1,217 research outputs found
Silver(I) Complexation of (Poly)aromatic Ligands. Structural Criteria for Depth Penetration into \u3cem\u3ecis\u3c/em\u3e-Stilbenoid Cavities
Silver(I) complexes with aromatic donors are thoroughly analyzed (with aid of the Cambridge Crystallographic Database) to identify the basic structural factors inherent to the bonding of an arene ligand. Most strikingly, the distance parameter d (which simply measures the normal separation of Ag from the mean aromatic plane) is singularly invariant at d = 2.41 ± 0.05 Å for all silver/arene complexes, independent of the hapticity (η1 or η2), hybridization, or multiple coordination. As such, a systematic series of stilbenoid ligands has been successfully designed to precisely modulate the penetration of silver(I) into the ligand cleft, and a multicentered poly(arene) ligand (X) designed to form a one-dimensional assembly of Ag/arene units. Simply stated, the depth penetration of silver(I) into the aromatic cavities of various cis-stilbenoid donors can be precisely predicted with a single parameter γ that measures the separation of the two cofacial aryl groups comprising the cleft. This simple geometric consideration must be taken into account in any successful design of novel (poly)aromatic ligands for silver(I) complexation to constitute new molecular architectures
Structure factor and thermodynamics of rigid dendrimers in solution
The ''polymer reference interaction site model'' (PRISM) integral equation
theory is used to determine the structure factor of rigid dendrimers in
solution. The theory is quite successful in reproducing experimental structure
factors for various dendrimer concentrations. In addition, the structure factor
at vanishing scattering vector is calculated via the compressibility equation
using scaled particle theory and fundamental measure theory. The results as
predicted by both theories are systematically smaller than the experimental and
PRISM data for platelike dendrimers.Comment: 7 pages, 5 figures, submitte
A Versatile Synthesis of Electroactive Stilbenoprismands for Effective Binding of Metal Cations
A versatile synthesis of a new class of polyaromatic receptors (stilbenoprismands) containing a Δ-shaped cavity similar to that of the π-prismand together with an intimately coupled electroactive stilbenoid moiety was accomplished via an efficient intramolecular McMurry coupling reaction. The presence of the Δ-shaped cavity in stilbenoprismands allows an efficient binding of a single silver cation as probed by 1H NMR spectroscopy. Electron-rich stilbenoprismands undergo a ready oxidation to their highly robust cation−radical and dicationic salts. X-ray structure determination of a representative dicationic stilbenoprismand showed that the charges were largely localized on the tetraarylethylene moiety, which results in a twisting of the ethylenic C═C bond by ∼35°. Moreover, the electronic coupling among the stilbenoid and π-prismand moieties in various stilbenoprismands was briefly probed by optical methods
Diversity of secondary metabolites from Genus Artocarpus (Moraceae)
Abstrak. Hakim A. 2010. Keanekaragaman metabolit sekunder Genus Artocarpus (Moraceae). Nusantara Bioscience 2:146-156.
Beberapa spesies dari genus Artocarpus (Moraceae) telah diteliti kandungan bahan alamnya. Metabolit sekunder yang berhasil diisolasi
dari genus Artocarpus terdiri dari terpenoid, flavonoid, stilbenoid, arilbenzofuran, neolignan, dan adduct Diels-Alder. Kelompok
flavonoid merupakan senyawa yang paling banyak ditemukan dari tumbuhan Artocarpus. Senyawa flavonoid yang telah berhasil
diisolasi dari tumbuhan Artocarpus memiliki kerangka yang beragam seperti calkon, flavanon, flavan-3-ol, flavon sederhana,
prenilflavon, oksepinoflavon, piranoflavon, dihidrobenzosanton, furanodihidrobenzosanton, piranodihidrobenzosanton, kuinonosanton,
siklolopentenosanton, santonolid, dihidrosanton.
Kata kunci: Artocarpus, Moraceae, flavonoid, Diels-Alder, metabolit sekunder
Structure and thermodynamics of platelet dispersions
Various properties of fluids consisting of platelike particles differ from
the corresponding ones of fluids consisting of spherical particles because
interactions between platelets depend on their mutual orientations. One of the
main issues in this topic is to understand how structural properties of such
fluids depend on factors such as the shape of the platelets, the size
polydispersity, the orientational order, and the platelet number density. A
statistical mechanics approach to the problem is natural and in the last few
years there has been a lot of work on the study of properties of platelet
fluids. In this contribution some recent theoretical developments in the field
are discussed and experimental investigations are described.Comment: 23 pages, 18 figure
Efficient Tree Tensor Network States (TTNS) for Quantum Chemistry: Generalizations of the Density Matrix Renormalization Group Algorithm
We investigate tree tensor network states for quantum chemistry. Tree tensor
network states represent one of the simplest generalizations of matrix product
states and the density matrix renormalization group. While matrix product
states encode a one-dimensional entanglement structure, tree tensor network
states encode a tree entanglement structure, allowing for a more flexible
description of general molecules. We describe an optimal tree tensor network
state algorithm for quantum chemistry. We introduce the concept of
half-renormalization which greatly improves the efficiency of the calculations.
Using our efficient formulation we demonstrate the strengths and weaknesses of
tree tensor network states versus matrix product states. We carry out benchmark
calculations both on tree systems (hydrogen trees and \pi-conjugated
dendrimers) as well as non-tree molecules (hydrogen chains, nitrogen dimer, and
chromium dimer). In general, tree tensor network states require much fewer
renormalized states to achieve the same accuracy as matrix product states. In
non-tree molecules, whether this translates into a computational savings is
system dependent, due to the higher prefactor and computational scaling
associated with tree algorithms. In tree like molecules, tree network states
are easily superior to matrix product states. As an ilustration, our largest
dendrimer calculation with tree tensor network states correlates 110 electrons
in 110 active orbitals.Comment: 15 pages, 19 figure
Molecular Recognition of NO/NO\u3csup\u3e+\u3c/sup\u3e via Multicenter (Charge-Transfer) Binding to Bridged Diarene Donors. Effect of Structure on the Optical Transitions and Complexation Thermodynamics
Bridged diarenes form very strong [1:1] complexes with nitrosonium/nitric oxide in which the NO moiety is optimally sandwiched in the cleft between a pair of cofacial aromatic rings which act as a molecular “Venus flytrap”. The spectral features of these associates are generally similar to those for [1:1] and [2:1] nitrosonium complexes with mononuclear alkyl-substituted benzenes, and they are appropriately described within the LCAO molecular-orbital methodology and the Mulliken (charge-transfer) formulation of donor/acceptor electronic transitions. The thermodynamics study indicates that the efficient binding is determined by (i) the close matching of the donor/acceptor redox potentials and (ii) the ability of bridged diarenes for multicentered interactions with a single NO moiety. The best fit of the electronic and structural parameters is provided by a calixarene host that allows the interacting centers to be arranged in a manner similar to those extant in [2:1] nitrosonium complexes with analogous (nonbridged) aromatic donors; this results in its very strong noncovalent binding with nitrosonium/nitric oxide with the formation constant of KB ≈ 108 M-1 and free-energy change of −ΔG° = 45 kJ mol-1. Such strong, selective, and reversible bindings of nitrosonium/nitric oxide by (cofacial) aromatic centers thus provide the basis for the development of efficient NO sensors/absorbents and also suggest their potential relevance to biochemical systems
Grapevine shoot extract rich in trans-resveratrol and trans-ε-viniferin: evaluation of their potential use for cardiac health
A grapevine shoot extract (GSE) was obtained using ultrasound-assisted extraction and characterized. The main phenolic constituents were identified as stilbenoids. Among them, trans-resveratrol and trans-ε-viniferin stood out. The GSE was administered to an isoproterenol-induced myocardial injury animal model. The extract alleviated the associated symptoms of the administration of the drug, i.e., the plasma lipid profile was improved, while the disturbed plasma ion concentration, the cardiac dysfunction markers, the DNA laddering, and the necrosis of myocardial tissue were diminished. This effect could be related to the anti-oxidative potential of GSE associated with its antioxidant properties, the increased levels of endogenous antioxidants (glutathione and enzymatic antioxidants), and the diminished lipid peroxidative markers in the heart. The results also revealed angiotensin-converting enzyme (ACE)-inhibitory activity, which indicated the potential of GSE to deal with cardiovascular disease events. This work suggests that not only trans-resveratrol has a protective role in heart function but also GSE containing this biomolecule and derivatives. Therefore, GSE has the potential to be utilized in the creation of innovative functional ingredients.Ministry of Science and Innovation (MCIN) of Spain for the Ramón y Cajal grant (RYC2020-030546-I/AEI/10.13039/501100011033). European Social Fund. “Programme of Requalification of the Spanish University System” 2021–2023—Margarita Salas. MCIN/AEI/10.13039/501100011033, grant PID2020-112594RB-C31, “ERDF A way of making Europe”. “Researchers Supporting Project (RSP2023R17) at King Saud University
Vitis OneGenE: a causality-based approach to generate gene networks in Vitis vinifera sheds light on the laccase and dirigent gene families
9openInternationalBothThe abundance of transcriptomic data and the development of causal inference methods have paved the way for gene network analyses in grapevine. Vitis OneGenE is a transcriptomic data mining tool that finds direct correlations between genes, thus producing association networks. As a proof of concept, the stilbene synthase gene regulatory network obtained with OneGenE has been compared with published co-expression analysis and experimental data, including cistrome data for MYB stilbenoid regulators. As a case study, the two secondary metabolism pathways of stilbenoids and lignin synthesis were explored. Several isoforms of laccase, peroxidase, and dirigent protein genes, putatively involved in the final oxidative oligomerization steps, were identified as specifically belonging to either one of these pathways. Manual curation of the predicted sequences exploiting the last available genome assembly, and the integration of phylogenetic and OneGenE analyses, identified a group of laccases exclusively present in grapevine and related to stilbenoids. Here we show how network analysis by OneGenE can accelerate knowledge discovery by suggesting new candidates for functional characterization and application in breeding programs.openPilati, Stefania; Malacarne, Giulia; Navarro-Payá, David; Tomè, Gabriele; Riscica, Laura; Cavecchia, Valter; Matus, José Tomás; Moser, Claudio; Blanzieri, EnricoPilati, S.; Malacarne, G.; Navarro-Payá, D.; Tomè, G.; Riscica, L.; Cavecchia, V.; Matus, J.T.; Moser, C.; Blanzieri, E
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