Unique Ring Research Articles

N-fused porphyrin with pyridinium side-arms: a new class of aromatic ligand with DNA-binding ability

N-fused porphyrin (NFP) is a porphyrin analogue with an 18π tetrapyrrolic macrocycle, in which a unique tripentacyclic ring is embedded. While the optical properties of NFP of absorbing and emitting near-infrared (NIR) light around 1000 nm are promising for its application to NIR technology, its unique structure is also attractive as a platform to construct a novel class of DNA-binding ligands. Herein, we have synthesized a water-soluble derivative of NFP (pPyNFP) possessing four cationic pyridinium substituents and examined its acid/base behaviors and interactions with various forms of DNAs in aqueous solution. pPyNFP interacts with ssDNA and dsDNA electrostatically. pPyNFP also interacts with a G-quadruplex DNA derived from the human telomeric sequence and causes a characteristic spectral change of the G-quadruplex DNA, which suggests that pPyNFP modulates the Na(+)-induced (2 + 2) antiparallel G-quadruplex to the all-parallel structure.

4,4′-Bis(2,2-diphenylvinyl)-1,1′-biphenyl

The title mol­ecule, C40H30, lies on an inversion center. The two unique phenyl rings form dihedral angles of 51.98 (8) and 67.58 (8)° with the essentially planar biphenyl unit [maximum deviation = 0.0360 (14) Å].

Cloning of the biosynthetic gene cluster for naphthoxanthene antibiotic FD-594 from Streptomyces sp. TA-0256

FD-594 is an unique pyrano[4',3':6,7]naphtho[1,2-b]xanthene polyketide with a trisaccharide of 2,6-dideoxysugars. In this study, we cloned the FD-594 biosynthetic gene cluster from the producer strain Streptomyces sp. TA-0256 to investigate its biosynthesis. The identified pnx gene cluster was 38143 bp, consisting of 40 open reading frames, including a minimal PKS gene, TDP-olivose biosynthetic genes, two glycosyltransferase genes, two methyltransferase genes and many oxygenase/reductase genes. Most of these enzymes coded in the pnx cluster were reasonably assigned to a plausible biosynthetic pathway for FD-594, in which an unique ring opening process via Baeyer-Villiger-type oxidation catalyzed by a putative flavin adenine dinucleotide (FAD)-dependent monooxygenase, is speculated to lead to the unique xanthene structure. To clarify the involvement of pnx genes in the FD-594 biosynthesis, a glycosyltransferase, PnxGT2, and a methyltransferase, PnxMT2, were characterized enzymatically with the recombinant proteins expressed in Escherichia coli. As a result, PnxGT2 catalyzed the triple olivose transfers to the FD-594 aglycon with TDP-olivose as the glycosyl donor to afford triolivoside. Surprisingly, in the PnxGT2 enzymatic reaction, tetraolivoside and pentaolivoside were significantly detected along with the expected triolivoside. To our knowledge, PnxGT2 is the first contiguous oligosaccharide-forming glycosyltransferase in secondary metabolism. Furthermore, addition of PnxMT2 and S-adenosyl-L-methionine into the PnxGT2 reaction mixture afforded natural FD-594 to confirm that the PnxGT2 reaction product was the expected regiospecifically glycosylated compound. Consequently, the identified pnx gene cluster appears to be involved in FD-594 biosynthesis.

Lyconadins C and F, new Lycopodium alkaloids from Lycopodium complanatum

New Lycopodium alkaloids, lyconadins C (1) and F (2), were isolated from the club moss Lycopodium complanatum. Lyconadin C (1) is a new C16N2-type Lycopodium alkaloid possessing unique fused-tetracyclic ring system consisting of a cycloheptene ring fused to a decahydroquinoline and pyridone rings. Lyconadin F (2) possesses a primary amide moiety in its molecular, which is the first example of Lycopodium alkaloids. Biogenetically, lyconadins C (1) and F (2) might be related to lyconadins A (4) and B (5). The structures and relative stereochemistry of 1 and 2 were elucidated on the basis of spectroscopic data. The absolute stereochemistry of 2 was elucidated by chemical correlations with lyconadin B (5) through hemiaminal form of lyconadin F (3).

Site fidelity and longevity of the Karoo Thrush Turdus smithi (Bonaparte 1850) in an urban environment

Turdus smithi, formerly a subspecies of T. olivaceus, has been elevated to species status, resulting in a void in our knowledge on this species. Although both T. smithi and T. olivaceus are common garden birds throughout their ranges, most studies to date have focused on T. olivaceus. These studies found that T. o. olivaceus reach ages in excess of 11 years and maintain territories of 10 000–13 000 m2. The present study investigated site fidelity and longevity of an urban T. smithi population at the University of Pretoria main campus in Gauteng. Thrushes were ringed with unique colour ring combinations and identified by resighting them later. We found that T. smithi individuals have high site fidelity, with some thrushes being present in their same home ranges nearly nine years after being ringed, and suspect that they occupied these territories continuously between ringing and resighting. We found that T. smithi maintain larger home ranges than T. olivaceus individuals, and have a similar maximum longevity. We propose that adult thrushes are able to persist in a given home range because they are able to avoid resident predators, e.g. feral cats Felis sylvestris catus, by accurately predicting their hunting strategies.

A novel ring-expanded product with enhanced tyrosinase inhibitory activity from classical Fe-catalyzed oxidation of rosmarinic acid, a potent antioxidative Lamiaceae polyphenol

The iron-ion catalyzed oxidation of the ethanol solution of rosmarinic acid, a potent antioxidant polyphenol of Lamiaceae (Labiatae) plants, afforded a highly tyrosinase-inhibitory active product. The structure of the active product in the oxidation product mixture was determined using extensive NMR spectroscopy to have a novel oxygen-containing seven-membered ring system. The formation mechanism of the unique ring structure from the catechol part of the rosmarinic acid was proposed.

Probing the active-site requirements of human intestinal N-terminal maltase-glucoamylase: Synthesis and enzyme inhibitory activities of a six-membered ring nitrogen analogue of kotalanol and its de-O-sulfonated derivative

In order to probe the active-site requirements of the human N-terminal subunit of maltase-glucoamylase (ntMGAM), one of the clinically relevant intestinal enzymes targeted for the treatment of type-2 diabetes, the syntheses of two new inhibitors are described. The target compounds are structural hybrids of kotalanol, a naturally occurring glucosidase inhibitor with a unique five-membered ring sulfonium-sulfate inner salt structure, and miglitol, a six-membered ring antidiabetic drug that is currently in clinical use. The compounds comprise the six-membered ring of miglitol and the side chain of kotalanol or its de-O-sulfonated derivative. Inhibition studies of these hybrid molecules with human ntMGAM indicated that they are inhibitors of this enzyme with comparable K i values to that of miglitol (kotalanol analogue: 2.3 ± 0.6 μM; corresponding de-O-sulfonated analogue: 1.4 ± 0.5 μM; miglitol: 1.0 ± 0.1 μM). However, they are less active compared to kotalanol ( K i = 0.19 ± 0.03 μM). These results suggest that the 3T 2 enzyme-bound conformation of the five-membered thiocyclitol moiety of the kotalanol class of compounds more closely resembles the 4H 3 conformation of the proposed transition state for the formation of an enzyme–substrate covalent intermediate in the glycosidase hydrolase family 31 (GH31)-catalyzed reaction.

Integral domains having a unique Kronecker function ring

We study the class of integrally closed domains having a unique Kronecker function ring, or equivalently, domains in which the completion (or b -operation) is the only e.a.b star operation of finite type. Such domains are a generalization of Prüfer domains and have fairly simple sets of valuation overrings. We give characterizations by studying valuation overrings and integral closure of finitely generated ideals. We provide new examples of such domains and show that for several well-known classes of integral domains the property of having a unique Kronecker function ring makes them fall into the class of Prüfer domains.

On Rings Whose Reflexive Ideals are Principal

We call a prime Noetherian maximal order R a pseudo-principal ring if every reflexive ideal of R is principal. This class of rings is a broad class properly containing both prime Noetherian pri-(pli) rings and Noetherian unique factorization rings (UFRs). We show that the class of pseudo-principal rings is closed under formation of n × n full matrix rings. Moreover, we prove that if R is a pseudo-principal ring, then the polynomial ring R[x] is also a pseudo-principal ring. We provide examples to illustrate our results.

Protulactones A and B: Two New Polyketides from the Marine-derived Fungus Aspergillus sp. SF-5044

Protulactones A (1) and B (2), two new polyketide-derived fungal metabolites, have been isolated from an EtOAc extract of the marine-derived fungus Aspergillus sp. SF-5044 by various chromatographic methods. The structures of 1 and 2 were mainly determined by analysis of the NMR spectroscopic data and MS data, along with chemical methods such as Mosher method. Protulactones A (1) and B (2) are new members of polyketide-derived secondary metabolites, possessing unique ring systems among the fungal metabolites produced by the genus Aspergillus.

Holed nanostructures formed by aluminum droplets on a GaAs substrate

We have studied the morphology evolution of holed nanostructures formed by aluminum droplet epitaxy on a GaAs surface. Unique outer rings with concentric inner holed rings were observed. Further, an empirical equation to describe the size distribution of the outer rings in the holed nanostructures has been established. The contour line generated by the equation provides physical insights into quantum ring formation by droplets of group III materials on III–V substrates. Open image in new window

Digital system of invariant correlation to position and rotation

A new correlation digital system invariant to position and rotation is presented. This new algorithm requires low computational cost, because it uses uni-dimensional signatures (vectors). The signature of the target so like the signature of the object to be recognized in the problem image is obtained using a binary ring mask constructed based on the real positive values of the Fourier transform of the corresponding image. In this manner, each image will have one unique binary ring mask, avoiding in this form the relevant information leak. Using linear and non-linear correlations, this methodology is applied first in the identification of the alphabet letters in Arial font style and then in the classification of fossil diatoms images. Also, this system is tested using the diatom images with additive Gaussian noise. The non-linear correlation results were excellent, obtaining in this way a simple but efficient method to achieve rotation and translation invariance pattern recognition.

A selective turn-on fluorescent sensor for Cu(II) and its application in imaging in living cells

A novel fluorescent sensor 4-((E)-(N-(rhodamine-6G)lactam-ethylenediamineimino)methyl)benzene-1,3-diol (1), which has a unique spirolactam ring formation, show a reversible, selective, and sensitive fluorescence enhancement response to Cu(II) at biological pH value for practical use. Also, the selectivity of this system for Cu(II) over other metal ions is remarkably high, and its sensitivity is below 2ppb in methanol solutions. Furthermore, its high cell permeability grants the access to employ 1 as Cu(II) detector in living cells.

Chloramultiols A−F, Lindenane-Type Sesquiterpenoid Dimers from Chloranthus multistachys

Six new highly complex lindenane-type sesquiterpenoid dimers, chloramultiols A-F (1-6), along with six known analogues, were isolated from the whole plant of Chloranthus multistachys. The structures of 1-6 were elucidated on the basis of mass spectrometry (MS) and 1D and 2D NMR spectroscopic analysis. Among them, compounds 1 and 6 contain a unique 18-membered macrocyclic triester ring. All compounds isolated were evaluated for the inhibition of the growth of five tumor cell lines.

Unprecedented 1,3-Dipolar Cycloaddition: From 1,4,5,8-Naphthalene Bisimides to a New Heterocyclic Skeleton

1,4,5,8-Naphthalene bisimides react as dipolarophiles with in situ formed azomethine ylides. Double 1,3-dipolar cycloaddition is followed by unique ring rearrangement and leads to the formation of two six-membered rings. The formation of hexacyclic products is rationalized based on DFT calculations.

Asymmetric total synthesis of vindoline.

A concise asymmetric total synthesis of (-)-vindoline (1) is detailed based on a tandem intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole inspired by the natural product structure, in which the tether linking the initiating dienophile and oxadiazole bears a chiral substituent that controls the facial selectivity of the initiating Diels-Alder reaction and sets absolute stereochemistry of the remaining six stereocenters in the cascade cycloadduct. This key reaction introduces three rings and four C-C bonds central to the pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural product in a single step. Implementation of the approach also required the development of a unique ring expansion reaction to provide a six-membered ring suitably functionalized for introduction of the Delta (6, 7)-double bond found in the core structure of vindoline and defined our use of a protected hydroxymethyl group as the substituent used to control the stereochemical course of the cycloaddition cascade.

Pisiferdiol and pisiferic acid isolated from Chamaecyparis pisifera activate protein phosphatase 2C in vitro and induce caspase-3/7-dependent apoptosis via dephosphorylation of Bad in HL60 cells

Protein phosphatase 2C (PP2C) dephosphorylates a broad range of substrates and regulates apoptosis, stress response and growth-related pathways. In the course of screening for PP2C activators from natural sources, we isolated abietane-type diterpenes, pisiferdiol and pisiferic acid from Chamaecyparis pisifera. Pisiferdiol having a unique seven-membered ring showed more specific PP2C activation activity (1.3-fold at 100 microM) than pisiferic acid having a normal six-membered ring and oleic acid, which is known to activate PP2C. Pisiferdiol and pisiferic acid showed mixed-type activation with respect to alpha-casein, and this differed from the non-competitive activation of oleic acid in vitro. In vivo, the cytotoxicity of pisiferdiol toward human promyelocytic leukemia cell line HL60 with an IC(50) value of 18.3 microM was 2-fold and 7-fold stronger than those of pisiferic acid and oleic acid, and pisiferdiol induced apoptosis through a caspase 3/7-dependent mechanism involving the dephosphorylation of Bad(1), which is a PP2C substrate. We thus conclude that pisiferdiol and pisiferic acid are novel PP2C activators, and the more specific activator, pisiferdiol, may be a useful chemical probe to study PP2C-mediated signaling pathways, and a lead compound for pharmaceutical agents.

A new variant of saponite‐rich micrometeorites recovered from recent Antarctic snowfall

Abstract– Eight saponite‐rich micrometeorites with very similar mineralogy were found from the recent surface snow in Antarctica. They might have come to Earth as a larger meteoroid and broke up into pieces on Earth, because they were recovered from the same layer and the same location of the snow. Synchrotron X‐ray diffraction (XRD) analysis indicates that saponite, Mg‐Fe carbonate, and pyrrhotite are major phases and serpentine, magnetite, and pentlandite are minor phases. Anhydrous silicates are entirely absent from all micrometeorites, suggesting that their parental object has undergone heavy aqueous alteration. Saponite/serpentine ratios are higher than in the Orgueil CI chondrite and are similar to the Tagish Lake carbonaceous chondrite. Transmission electron microscope (TEM) observation indicates that serpentine occupies core regions of fine‐grained saponite, pyrrhotite has a low‐Ni concentration, and Mg‐Fe carbonate shows unique concentric ring structures and has a mean molar Mg/(Mg + Fe) ratio of 0.7. Comparison of the mineralogy to hydrated chondrites and interplanetary dust particles (IDPs) suggests that the micrometeorites are most similar to the carbonate‐poor lithology of the Tagish Lake carbonaceous chondrite and some hydrous IDPs, but they show a carbonate mineralogy dissimilar to any primitive chondritic materials. Therefore, they are a new variant of saponite‐rich micrometeorite extracted from a primitive hydrous asteroid and recently accreted to Antarctica.

Low grade mosaic for a complex supernumerary ring chromosome 18 in an adult patient with multiple congenital anomalies

BackgroundSeveral cases have been reported of patients with a ring chromosome 18 replacing one of the normal chromosomes 18. Less common are patients with a supernumerary ring chromosomes 18. High resolution whole genome examination in patients with multiple congenital abnormalities might reveal cytogenetic abnormalities of an unexpected complexity.ResultsWe report a 24 years old male patient with lower spinal anomalies, hypospadia, bifid scrotum, cryptorchism, anal atresia, kidney stones, urethra anomalies, radial dysplasia, and a hypoplastic thumb. Some of the anomalies overlap with the VACTERL association. Chromosome analysis of cultured peripheral blood lymphocytes revealed an additional ring chromosome in 13% of the metaphases. Both parents had a normal karyotype, demonstrating the de novo origin of this ring chromosome. FISH analysis using whole chromosome paints showed that the additional chromosomal material was derived from chromosome 18. Chromosome analysis of cultured fibroblasts revealed only one cell with the supernumerary ring chromosome in the 400 analyzed. To characterize the ring chromosome in more detail peripheral blood derived DNA was analyzed using SNP-arrays. The array results indicated a 5 Mb gain of the pericentromeric region of chromosome 18q10-q11.2. FISH analysis using BAC-probes located in the region indicated the presence of 6 signals on the r(18) chromosome. In addition, microsatellite analysis demonstrated that the unique supernumerary ring chromosome was paternally derived and both normal copies showed biparental disomy.ConclusionsWe report on an adult patient with multiple congenital abnormalities who had in 13% of his cells a unique supernumerary ring chromosome 18 that was composed of 6 copies of the 5 Mb gene rich region of 18q11.

FLASH, a Proapoptotic Protein Involved in Activation of Caspase-8, Is Essential for 3′ End Processing of Histone Pre-mRNAs

3' end processing of histone pre-mRNA requires U7 snRNP, which binds downstream of the cleavage site and recruits the endonuclease CPSF-73. U7 snRNP contains a unique Sm ring in which the canonical SmD2 protein is replaced by Lsm11. We used the yeast two-hybrid system to identify binding partners of Lsm11 and selected the proapoptotic protein FLASH. Human FLASH interacts with Lsm11 in vitro and stimulates 3' end processing of histone pre-mRNA in mammalian nuclear extracts. We also identified the FLASH ortholog in Drosophila and demonstrate that it interacts with Lsm11 in vitro and in vivo. Drosophila FLASH localizes to histone locus bodies, and its depletion from fly cells inhibits U7-dependent processing, resulting in polyadenylation of histone mRNAs. These results demonstrate that FLASH is an essential factor required for 3' end maturation of histone mRNAs in both vertebrates and invertebrates and suggest a potential link between this process and apoptosis.