Comparison of 17beta-estradiol structures from x-ray diffraction and solution NMR

The NMR-derived structure of estrogen (17beta-estradiol, E2), the drug of choice for postmenopausal women, was compared with a recent literature crystal x-ray structure of Fab-bound E2. 1H and 13C NMR spectra of E2 were acquired in DMSO-d6. Assignments were obtained from an analysis of DQF-COSY, TOCSY, HETCOR, HMQC and HMBC 2D NMR spectra. The 1H and 13C NMR assignments are the first reported for E2 in DMSO-d6. Two solution structures, S1 and S2, were obtained with molecular modeling using NOE constraints. S1 overlaps with the crystal structure for all rings. S2 shows prominent differences in the C-ring (C9--C11--C12--C13) segment, which deviates from a chair conformation, and excellent overlap in the A-, B- and D-rings of E2. The C-ring in S2 adopts a boat conformation as opposed to a chair conformation in the x-ray and S1 structures. The S2 structure is about 6 degrees more twisted than the bound x-ray and S1 models. The S1, S2 and x-ray structures had ring bowing values of 10.1 +/- 0.3, 11 +/- 1 and 10.37 degrees , respectively. Of the 100 solution conformers generated, 83 had S1 conformation and 17 had S2 conformation, with average internal energies of 112 +/- 2 and 141 +/- 2 kcal mol(-1), respectively. The 100 S1- and S2- derived conformers showed a r.m.s.d. of 0.72 A for all atoms. The x-ray, S1 and S2 C18--O17 distances were 2.93, 2.92 +/- 0.01 and 2.93 +/- 0.01 A, respectively, and the O3--O17 distances were 11.06, 11.18 +/- 0.12, and 10.89 +/- 0.05 A, respectively.     

Comparison of the phytoestrogen trans-resveratrol (3,4',5-trihydroxystilbene) structures from x-ray diffraction and solution NMR

The NMR-derived solution structure of trans-3,4',5-trihydroxystilbene (resveratrol) was compared with two recent literature crystal x-ray structures, resveratrol in complex with human transthyretin (TTR-RES) from 1DVS.pdb and resveratrol bound to chalcone synthase (CHS-RES) from 1CGZ.pdb. 1H and 13C NMR spectra of resveratrol were acquired in DMSO-d6. Assignments were obtained from an analysis of DQF-COSY, TOCSY, DEPT, HMQC/HSQC, HMBC and INADEQUATE NMR spectra. Past 1H and 13C NMR literature assignments are corrected. The dihedral angle 2-1-1'-2' provides an indication of the relative spatial orientation of the two phenolic rings. Values of 1.62, - 54.10 and 12.6 +/- 1.1 degrees were found for the 1DVS.pdb, 1CGZ.pdb and NMR resveratrol structures, respectively. The 1DVS.pdb resveratrol structure is 'flat' with the two phenolic rings along the same plane. The 1CGZ.pdb structure has these two rings almost orthogonal to each other, and the NMR structure has these two rings much closer to being along the same plane. The angles 1-alpha--alpha' and 1'-alpha'--alpha are along the same trace and of similar magnitude for the 1CGZ.pdb and NMR resveratrol structures. For the 1DVS.pdb resveratrol structure, these angles are about 7-10 degrees greater, with alpha and alpha' being 180 degrees out-of-phase from the other two structures. The alpha rings did not overlap, with the NMR result representing a 'median model' of the two x-ray structures.     

Calorimetry in nonstandard conditions: The noncrystalline phases of linear polyethylene

A linear Union Carbide PE (UC) has been analyzed by nonstandard calorimetry with a common DSC calorimeter and a Setaram C80 calorimeter. Nonstandard calorimetry entails using a low rate of heating (0.5–1 K/min), a small mass (0.5–1.5 mg), and an open cell (O‐cell) instead of the standard C‐cell. Events in O‐cells overlap less and occur with a faster kinetics than in C‐cells. PE crystals are nascent, solution‐grown (S‐grown), press‐grown (P‐grown), and strained by extrusion. In Part A, the traces show that the phase‐changes in the melt, previously observed in a C80 calorimeter (slow T‐ramp) and characterized by ΔH_network, can be observed with a common DSC in nonstandard conditions. In Part B, the difference between the C‐ and O‐cells and the changes in the main peak enthalpy (ΔH_ortho) are of interest. The main result is that, in O‐cells, the value of ΔH_ortho around T_ortho, exceeds unambiguously in certain conditions ΔH_ortho found for perfect orthorhombic crystals. The main endotherm contains then another contribution, namely ΔH_network. Crystal reorganization during the slow T‐ramp is followed in the C‐ and O‐cells on S‐grown crystals. In O‐cells, lamellar thickening observed in the slow‐ramp is more extensive. The ease of phase‐change depends on the sample history. It is as follows: strained‐part extruded > nascent > S‐grown > P‐grown. Co‐operative chain motions are more hindered in the standard C‐cells than in the O‐cells. In Part C, lower values of m succeed in bringing phase‐changes in P‐grown (O‐cells) samples. The origin of the events is discussed: three processes are thought to contribute to the phase‐changes namely, melting of strained short‐range order, activation of vibrations in the CH₂ groups, and fast decay of chain orientation which occurs simultaneously with melting. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1932–1949, 2007     

New ceramic microfiltration membranes from mineral coal fly ash

This work aims to develop a new mineral porous tubular membrane based on mineral coal fly ash. Finely ground mineral coal powder was calcinated at 700 °C for about 3 h. The elaboration of the mesoporous layer was performed by the slip casting method using a suspension made of the mixture of fly ash powder, water and PVA. The obtained membrane was submitted to a thermal treatment which consists in drying at room temperature for 24 h then a sintering at 800 °C. SEM photographs indicated that the membrane surface was homogeneous and did not present any macro defects (cracks, etc.). The average pore diameter of the active layer was 0.25 μm and the thickness was around 20 μm. The membrane permeability was 475 l/h m² bar.This membrane was applied to the treatment of the dying effluents generated by the washing baths in the textile industry. The performances in term of permeate flux and efficiency were determined and compared to those obtained using a commercial alumina microfiltration membrane. Almost the same stabilised permeate flux was obtained (about 100 l/h m²). The quality of permeate was almost the same with the two membranes: the COD and color removal was 75% and 90%, respectively.     

Mechanistic insights into the reductive dehydroxylation pathway for the biosynthesis of isoprenoids promoted by the IspH enzyme

Here, we report an integrated quantum mechanics/molecular mechanics (QM/MM) study of the bio-organometallic reaction pathway of the 2H⁺/2e^– reduction of (E)-4-hydroxy-3-methylbut-2-enyl pyrophosphate (HMBPP) into the so called universal terpenoid precursors isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), promoted by the IspH enzyme. Our results support the viability of the bio-organometallic pathway through rotation of the OH group of HMBPP away from the [Fe₄S₄] cluster at the core of the catalytic site, to become engaged in a H-bond with Glu126. This rotation is synchronous with π-coordination of the C2C3 double bond of HMBPP to the apical Fe atom of the [Fe₄S₄] cluster. Dehydroxylation of HMBPP is triggered by a proton transfer from Glu126 to the OH group of HMBPP. The reaction pathway is completed by competitive proton transfer from the terminal phosphate group to the C2 or C4 atom of HMBPP.     

MRS study of the effects of minocycline on markers of neuronal and microglial integrity in ALS

Objective

Magnetic resonance spectroscopy (MRS) allows to monitor brain metabolites noninvasively in amyotrophic lateral sclerosis (ALS). The objective of this study was to use MRS to monitor the effect of minocycline treatment (200 mg/day) over a short period (6 weeks) on the brain metabolites in the precentral gyrus and brainstem in newly diagnosed ALS patients.

Methods

Ten ALS patients (not on riluzole treatment) were recruited and submitted to single-voxel proton MRS longitudinal examinations (1) before minocycline treatment, (2) 3 weeks and (3) 6 weeks after initiation of treatment.

Results

Results did not show the expected decrease of N-acetylaspartate/creatine (NAA/Cr) in the precentral gyrus, and an increased NAA/Cr ratio in the brainstem suggested neuronal recovery. The myo-inositol (mI)/Cr ratio was unchanged in the precentral gyrus, but increased in the brainstem, indicating a glial reaction.

Conclusions

MRS results suggest that minocycline treatment could be beneficial in the early stages of ALS.     

Density functional theory study on two D-π-A-type organic dyes containing different anchoring groups for dye-sensitized solar cells

The electronic structure and absorption spectra of two D-π-A-type organic dyes with different anchoring groups have been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The effect of anchoring groups on the electronic absorption of the free dyes on (TiO₂)₉ has been studied for the two carbazole dyes (MK1 and MK2). Results from DFT calculations indicate that hydroxamic acid anchoring group in MK2 lead to much stronger intermolecular charge transfer and adsorption energies on (TiO₂)₉ cluster. The effect of four different XC functionals (B3LYP, ωB97xD, M06-2X, and CAM-B3LYP) on the transition energies has been tested in order to explore the valid functional for the studied system. The wavelength values from the ωB97xD/6-31+G** level of theory are in excellent agreement with experimental data so this functional was considered to calculate the electronic absorption of the two studied dyes. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the gap energy (H–L) of the studied dyes are slightly influenced by change of anchoring group. Results reveal that the LUMO energy levels of all studied dyes are higher than the conduction band (CB) of TiO₂ (??4.00 eV). Deprotonation process enhances the efficiency of dye-sensitized solar cells during decreasing adsorption energy of dyes with (TiO₂)₉ cluster.

Graphical abstract

     

5-epi-Canadensene and other novel metabolites of Taxus canadensis

The Canadian yew distinguishes itself from other yews by the nature of its taxane metabolites. We are now reporting a new canadensene taxane whose stereochemistry is rigorously established. The three-dimensional structures of canadensene, 5-epi-canadensene and three other related bicyclic taxanes isolated from other yews were calculated using distance constraints derived from NMR data. The stereochemistry of the substituents, the polar acetate groups and the double bonds determine the 3D models. In addition, three new taxanes were also characterized and some biosynthetic speculations are presented.     

Elliptic cavity in a three-dimensional anisotropic body with inclined strata deformed by line loads and dislocations

Summary Analytical solutions are proposed for the stress and displacement fields in a quasi three-dimensional elastic anisotropic body containing an elliptic cavity or rigid inclusion. The directions of the principal elastic axes are allowed to be inclined arbitrarily with respect to the axes of the elliptic cavity. As an application, expressions for the stress intensity factors are formulated when the cavity reduces to a colinear crack.     

Quantitative MRS study of Baló's concentric sclerosis lesions

Baló's concentric sclerosis (BCS) lesions display specific metabolite changes detected by magnetic resonance spectroscopy (MRS). We report on two cases of BCS lesions examined by MRS; the first case was evaluated 36 days after the onset of symptoms, whereas the second case was evaluated 9 days after the onset of symptoms. MRS data were obtained from single voxels located in the lesion and in the contralateral region. Relative to the creatine/phosphocreatine peak, BCS lesions displayed decreases of N-acetyl aspartate and increases of choline, myo-inositol (mI), glutamine/glutamate (Glx), lactate and lipid+macromolecule signals, in agreement with previous reports. In addition, previously unreported decreases of mI (-19% to -29%) and increases of Glx (+55% to +198%) were measured; these could be useful in characterizing BCS lesions.