Three photothermal-responsive α-cyclodextrin-based [2]rotaxanes were prepared via the copper(i)-catalyzed azide-alkyne cycloaddition, in which the α-cyclodextrin ring was threaded onto the azobenzene dumbbell component. The difference between the three [2]rotaxanes are the length of the ethylene glycol repeating chains connected between the azobenzene and triazole units in the dumbbell components. The α-cyclodextrin rings in the [2]rotaxanes can be reversibly switched between the azobenzene unit and triazole/ethylene glycol unit driven by the trans-cis isomerization of the azobenzene unit. The trans-to-cis isomerization of the azobenzene unit under UV light irradiation (365 nm) leads the α-cyclodextrin ring moving to the triazole/ethylene glycol unit, while the cis-to-trans isomerization of the azobenzene unit under either visible light irradiation or heating enables the α-cyclodextrin ring shuttling back to the azobenzene station. The different ethylene glycol repeating chains in the ...
The focus of this thesis is the incorporation of the 1,2-bis(pyridinium)ethane motif into new [2]rotaxane ligands for the purpose of developing new metal organic rotaxane frameworks (MORFs). Both new stoppers that can act as ligands as well as new crown ethers with appended donors were synthesized and these components combined to create new [2]rotaxane ligands and eventually new MORFs. Chapter 2, looks at the synthesis and coordination chemistry of a [2]rotaxane containing terpyridine stoppers. The [2]rotaxane was shown to form mixed ligand complexes with RuII, AgI, ZnII, and PdII. The complexes were studied in solution by NMR, and UV/vis spectroscopy and mass spectrometry and in the solid state by X-ray crystallography. Chapter 3 and 4, focuses on the synthesis of new tetrasubstituted dibenzo-24-crown-8 ethers and their inclusion into [2]pseudorotaxanes and [2]rotaxanes. The new [2]pseudorotaxanes and [2]rotaxanes were characterized in solution by NMR spectroscopy and mass spectrometry and in the solid
Based on the concept of covalent capture of supramolecular assemblies, the idea of mechanical encapsulation is exploited for the protection and delivery of peptidebased molecules. This thesis aims to establish a general method for the encapsulation of peptides within a rotaxane structure, as well as studying their mode of release under specific stimuli. The synthesis of such structures, relying on the elongation of short peptido[2]rotaxanes, is applied to the design of rotaxane peptide carriers whose function is to protect against biological degradation and release peptides under a biological stimulus. These molecules are composed of a rotaxane-encapsulated peptide bearing a biodegradable stopper, the enzyme-specific cleavage of which triggers peptide release, via dethreading. The synthesis and in vitro assessment of rotaxane carriers as agents for anti-cancer therapy will be described in detail. The future challenges and potential applications of the proposed systems will be addressed ...
This dissertation focuses on studies of mechanically interlocked molecules (MIMs) specifically [2]rotaxanes in three principle areas: (1) creating [2]rotaxane linkers to incorporate into metal-organic frameworks (MOFs); (2) studying the rate of shuttling motion in solution and finally (3) investigating the shuttling motion inside the MOF. Chapter 1 provides a brief introduction to MIMs, rotaxanes, MOFs and all previous studies on dynamic motions of MIMs in MOFs. Chapter 2 describes a [2]rotaxane linker with donor atoms attached to both the axle and the wheel. The linker contains four carboxylate groups attached to a rigid, H-shaped axle and two carboxylate units appended to a crown ether wheel. In the resulting Zn-based MOF, three independent 3-periodic frameworks (threefold interpenetration) are interconnected only by virtue of the threading of their individual components in the rotaxane linker. In Chapter 3, a [2]rotaxane linker was synthesized which combines an H-shaped axle containing four 3
Transformation of mechanically interlocked molecules (e.g., rotaxanes and catenanes) into nanoscale materials or devices is an important step towards their real applications. In our current work, an azobenzene-modified β-cyclodextrin (β-CD) derivative that can form a self-inclusion complex in aqueous solution was prepared. The self-included β-CD derivative was then functionalized onto a gold nanoparticle (AuNP) surface via a ligand-exchange reaction in aqueous solution, leading to the formation of AuNP-[1]rotaxane hybrids. Corresponding non-self-included β-CD derivative functionalized AuNPs were also developed in a DMF/H2O mixture solution for control experiments. These hybrids were fully characterized by UV-vis and circular dichroism spectroscopies, together with transmission electron microscopy (TEM). The competitive binding behavior of the hybrids with an adamantane dimer was investigated.
Mechanically interlocked molecules (MIMs) have been attracting increasing interest since their emergence in the 1960s. The development of passive template and active template synthetic approaches facilitated the rapid growth in synthesis of various functionalised mechanically interlocked molecules (MIMs), allowing for a wide range of applications. In this thesis, Chapter 1 will discuss the synthetic methodologies from earliest statistical methods to passive templates and the latest active templates. Amongst the active template methodologies, the Cu catalysed alkyne azide cycloaddition (AT-CuAAC), together with its introduction, mechanistic studies as well as its application in syntheses of various functionalised rotaxanes will be presented. Chapter 2 will illustrate the discovery of an unexpected dinuclear Cu(I) complex during the investigation of an AT-CuAAC reaction and its selective demetallation. Chapter 3 highlights the important role of the mechanical geometry on stabilising a Pt(II) ...
Abstract: The anion-templated synthesis of three novel halogen-bonding 5-halo-1,2,3-triazolium axle containing [2]rotaxanes is described, and the effects of altering the nature of the halogen-bond donor atom together with the degree of inter-component preorganisation on the anion-recognition properties of the interlocked host investigated. The ability of the bromotriazolium motif to direct the halide-anion-templated assembly of interpenetrated [2]pseudorotaxanes was studied initially; bromide was found to be the most effective template. As a consequence, bromide anion templation was used to synthesise the first bromotriazolium axle containing [2]rotaxane, the anion-binding properties of which, determined by 1H NMR spectroscopic titration experiments, revealed enhanced bromide and iodide recognition relative to a hydrogen-bonding protic triazolium rotaxane analogue. Two halogen-bonding [2]rotaxanes with bromo- and iodotriazolium motifs integrated into shortened axles designed to increase ...
The desire to sequence DNA is fueled by the knowledge that the information locked inside of genomes can help fields as varied as molecular medicine, bioarcheology, forensics, and environmental science. The challenge is to establish a method that is more cost effective and faster than the ones currently available. Many new sequencing technologies are being developed to achieve these goals. Our technique takes advantage of the atomic force microscopes (AFM) ability to detect piconewton scale forces in order to read off sequencing information based on the interaction of nucleotides with a cyclodextrin. We have successfully completed two of the major pieces needed to sequence DNA with an AFM. The problem of nonspecific adhesion of single-stranded DNA with both hydrophobic and hydrophilic surfaces was overcome by using poly (ethylene glycol) passivation layer. The creation of a rotaxane to put on the surface was accomplished involving DNA with a carbon chain, cyclodextrin that will thread the chain, and a
The first lanthanide cation-templated synthesis of an interlocked structure is demonstrated through an interpenetrated assembly between a pyridine N-oxide threading component coordinating to a lanthanide cation complexed within a macrocycle. Stoppering of the pseudo-rotaxane assembly allows for preparation o
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TY - JOUR. T1 - Axle length effect on photoinduced electron transfer in triad rotaxane with porphyrin, [60]fullerene, and triphenylamine. AU - Sandanayaka, Atula S.D.. AU - Sasabe, Hisahiro. AU - Araki, Yasuyuki. AU - Kihara, Nobuhiro. AU - Furusho, Yoshio. AU - Takata, Toshikazu. AU - Ito, Osamu. PY - 2010/4/29. Y1 - 2010/4/29. N2 - Photoinduced multiple electron-transfer processes of a newly synthesized rotaxane with one acceptor and two donors are studied with the time-resolved fluorescence and absorption methods. In this rotaxane, zinc porphyrin (ZnP) with a crown-ether necklace is employed as a photosensitized electron donor; through the crown-ether, a short axle with C60 and triphenylamine (TPA) at both terminals is penetrating as an electron acceptor and a hole-shift, respectively (abbreviated as (ZnP;C60-(AS)-TPA) Rot). The time-resolved fluorescence and transient absorption measurements reveal that the through-space electron-transfer processes take place via the excited states of the ...
Catenanes, rotaxanes and knots are characterized by their mechanically interlocked architectures. These molecules are of interest to scientists due to their rare and curious presence in nature, difficulty to synthesize, and potential for use in molecular machines. While synthetic organic chemists have made great strides in creating these entangled structures, very few examples exist in protein-based biological macromolecules. Lasso peptides are one of the only naturally occurring examples of a [1]rotaxane structure in protein space. These molecules are ribosomally synthesized and post-translationally modified into their unique threaded fold. Many of these peptides harbor native biological activity and impressive topological stability, and their potential use as a bioactive scaffold has motivated research in the field. While many approaches to engineer these molecules focus on genetic transformation, we show that altering the chemistry/shape of these structures in vitro offers a new route for ...
NTCDI is redox-active, forming stable radical anions near -1.10 V vs. Fc/Fc+.[5] Its ability to accept electrons reflects the presence of an extended conjugated ring system and the electron withdrawing groups (carbonyl centers). NDI is used in supramolecular chemistry owing to its tendency to form charge-transfer complexes with crown ethers, e.g., to give rotaxanes and catenanes. As another consequence of their planar structure and electron-acceptor properties, NDIs intercalate into DNA. It is also suitable for fabrication of soft electronic devices.[6]. ...
A strategy to enhance drug effectiveness while minimizing controversial effects consists in exploiting host-guest interactions. Moreover, these phenomena can induce the self-assembly of physical hydrogels as effective tools to treat various pathologies (e.g., chronic wounds or cancer). Here, two Poloxamers®/Pluronics® (P407/F127 and P188/F68) were utilized to synthesize various LEGO-like poly(ether urethane)s (PEUs) to develop a library of tunable and injectable supramolecular hydrogels for drug delivery. Three PEUs were synthesized by chain extending Poloxamer/Pluronic with 1,6-cyclohexanedimethanol or N-Boc serinol. Other two amino-functionalized and highly responsive polymers were obtained thorough Boc-group cleavage. For hydrogel design, the spontaneous self-assembly of the poly(ethylene oxide) domains of PEUs with α-cyclodextrins was exploited to form poly(pseudo)rotaxanes (PPRs). PPR-derived channel-like crystals were characterized by X-Ray powder diffraction, Infra-Red and Proton ...
We design and synthesise new molecular materials, and explore how their properties relate to their molecular structures. This is molecular engineering - engineering at the nano-scale. We use non-covalent self-assembly to control the behaviour of organic semiconductors and dyes, for diverse applications. Our core technique is synthesis, but we also do many other types of experiments, from biological testing to solid-state physics. We explore the conformational, electronic and recognition properties of our compounds using a wide range of spectroscopic and analytical techniques, and we collaborate closely with physicists, physical chemists and biologists.. Projects are being pursued in the following areas: (1) Light-harvesting π-conjugated porphyrin arrays; (2) Photoactive molecules as tools for biomedical research; (3) Single-molecule electronic devices; (4) Polyyne rotaxanes and catenanes; (5) Understanding cooperatively and molecular recognition; (6) Luminescent insulated molecular ...
Description of the Petru Poni Institute of Macromolecular Chemistry. The Petru Poni Institute of Macromolecular Chemistry is an institute of excellence of the Romanian Academy and concentrates on basic and applied research in polymer chemistry and physics. The research topics are directed towards multifunctional polymeric materials (smart polymers, photoactive polymers, thin films, micro/nanoparticles); supramolecular chemistry (rotaxanes, self assembling systems); bioactive/biocompatible polymers based on natural and synthetic polymers (controlled drug release, tissue engineering); management of polymer wastes; polymers for environment protection (degraded soil regeneration, water purification). The Institute employs 284 people including about 110 researchers and 55 PhD students. The main expertise of the research staff is on organic and polymer chemistry (synthesis by conventional and unconventional methods, structural characterisation), polymer physics (solution and solid state thermal, ...
Charlie McTernan is a physical sciences group leader at the Francis Crick Institute in London, and a lecturer at the Department of Chemistry at Kings College London. He is a supramolecular chemist, investigating how artificial molecular machines and metal-organic capsules can be applied in biomedical science. Charlie Thomas McTernan was born in London and studied Chemistry at Hertford College, University of Oxford. His Part II project was conducted under the supervision of Prof. Tim Donohoe, investigating the synthesis of isoquinoline motifs using palladium-catalyzed α-arylation.. He joined Prof. David Leighs group in 2013, funded by a University of Manchester Deans Faculty Award. His doctoral research included the synthesis of artificial molecular machines, switchable catalysts, and rotaxanes.. In September 2017 he joined the Nitschke Research Group as a postdoctoral researcher. In September 2018 he began his Leverhulme Early Career Research Fellowship, jointly funded by the Isaac Newton ...
One exciting aspect of the living/non-living classification is the new synthesis of both organic and inorganic materials. Scientists are creating de novo engineered proteins and other biological materials, non-naturally occurring inorganic materials with superior properties using molecular manufacturing techniques and hybrid organic-inorganic materials, with the best of organic and inorganic properties in one object, for example rotaxanes which could be used in quantum computing ...
Non-Linear Optical Properties of Matter: From Molecules to Condensed Phases attempts to draw together both theory and application in this field. As such it will be of interest to both experimentalists and theoreticians alike. Divided into two parts, Part 1 is concerned with the theory and computing of non-linear optical (NLO) properties while Part 2 reviews the latest developments in experimentation.. Part 1: Surveys the current advances in the computation of the NLO properties of molecules, crystalline solids and nano-particles. It examines the methods employed to compute the properties of both microscopic and macroscopic forms of matter.. Part 2: Covers the recent advances on the NLO properties of organometallic compounds, rotaxanes, glasses, Langmuir-Blodget films, gold and silver nano-particles etc. Strategies to develop novel NLO materials are also discussed along with the Hyper-Rayleigh scattering technique.. This book will be invaluable to researchers and students in academia and ...
Molecular Electronics: Rotaxane Switching Remnant Current Measurements Figure 6. (a) UV-vis absorption spectra of [2]-rotaxane molecules in CHCl 3 solution with the cyclophane ring either on the TTF group (green line), or the napthalene group (red line). Adapted from Ballardini et al, New J. Chem (b) Surface plasmon spectrum of Al-Au junction (white) and Al- rotaxane-Au junction (green). This rotaxane exhibited mixed conformations (red and green from (a)) in solution, which is also observed in the solid state device. Absorbance (a.u.) (a) Figure 7. Remnant current measurement of a [2]-rotaxane Langmuir Blodgett monolayer between Al and Au electrodes. We observed voltage-induced switching very similar to that of Luo, ChemPhysChem, The red trace is the remnant current measured at a constant voltage of 100 mV, and the black trace is the applied write voltage. Repeated cycling (b) shows an initial decay in remnant current, after which the switching magnitude stabilizes. Absorbance (a.u.) (b) wavelength
Squaraine dyes are a class of organic dyes with strong and narrow absorption bands in the near infrared. Despite high molar absorptivities and fluorescence quan...
A recent trend in DNA nanotechnology consists of the assembly of architectures with dynamic properties that can be regulated by employing external stimuli. Reversible processes are important for implementing molecular motion into DNA architectures as
TY - JOUR. T1 - Synthesis and two-photon spectrum of a bis(porphyrin)-substituted squaraine. AU - Odom, Susan A.. AU - Webster, Scott. AU - Padilha, Lazaro A.. AU - Peceli, Davorin. AU - Hu, Honghua. AU - Nootz, Gero. AU - Chung, Sung Jae. AU - Ohira, Shino. AU - Matichak, Jonathan D.. AU - Przhonska, Olga V.. AU - Kachkovski, Alexei D.. AU - Barlow, Stephen. AU - Brédas, Jean Luc. AU - Anderson, Harry L.. AU - Hagan, David J.. AU - Van Stryland, Eric W.. AU - Marder, Seth R.. PY - 2009/6/10. Y1 - 2009/6/10. N2 - (Figure Presented) A chromophore in which zinc porphyrin donors are linked through their meso positions by ethynyl bridges to a bis(indolinylidenemethyl) squaraine core has been synthesized using Sonogashira coupling. The chromophore exhibits a two-photon absorption spectrum characterized by a peak cross section of 11000 GM and, more unusually, also exhibits a large cross section of ,780 GM over a photon-wavelength window 750 nm in width.. AB - (Figure Presented) A chromophore in which ...
Provides an aqueous formulation of the lipophilic squaraine rotaxane dye, SRfluor® 680 phenyl, in micelles composed of DPPE-PEG2000 which is known to accumulate in interscapular brown adipose tissue in mice. Spectral properties: abs max = 646 nm and emission max = 670 nm in PBS ...
By sequestering the common lithium counterion PF6- in a supramolecular complex, chemists have found they can enhance the cations conductivity and how much current it generates-a finding that could lead to better lithium-ion batteries. MITs Jeremiah A. Johnson, Yang Shao-Horn, and Bo Qiao came up with the idea after a talk Qiao gave during his first week as a postdoc at MIT. Qiao spoke about his doctoral work with cyanostar, a macrocycle that forms a supramolecular complex with PF6- in a 2:1 ratio (shown). LiPF6 is one of the most common salts used as a Li+ source in Li batteries, Johnson says. The chemists realized that if they could bind the anion of that salt with cyanostar, it could dramatically affect the properties of LiPF6. They reasoned that capturing the counterion would spur the salt to break up into free ions and that the large supramolecular complex would diffuse slowly compared with free Li+. Experiments bore out this hypothesis (J. Am. Chem. Soc. 2018, DOI: ...
New fluorescent molecular probes, which can selectively target specific cell surface receptors, are needed for microscopy, in vivo imaging, and image guided surgery. The preparation of multivalent probes using standard synthetic chemistry can be a laborious process due to low reaction yields caused by steric effects. In this study, fluorescent molecular probes were prepared by a programmed non‐covalent pre‐assembly process that used a near‐infrared fluorescent squaraine dye to thread a macroc…. ...
New fluorescent molecular probes, which can selectively target specific cell surface receptors, are needed for microscopy, in vivo imaging, and image guided surgery. The preparation of multivalent probes using standard synthetic chemistry can be a laborious process due to low reaction yields caused by steric effects. In this study, fluorescent molecular probes were prepared by a programmed non‐covalent pre‐assembly process that used a near‐infrared fluorescent squaraine dye to thread a macroc…. ...
Cellulose, chitin and related polysaccharides are key renewable sources of organic molecules and materials. However, poor solubility tends to hamper their exploitation. Synthetic receptors could aid dissolution provided they are capable of cooperative action, for example by multiple threading on a single polysaccharide molecule. Here we report a synthetic receptor designed to form threaded complexes (polypseudorotaxanes) with these natural polymers. The receptor binds fragments of the polysaccharides in aqueous solution with high affinities (Ka up to 19,000 M−1), and is shown-by nuclear Overhauser effect spectroscopy-to adopt the threading geometry. Evidence from induced circular dichroism and atomic force microscopy implies that the receptor also forms polypseudorotaxanes with cellulose and its polycationic analogue chitosan. The results hold promise for polysaccharide solubilization under mild conditions, as well as for new approaches to the design of biologically active molecules. Full ...
Cellulose, chitin and related polysaccharides are key renewable sources of organic molecules and materials. However, poor solubility tends to hamper their exploitation. Synthetic receptors could aid dissolution provided they are capable of cooperative action, for example by multiple threading on a single polysaccharide molecule. Here we report a synthetic receptor designed to form threaded complexes (polypseudorotaxanes) with these natural polymers. The receptor binds fragments of the polysaccharides in aqueous solution with high affinities (Ka up to 19,000 M−1), and is shown-by nuclear Overhauser effect spectroscopy-to adopt the threading geometry. Evidence from induced circular dichroism and atomic force microscopy implies that the receptor also forms polypseudorotaxanes with cellulose and its polycationic analogue chitosan. The results hold promise for polysaccharide solubilization under mild conditions, as well as for new approaches to the design of biologically active molecules.. ...
The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.
This paper describes the philosophy to design, and a procedure to construct polyrotaxane-type gene carriers, together with the proof of their ability to conjunctively cooperate in order to generate cargo-complexes with dsDNA, able to efficiently transfect cultured cells. The main feature of these entities is Frontiers in Supramolecular and Macromolecular Science symposium
The synthesis and electrochem. properties of the macrocycle-contg. polythiophene I are described. I forms a self-assembled pseudopolyrotaxane in the presence of $π$-deficient guests such as paraquat and 1,1-bis(4-fluorobenzyl)-2,2-bipyridyl. Pseudopolyrotaxane formation results in both an anodic shift in the oxidn. potential of the polymer as well as a significant decrease in its max. cond. (ca. 52% at 45 mM guest). This effect is completely reversible. For comparative purposes, a nonmacrocyclic model polymer was also studied and showed no significant change in max. cond. under identical conditions. The results clearly demonstrate that the chemoresistive response is a direct result of host-guest complexation. Such a chemoresistor approach is an attractive route into conducting polymer-based sensors wherein resistivity is attenuated by perturbations arising from host-guest interactions. [on SciFinder(R)]. ...
The course is focused on the interaction of photons with organic molecules, molecular crystals and polymers. The primary processes of optical absorption, fluorescence, phosphorescence, non-radiative transitions and generation of excited species, such as excitons, excimers, exciplexes and photoinduced charge transfer states, are discussed in detail. The explanation of basic terms is followed by a complex analysis of photophysical and photochemical processes, such as photochromism, photoconductivity, electroluminescence, photodielectric effect, excitation energy transfer, photosynthesis, photodegradation of materials and some non-linear optical effects. From the application point of view, the principles of basic molecular optoelectronic elements, such as optical memories, photodetectors, solar cells, electroluminescent displays and non-linear optical elements (photorefractive and holographic memories) are discussed. From the chemical point of view, examples are mentioned of relations of molecular ...
Photochemical and photophysical processes in biomolecules are intimately involved in a multitude of functional processes, that include vision, photosynthesis, molecular recognition, gene replication, etc., and can be utilized in areas such as photodynamic therapy. Such processes in DNA are also of interest to both the biological and materials communities as memory devices and structural building blocks. Malign consequences of mis-function in higher life forms can include blindness (retinal pigmentosa), as well as photomutation leading, in DNA, to the primary cause of various types of cancer which (when light induced) can lead to melanomas.. At the higher level of biomolecular complexity, DNA-protein photolesions remain one of the least well characterised systems. Static and kinetic site-specific protein-DNA photocrosslinking has major implications for transcription in general, for the topology determinants specifically for RNA polymerase II transcription, and the mechanistic determinants of ...
Photochemical and photophysical processes in biomolecules are intimately involved in a multitude of functional processes, that include vision, photosynthesis, molecular recognition, gene replication, etc., and can be utilized in areas such as photodynamic therapy. Such processes in DNA are also of interest to both the biological and materials communities as memory devices and structural building blocks. Malign consequences of mis-function in higher life forms can include blindness (retinal pigmentosa), as well as photomutation leading, in DNA, to the primary cause of various types of cancer which (when light induced) can lead to melanomas.. At the higher level of biomolecular complexity, DNA-protein photolesions remain one of the least well characterised systems. Static and kinetic site-specific protein-DNA photocrosslinking has major implications for transcription in general, for the topology determinants specifically for RNA polymerase II transcription, and the mechanistic determinants of ...
The synthesis of a peptide-containing lasso molecular switch by a self-entanglement strategy is described. The interlocked [1] rotaxane molecular machine consists of a benzometaphenylene[25]crown-8 (BMP25C8) macrocycle surrounding a molecular axle. This molecular axle contains a tripeptidic sequence and two molecular stations: a N-benzyltriazolium and a pH-sensitive anilinium station. The tripeptide is located between the macrocycle and the triazolium station, so that its conformation can be tailored depending on the shuttling of the macrocycle from one station to the other. At acidic pH, the macrocycle resides around the anilinium moiety, whereas it shuttles around the triazolium station after deprotonation. This molecular machinery thus forces the lasso to adopt a tightened or a loosened conformation.
Carefully chosen ratios of metal ions and bridging ligands form a wide variety of polyhedral cages in solution. Chemists often have tuned the geometry and polarity of these cages to accommodate particular molecular guests. Rizzuto et al. report a pair of larger cages that, in a similar vein, stabilize unusual coordination complexes. An initial cage with rhodium and cadmium nodes accommodated a cadmium complex coordinated by five pyrazine ligands and a water molecule. An expanded cage assembled from zinc porphyrins accommodated a rotaxane, a macrocycle threaded on an axle coordinated to the cage walls.. J. Am. Chem. Soc. 140, 11502 (2018).. ...
Scientists have invented a nanomachine that mimics the function of the ribosome, which is the molecular machine that translates the genetic code into the bodys proteins.. Dave Leigh, a synthetic chemist at the University of Manchester, UK, and his team published their findings in the journal Science¹. The machine is much simpler than the ribosome, and at about one-tenth of the size and very slow. It destroys the code it reads and only produces short chunks of peptides, but some of these tactics could be used to make useful chemicals.. The machine built by Leigh and his team relies on a rotaxane, a large molecular ring threaded into another molecule that acts like an axle, which is lined with three amino acids. A chain of three amino acids hangs from the outer edge of the ring. One of these amino acids is cysteine, which contains a crucial sulfur-containing thiol group.. When the system is heated up, the thiol group plucks an amino acid from the axle and transfers it to the end of the chain. ...
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Page contains details about iota carrageenan-FeII supramolecular complexes . It has composition images, properties, Characterization methods, synthesis, applications and reference articles : nano.nature.com
Formation of a guanine tetrad on a tetracationic fourfold rotaxane template composed of a porphyrin and a phthalocyanine (Sch. Sci., Nagoya Univ.; Münster Univ.; Grad. Sch. Human and Environ. Stud., Kyoto Univ.) º KURACHI, Yuki; YAMADA, Yasuyuki; RADUNSKY, Christian; MÜLLER, Jens; KATO, Tatsuhisa; TANAKA, Kentaro. ...
Temporal correlations of sunlight may assist photoprotection in bacterial photosynthesis, New Journal of Physics 22 (2020) 073042. A Complex Comprising a Cyanine Dye Rotaxane and a Porphyrin Nanoring as a Model Light‐Harvesting System, Angewandte Chemie, Int. Ed. 59 (2020) 1. Experimental control of the degree of non-classicality via quantum coherence, Quantum Science and Technology, 5 (2020) 4LT01. ...
TY - JOUR. T1 - The significance of hydrated surface molecular mobility in the control of the morphology of adhering fibroblasts. AU - Seo, Ji Hun. AU - Kakinoki, Sachiro. AU - Inoue, Yuuki. AU - Nam, Kwangwoo. AU - Yamaoka, Tetsuji. AU - Ishihara, Kazuhiko. AU - Kishida, Akio. AU - Yui, Nobuhiko. PY - 2013/4. Y1 - 2013/4. N2 - The effects of the hydrated molecular mobility and the surface free energy of polymer surfaces on fibronectin adsorption and fibroblast adhesion were investigated. ABA-type block copolymers composed of polyrotaxane (PRX) with different number of threaded α-cyclodextrin (α-CD), random copolymers with similar chemical composition to the PRX block copolymers, and conventional polymers were prepared to determine a wide range of hydrated molecular mobility (Mf) values estimated by quartz crystal microbalance-dissipation (QCM-D) measurements. Fibronectin adsorption was highly dependent on surface free energy, and high surface fibronectin density resulted in a large projected ...
New polyrotaxane based on PDMS New method for synthesis of new block copolymers New application for PDMS based copolymers as thermoreversible block
Femtosecond optical spectroscopy is a unique tool for the study of the dynamics of ultrafast light-triggered processes in physics, chemistry, and biology, such as translation or rotation of parts of a molecule, transport of energy or charge, formation or breaking of a chemical bond. Such elementary reactions typically take place on timescales ranging from 10 to 100 fs, which are the times characteristic for the motion of nuclei over interatomic distances, i.e. for molecular vibrations.. The basic time-resolved optical experiment is the so-called pump-probe. In this technique a first light pulse, the pump pulse, triggers a photoinduced process; the subsequent system evolution is monitored by a delayed probe pulse. The temporal resolution of the experiment is determined by the duration of pump and probe pulses, so that very short pulses are necessary in order to observe fast processes. In addition, the need to excite a system on resonance and probe optical transitions occurring at different ...
As part of our investigations of dihydropyrimidine derivatives (Anuradha et al., 2009, 2012) to compare their chemical and biological activities, we have undertaken the X-ray crystal structure analysis of the title compound.. In the title molecule, C16H20N2OS (Fig.1), the heterocyclic ring adopts a slightly distorted flattened boat conformation, and the plane through the four coplanar atoms( C2, N3, C5 and C6) makes a dihedral angle of 86.98 (6)° with the benzene ring. The thione, acetyl and methyl groups have equatorial orientations with respect to the attached heterocyclic ring, whereas the isopropylphenyl group has an axial orientation.. Intermolecular N1-H1···O51, N3-H3···S2 and C61-H61B···S2 hydrogen bonds are found in the crystal structure. A weak intramolecular C61-H61A···O51 hydrogen bond is also observed (Fig. 2, Table 1).. ...
Zhang, W. et al. ORGN 414-Folding polyrotaxanes using secondary noncovalent bonding interactions. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 235, (AMER CHEMICAL SOC 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, 2008). ...
0158],56, In the above item ,54, or ,55,, 4) the step of chemically crosslinking may be carried out by G) the crosslinking reaction through addition of a crosslinking agent, and the crosslinking agent may be selected from the group consisting of cyanuric chloride, trimesoyl chloride, terephthaloyl chloride, epichlorohydrin, dibromobenzene, glutaraldehyde, aliphatic polyfunctional isocyanate, aromatic polyfunctional isocyanate, tolylene diisocyanate, hexamethylene diisocyanate, divinyl sulfone, 1,1-carbonyldiimidazole, alkoxysilanes and derivatives thereof, and photo-crosslinking reaction initiators. Furthermore, the photo-crosslinking reaction initiator may be at least one selected from the group consisting of quinones, aromatic ketones, benzoin, benzoin ethers, biimidazole compounds and derivatives thereof, N-phenylglycines, combinations of thioxanthones and alkylaminobenzoic acid, combinations of biimidazole compounds and derivatives thereof and Michlers ketones, acridines, and oxime esters. ...
The first part of this Lecture will introduce the concept of molecular recognition, overview major forces of molecular self-assembly and cover several important historical milestones of the field such as the recent Nobel Prize in Chemistry 2016. We will cover many textbook examples of self-assembled systems including molecular (crown ethers, cyclodextrine and calixarenes) as well as biological (proteins, DNA) systems and slowly go up in complexity talking about rotaxanes and catenanes as precursors for the topic of molecular machines. Following examples will present self-assembled systems of various dimensionalities: 0D (micelles, fullerenes), 1D (carbon nanotubes), 2D (self-assembled monolayers, Langmuir-Blodgett films, graphene) and 3D (block copolymers, liquid crystals). We will spend much time trying to classify and sort out non-covalent interactions (e.g. van der Waals forces) that are very important in the world of molecular self-assembly. At the end of this first part, we will look at the ...
Crown ethers are heterocyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy (-CH2CH2O-). Important members of this series are the tetramer (n = 4, or four ethyleneoxy units), the pentamer (n = 5), and the hexamer (n = 6). The term crown refers to the resemblance between the structure of a crown ether bound to a cation, and a crown sitting on a head. The first number in the name of a crown ether refers to the number of atoms in the cycle, and the second number refers to the number of those atoms that are oxygen. Crown ethers are much broader than the oligomers of ethylene oxide; an important group is derived from catechol.. Crown ethers strongly bind certain cations, forming complexes. The oxygen atoms are well situated to coordinate with a cation located within the ring, whereas the exterior of the ring is hydrophobic (repels water and polar and ionic substances). The ...
The present thesis describes the construction of differently shaped di- to hexavalent crown ethers by coordination-driven self-assembly and their investigations according (pseudo¬-) rotaxane formation and kinetics of the dynamic ligand exchange. First, bipyridine and terpyridine ligand moieties as well as crown ether host moieties were synthesized. Then a toolbox of crown ether-substituted bi- and terpyridines was created by connecting the host and ligand moieties by Sonogashira reaction. In order to obtain predefined structures in the desired assemblies the ligands were designed applying the directional bonding approach. The prepared ligands were connected by coordination-driven self-assembly with several 3d transition metal (Fe(II), Co(II), Ni(II)) and ruthenium(II) ions providing the corresponding di- to hexavalent crown ether-substituted complexes. Whereas complex formation with ruthenium(II) ions provides kinetically inert complexes with moderate yields, coordination of the ligands to 3d ...
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DNA viruses, such as herpes simplex virus type 1 (HSV-1), Simian virus 40 (SV40), and Cytomegaloviruses (CMV), start their replicative processes and transcription at specific nuclear domains known as ND10 (nuclear domain 10, also called PML bodies). It has been previously determined that for HSV-1 and SV40, a short DNA sequence and its binding protein are required and sufficient for cell localization of viral DNA replication and gene transcription. Our recent observations provide evidence that a foreign (not endogenous) DNA/protein complex in the nucleus recruits ND10 proteins. First, the complexes formed from the bacterial lac operator DNA and its binding protein (lac repressor), or from HPV11 (human papillomavirus 11) origin DNA and its binding protein (E2), co-localized with different ND10 proteins. Second, the HSV-1 amplicon without inserted lac operator DNA repeats distributed in the nucleus randomly, whereas the amplicon with lac operator DNA repeats associated with ND10, suggesting that DNA
Principal Investigator:YUI Nobuhiko, Project Period (FY):1997 - 2000, Research Category:Grant-in-Aid for Scientific Research (B)., Section:一般, Research Field:Biomedical engineering/Biological material science
TY - JOUR. T1 - Crowning proteins. T2 - Modulating the protein surface properties using crown ethers. AU - Lee, Cheng Chung. AU - Maestre-Reyna, Manuel. AU - Hsu, Kai Cheng. AU - Wang, Hao Ching. AU - Liu, Chia I.. AU - Jeng, Wen Yih. AU - Lin, Li Ling. AU - Wood, Richard. AU - Chou, Chia Cheng. AU - Yang, Jinn Moon. AU - Wang, Andrew H J. PY - 2014/11/24. Y1 - 2014/11/24. N2 - Crown ethers are small, cyclic polyethers that have found wide-spread use in phase-transfer catalysis and, to a certain degree, in protein chemistry. Crown ethers readily bind metallic and organic cations, including positively charged amino acid side chains. We elucidated the crystal structures of several protein-crown ether co-crystals grown in the presence of 18-crown-6. We then employed biophysical methods and molecular dynamics simulations to compare these complexes with the corresponding apoproteins and with similar complexes with ring-shaped low-molecular-weight polyethylene glycols. Our studies show that crown ...
We report the preparations and electron spin resonance (ESR) studies of a series of Cs+ and Rb+ crown ether (15-crown-5 and 18-crown-6) salts of [TcNCl4]- and [MoOCl4]-, and a new refinement of the X-ray structure of [Cs(18-crown-6)] [TcNCl4] involving a twinned P4/n scattering model. This refinement addresses some unsatisfactory aspects of the original disordered model. The structure consists of an infinite sandwich Cs+ cation/crown ether configuration and polymeric [TcNCL4]- anions, with Tc≡N distances of 1.561(36) Å, and anti-parallel chains of ---Tc≡N---Tc≡N ---with Tc···Tc separations of 4.275(4) Å. The structure determination of [Rb(15-crown-5)2][TcNCl4(OH2)] is also described and shows a lattice containing 2:1 sandwich-type crown ether/alkali-metal cations and isolated anions in the disordered lattice. The presence of Tc≡N infrared stretching frequencies at ca. 1074 cm-1 indicates the absence of strong electron donors coordinated to Tc in the sixth position (i. e. ...
Introduction. DNA nanotechnology has evolved from Ned Seemans work on immobile DNA junctions and his vision about organizing proteins and other materials in lattices created by such junctions [1,2].The first revolution in the field was the development of tile-based 2D structures in the late nineties, as such structures enabled imaging by atomic force microscopy and provided new structural Cited by: 7.
TY - JOUR. T1 - Computational studies of sialyllactones. T2 - Methods and uses. AU - Parrill, Abby L.. AU - Mamuya, Nellie. AU - Dolata, Daniel P.. AU - Gervay-Hague, Jacquelyn. PY - 1997. Y1 - 1997. N2 - N-Acetylneuraminic acid (1) is a common sugar in many biological recognition processes. Neuraminidase enzymes recognize and cleave terminal sialic acids from cell surfaces. Viral entry into host cells requires neuraminidase activity, thus inhibition of neuraminidase is a useful strategy for development of drugs for viral infections. A recent crystal structure for influenza viral neuraminidase with sialic acid bound shows that the sialic acid is in a boat conformation [Prot Struct Funct Genet 14: 327 (1992)]. Our studies seek to determine if structural pre-organization can be achieved through the use of sialyllactones. Determination of whether siallylactones are pre-organized in a binding conformation requires conformational analysis. Our inability to find a systematic study comparing the ...
TY - JOUR. T1 - Cytenamide acetic acid solvate. AU - Johnston, Andrea. AU - Florence, A.J.. AU - Fabianni, F.J.A.. AU - Shankland, K.. AU - Bedford, C.T.. PY - 2008/6. Y1 - 2008/6. N2 - In the crystal structure of the title compound (systematic name: 5H-dibenzo[a,d]cycloheptatriene-5-carboxamide ethanoic acid solvate), C16H13NO·C2H4O2, the cytenamide and solvent molecules form a hydrogen-bonded R22(8) dimer motif, which is further connected to form a centrosymmetric double ring motif arrangement. The cycloheptene ring adopts a boat conformation and the dihedral angle between the least-squares planes through the two aromatic rings is 54.7 (2)°.. AB - In the crystal structure of the title compound (systematic name: 5H-dibenzo[a,d]cycloheptatriene-5-carboxamide ethanoic acid solvate), C16H13NO·C2H4O2, the cytenamide and solvent molecules form a hydrogen-bonded R22(8) dimer motif, which is further connected to form a centrosymmetric double ring motif arrangement. The cycloheptene ring adopts a ...
Im looking for an English term for something. Not so long ago I read an article in a Danish Scientific Online Periodical about pieces of DNA floating freely in the cells.( I have forgotten the Danish term too). They were supposed to stem from deletions of genes or similar events . The context was, that they were suspected to be cancerogenic. I was trying to google intracellular and intranuclear DNA, but I did not find such a context. Does anybody know what Im talking about ...
The slow addition of NO to a CCl4 solution Of VCl4 reproducibly forms the known polymer [V(NO)(3)Cl-2](n) as a dark brown powder. Treatment of a CH2Cl2 suspension of [V(NO)(3)Cl-2], with excess THF generates mer-(THF)(3)V(NO)Cl-2 (1) which can be isolated as an orange crystalline material in 55% yield. The reaction of 1 with excess MeCN or 1 equiv of trimpsi (trimpsi = (BuSi)-Bu-t(CH2PMe2)(3)) provides yellow-orange (MeCN)(3)V(NO)Cl-2.MeCN (2.MeCN) and yellow (trimpsi)V(NO)Cl-2 (3), respectively. A black, crystalline complex formulated as [NO][VCl5] (4) is formed by the slow addition of NO to neat VCl4 or by the reaction of excess CINO with neat VCl4. Complex 4 is extremely air- and moisture-sensitive, and IR spectroscopy suggests that in solutions and in the gas phase it dissociates back into VCl4 and CINO. Reaction of 4 with excess [NEt3(CH2Ph)]Cl generates [NEt3(CH2Ph)](2)[VCl6].2CH(2)Cl(2) (5.2CH(2)Cl(2)), which can be isolated as deep-red crystals in 51% yield. All new complexes have been ...
Fuchsin definition, a greenish, water-soluble, solid, coal-tar derivative, obtained by the oxidation of a mixture of aniline and the toluidines, that forms deep-red solutions: used chiefly as a dye. See more.
Synonyms for parallelogram condenser in Free Thesaurus. Antonyms for parallelogram condenser. 4 synonyms for condenser: capacitor, electrical condenser, capacitance, optical condenser. What are synonyms for parallelogram condenser?
News Analysis Scientists Continue to Use Outdated Methods The use of underperforming computational tools is a major offender in sciences reproducibility crisis-and theres growing momentum to avoid it.. ...
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Macrocyclic molecules such as crown ethers have useful ion-binding properties, and their incorporation into a matrix can create materials with new properties, especially if these ring structures are left free for binding metals. Sharma and Clearfield have now found that derivatized crown ethers bearing a phosphonate group can self-assemble into well-defined leaflet structures in the presence of the divalent metal ions Co2+ and Cd2+. In the Co2+ complex (2), the metal does not coordinate with the phosphonates; the self-assembly proceeds through hydrogen bonding to form a polyphosphonate chain. In the Cd2+ complex, the Cd cations form part of a more complicated one-dimensional polymer network.-PDS. J. Am. Chem. Soc.122, 1558 (2000).. ...
The Weak-Link Approach (WLA) is a supramolecular coordination-based assembly methodology, first introduced in 1998 by the Mirkin Group at Northwestern University. This method takes advantage of hemilabile ligands, containing both strong and weak binding moieties, that can coordinate to metal centers and quantitatively assemble into a single condensed closed structure (Figure 1). Unlike other supramolecular assembly methods, the WLA allows for the synthesis of supramolecular complexes that can be modulated from rigid closed structures to flexible open structures through reversible binding events that occur at the structural metal centers. The approach is general and has been applied to a variety of metal centers and ligand designs (Figure 2) including those with utility in catalysis and allosteric regulation. To date, Rh(I), Ir(I), Pd(II), Ru(II), Cu(I), Ni(II), and Pt(II) have been used as metal precursors in the WLA. The key component that enables in situ control of supramolecular ...
Since eukaryotic intracellular region is compartmentalized by dynamic lipid bilayer membranes, biomolecules are transported via vesicles. At the target site, vesicles transfer the biomolecules by fusing with the target membrane. The membrane fusion between vesicles and plasma membrane involves protein supramolecular complex called tethering factor (Exocyst) that loosely and reversibly tethers both the membranes, and SNARE complex that fuses the vesicular and plasma membranes. Such sequential membrane fusion reactions mediated by protein-protein interactions are regulated by specific small GTPases such as Rab. Our laboratory determines the ternary structures of the complexes of small GTPases and their effectors, which are devoted for exocytosis, to elucidate the fundamental mechanism of membrane fusion regulated by small GTPases.. ...
International Lecture given by Professor Wolfgang Baumeister. In the past, macromolecular structures have been characterized by methods requiring their isolation and purification. When taken out of their functional context, information about their interactions within the cellular environment is lost. However, it is the interaction between the many molecular species inhabiting cells which underlies cellular functions. Many of them exist only fleetingly or, when integrated in supramolecular complexes, these may be rooted so deeply...
Calculated speciation curves for (a) 3,5-dnba and (b) 4-aba in methanol. Lines between points have been added as a guide to the eye. ...
The 40X objective is more sensitive to the position of and the opening of the condenser, than the lower power objectives. This is due to its higher N.A. The lower power objectives can function normally with a condenser partially closed or backed away from the stage but the 40X, with its N.A. of .65 or even possibly higher, requires the condenser to be at peak functioning, otherwise there will be a loss of resolution. As a general rule the condenser needs to be close enough to the slide with the 40X in order to establish Koehler illumination. If the microscope does not have Koehler illumination capability, the condenser still needs to be close to the slide: within 2 or 3 mm. The lower the condenser is, the lower the condensers N.A. is. If it is too low, it will have a lower N.A. than the 40X objective, and reduce its resolution. This isnt noticeable with the 20X because it probably has an N.A. of .40 or so , and a condenser much lower than the slide will still provide that N.A. to match the ...
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Methyl기를 포함하는 새로운 5종의 crown ether를 합성하였다. 2,3,4,5: 9,10,11,12-Dibenzo-8,8-dimethyl-15,18,1-trioxacycloeicosane, 2,3,4,5: 9,10,11,12-dibenzo-8,8-dimethyl-15,18,21,1-tetraoxacyclotricosane, 2,3,4,5 : 9,10,11,12-dibenzo-8,8-dimethyl-15,18,21,24,1-pentaoxacyclohexacosane, 2,3,4,5 : 9,10,11,12 : 22,23,24,25 : 29,30,31,32-tetrabenzo-8,8,28,28-tetramethyl-15,18,21,35,38,1-hexaoxacyclotetracontane 그리고 2,3,4,5 : 9,10,11,12 : 25,26,27,28:32,33,34,35-tetrabenzo-8,8,31,31-tetramethyl-15,18,21,24,38,41,44,1-octaoxacyclohexatetracontane은 (M = Na, K)존재하에서 4,4-isopropylidenediphenol과 di-, tri- 그리고 tetraethyleneglycol ditosylate의 반응에 의해 합성하였다. Diethyleneglycol ditosylate, triethyleneglycol ditosylate, tetraethyleneglycol ditosylate는 NaOH존재하에서 diethyleneglycol, triethyleneglycol 그리고 tetraethyleneglycol과 p-toluenesulfonylchloride의 반응에 의해 합성하였다 ...
Oktava MK102 set with three capsules - cardioid, hyper and omni, along with a 10dB attenuator and original mic clip. This is a genuine Russian microphone - comes in original box with manual (in Russian!).. Good used condition. Tested and fully working.. ...