Structure Of Supramolecular Complexes Research Articles

Microfabricated platforms to modulate and monitor T cell synapse assembly

Immunological synapse (IS) is a complex supramolecular structure formed at the interface between T cells and antigen presenting cells (APCs) during T cell antigen recognition. Microfabricated platforms have made great contributions to our understanding of the assembly dynamics and functional roles of the T cell synapses over the last decade. Here, we review three different types of microfabricated platforms developed to modulate and monitor the T cell synapse assembly. Firstly, multi-protein micropatterned surfaces presenting key ligands for T cell activation that can modulate the spatial distribution of receptors/signaling molecules in T cell synapses are described. Secondly, micropatterned supported bilayers that can modulate the dynamics of T cell receptor (TCR) microclusters are introduced. Lastly, T-APC pair arrays that allow for improved fluorescence live cell imaging are discussed.

Oxidation of Dimethylplatinum(II) Complexes with a Dioxirane: The Viability of Oxoplatinum(IV) Intermediates

The complexes [PtMe2(NN)] (NN = 2,2′-bipyridine = bipy, 1a; NN = di-2-pyridylamine = dpa, 1b; NN = di-2-pyridyl ketone = dpk, 1c) react with dimethyldioxirane in moist acetone to give the hydroxoplatinum(IV) complexes [Pt(OH)2Me2(NN)] (NN = bipy, 2a; NN = dpa, 2b, or [Pt(OH)Me2(dpkOH)], 3). Complex 2a crystallizes as the hydrate 2a·7H2O, which has a complex supramolecular network structure formed through hydrogen bonding between PtOH groups and water molecules. Attempts to trap a potential oxoplatinum(IV) intermediate in these reactions were unsuccessful, and computational studies suggest that oxoplatinum(IV) intermediates are improbable. It is suggested that oxygen atom transfer from the dioxirane to platinum is coupled to proton addition to give the hydroxoplatinum group directly.

Assembly and stability of flagellar motor in Escherichia coli

Bacterial flagellar motor is a highly ordered and complex supramolecular structure that powers rotation of flagella and serves as a type III export apparatus for flagellar assembly. Motor biogenesis represents a formidable example of self-assembly, but little is known about early steps of the motor structure formation. Here we used a combination of fluorescence microscopy techniques to dissect the order of the motor assembly in Escherichia coli cells, to map in vivo the underlying protein interactions and to investigate dynamics of protein exchange in the assembled motor structure. Our data suggest that motor self-assembly is initiated by oligomerization of the membrane export apparatus protein FlhA, which is followed by the recruitment of the MS ring component FliF and by the ordered association of other motor proteins. The assembly process combines the hierarchy with cooperativity, whereby the association of each subsequent motor structure stabilizes the growing assembly. Our results provide a novel and so far the most complete view of the early steps in flagellar motor assembly and improve understanding of the motor structure and regulation.

Linear polymer of a copper(II) complex and its supramolecular selectivity

The supramolecular framework [Cu2(TU)4 · (TAA)4] n (TU = thiourea; TAA = 2-(2-imino-4-oxo-5-thiazolidinylidene)acetic anion) has been synthesized by reaction of CuCl2 · 2H2O with meso-2,3-dibromosuccinic acid and thiourea. The one-dimensional supramolecular structure of the title complex is constructed through bridge-linkage of the S atoms on the thioureas between adjacent Cu(II) atoms, forming an infinite chain with lots of positive charges. Around the infinite chain, there are four groups of negatively charged hydrogen-bond tubes constructed by four TAA anions. The hydrogen-bond and ionic interactions between adjacent metal-organic polymeric chains and hydrogen-bond tubes form the three-dimensional supramolecular structure of the complex. Supramolecular selectivity from isomers of 2-(2-imino-4-oxo-5-thiazolidinylidene)acetic anion (TAA) has been studied by quantum calculation.

Synthesis and characterization of diorganotin(IV) derivatives from rhodanine (HRd): crystal structures of [(PhCH2)2Sn(Rd)(μ-OH)]2 and [n-Bu2Sn(Rd)(μ-OH)

The diorganotin(IV) complexes, [R2Sn(Rd)(μ-OH)]2 (R = Me (1), PhCH2 (2), n-Bu (3), Ph (4); HRd = rhodanine), have been synthesized and characterized by IR and multinuclear (1H, 13C, 119Sn) NMR spectroscopy. The structures of complexes 2 and 3 have been determined by single-crystal X-ray diffraction. Both crystal structures of 2 and 3 show the presence of asymmetrically bridging hydroxy groups leading to an Sn2O2 unit. Each atom in complex 1 is also coordinated by an N atom of ligand and two C atoms of the alkyl groups, so the Sn environment is based on a trigonal bipyramid. While in complex 2, a weak intermolecular Sn–O interaction has also been found between the two adjacent molecules, so the geometry of the Sn atom can be best described as six-coordinate octahedral. The salient feature of the supramolecular structure of complex 3 is that of a 1D polymer, in which the discrete molecules are connected through weak intermolecular Sn ··· O interactions.

Supramolecular Silanol Chemistry: Inclusion Complexes of 1,3,5‐Tris(diisopropylhydroxysilyl)benzene and 4,4′‐Bis(pyridines) (Eur. J. Inorg. Chem. 17/2006)

AbstractThe cover picture shows the supramolecular structure of an inclusion complex between the trisilanol 1,3,5‐(HOiPr2Si)3C6H3 and trans‐bis(4‐pyridyl)ethylene (bpe). The trisilanol molecules are associated by SiO–H···O(H)Si hydrogen bonds, giving rise to the formation of 1D (horizontal) chains. The bpe molecules resemble pillars that are situated perpendicularly to the 1D chains and linked by SiO–H···N hydrogen bonds. The supramolecular motif is somewhat reminiscent of the Acropolis of Selinunte built 650 BC in Sicily, a masterpiece of classical Greek architecture. Details of synthesis and structures of supramolecular complexes between the trisilanol 1,3,5‐(HOiPr2Si)3C6H3 and a number of 4,4′‐bis(pyridine) compounds are described in the article by J. Beckmann and S. L. Jänicke on p. 3351 ff.

Preparation and disordered crystal structure of (18-crown-6)ammonium isothiocyanate hemihydrate

A crystalline complex salt, (18-crown-6)ammonium isothiocyanate hemihydrate [NH4+(18C6)]·SCN−·0.5H2O, was prepared and studied by single-crystal X-ray diffraction. The crystal structure of this salt is highly disordered: Almost all the constituents (except the water molecule) are disordered over two different orientations: major and less occupied or weakly occupied. The geometric parameters (bond lengths, bond angles, etc.) of the molecular and ionic constituents of the salt were determined with reasonable accuracy, and the crystal packing was elucidated. The sale forms in the crystal a complex tetrahedral supramolecular hydrogen-bonded structure consisting of one water molecule, two complex cations [NH4+(18C6)], and two SCN− anions.

Physiopathology of the repair process of lesions of Achilles tendon

The tendon is composed of highly organized collagen fibers that form a complex supramolecular structure. After lesions, the organization and composition of the tendon are not completely restored. Our purpose was to evaluate if the application of Aloe vera improves tendon healing, considering the effectiveness in the stimulus of collagen synthesis.The calcaneal tendon of male Wistar rats was partially transected with subsequent topical application of A. vera ointment at the injury. The animals were separated into groups with tendons treated with the A. vera extract for 7 days and excised on the 7th, 14th and 21st days after surgery; control rats received only ointment base without plant extract.Morphological analysis using polarization microscopy showed that the entire tendon undergoes a remodeling process, with disorganized collagen fibers by days 7 and 14 in plant-treated and non‐treated groups and with a higher birefringence in tendons of the plant-treated group on the 21st day. A higher concentration of hydroxyproline was found in plant-treated tendons on days 7 and 14 compared with their controls. Western blots showed lower amounts of type I collagen in the plant-treated group on day 14 compared with the control. MMP-9 diminished 14 days after lesion and the active isoform of MMP-2 increased on day 21 in plant-treated groups.The present study indicates a beneficial effect of A. vera in the tissue reorganization in the transected region of the tendon 21 days after injury and is supported by an increase of active MMP-2.

Spectral properties and structures of supramolecular complexes of naphthylpyridine with β-cyclodextrin

The electronic absorption and fluorescence spectra of 4-(2-naphthyl)pyridine (1) and N-methyl-4-(2-naphthyl)pyridinium perchlorate (2+·ClO4−) were studied in aqueous solutions in the absence and presence of β-cyclodextrin (β-CD). In aqueous solutions and organic solvents in the presence of water or H+ ions, compound 1 exhibits intense fluorescence with a maximum at 21 270 cm−1, and its quantum yield in an aqueous solution is 0.9±0.09. The same fluorescence spectrum was detected for an aqueous solution of 2+·ClO4−. In an aqueous solution, compound 1 and β-CD form stable fluorescing supramolecular 2:2 complexes, whose structure was calculated by the quantum-chemical MNDO/PM3 method. The formation of these complexes induces a hypsochromic shift of the fluorescence maximum of 1 by 5000 cm−1. The stability constant of the complex is ∼2·103 L mol−1. A decrease in the pH results in the formation of a protonated form of 1(1·H+) and destruction of the complex, thus favoring the escape of the substrate from the β-CD cavity. The quantum-chemical calculations showed that the insertion of 1 into the β-CD cavity is thermodynamically more favorable than hydration; on the contrary, the formation of 1·H+ increases dramatically the hydration energy, which promotes the escape of 1·H+ from the β-CD cavity; cation 2+ does not form a complex with β-CD; in the thermodynamically most favorable 2:2 complex, the naphthalene fragments of two molecules 1 are parallel to each other in a broad section of the β-CD dimer constructed according to the head-to-head type.

Synthesis and structure of supramolecular complexes between 1-alkynyl(phenyl)(tetrafluoroborato)-λ 3-iodanes and 18-crown-6

Slow evaporation of a solution of 1-decynyl(phenyl)(tetrafluoroborato)-λ 3-iodane and 18-crown-6 in dichloromethane–diethyl ether–hexane gave a supramolecular 1:1 complex, while 3,3-dimethyl-1-butynyl- and phenylethynyl(phenyl)(tetrafluoroborato)-λ 3-iodanes afforded 2:1 complexes. Complexation with 18-crown-6 increased the thermal stability of the phenylethynyl-λ 3-iodane. Solid state and solution structures of these complexes were examined by single crystal X-ray analyses, 1H and 13C NMR spectra, and cold-spray ionization MS. Binding constants were measured by 1H NMR titrations.

The Close-Knit Supramolecular Network of Bis[(tert-butyl isocyanide)gold(I)] 1,3,4-Thiadiazole-2,5-disulfide

Treatment of 2 molar equiv of (tBuNC)AuCl with 1 equiv of the dipotassium salt of 2,5-dimercapto-1,3,4-thiadiazole, K2(SSS), results in the formation of the crystalline product [(tBuNC)Au]2(SSS) in addition to polymeric material. A crystallographic study reveals a complex supramolecular structure for the crystalline product resembling a “knitted” network containing six independent gold centers.

A Freeze-Fracture Study of Nuclear Pore Complex Structure in Intact Dunaliella Cells

Abstract The nuclear envelope in all eukaryotic cells is perforated by nuclear pores, that consist of the nuclear pore complex (NPC). The NPC is a highly complex supramolecular structure that plays a pivotal role in the trafficking of macromolecules and particles between the nucleus and the cytoplasm. During the past two decades a large body of information has accumulated on both the structure and role of the NPC. The diameter of NPC is about 120 nm and is composed of approximately 100 proteins. The NPC structure has been elucidated using various electron microscopy techniques. The basic structure of the NPC is comprised of three concentric rings, each displaying an 8-fold symmetry. The cytoplasmic and nuclear rings are vertically integrated by eight spokes that approximately span the width of the nuclear envelope. A set of eight fibers extends from the nucleoplasmic ring into the nucleus, and are joined at the distal ends by a ring to form the so called basket.

Disordered Crystal Structure of the 1:3 Solvated Molecular Ionic Complex of 1,10-Diaza-18-crown-6 with (+)-Tartaric Acid

The disordered crystal structure of the 1:3 solvated molecular ionic complex of 1,10-diaza-18-crown-6 with (+)-tartaric acid [C12H28N2O4]2+·2C4H5O6-·C4H6O6·1.5CH3OH·1.7H2O (I) was investigated by XRD analysis. Crystals I are monoclinic: space group P21, a = 9.662(2), b = 13.618(5), c = 14.316(3) A, β = 93.97(2)°, Z = 2. Structure I was solved by direct methods and refined by the full-matrix least-squares procedure anisotropically to R = 0.081 for all 3539 unique measured reflections (CAD-4 automatic diffractometer, λCuKα). In structure I, the solvated methanol and water molecules are disordered on many sites. The DA18C6 dication is also disordered and has two different asymmetric conformations. The two tartrate anions lie on different sides of the cavity of the DA18C6 dication, whose two NH2+ groups each forms two H-bonds of N–H...O type with each of the tartrate anions. The (+)-tartaric acid molecule and the solvated molecules are not involved in the H-bonds with the DA18C6 dication. The molecular ionic complex I exists in crystal as a complex infinite three-dimensional supramolecular structure.

Molecular and supramolecular structures of complexes formed by polyelectrolyte‐surfactant interactions: effects of charge density and compositions

Molecular and supramolecular structures of complexes formed by polyelectrolyte‐surfactant interactions: effects of charge density and compositions

Complexation of C60 with hexahomooxacalix[3]arenes and supramolecular structures of complexes in the solid state

Hexahomooxacalix[3]arenes 1–5, which possess a variety of substituents on their upper rim, have captured fullerene C60 in toluene with association constants of Ka = 9.1–35.6 dm3 mol–1; X-ray analysis of the complex of C60 and 4 indicated that a van der Waals attractive interaction is the dominant driving force which brings the hexagonal faces of the C60 close to both the aromatic rings and the dibenzyl ether oxygen of 4.

Piero Pino

AbstractPiero Pino was at the same time an inspired teacher, a creative scientist and an endless organizer. His culture was also very broad allowing him to donate the scientific community valuable contributions in organic and organometallic chemistry, in catalysis and polymer science. In this last field Pino was really a pioneer in combining the molecular approach to the complex supramolecular structure of polymeric materials, and indicated the routes to tailor‐made polymers on the basis of the molecular control of the structure during the polymerization process.Many examples of this approach can be found looking at his impressive and outstanding scientific production where the fundamental aspects were constantly preeminent without disregarding possibilities of technological developments.Thus his name is significantly related to isotactic poly(propylene) where he acted as the real “right hand” of Professor Giulio Natta at the Politecnico (Milano) during the early 50s and gave a remarkable support to make the discovery a still unique scientific event and successively a very important industrial reality. The relevant structural and catalytic questions connected to the stereospecific polymerization where thoroughly investigated by Pino in Pisa, where during 12 years (1956‐1967) he used chiral reagents and monomers to disclose the enantiomorphic sites character and clarify the relations between stereoregularity and optical activity in macromolecules.Successively at the Polytechnic (ETH) in Zürich, Pino approached with renewed enthusiasm the study of homogeneous catalysis for the synthesis of macromolecules, and his very strong chemical culture allowed once again important contributions to the stereochemical features of 1‐olefins polymerization by metallocene catalysts and to the synthesis of CO/1‐olefin alternating copolymers.This is only the mainline of Professor Pino's scientific contribution to macromolecular science; many others aspects were indeed developed thanks to his skilled scientific capacity.Piero Pino died untimely in 1989 and his death was a big lost for the world polymer community, but his memory will certainly survive for many future generations of polymer scientists.

Molecular dynamics of amphotericin B I. Single molecule in vacuum and water

Molecular dynamics simulations were performed for an antifungal polyene antibiotic amphotericin B (AMB). A single molecule of the AMB was modeled in vacuum as well as in water. In the latter case it was surrounded by 354 SPC water molecules and a periodic boundary condition was applied. An amino-sugar mycosamine ring was found to be rigid in the conditions studied. The mean orientation of this ring in relation to a macrolide ring was found to be common in both simulations and similar to that observed in a crystal of N-iodoacetyl derivative. A large flexibility of the amino-sugar orientation was observed in vacuum in contrast to water simulation. Several conformers of the macrolide ring were observed in vacuum as well as in water simulation. Interactions which may force these conformational transitions have been proposed. The structuring of the water molecules around polar and ionizable parts of the AMB molecule were analysed. The influence of the dynamic behavior of the AMB on structures of supramolecular complexes containing this antibiotic is discussed.

Ganglioside GM1 and its semisynthetic lysogangliosides reduce glutamate neurotoxicity by a novel mechanism.

In the brain interneuronal communications occur at synapses. Synapses are specialized junctions between the presynaptic terminals of the afferent neurons and the receiving part of the postsynaptic neurons: the pre- and postsynaptic components are separated by a space termed a synaptic gap. Nerve impulses reaching the presynaptic terminal release a transmitter which is stored in synaptic vesicles preferentially located in the nerve terminal. The transmitter is released into the synaptic gap and diffuses in this space thereby reaching specific sites that bind the transmitter with high affinity. These transmitter recognition sites are part of a more complex supramolecular structure termed transmitter receptor(s) which are located on the post and presynaptic component of the synaptic junction. There are two structurally and functionally distinct types of transmitter receptors (ionotropic and metabotropic) which differ by the mechanism attending the transduction of the transmitter signals into specific receptor responses. Both transduction mechanisms generate a metabolic event of high functional significance for the receiving neuron. When metabotropic receptors (Fig. 1) are activated by the transmitter, the catalytic activity of specific enzymes which are coupled to the receptor increases. Upon binding of the transmitter, greater amounts of the products of the receptor-linked enzyme (second messenger) are produced inside the receiving neuron. This messenger diffuses into accessible intraneuronal metabolic compartments of the receiving neuron thereby activating a specific key enzyme (often a protein kinase) which triggers a cascade of metabolic events.

ChemInform Abstract: CRYSTAL AND SUPRAMOLECULAR STRUCTURES OF COMPLEXES OF BF3NH3 AND BH3NH3 WITH 18‐CROWN‐6

Chemischer InformationsdienstVolume 15, Issue 20 Physical Organic Chemistry ChemInform Abstract: CRYSTAL AND SUPRAMOLECULAR STRUCTURES OF COMPLEXES OF BF3NH3 AND BH3NH3 WITH 18-CROWN-6 H. M. COLQUHOUN, H. M. COLQUHOUNSearch for more papers by this authorG. JONES, G. JONESSearch for more papers by this authorJ. M. MAUD, J. M. MAUDSearch for more papers by this authorJ. F. STODDART, J. F. STODDARTSearch for more papers by this authorD. J. WILLIAMS, D. J. WILLIAMSSearch for more papers by this author H. M. COLQUHOUN, H. M. COLQUHOUNSearch for more papers by this authorG. JONES, G. JONESSearch for more papers by this authorJ. M. MAUD, J. M. MAUDSearch for more papers by this authorJ. F. STODDART, J. F. STODDARTSearch for more papers by this authorD. J. WILLIAMS, D. J. WILLIAMSSearch for more papers by this author First published: May 15, 1984 https://doi.org/10.1002/chin.198420058AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume15, Issue20May 15, 1984 RelatedInformation