Comparison of Nonheme Manganese- and Iron-Containing Flavone Synthase Mimics

Heme and nonheme-type flavone synthase enzymes, FS I and FS II are responsible for the synthesis of flavones, which play an important role in various biological processes, and have a wide range of biomedicinal properties including antitumor, antimalarial, and antioxidant activities. To get more insight into the mechanism of this curious enzyme reaction, nonheme structural and functional models were carried out by the use of mononuclear iron, [Fe^II(CDA-BPA*)]²⁺ (6) [CDA-BPA = N,N,N’,N’-tetrakis-(2-pyridylmethyl)-cyclohexanediamine], [Fe^II(CDA-BQA*)]²⁺ (5) [CDA-BQA = N,N,N’,N’-tetrakis-(2-quinolilmethyl)-cyclohexanediamine], [Fe^II(Bn-TPEN)(CH₃CN)]²⁺ (3) [Bn-TPEN = N-benzyl-N,N’,N’-tris(2-pyridylmethyl)-1,2-diaminoethane], [Fe^IV(O)(Bn-TPEN)]²⁺ (9), and manganese, [Mn^II(N4Py*)(CH₃CN)]²⁺ (2) [N4Py* = N,N-bis(2-pyridylmethyl)-1,2-di(2-pyridyl)ethylamine)], [Mn^II(Bn-TPEN)(CH₃CN)]²⁺ (4) complexes as catalysts, where the possible reactive intermediates, high-valent Fe^IV(O) and Mn^IV(O) are known and well characterised. The results of the catalytic and stoichiometric reactions showed that the ligand framework and the nature of the metal cofactor significantly influenced the reactivity of the catalyst and its intermediate. Comparing the reactions of [Fe^IV(O)(Bn-TPEN)]²⁺ (9) and [Mn^IV(O)(Bn-TPEN)]²⁺ (10) towards flavanone under the same conditions, a 3.5-fold difference in reaction rate was observed in favor of iron, and this value is three orders of magnitude higher than was observed for the previously published [Fe^IV(O)(N2Py2Q*)]²⁺ [N,N-bis(2-quinolylmethyl)-1,2-di(2-pyridyl)ethylamine] species.     

Determination of Pentacyclic Triterpenes from Betula utilis by High-Performance Liquid Chromatography and High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

A rapid and reliable method was developed and validated for determining betulin and betulinic acid in bark in Betula utilis by high-resolution magic angle spinning ¹H nuclear magnetic resonance (HR-MAS NMR) spectroscopy. HR-MAS NMR spectroscopy clearly distinguished the resonances of betulin and betulinic acid in the bark of all accessions of B. utilis. The concentrations of betulin and betulinic acid were calculated and added to the spectra. The determination of the targeted metabolites in chloroform extract of bark of each accession of B. utilis was performed by high-performance liquid chromatography (HPLC). Quantitatively, betulin was present at higher concentrations than betulinic acid in all accessions. The HR-MAS NMR and HPLC results showed that betulin and betulinic acid varied significantly among accessions of B. utilis. Principal component analysis of the NMR and HPLC results provided classification into three metabolic groups in which the betulin concentration was high, moderate, or low. The results show that HR-MAS NMR is rapid for fingerprinting of betulin and betulinic acid in the bark of B. utilis, while minimizing the drawbacks associated with solvent extraction.     

The False Vocal Folds: Shape and Size in Frontal View During Phonation Based on Laminagraphic Tracings

The geometry of the false vocal fold region during phonation is important to the understanding of the aerodynamics and acoustics of voice. The shape and dimensions of this region during phonation were estimated using laminagraphic tracings of the larynx. Laminagrams from two previous studies, one with non-singer subjects (Experiment I, Hollien and Colton, 1969) and the other with singers (Experiment II, Wilson, 1972), were traced, photocopied, and measured. Statistical analysis showed significantly greater false vocal fold height in males than females for both experiments. The false vocal fold gap was also significantly greater in males than females for Experiment II, but reached only borderline significance for Experiment I. For each gender, most of the linear measures were greater in Experiment I when compared to Experiment II; these differences may be passive in nature (due to actual differences in subject size) or active (due to muscle contraction that displaced the false vocal folds during singing).     

Synthesis and characterization of some bis(cyclopentadienyl)titanium(IV) complexes with internally functionalized oximes(LH): sol–gel transformations of Cp2TiCl2, Cp2TiClL and Cp2TiL2 to nano‐sized anatase titania

Some bis(cyclopentadienyl)titanium(IV) complexes of the type [Cp₂TiCl_2?n{L}_n] {where, n = 1 or 2; L = ONC(R)Ar; R = H or CH₃ and Ar = C₅H₄N‐2, C₄H₃O‐2 or C₄H₃S‐2} have been synthesized by the metathetical reactions of Cp₂TiCl₂ with the sodium salt of internally functionalized oximes in 1:1 and 1:2 stoichiometry in anhydrous THF. All these red to brown colored solid derivatives have been characterized by elemental analyses, FT‐IR and NMR (¹H and ¹³C{¹H}) spectral studies. The FAB mass spectra of some representative derivatives indicate their monomeric nature. Oximato ligands in all the complexes appear to bind the titanium via N and O in a dihapto ( ‐N, O) manner in the solid state. Thermogravimetric curves of [Cp₂TiCl{ONC(CH₃)C₅H₄N‐2}] and [Cp₂Ti{ONC(CH₃)C₅H₄N‐2}₂] suggest the formation of hybrid materials CpTiO(Cl) and Cp₂TiO, respectively, as the final products at 900 °C under nitrogen atmosphere. Sol–gel transformations of Cp₂TiCl₂, [Cp₂TiCl{ONC(CH₃)C₅H₄N‐2}] and [Cp₂Ti{ONC(CH₃)C₅H₄N‐2}₂] yielded titania a–c, respectively, at low sintering temperature (600 °C). The powder XRD patterns, IR as well as Raman spectra of all these oxides indicate the formation of nano‐sized anatase phase. The SEM images of titania a–c indicate agglomers like surface morphologies. The absorption spectra of a–c exhibit an energy band gap in the range of 3.47–3.71 eV. Copyright © 2011 John Wiley & Sons, Ltd.     

Octadecyl-bonded silica membrane disk modified with Cyanex302 for pre-concentration and determination of iron in food products

A simple and rapid method using an octadecyl-bonded silica membrane disk impregnated with Cyanex302 is described for the pre-concentration and determination of iron. The influence of various parameters on sorption and elution of Fe(III) were systematically investigated. The sorption of Fe(III) at pH 3.2 was quantitative (99.3 +/- 1.1%). It was completely recovered using 20 mL 5.0 M HCI and determined by flame atomic absorption spectrometry. Breakthrough volume of the modified disk for Fe(III) was >2000 mL, pre-concentration factor was >100, and reusability up to 28 cycles. The LOD and LOQ for Fe(III) were 0.45 microg/L and 1.51 microg/L, respectively, while precision for its determination in terms of RSD was < or =2.1%. This method was applied for Fe(III) determination in milk, fortified flour, cocoa powder, tea, and black pepper. To validate the procedure, EPA Method Standard (QC standard 21) was analyzed for Fe(III).     

Solubility Behavior of Lornoxicam in Binary Solvents of Pharmaceutical Interest

The solubility behavior of lornoxicam was studied in binary solvent systems. Solutions containing an excess of drug were shaken for 72?h at 25?°C, filtered and analyzed. To understand the solute?Csolvent interactions, ideal, Hildebrand?CScatchard and extended Hildebrand solubility approaches were used. The ideal solubility of lornoxicam was calculated from the enthalpy of fusion. The molar enthalpy of fusion was obtained from DSC studies. The experimental mole fraction solubility deviated from the ideal mole fraction solubility, indicating self-association of solute, or solvent, or both in solution. The solubility behavior failed to satisfy the Hildebrand?CScatchard equations. The solubilities of lornoxicam were back calculated with an interaction energy term ??W?? and a rational activity coefficient term ??(log₁₀ ?? ₂)/A??. These parameters were regressed against a polynomial function of ?? ₁, the solubility parameter of the solvent mixture. The solubility behavior of lornoxicam obeyed the extended Hildebrand equation. The solubility parameter of lornoxicam ?? ₂ was found to be 27 MPa^1/2.     

Sorption studies of U(VI) on Amberlite XAD-2 resin impregnated with Cyanex272

U(VI) sorption from nitric media using Cyanex272 impregnated on Amberlite XAD-2 resin has been studied using batch method. The influence of different experimental parameter such as aqueous acidity, effect of time, influence of eluting agents on U(VI) uptake was evaluated. The maximum sorption capacity of 0.168?mmol?g^?1 of U(VI) evaluated based upon these studies. Sorption of U(VI) follows both the Langmuir and Freundlich adsorption isotherms.     

Synthesis of 8-aryl substituted benzo[a]phenanthridine derivatives by consecutive three component tandem reaction and 6-endo carbocyclization

A concise construction of benzo[a]phenanthridines involving multicomponent tandem reaction/carbocyclization in a sequential format is described. The reaction proceeds initially via formation of a 4-aryl-3-arylethynyl-isoquinoline from 2-bromobenzaldehyde/tert-butylamine/1,3-diyne in a three component format followed by a second ring closure either via gold/silver catalyzed intramolecular hydroarylation or via iodo-catalyzed regioselective 6-endo-dig electrophilic cyclization. The salient feature of the strategy involves a three component reaction followed by transformation of the resulting product in to polyheterocycles with increased structural complexity in two steps.     

Möbius Polynomials of Face Posets of Convex Polytopes

The Möbius polynomial is an invariant of ranked posets, closely related to the Möbius function. In this paper, we study the Möbius polynomial of face posets of convex polytopes. We present formulas for computing the Möbius polynomial of the face poset of a pyramid or a prism over an existing polytope, or of the gluing of two or more polytopes in terms of the Möbius polynomials of the original polytopes. We also present general formulas for calculating Möbius polynomials of face posets of simplicial polytopes and of Eulerian posets in terms of their f-vectors and some additional constraints.