a hyperbranched core and evaluating different core sizes and degrees of fluorinated shell functionalization, we optimized the process to a more convenient synthesis and higher porosities. The new hyperbranched polyglycerol porogens produced more pores and can be used to prepare microspheres with porosity up to 12% (v/v). The presented preparation forms pores with a perfluoroalkyl-functionalized surface that enables the resulting microspheres to act as supramolecular host systems. The microspheres can incorporate gases into the pores and actives in the polymer matrix, while the perfluoroalkylated pore surface can be used to immobilize perfluoro-tagged molecules onto the pores by fluorous-fluorous interaction. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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11 pages, 1488 KiB

Open AccessArticle

Structure-Based Optimization of Inhibitors of the Aspartic Protease Endothiapepsin

by Alwin M. Hartman, Milon Mondal, Nedyalka Radeva, Gerhard Klebe and Anna K. H. Hirsch

Int. J. Mol. Sci. 2015, 16(8), 19184-19194; https://doi.org/10.3390/ijms160819184 - 14 Aug 2015

Cited by 14 | Viewed by 7229

Abstract

Aspartic proteases are a class of enzymes that play a causative role in numerous diseases such as malaria (plasmepsins), Alzheimer’s disease (β-secretase), fungal infections (secreted aspartic proteases), and hypertension (renin). We have chosen endothiapepsin as a model enzyme of this class of enzymes, [...] Read more.

Aspartic proteases are a class of enzymes that play a causative role in numerous diseases such as malaria (plasmepsins), Alzheimer’s disease (β-secretase), fungal infections (secreted aspartic proteases), and hypertension (renin). We have chosen endothiapepsin as a model enzyme of this class of enzymes, for the design, preparation and biochemical evaluation of a new series of inhibitors of endothiapepsin. Here, we have optimized a hit, identified by de novo structure-based drug design (SBDD) and DCC, by using structure-based design approaches focusing on the optimization of an amide–π interaction. Biochemical results are in agreement with SBDD. These results will provide useful insights for future structure-based optimization of inhibitors for the real drug targets as well as insights into molecular recognition. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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13 pages, 1359 KiB

Open AccessArticle

Generation of a Multicomponent Library of Disulfide Donor-Acceptor Architectures Using Dynamic Combinatorial Chemistry

by Wojciech Drożdż, Michał Kołodziejski, Grzegorz Markiewicz, Anna Jenczak and Artur R. Stefankiewicz

Int. J. Mol. Sci. 2015, 16(7), 16300-16312; https://doi.org/10.3390/ijms160716300 - 17 Jul 2015

Cited by 10 | Viewed by 7471

Abstract

We describe here the generation of new donor-acceptor disulfide architectures obtained in aqueous solution at physiological pH. The application of a dynamic combinatorial chemistry approach allowed us to generate a large number of new disulfide macrocyclic architectures together with a new type of [...] Read more.

We describe here the generation of new donor-acceptor disulfide architectures obtained in aqueous solution at physiological pH. The application of a dynamic combinatorial chemistry approach allowed us to generate a large number of new disulfide macrocyclic architectures together with a new type of [2]catenanes consisting of four distinct components. Up to fifteen types of structurally-distinct dynamic architectures have been generated through one-pot disulfide exchange reactions between four thiol-functionalized aqueous components. The distribution of disulfide products formed was found to be strongly dependent on the structural features of the thiol components employed. This work not only constitutes a success in the synthesis of topologically- and morphologically-complex targets, but it may also open new horizons for the use of this methodology in the construction of molecular machines. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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14 pages, 2873 KiB

Open AccessArticle

Molecularly Imprinted Composite Membranes for Selective Detection of 2-Deoxyadenosine in Urine Samples

by Sonia Scorrano, Lucia Mergola, Maria Pia Di Bello, Maria Rosaria Lazzoi, Giuseppe Vasapollo and Roberta Del Sole

Int. J. Mol. Sci. 2015, 16(6), 13746-13759; https://doi.org/10.3390/ijms160613746 - 16 Jun 2015

Cited by 34 | Viewed by 6120

Abstract

An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. In this work, a [...] Read more.

An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. In this work, a novel molecularly imprinted polymer composite membrane (MIM) was synthesized and employed for the selective detection in urine samples of 2-deoxyadenosine (2-dA), an important tumoral marker. By thermal polymerization, the 2-dA-MIM was cross-linked on the surface of a polyvinylidene-difluoride (PVDF) membrane. By characterization techniques, the linking of the imprinted polymer on the surface of the membrane was found. Batch-wise guest binding experiments confirmed the absorption capacity of the synthesized membrane towards the template molecule. Subsequently, a time-course of 2-dA retention on membrane was performed and the best minimum time (30 min) to bind the molecule was established. HPLC analysis was also performed to carry out a rapid detection of target molecule in urine sample with a recovery capacity of 85%. The experiments indicated that the MIM was highly selective and can be used for revealing the presence of 2-dA in urine samples. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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19 pages, 4040 KiB

Open AccessArticle

Supramolecular Phase-Selective Gelation by Peptides Bearing Side-Chain Azobenzenes: Effect of Ultrasound and Potential for Dye Removal and Oil Spill Remediation

by Jürgen Bachl, Stefan Oehm, Judith Mayr, Carlos Cativiela, José Juan Marrero-Tellado and David Díaz Díaz

Int. J. Mol. Sci. 2015, 16(5), 11766-11784; https://doi.org/10.3390/ijms160511766 - 22 May 2015

Cited by 42 | Viewed by 8067

Abstract

Phase selective gelation (PSG) of organic phases from their non-miscible mixtures with water was achieved using tetrapeptides bearing a side-chain azobenzene moiety. The presence of the chromophore allowed PSG at the same concentration as the minimum gelation concentration (MGC) necessary to obtain the [...] Read more.

Phase selective gelation (PSG) of organic phases from their non-miscible mixtures with water was achieved using tetrapeptides bearing a side-chain azobenzene moiety. The presence of the chromophore allowed PSG at the same concentration as the minimum gelation concentration (MGC) necessary to obtain the gels in pure organic phases. Remarkably, the presence of the water phase during PSG did not impact the thermal, mechanical, and morphological properties of the corresponding organogels. In the case of miscible oil/water mixtures, the entire mixture was gelled, resulting in the formation of quasi-hydrogels. Importantly, PSG could be triggered at room temperature by ultrasound treatment of the mixture or by adding ultrasound-aided concentrated solution of the peptide in an oil-phase to a mixture of the same oil and water. Moreover, the PSG was not affected by the presence of salts or impurities existing in water from natural sources. The process could be scaled-up, and the oil phases (e.g., aromatic solvents, gasoline, diesel fuel) recovered almost quantitatively after a simple distillation process, which also allowed the recovery and reuse of the gelator. Finally, these peptidic gelators could be used to quantitatively remove toxic dyes from aqueous solutions. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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11 pages, 4621 KiB

Open AccessArticle

One-Pot Exfoliation of Graphite and Synthesis of Nanographene/Dimesitylporphyrin Hybrids

by M. Mar Bernal and Emilio M. Pérez

Int. J. Mol. Sci. 2015, 16(5), 10704-10714; https://doi.org/10.3390/ijms160510704 - 12 May 2015

Cited by 20 | Viewed by 6860

Abstract

A simple one-pot process to exfoliate graphite and synthesize nanographene-dimesitylporphyrin hybrids has been developed. Despite the bulky mesityl groups, which are expected to hinder the efficient π–π stacking between the porphyrin core and graphene, the liquid-phase exfoliation of graphite is significantly favored by [...] Read more.

A simple one-pot process to exfoliate graphite and synthesize nanographene-dimesitylporphyrin hybrids has been developed. Despite the bulky mesityl groups, which are expected to hinder the efficient π–π stacking between the porphyrin core and graphene, the liquid-phase exfoliation of graphite is significantly favored by the presence of the porphyrins. Metallation of the porphyrin further enhances this effect. The resulting graphene/porphyrin hybrids were characterized by spectroscopy (UV-visible, fluorescence, and Raman) and microscopy (STEM, scanning transmission electron microscopy). Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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13 pages, 1574 KiB

Open AccessArticle

Hierarchically Ordered Supramolecular Protein-Polymer Composites with Thermoresponsive Properties

by Salla Välimäki, Joona Mikkilä, Ville Liljeström, Henna Rosilo, Ari Ora and Mauri A. Kostiainen

Int. J. Mol. Sci. 2015, 16(5), 10201-10213; https://doi.org/10.3390/ijms160510201 - 5 May 2015

Cited by 14 | Viewed by 8787

Abstract

Synthetic macromolecules that can bind and co-assemble with proteins are important for the future development of biohybrid materials. Active systems are further required to create materials that can respond and change their behavior in response to external stimuli. Here we report that stimuli-responsive [...] Read more.

Synthetic macromolecules that can bind and co-assemble with proteins are important for the future development of biohybrid materials. Active systems are further required to create materials that can respond and change their behavior in response to external stimuli. Here we report that stimuli-responsive linear-branched diblock copolymers consisting of a cationic multivalent dendron with a linear thermoresponsive polymer tail at the focal point, can bind and complex Pyrococcus furiosus ferritin protein cages into crystalline arrays. The multivalent dendron structure utilizes cationic spermine units to bind electrostatically on the surface of the negatively charged ferritin cage and the in situ polymerized poly(di(ethylene glycol) methyl ether methacrylate) linear block enables control with temperature. Cloud point of the final product was determined with dynamic light scattering (DLS), and it was shown to be approximately 31 °C at a concentration of 150 mg/L. Complexation of the polymer binder and apoferritin was studied with DLS, small-angle X-ray scattering, and transmission electron microscopy, which showed the presence of crystalline arrays of ferritin cages with a face-centered cubic (fcc, \( Fm\overline{3}m \)) Bravais lattice where lattice parameter a = 18.6 nm. The complexation process was not temperature dependent but the final complexes had thermoresponsive characteristics with negative thermal expansion. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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15 pages, 2035 KiB

Open AccessArticle

Reconciling Experiment and Theory in the Use of Aryl-Extended Calix[4]pyrrole Receptors for the Experimental Quantification of Chloride–π Interactions in Solution

by Antonio Bauzá, David Quiñonero, Antonio Frontera and Pablo Ballester

Int. J. Mol. Sci. 2015, 16(4), 8934-8948; https://doi.org/10.3390/ijms16048934 - 22 Apr 2015

Cited by 12 | Viewed by 6716

Abstract

In this manuscript we consider from a theoretical point of view the recently reported experimental quantification of anion–π interactions (the attractive force between electron deficient aromatic rings and anions) in solution using aryl extended calix[4]pyrrole receptors as model systems. Experimentally, two series of [...] Read more.

In this manuscript we consider from a theoretical point of view the recently reported experimental quantification of anion–π interactions (the attractive force between electron deficient aromatic rings and anions) in solution using aryl extended calix[4]pyrrole receptors as model systems. Experimentally, two series of calix[4]pyrrole receptors functionalized, respectively, with two and four aryl rings at the meso positions, were used to assess the strength of chloride–π interactions in acetonitrile solution. As a result of these studies the contribution of each individual chloride–π interaction was quantified to be very small (<1 kcal/mol). This result is in contrast with the values derived from most theoretical calculations. Herein we report a theoretical study using high-level density functional theory (DFT) calculations that provides a plausible explanation for the observed disagreement between theory and experiment. The study reveals the existence of molecular interactions between solvent molecules and the aromatic walls of the receptors that strongly modulate the chloride–π interaction. In addition, the obtained theoretical results also suggest that the chloride-calix[4]pyrrole complex used as reference to dissect experimentally the contribution of the chloride–π interactions to the total binding energy for both the two and four-wall aryl-extended calix[4]pyrrole model systems is probably not ideal. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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12 pages, 1857 KiB

Open AccessArticle

Revisiting the Formation and Tunable Dissociation of a [2]Pseudorotaxane Formed by Slippage Approach

by Ken Cham-Fai Leung, Kwun-Ngai Lau and Wing-Yan Wong

Int. J. Mol. Sci. 2015, 16(4), 8254-8265; https://doi.org/10.3390/ijms16048254 - 13 Apr 2015

Cited by 3 | Viewed by 6510

Abstract

A new [2]pseudorotaxane DB24C8É1-H·PF₆ with dibenzo[24]crown-8 (DB24C8) crown ether-dibenzylammonium (1-H·PF₆) binding which was formed by slippage approach at different solvents and temperature, had been isolated and characterized by NMR spectroscopy and mass spectrometry. [...] Read more.

A new [2]pseudorotaxane DB24C8É1-H·PF₆ with dibenzo[24]crown-8 (DB24C8) crown ether-dibenzylammonium (1-H·PF₆) binding which was formed by slippage approach at different solvents and temperature, had been isolated and characterized by NMR spectroscopy and mass spectrometry. The [2]pseudorotaxane DB24C8É1-H·PF₆ was stable at room temperature. The dissociation rate of [2]pseudorotaxane DB24C8É1-H·PF₆ could be tuned by using different stimuli such as triethylamine (TEA)/diisopropylethylamine (DIPEA) and dimethyl sulfoxide (DMSO). In particular, the dissociation of [2]pseudorotaxane DB24C8É1-H·PF₆ by an excess of TEA/DIPEA base mixture possessed a long and sustained, complete dissociation over 60 days. Other stimuli by DMSO possessed a relatively fast dissociation over 24 h. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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15 pages, 1070 KiB

Open AccessArticle

Surface Modification of ZnO Nanorods with Hamilton Receptors

by Lukas Zeininger, Martin Klaumünzer, Wolfgang Peukert and Andreas Hirsch

Int. J. Mol. Sci. 2015, 16(4), 8186-8200; https://doi.org/10.3390/ijms16048186 - 13 Apr 2015

Cited by 7 | Viewed by 7216

Abstract

A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. [...] Read more.

A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. Synthesized zinc oxide nanorods [ZnO] were used for surface functionalization. The wet-chemical functionalization procedure towards monolayer-grafted particles [ZnO-HR] is described and a detailed characterization study is presented. In addition, the detection of specific cyanurate molecules is demonstrated. The hybrid structures [ZnO-HR-CA] were stable towards agglomeration and exhibited enhanced dispersability in apolar solvents. This observation, in combination with several spectroscopic experiments gave evidence of the highly directional supramolecular recognition at the surface of nanoparticles. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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16 pages, 6024 KiB

Open AccessArticle

Supramolecular Cationic Assemblies against Multidrug-Resistant Microorganisms: Activity and Mechanism of Action

by Letícia Dias De Melo Carrasco, Jorge Luiz Mello Sampaio and Ana Maria Carmona-Ribeiro

Int. J. Mol. Sci. 2015, 16(3), 6337-6352; https://doi.org/10.3390/ijms16036337 - 19 Mar 2015

Cited by 29 | Viewed by 7002

Abstract

The growing challenge of antimicrobial resistance to antibiotics requires novel synthetic drugs or new formulations for old drugs. Here, cationic nanostructured particles (NPs) self-assembled from cationic bilayer fragments and polyelectrolytes are tested against four multidrug-resistant (MDR) strains of clinical importance. The non-hemolytic poly(diallyldimethylammonium) [...] Read more.

The growing challenge of antimicrobial resistance to antibiotics requires novel synthetic drugs or new formulations for old drugs. Here, cationic nanostructured particles (NPs) self-assembled from cationic bilayer fragments and polyelectrolytes are tested against four multidrug-resistant (MDR) strains of clinical importance. The non-hemolytic poly(diallyldimethylammonium) chloride (PDDA) polymer as the outer NP layer shows a remarkable activity against these organisms. The mechanism of cell death involves bacterial membrane lysis as determined from the leakage of inner phosphorylated compounds and possibly disassembly of the NP with the appearance of multilayered fibers made of the NP components and the biopolymers withdrawn from the cell wall. The NPs display broad-spectrum activity against MDR microorganisms, including Gram-negative and Gram-positive bacteria and yeast. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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15 pages, 1118 KiB

Open AccessArticle

Multifunctional Composites of Chiral Valine Derivative Schiff Base Cu(II) Complexes and TiO₂

by Yuki Takeshita, Kazuya Takakura and Takashiro Akitsu

Int. J. Mol. Sci. 2015, 16(2), 3955-3969; https://doi.org/10.3390/ijms16023955 - 12 Feb 2015

Cited by 13 | Viewed by 6691

Abstract

We have prepared four new Cu(II) complexes containing valine moieties with imidazole ligands at the fourth coordination sites and examined their photo-induced reactions with TiO₂ in order of understanding the reaction mechanisms. Under a nitrogen atmosphere, the intermolecular electron transfer reactions (essentially [...] Read more.

We have prepared four new Cu(II) complexes containing valine moieties with imidazole ligands at the fourth coordination sites and examined their photo-induced reactions with TiO₂ in order of understanding the reaction mechanisms. Under a nitrogen atmosphere, the intermolecular electron transfer reactions (essentially supramolecular interactions) of these systems, which resulted in the reduction of Cu(II) species to Cu(I) ones, occurred after UV light irradiation. In this study, we have investigated the conditions of the redox reactions in view of substituent effects of aldehyde moieties. The results of cyclic voltammetry (CV) on an rotating ring-disk electrode (RRDE) suggested that the substitution effects and redox potentials were correlated. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were also performed to simulate the UV–Vis and circular dichroism (CD) spectra; the results revealed a reasonably good correlation between the substituent effects and the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals (HOMO-LUMO) gaps associated with the most intense transition bands. In addition, we summarized the substitution effects of Cu(II) complexes for their corresponding UV light-induced reactions. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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21 pages, 3536 KiB

Open AccessArticle

Exploiting β-Cyclodextrin in Molecular Imprinting for Achieving Recognition of Benzylparaben in Aqueous Media

by Saliza Asman, Sharifah Mohamad and Norazilawati Muhamad Sarih

Int. J. Mol. Sci. 2015, 16(2), 3656-3676; https://doi.org/10.3390/ijms16023656 - 6 Feb 2015

Cited by 49 | Viewed by 8771

Abstract

The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting [...] Read more.

The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting the –OH group of MAA and one of the primary –OH groups of β-CD. This monomer comprised of triple interactions that included an inclusion complex, π–π interaction, and hydrogen bonding. To demonstrate β-CD performance in MIPs, two MIPs were prepared; molecularly imprinted polymer-methacrylic acid functionalized β-cyclodextrin, MIP(MAA-β-CD), and molecularly imprinted polymer-methacrylic acid, MIP(MAA); both prepared by a reversible addition fragmentation chain transfer polymerization (RAFT) in the bulk polymerization process. Both MIPs were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Brunauer-Emmett-Teller (BET). The presence of β-CD not only influenced the morphological structure, it also affected the specific surface area, average pore diameter, and total pore volume of the MIP. The rebinding of the imprinting effect was evaluated in binding experiments, which proved that the β-CD contributed significantly to the enhancement of the recognition affinity and selective adsorption of the MIP. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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17 pages, 966 KiB

Open AccessArticle

A Dynamic Combinatorial Approach for Identifying Side Groups that Stabilize DNA-Templated Supramolecular Self-Assemblies

by Delphine Paolantoni, Sonia Cantel, Pascal Dumy and Sébastien Ulrich

Int. J. Mol. Sci. 2015, 16(2), 3609-3625; https://doi.org/10.3390/ijms16023609 - 6 Feb 2015

Cited by 7 | Viewed by 6585

Abstract

DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of [...] Read more.

DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of the phosphodiester backbone of DNA. In order to probe the importance of secondary interactions and to identify side groups that stabilize these DNA-templated self-assemblies, we report herein the implementation of a dynamic combinatorial approach. We used an in situ fragment assembly process based on reductive amination and tested various side groups, including amino acids. The results reveal that aromatic and cationic side groups participate in secondary supramolecular interactions that stabilize the complexes formed with ssDNA. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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Review

Jump to: Research

24 pages, 5926 KiB

Open AccessReview

Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy

by Samuel Paul Jarvis

Int. J. Mol. Sci. 2015, 16(8), 19936-19959; https://doi.org/10.3390/ijms160819936 - 21 Aug 2015

Cited by 37 | Viewed by 12947

Abstract

A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated [...] Read more.

A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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26 pages, 2844 KiB

Open AccessReview

Supramolecular Approaches to Nanoscale Morphological Control in Organic Solar Cells

by Alexander M. Haruk and Jeffrey M. Mativetsky

Int. J. Mol. Sci. 2015, 16(6), 13381-13406; https://doi.org/10.3390/ijms160613381 - 11 Jun 2015

Cited by 28 | Viewed by 9567

Abstract

Having recently surpassed 10% efficiency, solar cells based on organic molecules are poised to become a viable low-cost clean energy source with the added advantages of mechanical flexibility and light weight. The best-performing organic solar cells rely on a nanostructured active layer morphology [...] Read more.

Having recently surpassed 10% efficiency, solar cells based on organic molecules are poised to become a viable low-cost clean energy source with the added advantages of mechanical flexibility and light weight. The best-performing organic solar cells rely on a nanostructured active layer morphology consisting of a complex organization of electron donating and electron accepting molecules. Although much progress has been made in designing new donor and acceptor molecules, rational control over active layer morphology remains a central challenge. Long-term device stability is another important consideration that needs to be addressed. This review highlights supramolecular strategies for generating highly stable nanostructured organic photovoltaic active materials by design. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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24 pages, 2312 KiB

Open AccessReview

Chemical Reactions Directed Peptide Self-Assembly

by Dnyaneshwar B. Rasale and Apurba K. Das

Int. J. Mol. Sci. 2015, 16(5), 10797-10820; https://doi.org/10.3390/ijms160510797 - 13 May 2015

Cited by 19 | Viewed by 10092

Abstract

Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a [...] Read more.

Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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24 pages, 7245 KiB

Open AccessReview

Limitations and Extensions of the Lock-and-Key Principle: Differences between Gas State, Solution and Solid State Structures

by Hans-Jörg Schneider

Int. J. Mol. Sci. 2015, 16(4), 6694-6717; https://doi.org/10.3390/ijms16046694 - 25 Mar 2015

Cited by 35 | Viewed by 9350

Abstract

The lock-and-key concept is discussed with respect to necessary extensions. Formation of supramolecular complexes depends not only, and often not even primarily on an optimal geometric fit between host and guest. Induced fit and allosteric interactions have long been known as important modifications. [...] Read more.

The lock-and-key concept is discussed with respect to necessary extensions. Formation of supramolecular complexes depends not only, and often not even primarily on an optimal geometric fit between host and guest. Induced fit and allosteric interactions have long been known as important modifications. Different binding mechanisms, the medium used and pH effects can exert a major influence on the affinity. Stereoelectronic effects due to lone pair orientation can lead to variation of binding constants by orders of magnitude. Hydrophobic interactions due to high-energy water inside cavities modify the mechanical lock-and-key picture. That optimal affinities are observed if the cavity is only partially filled by the ligand can be in conflict with the lock-and-key principle. In crystals other forces than those between host and guest often dominate, leading to differences between solid state and solution structures. This is exemplified in particular with calixarene complexes, which by X-ray analysis more often than other hosts show guest molecules outside their cavity. In view of this the particular problems with the identification of weak interactions in crystals is discussed. Full article

(This article belongs to the Special Issue Supramolecular Interactions)

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