Unique Ring Research Articles

Synthesis of Blue Emitting Alicyclic Polyimides using One-pot Alternating Copolymerization Method

A series of alternating copolyimides (altPIs) having highly blue fluorescing 9,10-diphenyl-anthracene units were synthesized and the photoluminescence of the altPIs were investigated. The alt-PIs were prepared by sequential addition of two diamines to a solution of spiroalicyclic tetracarboxylic dianhydride, rel[1R,5S,6R]-3-oxabicyclo[3.2.1]octane-2,4-dione-6-spiro-3--(tetrahydrofuran-2-,5--dione) (DAn), on the basis of the unique regioselective ring opening reactivity of DAn to the aromatic amines. The alternating structure of the polyimides was confirmed by comparison of its 1H NMR with that of the corresponding random counterparts. The altPIs showed glass transition temperature higher than 240°C. A 5% weight loss temperature was in a range of 335 to 376°C. The polyimides showed blue fluorescence (λmax = 435 to 436 nm) in DMSO solution with a fluorescence quantum yield of 0.64 to 0.77. In the film state, although small red shift was observed compared to the solution state, the altPIs gave blue emission (λmax = 437 to 447 nm).

QUANTUM UNIQUE FACTORISATION DOMAINS

We prove a general theorem showing that iterated skew polynomial extensions of the type that fit the conditions needed by Cauchon's deleting derivations theory and by the Goodearl–Letzter stratification theory are unique factorisation rings in the sense of Chatters and Jordan. This general result applies to many quantum algebras; in particular, generic quantum matrices and quantized enveloping algebras of the nilpotent part of a semisimple Lie algebra are unique factorisation domains in the sense of Chatters. The result also extends to generic quantum grassmannians (by using noncommutative dehomogenisation) and to the quantum groups 𝒪q (GLn) and 𝒪q (SLn).

Health Risk Behaviors In A Unique Population-First Ring Suburban Adolescents

This study aims to call attention to First Ring suburban communities as a unique and unrecognized population and to characterize health risk behaviors of adolescents within these communities. A risk behavior profile of the First Ring suburbs surrounding a large Midwestern city is presented and compared to the frequency of these behaviors in a national sample. In 2002, a representative sample of 3428 high school students from First Ring suburban communities in an urban county completed the Youth Risk Behavior Survey. A 20-item risk score composed of "current" risk behaviors was compiled in order to compare the relative number of risk behaviors exhibited by the First Ring schools to a 2001 national sample. Prevalence of individual behaviors was also determined and compared to data collected nationally. Prevalence was further subdivided by gender, race, and grade in order to explore risk groups within First Ring suburbs. Despite the perception that the "urbanization" of First Ring suburbs is synonymous with "urban" problems and risk behaviors, First Ring students reported significantly fewer current risk behaviors than did students nationally. Significant differences in behavior were found between First Ring and national gender and racial groups. Some patterns of behavior within gender and racial groups differed from national patterns. The commonly held presumption that First Ring suburbs are riskier for students due to increased urbanization of these communities appears unfounded. The contribution of these destructive misperceptions to social migration away from urban centers and the need for local data collection are discussed.

π-Bond cooperativity and anticooperativity effects in resonance-assisted hydrogen bonds (RAHBs)

Bond cooperativity effects, which are typical of ;resonant' chains or rings of pi-conjugated hydrocarbons, can also occur in hydrogen-bonded systems in the form of sigma-bond and pi-bond cooperativity or anticooperativity. sigma-Bond cooperativity is associated with the long chains of O-H...O bonds in water and alcohols while sigma-bond anticooperativity occurs when the cooperative chain is interrupted by a local defect reversing the bond polarity. pi-Bond cooperativity is the driving force controlling resonance-assisted hydrogen bonds (RAHBs), while pi-bond anticooperativity has never been considered so far and is investigated here by studying couples of hydrogen-bonded beta-enolone and/or beta-enaminone six-membered rings fused through a common C=O or C-C bond. The effect is studied by X-ray crystal structure determination of five compounds [(2Z)-1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione enol (1), (2Z)-1-(2-hydroxy-5-chlorophenyl)-3-phenyl-1,3-propanedione enol (2), (2Z)-1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione enol (3), (2Z)-1-(2-hydroxy-4-methyl-5-chlorophenyl)-3-phenyl-1,3-propanedione enol (4) and dimethyl(2E)-3-hydroxy-2-{[(4-chlorophenyl)amino]carbonyl}pent-2-enedioate (5)] and by extensive analysis of related fragments found in the CSD (Cambridge Structural Database). It is shown that fusion through the C=O bond is always anticooperative and such to weaken the symmetric O-H...O...H-O and N-H...O...H-N bonds formed, but not the asymmetric O-H...O...H-N bond. Fusion through the C-C bond may produce either cooperative or anticooperative hydrogen bonds, the former being more stable than the latter and giving rise to a unique resonance-assisted ten-membered ring running all around the two fused six-membered rings, which can be considered a type of tautomerism never described before.

Preparation of cyclic molecules bearing “strained” olefins using olefin metathesis

Recent advancements in metathesis catalyst design have allowed chemists to re-examine olefin metathesis as a route to systems bearing strained olefins embedded in their skeletons. Such ring systems include various azabicyclo [3.3.1] and [4.2.1] rings systems, the unique tricyclic ring system of the natural product ingenol, and strained macrocyclic systems exhibiting atropisomerism. Several examples of forming strained aromatic systems is also presented. The variety of different catalysts that have been developed allows for the possibility to select a catalyst having the necessary level of reactivity to access a strained system but also to avoid catalysts which may be so reactive as to favour ring-opening of the desired ring system.

Quest for the Rings. In Silico Exploration of Ring Universe To Identify Novel Bioactive Heteroaromatic Scaffolds

Bioactive molecules only contain a relatively limited number of unique ring types. To identify those ring properties and structural characteristics that are necessary for biological activity, a large virtual library of nearly 600 000 heteroaromatic scaffolds was created and characterized by calculated properties, including structural features, bioavailability descriptors, and quantum chemical parameters. A self-organizing neural network was used to cluster these scaffolds and to identify properties that best characterize bioactive ring systems. The analysis shows that bioactivity is very sparsely distributed within the scaffold property and structural space, forming only several relatively small, well-defined "bioactivity islands". Various possible applications of a large database of rings with calculated properties and bioactivity scores in the drug design and discovery process are discussed, including virtual screening, support for the design of combinatorial libraries, bioisosteric design, and scaffold hopping.

Manzamine B and E and ircinal A related alkaloids from an Indonesian Acanthostrongylophora sponge and their activity against infectious, tropical parasitic, and Alzheimer's diseases.

Four new manzamine-type alkaloids, 12,28-oxamanzamine E (2), 12,34-oxa-6-hydroxymanzamine E (3), 8-hydroxymanzamine B (5), and 12,28-oxaircinal A (11), were isolated from three collections of an Indonesian sponge of the genus Acanthostrongylophora together with 13 known manzamine alkaloids, ircinal A, ircinol A, xestomanzamine A, manzamines A, E, F, J, and Y, manadomanzamines A and B, neo-kauluamine, 8-hydroxymanzamine A, and manzamine A N-oxide. The structures of the new compounds were elucidated by means of 1D and 2D NMR spectroscopic methods. Three of these compounds (2, 3, and 11) possess a unique manzamine-type aminal ring system generated through an ether linkage between carbons 12-28 or between carbons 12-34. In the case of manzamine B and related metabolites, carbons 11 and 12 of the typical manzamine structure have an epoxide group and add to our growing understanding of manzamine structure-activity relationships (SAR) and metabolism. The bioactivity and SAR for a number of previously reported manzamine-related metabolites against malaria, leishmania, tuberculosis, and HIV-1 are also presented. Manzamine Y (9) showed significant inhibitory activity of GSK3, an enzyme implicated in Alzheimer's disease pathology. The toxicity of manzamine A and neo-kauluamine was evaluated against both medaka fry and eggs.

18-Deoxy-13β,14-dihydrolycoctam: the lycoctamone rearrangement confirmed

The structure of the title compound, C23H35NO4, contains a unique pentacyclic ring system wherein one cyclohexyl ring adopts a chair conformation, two cyclohexyl rings are in boat conformations, and a six-membered heterocyclic ring and a cyclopentyl ring are in envelope conformations. The structures of the lycoctamones, alpha,beta-unsaturated aldehydes produced by acid-catalyzed degradation of lactams of lycoctonine-type alkaloids, previously deduced from the results of extensive chemical investigations have been proven to be correct by the determination of the crystal structure of this compound.

4,4′-Bis(2,6-dichlorobenzylideneamino)biphenyl

The title molecule, C26H16Cl4N2, lies on a crystallographic inversion centre and is disordered. The dihedral angle between the two benzene rings of the central biphenyl unit is 34.4 (3)°. The unique benzene ring of the biphenyl group is essentially coplanar with the –C(H)=N– unit, whereas the 2,6-dichlorophenyl substituent is twisted with respect to it. The reason for the twisted conformation is attributed to steric crowding by the Cl atoms.

Dynamic molecular linkers of the genome: the first decade of SMC proteins

Structural maintenance of chromosomes (SMC) proteins are chromosomal ATPases, highly conserved from bacteria to humans, that play fundamental roles in many aspects of higher-order chromosome organization and dynamics. In eukaryotes, SMC1 and SMC3 act as the core of the cohesin complexes that mediate sister chromatid cohesion, whereas SMC2 and SMC4 function as the core of the condensin complexes that are essential for chromosome assembly and segregation. Another complex containing SMC5 and SMC6 is implicated in DNA repair and checkpoint responses. The SMC complexes form unique ring- or V-shaped structures with long coiled-coil arms, and function as ATP-modulated, dynamic molecular linkers of the genome. Recent studies shed new light on the mechanistic action of these SMC machines and also expanded the repertoire of their diverse cellular functions. Dissecting this class of chromosomal ATPases is likely to be central to our understanding of the structural basis of genome organization, stability, and evolution.

Strained, Stable 2‐Aza‐1‐Phosphabicyclo[n.1.0]alkane and ‐alkene Fe(CO)4 Complexes with Dynamic Phosphinidene Behavior

The synthesis of highly strained bicyclic phosphirane and phosphirene iron-tetracarbonyl complexes, that is, complexes with 2-aza-1-phosphabicyclo[n.1.0]alkanes and -alkenes (n = 3-5), is explored by using intramolecular cycloaddition of an in situ generated electrophilic phosphinidene complex, [R(iPr)NP=Fe(CO)(4)], to its C=C- and C[triple chemical bond]C-containing R substituent. Saturated bicyclic complexes 7 a-c with n = 4-2 are remarkably stable, as illustrated by the X-ray crystal structure for 7 b (n=3), yet all readily undergo retroaddition to react with phenylacetylene. Shuttling of the phosphinidene iron complex between two equivalent C=C groups is demonstrated for a 1-butene-substituted 2-aza-1-phosphabicyclo[3.1.0]hexane by selective (1)H NMR magnetization transfer from the phosphirane protons to the olefinic protons. Even the more strained unsaturated bicycles 17 a,b (n = 4,3) are surprisingly stable as illustrated by the X-ray crystal structure for 17 a (n = 4), but the smaller phosphabicyclo[3.1.0]hex-5-ene (17 c, n = 2) dimerizes to tricyclic 19 with a unique ten-membered heterocyclic ring; an X-ray crystal structure is reported. Like their saturated analogues also the bicyclic phosphirenes readily undergo retroaddition as shown by the reaction of their phosphinidene iron moiety with phenylacetylene.

Surface SN2 Reaction by H2O on Chlorinated Si(100)-2 × 1 Surface

The potential energy surfaces of one, two, and three water molecule sequential adsorptions on the symmetrically chlorinated Si(100)-2 x 1 surface were theoretically explored with SIMOMM:MP2/6-31G(d). The first water molecule adsorption to the surface dimer requires a higher reaction barrier than the subsequent second water molecule adsorption. The lone pair electrons of the incoming water molecule nucleophilically attack the surface Si atom to which the leaving Cl group is bonded, yielding an S(N)2 type transition state. At the same time, the Cl abstracts the H atom of the incoming water molecule, forming a unique four-membered ring conformation. The second water molecule adsorption to the same surface dimer requires a much lower reaction barrier, which is attributed to the surface cooperative effect by the surface hydroxyl group that can form a hydrogen bond with the incoming second water molecule. The third water molecule adsorption exhibits a higher reaction barrier than the first and the second water molecule adsorption channels but yields a thermodynamically more stable product. In general, it is expected that the surface Si-Cl bonds can be subjected to the substitution reactions by water molecules, yielding surface Si-OH bonds, which can be a good initial template for subsequent surface chemical modifications. However, oversaturations can be a competing side reaction under severe conditions, suggesting that the precise control of surface kinetic environments is necessary to tailor the final surface characteristics.

Radiation exposure from high-level radiation area and related mining and processing activities of Jos Plateau, central Nigeria

The Jos Plateau in central Nigeria is a high-radiation area, being the center of unique granitic alkaline ring complexes that are rich in accessory minerals of zircon, monazite, ilmenite, xenotime, thorite, and pyrochlore containing high concentrations of thorium and uranium. The several years of mining and processing of casseterite (tin ore) and columbite (niobium ore) in the Jos Plateau have generated large quantities of tailings that are rich in these radioactive minerals and are mostly dumped haphazardly in the environment. Radiation monitoring in the area and at some processing mills shows high levels of dose rate with values as high as 100 μSv h −1 for processed zircon. The in situ dose rate measurements for the public and workers showed that exposures significantly higher than the recommended values of 1 and 20 mSv year −1, respectively. Thoron ( 220Rn) and its short-lived decay products (Tn-d) exposure, long considered of low radiological significance in comparison to radon ( 222Rn) and decay products (Rn-d), are the most significant in the Jos area.

PF-AR NW14, a new time-resolved diffraction/scattering beamline

NW14 is a new insertion device beamline at the Photon Factory Advanced Ring (PF-AR), which is a unique ring with full-time single-bunched operation, aiming for timeresolved x-ray diffraction/scattering and XAFS experiments. The primary scientific goal of this beamline is to observe the ultrafast dynamics of condensed matter systems such as organic and inorganic crystals, biological systems and liquids triggered by optical pulses. With the large photon fluxes derived from the undulator, it should become possible to take a snapshoot an atomic-scale image of the electron density distribution. By combining a series of images it is possible to produce a movie of the photo-induced dynamics with 50-ps resolution. The construction of the beamline is being funded by the ERATO Koshihara Non-equilibrium Dynamics Project of the Japan Science and Technology Agency (JST), and the beamline will be operational from autumn 2005.

Hyers-Ulam-Rassias stability of Jordan homomorphisms on Banach algebras

We prove that a Jordan homomorphism from a Banach algebra into a semisimple commutative Banach algebra is a ring homomorphism. Using a signum effectively, we can give a simple proof of the Hyers-Ulam-Rassias stability of a Jordan homomorphism between Banach algebras. As a direct corollary, we show that to each approximate Jordan homomorphism from a Banach algebra into a semisimple commutative Banach algebra there corresponds a unique ring homomorphism near to.

The Unique Stacked Rings in the Nucleocapsid of the White Spot Syndrome Virus Virion Are Formed by the Major Structural Protein VP664, the Largest Viral Structural Protein Ever Found

One unique feature of the shrimp white spot syndrome virus (WSSV) genome is the presence of a giant open reading frame (ORF) of 18,234 nucleotides that encodes a long polypeptide of 6,077 amino acids with a hitherto unknown function. In the present study, by applying proteomic methodology to analyze the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of purified WSSV virions by liquid chromatography-mass spectrometry (LC-MS/MS), we found that this giant polypeptide, designated VP664, is one of the viral structural proteins. The existence of the corresponding 18-kb transcript was confirmed by sequencing analysis of reverse transcription-PCR products, which also showed that vp664 was intron-less. A time course analysis showed that this transcript was actively transcribed at the late stage, suggesting that this gene product should contribute primarily to the assembly and morphogenesis of the virion. Several polyclonal antisera against this giant protein were prepared, and one of them was successfully used for immunoelectron microscopy analysis to localize the protein in the virion. Immunoelectron microscopy with a gold-labeled secondary antibody showed that the gold particles were regularly distributed around the periphery of the nucleocapsid with a periodicity that matched the characteristic stacked ring subunits that appear as striations. From this and other evidence, we argue that this giant ORF in fact encodes the major WSSV nucleocapsid protein.

Steroids from the soft coral Dendronephthya sp.

Fifteen steroids were isolated from the soft coral Dendronephthya sp., of which five are determined as new compounds, namely (22 E)-3- O- β-formylcholest-5,22-diene ( 1), (22 E)-3- O- β-formyl-24-methyl-cholest-5,22-diene ( 2), 2-ethoxycarbonyl-2- β-hydroxy-A-nor-cholest-5-ene-4-one ( 3), (22 E)-2-ethoxycarbonyl-2- β-hydroxy-A-nor-cholest-5,22-diene-4-one ( 4), and (22 E)-2-ethoxycarbonyl-2- β-hydroxy-24-mthyl-A-nor-cholest-5,22-diene-4- one ( 5). 1 and 2 belonged to 3- O-formylated cholesterol analogues, and 3 to 5 are unique ring A-contracted steroids. Their structures were elucidated by extensive 2D NMR in association with IR, MS analysis.

Synthesis of Novel Fused Isoxazoles and Isoxazolines by Sequential Ugi/INOC Reactions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The quinoprotein dehydrogenases for methanol and glucose

This review summarises our current understanding of two of the main types of quinoprotein dehydrogenase in which pyrroloquinoline quinone (PQQ) is the only prosthetic group. These are the soluble methanol dehydrogenase and the membrane glucose dehydrogenase (mGDH). The membrane GDH has an additional N-terminal domain by which it is tightly anchored to the membrane, and a periplasmic domain whose structure has been modelled on the X-ray structure of the α-subunit of MDH which contains PQQ in the active site. This review discusses their structures and mechanisms, concentrating particularly on the pathways for electron transfer from the reduced PQQ, through the protein, to their electron acceptors. In MDH, this is the specific cytochrome c L, the electron transfer pathway probably involving the unique disulphide ring in the active site. By contrast, mGDH contains a permanently bound ubiquinone, which acts as a single electron carrier, mediating electron transfer through the protein to the membrane ubiquinone.

Synthetic studies of benzo[ b]pyrrolo[4,3,2- de][1,10]phenanthroline

6,11-Dihydrobenzo[ b]pyrrolo[4,3,2- de][1,10]phenanthroline-5,8-dione ( 6 ), which possesses a unique heterocyclic ring system similar to that in plakinidines A–D ( 1– 4 ), was synthesized from 2-acetyl-3′-nitrodiphenylamine ( 16 ) in nine steps.