Urea Complexes Research Articles

애반딧불이(Luciola lateralis)에 대한 살충제와 비료의 독성평가

시판되는 살충제 10종과 비료 6종에 대하여 애반딧불이 각 태별(유충, 성충, 알) 독성평가를 실내실험을 수행하였다. 3령유충에 대한 독성은 MEP, PAP, Assit, Fenthion, Diazinon, Burofezin fenobucarb, Cartap Buprofezin, Thiamethoxam, Fipronil은 80.0%이상 사망율률 보인 반면, IGR(곤충성장 저해제)계통인 Tebufenozide은 33,3%의 낮은 사망률을 보였다. 공시약제인 Assit, Cartap Buprofezin, Fenthion, PAP에 대한 3령 유충의 <TEX>$LC_{50}$</TEX>값(반수치사량)은 각각 1.03 ppm, 1.90 ppm, 10.26 ppm, 0.98 ppm이었다. 알에 대한 영향은 매우 높은 독성을 보였다. 반면에 Tebufenozide은 100%의 부화율을 보였다. 공시비료인 요소, 유안, 염화가리, 용성인비, 복합비료(17-21-17), 규산질비료에 유충을 72시간 노출시켰을 경우 각각 27.3%, 56.7%, 73.3%, 0.0%, 0.0%, 0.0%의 독성을 보였다. Toxicity of 10 registered insecticides and 6 fertilizers were tested against <TEX>$3^{rd}$</TEX> larva and adults of Korean firefly, Luciola lateralis Motschulsky(Coleoptera: Lampyridae). All experiments were tested at the recommended concentration of each inescticides by producer. MEP, PAP, Acephate, Fenthion, and Diazinon, which were organophates, a mixtures combined with Burofezin fenobucarb, Cartap buprofezin, and Thiamethoxam(Neonicotinoids), Fipronil(Phenylpyrazoles) showed more 80.0% mortality on larva and adults of L. lateralis. However, tebufenozide(I.G.R) showed low mortality of 33.3%. <TEX>$LC_{50}$</TEX> (ppm) value of Assit, Cartap buprofezin, Fenthion and PAP were showed 1.03 ppm, 1.90 ppm, 10.26 ppm, 0.98 ppm, respectively, against <TEX>$3^{rd}$</TEX> larva of L. lateralis. Effects against eggs showed very high toxicity. Otherwise, tebufenozide(I.G.R) was showed hatchability of 100%. Toxicity of Urea fertilizer, Ammonium sulfate, Potassium chloride, Fused phosphate, Complex fertilizer and Silicate fertilizer were showed the mortality with 27.3%, 56.7%, 73.3%, 0.0%, 0.0%, 0.0%, respectively, when exposed 72 hrs after treatment.

Polymorphism of urea–barbituric acid co-crystals

The crystal structures of three polymorphs found for the addition complex of urea and barbituric acid are described and compared. Two polymorphs are monoclinic, space groups P2(1)/c and Cc, whereas the third is triclinic, P1. The displacement of electron density towards the mesomeric forms, corresponding to the tautomeric forms of higher stability, of the barbituric acid molecule seem to influence the type of hydrogen bonds formed, which in turn determines the different packing topology in the polymorphs. While the polymorphic forms can be easily differentiated at the first-level graph-set analysis of their hydrogen-bonding patterns, a higher-level analysis enables important features of the mutual spatial arrangement of the structural components to be revealed.

Characterization of the stable and metastable poly(ethylene oxide)–urea complexes in electrospun fibers

AbstractSolution electrospinning was used for the first time to prepare nanofibers of the stable (α) and metastable (β) complexes between poly(ethylene oxide) (PEO) and urea. Both types of fibers were highly crystalline and presented a large level of molecular orientation. Detailed characterization of the ill‐studied β complex was performed using wide angle X‐ray diffraction (WAXD), infrared spectroscopy, and differential scanning calorimetry (DSC). Results reveal that it possesses a 3:2 PEO:urea stoichiometry and suggest that it belongs to the orthorhombic system with a = 1.907 nm, b = 0.862 nm, and c = 0.773 nm. The PEO chains are oriented along the fiber axis and present a conformation significantly affected by strong hydrogen bonding with urea when compared with the pure polymer and the stable complex. A layered structure model is suggested for the metastable complex, in which the urea molecules would be arranged into a ribbon‐like structure intercalated between two PEO layers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1903–1913, 2008

Optimizing Conditions for the Purification of Linoleic Acid from Sunflower Oil by Urea Complex Fractionation

AbstractThe separation and purification of linoleic acid (LA) from sunflower seed oil by urea complex fractionation was studied. Crystallization reaction conditions of urea inclusion were optimized using the response surface method, and the optimal model was developed. Using the linear weighting method of the fitting model for optimization, the optimal balance between the purity and the recovery of LA was obtained. Under optimal conditions, the purity of LA was 87.8%, and the recovery was 83.4% at a urea‐to‐fatty acids ratio (w/w) of 0.94, 95% ethanol‐to‐urea (v/w) of 5.00, a crystallization temperature of 18.0 °C, and a crystallization time of 5.0 h. Verification results revealed that the predicted values from these models were reasonably close to the experimentally observed values.

Electrospinning and Characterization of the Stable and “Metastable” Self-Assembled Poly(ethylene oxide)-Urea Complexes

ABSTRACTSolution electrospinning was used to prepare fibers of both the stable – trigonal α and “metastable” – orthorhombic β complexes between poly(ethylene oxide) (PEO) and urea. The 300-800 nm fibers were highly crystalline and both types presented a relatively large level of molecular orientation. Characterization of the poorly-studied β complex was performed using wide-angle X-ray diffraction, infrared spectroscopy, optical microscopy and differential scanning calorimetry. It was shown that β complex possesses a 3:2 PEO:urea stoichiometry, in contrast with a previously suggested 1:1 molar ratio, and that the α inclusion complex keeps the 4:9 molar ratio as when prepared by the conventional co-crystallization method. A new structural model was suggested for the β complex, in which the unit cell would contain 12 PEO repeat units (4 chains in the ab plane with 3 repeat units along the c axis) and 8 urea molecules arranged in a ribbon-like structure and intercalated between the two PEO layers. This layer-structured β complex is quite different from the usual channel-like α inclusion complex and results in different phase transitional properties.

Temperature effect on the volume properties of a bisurea aqueous solutions

The densities of aqueous solutions of bisurea (2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione) were measured using a vibrating-tube densimeter at 288.15, 298.15, 308.15, and 318.15 K in the concentration range up to ∼3·10−3 moles of solute (1000 g of H2O)−1 with the error at most ±5· 10−6 g cm−3 (reproducibility up to 2·10−6 g cm−3). The limiting partial molar volume and expansibility of bisurea in water were calculated. The bicyclic molecules under study form in aqueous solution H-bonded hydrate complexes with rather high structure-packing density. These complexes are more subjected to the destroying effect of temperature than the corresponding urea complexes. The hydration of bisurea weakens with the temperature increase.

The origins of femtomolar protein-ligand binding: hydrogen-bond cooperativity and desolvation energetics in the biotin-(strept)avidin binding site.

The unusually strong reversible binding of biotin by avidin and streptavidin has been investigated by density functional and MP2 ab initio quantum mechanical methods. The solvation of biotin by water has also been studied through QM/MM/MC calculations. The ureido moiety of biotin in the bound state hydrogen bonds to five residues, three to the carbonyl oxygen and one for each--NH group. These five hydrogen bonds act cooperatively, leading to stabilization that is larger than the sum of individual hydrogen-bonding energies. The charged aspartate is the key residue that provides the driving force for cooperativity in the hydrogen-bonding network for both avidin and streptavidin by greatly polarizing the urea of biotin. If the residue is removed, the network is disrupted, and the attenuation of the energetic contributions from the neighboring residues results in significant reduction of cooperative interactions. Aspartate is directly hydrogen-bonded with biotin in streptavidin and is one residue removed in avidin. The hydrogen-bonding groups in streptavidin are computed to give larger cooperative hydrogen-bonding effects than avidin. However, the net gain in electrostatic binding energy is predicted to favor the avidin-bicyclic urea complex due to the relatively large penalty for desolvation of the streptavidin binding site (specifically expulsion of bound water molecules). QM/MM/MC calculations involving biotin and the ureido moiety in aqueous solution, featuring PDDG/PM3, show that water interactions with the bicyclic urea are much weaker than (strept)avidin interactions due to relatively low polarization of the urea group in water.

Phenanthroline-Derived Ratiometric Chemosensor for Ureas

The syntheses of 1,10-phenanthroline fluorophore-based chemosensor 7 and its truncated analog 9 are reported. Interactions of these compounds with urea, thiourea, 1,3-dimethylurea, tetrahydropyrimidin-2(1H)-one, imidazolidin-2-one, and selected uronium salts were assessed by three-dimensional excitation-emission spectroscopy, UV-vis absorbance, and fluorescence titrations. Chemosensor 7 was found to be capable of distinguishing between neutral ureas and their salts, by producing a different optical response for each type of compounds. The complexation of urea by 7 was also studied by selective-NOE 1H NMR, 13C NMR (using 13C-labeled guest), and MALDI-TOF mass spectrometry. In addition, we performed DFT calculations (B3LYP 3-21g** level) for structures of complexes of 7 with urea, imidazolidin-2-one, and tetrahydropyrimidin-2(1H)-one. Development of chemosensor 7-type compounds in conjunction with differential excitation-emission spectroscopy represents an important step toward the development of novel tools for ureas and their salts analysis.

Uso de Enzimas de Tipo Ureasa en el Tratamiento de Aguas Residuales con Alto Contenido en Nitrógeno Orgánico

Some bacterial stock of the urease enzymes producer family were used, with the purpose of treating an industrial wastewater with urea content coming from a industrial urea complex, to reduce the organic nitrogen content to ammonia. To accomplish this objectives, a characterization of the wastewater was done, to identifies the organic nitrogen concentration present in the wastewater, the bacteria source generating the urease enzyme for the waste treatment were identified, and the conditions for the growth of the bacteria were established in the lab. The results show that it is possible the biodegradation using the urease enzymes kind, like Klebsiella Pneumoniae and Proteus Mirabilis, hydrolyzing the urea to ammonia and water. The Proteus Mirabilis was able to degrade the organic nitrogen with a conversion higher than 90%. From the kinetic study, the biodegradation reaction is a first order reaction with a constant kinetics rate of 0,4195 h -1 at 37 o C.

Highly Oriented Electrospun Fibers of Self-Assembled Inclusion Complexes of Poly(ethylene oxide) and Urea

Highly Oriented Electrospun Fibers of Self-Assembled Inclusion Complexes of Poly(ethylene oxide) and Urea

Bis(formamidine–urea) Complexes of NiII and CuII:Synthesis, Characterization, and Reactivity

AbstractA novel chelating chiral bis(formamidine–urea) ligand was synthesized and used to prepare the corresponding NiII and CuII complexes. Spectroscopic and X‐ray crystallographic analysis of the former revealed that the urea moiety of the acyclic tetradentate ligand is deprotonated and binds to the square‐planar Ni2+ ion through amide nitrogen atoms. This complex showed quasi‐reversible redox behavior in cyclic voltammetry, with E1/2 = 640 mV vs. Cp2Fe+/Cp2Fe corresponding to the NiIII/NiII couple. The Cu complex was shown by EPR spectroscopy to also adopt a square‐planar geometry [g∥ = 2.25 (A∥ = 184 G), g⟂ = 2.06 at 6 K], and reduction was found to be irreversible, perhaps due to the rigid nature of the tetradentate ligand. The nickel complex was found to be a modestly active catalyst for epoxidation of electron‐richalkenes under Mukaiyama’s conditions, likely involving a radical mechanism. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2006)

A facile access to bridged 1,2,4-trioxanes

Bicyclo[3.2.1] type 1,2,4-trioxanes are readily synthesized from precursors that may form intramolecular hemiketals using UHP (H 2O 2–urea complex) as the source of the peroxy bond and p-TsOH or CSA as the catalyst. The ring closure through an intramolecular Michael addition occurred in a highly stereoselective way, giving only one diasteromer as shown by the NMR spectra.

Relative Delivery Efficiency and Convenience of Spray and Ointment Formulations of Papain/Urea/Chlorophyllin Enzymatic Wound Therapies

To determine the relative delivery efficiency and user preference for spray and ointment formulations containing papain, urea, and chlorophyllin copper complex sodium (papain/urea/chlorophyllin copper complex). Participants applied both a spray and 3 ointment formulations of papain/urea/chlorophyllin copper complex to identical wound models. The average amount of product used per application was determined by weighing the bottle or tube before the study and after completion of the study. Participants were also asked to fill out a questionnaire regarding their preferences for the two formulations. The amount of product used per wound application was 30% less with the spray formulation; resulting in 29% more wound applications per container. Over 80% of the study participants found the spray easier and quicker to use than the ointments. The spray formulation of papain/urea/chlorophyllin copper complex resulted in less product use per wound application than did 3 different ointment formulations. Participants expressed a favorable impression of practical benefits of the spray formulation including a reduced risk of wound contamination.

Urea Transport in Bacteria: Acid Acclimation by Gastric Helicobacter spp

Urea transporters in bacteria are relatively rare. There are three classes, the ABC transporters such as those expressed by cyanobacteria and Corynebacterium glutamicum, the Yut protein expressed by Yersinia spp and the UreI expressed by gastric Helicobacter spp. This review focuses largely on the UreI proton-gated channel that is part of the acid acclimation mechanism essential for gastric colonization by the latter. UreI is a six-transmembrane polytopic integral membrane protein, N and C termini periplasmic, and is expressed in all gastric Helicobacter spp that have been studied but also in Helicobacter hepaticus and Streptococcus salivarius. The first two are proton-gated, the latter is pH insensitive. Site-directed mutagenesis and chimeric constructs have identified histidines and dicarboxylic amino acids in the second periplasmic loop of H. pylori and the first loop of H. hepaticus UreI and the C terminus of both as involved in a hydrogen-bonding dependence of proton gating, with the membrane domain in these but not in the UreI of S. salivarius responding to the periplasmic conformational changes. UreI and urease are essential for gastric colonization and urease associates with UreI during acid exposure, facilitating activation of the UreA and UreB apoenzyme complex by Ni2+ insertion by the UreF-UreH and UreE-UreG assembly proteins. Transcriptome analysis of acid responses of H. pylori also identified a cytoplasmic and periplasmic carbonic anhydrase as responding specifically to changes in periplasmic pH and these have been shown to be essential also for acid acclimation. The finding also of upregulation of the two-component histidine kinase HP0165 and its response element HP0166, illustrates the complexity of the acid acclimation processes involved in gastric colonization by this pathogen.

Isolation and melting properties of branched‐chain esters from lanolin

AbstractSaturated branched FA and their derivatives are both biodegradable and stable to oxidation. Their m.p. are expected to be enough lower than their straight‐chain counterparts to make them ideal as biolubricants. But physical property data for branched fatty esters are limited. In this study, a complex mixture of branched methyl esters was obtained from lanolin through saponification, extraction of unsaponifiables, and methylation. Hydroxy compounds were removed by chromatography on alumina. Vacuum spinning‐band distillation separated the mixture roughly by chain length. Countercurrent urea complex formation and low‐temperature crystallization separated even‐chain iso‐and odd‐chain anteiso‐methyl esters of chain lengths 14 through 18 at &gt;95% purity. Transesterification was used to convert methyl esters to isopropyl esters. The m.p. and heat of fusion of each ester were determined by DSC. NMR was used to verify the structure of branched esters.

A Continuous-Flow Process for Natural Product Synthesis

A continuous-flow reactor system was designed and used for the synthesis of a neolignan natural product, grossamide (8). The polymer-supported HOBt packed in the column (Reagent 4) was activated by flowing the DMF solution of ferulic acid (1), PyBrOP (2), and DIPEA. After washing the unreacted materials out, the THF solution of amine 3 was flowed into the first column. The output was then directed through the second column containing a sulfonic acid resin (Reagent 5) as a scavenger to afford amide 6 in 90% conversion. Amide 6 was diluted with a solution of hydrogen peroxide urea complex and sodium dihydrogen phosphate buffer in acetone-water. The combined flow was then passed through the third column packed with an immobilized peroxidase on silica (Reagent 7) to give grossamide.

Synthesis and characterization of some oxodiperoxo molybdenum(VI) complexes of Morpholinomethyl urea and related ligands

The oxodiperoxo complexes of Mo(VI) of the type [MoO(O2)2L], where L = Morpholinomethyl urea, morpholinomethyl thiourea, piperidinomethyl urea, piperidinomethyl thiourea, pyrrolidinomethyl urea, and pyrrolidinomethyl thiourea have been synthesized and characterized by elemental analysis, molar conductance, IR, UV-Vis, and TGA/DTA techniques. It is shown that the ligands coordinate to the metal ion in a symmetrical bidentate fashion through heterocyclic nitrogen and carbonyl oxygen or thiocarbonyl sulfur. Thermal studies indicate continuous weight loss until a stable oxide is formed.

Anion-binding mode in a sulfanylphenyl urea complex: solid state symmetry breaking and solution chelation

An anion-bridged, hydrogen bonded coordination polymer apparently adapts its symmetry to form a Z′ = 1 or 2 structure according to the hydrogen bonding demands of the anion, and in solution there is evidence for a discrete anion-binding coordination complex.

Synthesis, infrared spectra and thermal investigation of gold(III) and zinc(II) urea complexes. A new procedure for the synthesis of basic zinc carbonate

Reaction of urea with sodium tetrachloroaurate(III) dihydrate and zinc(II) chloride has been investigated at room and elevated temperature (∼90°C) producing three new compounds: [Au(urea)4]Cl3·2H2O, [Au2(NH2)2Cl2(NCO)(OH)]·H2O and 2ZnCO3·3Zn(OH)2. The infrared spectra were recorded and the observed bands were assigned. The binuclear gold complex and basic zinc carbonate basic were also investigated by thermal analysis, and general mechanisms describing their decompositions are suggested.

Soft chemical routes to semiconductor nanostructures

Soft chemistry has emerged as an important means of generating nanocrystals, nanowires and other nanostructures of semiconducting materials. We describe the synthesis of CdS and other metal chalcogenide nanocrystals by a solvothermal route. We also describe the synthesis of nanocrystals of AlN, GaN and InN by the reaction of hexamethyldisilazane with the corresponding metal chloride or metal cupferronate under solvothermal conditions. Nanowires of Se and Te have been obtained by a self-seeding solution-based method. A single source precursor based on urea complexes of metal chlorides gives rise to metal nitride nanocrystals, nanowires and nanotubes. The liquidliquid interface provides an excellent medium for preparing single-crystalline films of metal chalcogenides.