Phenol-derived electrophiles are favorable substrates because phenols are naturally abundant or can be readily prepared from other aromatic compounds. However, the cleavage of aromatic C-O bonds is a great challenge because of their high energy. K(2)CO(3)-catalyzed intramolecular cyclization of 1-(2-alkoxyphenyl)-3-akylpropane-1,3-dione and 3-(alkylimino)-1-(2-methoxyphenyl)-2-methylpropan-1-one derivatives via the selective cleavage of aromatic C-O ...

Density functional theory computations have been carried out to study the mechanism of hydrogenation-based transformation of dimethyl carbonate to methanol, catalyzed by Ru(II)PNN catalyst. The energetic results show that the catalytic transformation includes three sequential stages consistently involving the catalyst: (stage I) transformation of dimethyl carbonate (3) to methyl formate ...

The kink turn (k-turn) is a frequently occurring motif, comprising a bulge followed by G•A and A•G pairs that introduces a sharp axial bend in duplex RNA. Natural k-turn sequences exhibit significant departures from the consensus, including the A•G pairs that form critical interactions stabilizing the core of the structure. ...

Doubling up: Two CH bond activations took place efficiently upon treatment of 1 with a rhodium catalyst to form dehydrogenative cyclization products 2. Furthermore, 3 undergoes similar cyclization and subsequent decarboxylation through the cleavage of two CH bonds and one CC bond. Both reactions provide straightforward routes to the fluorene ...

In comparison to the different fermentation modes for the production of acetone, butanol and ethanol (ABE) researched to date, the continuous fermentation is the most economically favored. Continuous fermentation with two or more reactor cascade is reported to be the most efficient as it results in a more stable solvent ...

By introducing an additional hydrogen bond to hydrogen bond interaction in the force field of the CSAW (Conditioned Self-Avoiding Walk) model, we investigate into the mechanism of antiparallel β-sheet formation based on the folding of a short polyalanine in gas phase. Through our numerical simulation, we detect the possible presence ...

We report on various nanocarbons formed from a unique structural pattern containing two pentagons, three hexagons, and two heptagons, resulting from local rearrangements around a divacancy in pristine graphene, or nanotubes. This defect can be inserted in sheets or tubes either individually or as extended defect lines. Sheets or tubes ...

The cocrystal formation of indomethacin (IMC) and saccharin (SAC) by mechanical cogrinding or thermal treatment was investigated. The formation mechanism and stability of IMC-SAC cocrystal prepared by cogrinding process were explored. Typical IMC-SAC cocrystal was also prepared by solvent evaporation method. All the samples were identified and characterized by using ...

The eggs of the mosquitoAedes aegyptipossess the ability to undergo an extended quiescence hosting a fully developed 1(st) instar larvae within the chorion. As a result of this life history traitpharate larvae can withstand months of quiescence inside the eggwhere they depend on stored maternal reserves.A. aegypti mosquitoes are frequently ...

Use of modified atmospheres with depleted O(2) and/or elevated CO(2) is an environmentally friendly alternative to currently used fumigants for control of stored grain insect pests. In the present study, we examined the impact ofhypoxia and hypercapnia on cowpea bruchids(Callosobruchusmaculatus), a storage pest of cowpea and other legumes. Two O(2)/CO(2)combinationswere ...

Measurements of normoxic, hypoxic (15% or 10% O(2)) and post-hypoxic oxygen consumption ( [Formula: see text] ) were conducted in chicken embryos every other day between embryonic day 3 (E3) and day 19 (E19), out of a total embryogenic period of 20.5 days. The results indicated that, irrespective of age, ...

Urban stormwater runoff is composed of a mixture of components, including polycyclic aromatic hydrocarbons, metals, deicing agents, and many others. The fate of these chemicals is often in stormwater detention ponds that are used by amphibians for breeding. Among aquatic organisms, the toxic mechanism for many metals involves interference with ...

Highly efficient C-O bond formation has been developed via carboxylic acid catalyzed reaction of 1-acetylcyclopropanecarboxamides with N-halosuccinimide (NXS), which provides strategically novel and atom-economic access to biologically important 5-amino-3(2H)-furanones. The mechanism of halonium-initiated tandem oxa-cyclization and ring opening of cyclopropane was proposed. A variety of nucleophiles were found to open ...

A series of chiral bicyclic [2.2.2]diene ligands gave variable ee values for Rh-catalysed asymmetric conjugate addition to an acyclic enone. The interplay between electronic and steric effects was captured in a robust predictive quantitative structure-property relationship (QSPR) model for enantioselectivity.

The authors describe the interaction of biological nanostructures formed by β(2) -microglobulin amyloid fibrils with three-dimensional silicon microstructures consisting in periodic arrays of vertical silicon walls (≈3 μm-thick) separated by 50 μm-deep air gaps (≈5 μm-wide). These structures are of great interest from a biological point of view since they ...

Complete removal of heavy metal from complex heavy-metal wastewater (CHMW) requires advanced technology. This study investigated the feasibility of a multi-staged ferrite process (MSFP) for treating CHMW, containing Cd, Cu, Pb, Cr, Zn, Ag, Hg, Ni, Sn and Mn. Our experimental results showed that most of the supernatants after conventional ...

Subtle non-covalent forces like π-π interactions play an import role in the folding of biological macromolecules such as DNA and proteins. We herein describe a system, where such interactions on the outside of a molecular capsule trigger a selective change of its structure as self-assembled receptor.

A number of platinum(II) complexes with ammine or 1R,2R-diaminocyclohexane as carrier ligands and 1-(methoxy-substituted benzyl) azetidine-3,3-dicarboxylate as leaving groups were synthesized and spectrally characterized. Biological evaluation in vitro showed that some of compounds showed positive antitumor activity. In particular, complex 3a, (1R,2R-diaminocyclohexane)[1-(3-methoxylbenzyl) azetidine-3,3-dicarboxylato)-O,O'] platinum(II), possessed a potent antitumor effect comparable ...

The plethora of actions of 1α,25-dihydroxyvitamin D(3), the active form of the seco-steroid hormone vitamin D, in various systems suggested wide clinical applications in treatments for renal osteodystrophy, osteoporosis, psoriasis, cancer, autoimmune diseases and prevention of graft rejection. However, the major side-effects of hypercalcemia of VDR ligands limit their use. ...

Analogs of 3'-amino-5-hydroxy-3,6,7,8,4'-pentamethoxy-flavone, a strongly cytotoxic and antimitotic semisynthetic flavone, were synthesized in the aurone, isoflavone and isoflavanone series. Comparison of the biological activity of these new compounds with the reference showed a potent cytotoxicity only in the flavone series. Influence of the hydroxy group (at C-5 in flavones, at ...

Redox reactions of tyrosine play key roles in many biological processes, including water oxidation and DNA synthesis. We first review the redox properties of tyrosine (and other phenols) in small molecules and related polypeptides, then report work on (H20)/(Y48)-modified Pseudomonas aeruginosa azurin. The crystal structure of this protein (1.18Å resolution) ...

Two β-sheet arrangements: Polyalanines have been shown to adopt two different antiparallel crystal packing arrangements, depending on the length of the polymers. Short polymers that contain six alanine residues or fewer adopt a rectangular packing arrangement, whereas longer polymers are packed in a staggered pattern. The elucidation of these structures ...

The importance of noncovalent interactions in the realm of biological materials continues to inspire efforts to create artificial supramolecular polymeric architectures. These types of self-assembled materials hold great promise as environmentally stimuli-responsive materials because they are capable of adjusting their various structural parameters, such as chain length, architecture, conformation, and ...

We report here an exhaustive and complete conformational study on the conformational potential energy hypersurface (PEHS) of dopamine (DA) interacting with the dopamine D2 receptor (D2-DR). A reduced 3D model for the binding pocket of the human D2-DR was constructed based on the theoretical model structure of bacteriorhodopsin. In our ...

Nitric oxide plays an important role in various biological processes, such as neurotransmission, blood pressure control, immunological responses, and antioxidant action. The control of its local concentration, which is crucial for obtaining the desired effect, can be achieved with exogenous NO-carriers. Coordination compounds, in particular ruthenium(III) and (II) amines, are ...

The anaerobic oxidation of methane (AOM) with sulphate, an area currently generating great interest in microbiology, is accomplished by consortia of methanotrophic archaea (ANME) and sulphate-reducing bacteria. The enzyme activating methane in methanotrophic archaea has tentatively been identified as a homologue of methyl-coenzyme M reductase (MCR) that catalyses the methane-forming ...

The growing interest in1α,25(OH)(2)D(3), the hormonally active form of vitamin D(3), has prompted numerous efforts to synthesize vitamin D analogs as potential therapeutic agents, and some of these are already on the market and in clinical development. Although most vitamin D preparations developed thus far have focused on side-chain modifications, ...

The crystal structure of the interferon-induced member of the dynamin family MxA presented by Gao et al. (2011) in this issue of Immunity reveals the molecule's higher-order structure, thereby providing insight into the protein's antiviral action as a molecular machine.

The single handedness of biological molecules has fascinated scientists and laymen alike since Pasteur's first painstaking separation of the enantiomorphic crystals of a tartrate salt over 150 years ago. More recently, a number of theoretical and experimental investigations have helped to delineate models for how one enantiomer might have come ...

Ringfused bicyclic 2-pyridones exhibit interesting biological properties against pili assembly in uropathogenic E. coli1 as well as curli formation2. In the strive for new ring-fused central fragments highly selective synthetic routes to the 2-furanone or 2-pyrone containing tricyclic scaffolds 1 and 2 have been developed.

Psychotripine, a trimeric pyrroloindoline derivative with an unprecedented hendecacyclic system bearing a hexahydro-1,3,5-triazine unit, was isolated from the leaves of Psychotria pilifera. The structure was elucidated on the basis of spectroscopic and quantum theory. A possible biogenesis was also postulated.

A review of thermodynamic, materials science, and rheological liquid crystal models is presented and applied to a wide range of biological liquid crystals, including helicoidal plywoods, biopolymer solutions, and in-vivo liquid crystals. The distinguishing characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials ...

Calocetriol (1), diacetylcalocediol (2), and ferrugimenthenol (3) were isolated from the bark of Calocedrus macrolepis var. formosana. Among them, 1 and 2 are secoabietane-type diterpenoids, and 3, with a novel C(20) C(10) skeleton, is classified as a meroterpenoid. The structures of 1-3 were elucidated by spectroscopic analyses, and their biological ...

The role of agostic bonds in chemistry is highlighted. In particular, attention is given to the origin of the term, methods of investigations and their function in chemistry.

Elucidating the underlying molecular mechanisms of protein folding and function is a very exciting and active research area, but poses significant challenges. This is due in part to the fact that existing experimental techniques are incapable of capturing snapshots along the 'reaction coordinate' in question with both sufficient spatial and ...

G protein-coupled receptors (GPCRs) are intensely studied as drug targets and for their role in signaling. With the determination of the first crystal structures, interest in structure-based ligand discovery increased. Unfortunately, for most GPCRs no experimental structures are available. The determination of the D(3) receptor structure and the challenge to ...

Osteoporosis represents a major public health problem and increases patient morbidity through its association with fragility fractures. Among the different treatments proposed, strontium-based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk. While the localization of Sr(2+) cations in the bone matrix ...

The sorbicillinoids are a family of hexaketide metabolites that have been isolated from a variety of fungal sources, collected from both marine and terrestrial sources. Since 1948, the family has grown in size to include over 50 members, many of which have complex, highly oxygenated, bicyclic and tricyclic frameworks. In ...

This paper reviews the progress made recently in synthesis and applications of spherical silica micro/nanomaterials with multilevel (hierarchical) structures. The spherical silica micro/nanomaterials with hierarchical structures are classified into four main structural categories that include (1) hollow mesoporous spheres, (2) core-in-(hollow porous shell) spheres, (3) hollow spheres with multiple porous ...

Controlled hydrolysis of donor-substituted titanium-salan complexes led to the formation of well-defined dinuclear complexes. Structure determination by means of X-ray and NMR-studies revealed the presence of a single μ-oxo bridge and one labile alkoxide ligand per titanium center. Concomitant cytotoxicity assays of the isolated dinuclear complexes showed cytotoxicities in the ...

A novel facile synthesis led to pyridine-2-one target structures of which first series with varying substituents have been yielded and biologically characterized as novel multidrug resistance (MDR) modulators inhibiting P-glycoprotein (P-gp). Structure-activity relationships prove a dependency of the MDR-modulating properties from the kind and positioning of hydrogen bond acceptor functions ...

The crystal structure and pro-inflammatory property of a lectin from the seeds of Dioclea wilsonii (DwL) were analyzed to gain a better understanding of structure/function relationships of Diocleinae lectins. Following crystallization and structural determination by standard molecular replacement techniques, DwL was found to be a tetramer based on PISA analysis, ...

Materials science will play a key role in the further development of emerging solutions for the increasing problems of energy and environment. Materials found in nature have many inspiring structures, such as hierarchical organizations, periodic architectures, or nanostructures, that endow them with amazing functions, such as energy harvesting and conversion, ...

The anticancer prodrug 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS119) selectively releases a short-lived cytotoxin following enzymatic reduction in hypoxic environments found in solid tumors. KS119, in addition to two enantiomers, has two stable atropisomers (conformers differing in structure owing to hindered bond rotation) that interconvert at 37 °C in aqueous solution by first-order kinetics ...

Two dinuclear oxo-bridged organogold(iii) compounds, namely [(N,N,C)(2)Au(2)(μ-O)][PF(6)](2) (with N,N,CH = 6-(1-methylbenzyl)-2,2'-bipyridine, Au(2)O1; or 6-(1,1-dimethylbenzyl)-2,2'-bipyridine, Au(2)O2), were previously prepared and characterised. Their solution chemistry under physiological-like conditions has been investigated here as well as their in vitro antiproliferative properties. Notably, these compounds reveal a marked redox stability even in the presence ...

In the title hydrated mol-ecular salt, C(18)H(23)N(2) (+)·C(6)H(4)ClO(3)S(-)·H(2)O, which shows moderate biological activity against methicillin-resistant Staphylococcus aureus (MRSA), one ethyl group of the 2-[4-(diethyl-amino)-styr-yl]-1-methyl-pyridinium cation is disordered over two orientations in a 0.604 (13):0.396 (13) ratio. The main part of the cation is nearly planar with a dihedral angle of 4.50 (10)° between ...

Glutathionylcobalamin (GSCbl) is a unique, biologically relevant cobalamin featuring an axial Co-S bond that distinguishes it from the enzymatically active forms of vitamin B(12), which possess axial Co-C bonds. GSCbl has been proposed to serve as an intermediate in cobalamin processing and, more recently, as a therapeutic for neurological disorders ...

The introduction of multifunctionalities for tumour targeting is becoming a popular strategy toward the development of new therapeutic agents. In particular, the multifaceted potential of ruthenium(ii)-arene complexes show great promise as chemotherapeutics. An ever-increasing number of papers dealing with the integration of ruthenium complexes with biologically active molecules to derive ...

Gold complexes have been explored as metallodrugs with great potential applications as antitumoral agents. In particular, gold-phosphine derivatives seemed quite promising since the use of the antiarthritic auranofin drug (thiolate-Au-PEt(3) complex) presented also biological activity against different cancer cells. So, different auranofin analogues have been explored within this context and ...

Crystals of many important biological macromolecules diffract to limited resolution, rendering accurate model building and refinement difficult and time-consuming. We present a torsional optimization protocol that is applicable to many such situations and combines Protein Data Bank-based torsional optimization with real-space refinement against the electron density derived from crystallography or ...