Use of the tubulin bound paclitaxel conformation for structure-based rational drug design

A new computational docking protocol has been developed and used in combination with conformational information inferred from REDOR-NMR experiments on microtubule bound 2-(p-fluorobenzoyl)paclitaxel to delineate a unique tubulin binding structure of paclitaxel. A conformationally constrained macrocyclic taxoid bearing a linker between the C-14 and C-3'N positions has been designed and synthesized to enforce this "REDOR-taxol" conformation. The novel taxoid SB-T-2053 inhibits the growth of MCF-7 and LCC-6 human breast cancer cells (wild-type and drug resistant) on the same order of magnitude as paclitaxel. Moreover, SB-T-2053 induces in vitro tubulin polymerization at least as well as paclitaxel, which directly validates our drug design process. These results open a new avenue for drug design of next generation taxoids and other microtubule-stabilizing agents based on the refined structural information of drug-tubulin complexes, in accordance with typical enzyme-inhibitor medicinal chemistry precepts.     

Inclusion Complex between Local Anesthetic/2-hydroxypropyl-β-cyclodextrin in Stealth Liposome

The drugs delivery system in the treatment of diseases has advantages such as reduced toxicity, increased availability of the drug, etc. Therefore, studies of the supramolecular interactions between local anesthetics (LAs) butamben (BTB) or ropivacaine (RVC) complexed with 2-hydroxypropyl-β-cyclodextrin (HP-βCD) and carried in Stealth liposomal (SL) are performed. ¹H-NMR nuclear magnetic resonance (DOSY and STD) were used as the main tools. The displacements observed in the ¹H-NMR presented the complexion between LAs and HP-βCD. The diffusion coefficients of free BTB and RVC were 7.70 × 10⁻¹⁰ m² s⁻¹ and 4.07 × 10⁻¹⁰ m² s⁻¹, and in the complex with HP-βCD were 1.90 × 10⁻¹⁰ m² s⁻¹ and 3.64 × 10⁻¹⁰ m² s⁻¹, respectively, which indicate a strong interaction between the BTB molecule and HP-βCD (98.3% molar fraction and Ka = 72.279 L/mol). With STD-NMR, the encapsulation of the BTB/HP-βCD and RVC/HP-βCD in SL vesicles was proven. Beyond the saturation transfer to the LAs, there is the magnetization transfer to the hydrogens of HP-βCD. BTB and RVC have already been studied in normal liposome systems; however, little is known of their behavior in SL.     

Elemental analysis of particulate matter in a metal workshop and of biological samples from exposed workers

During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM_2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m³, respectively, whereas in the nearby city, daily PM_2.5 concentrations are on average 11 μg/m³. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded.     

Tests of ordered hypotheses in linkage in heredity

The asymptotic null distribution of the likelihood ratio test for two cases of ordered hypotheses in a particular genetic model is considered. A simple iterative process is proposed in order to get the restricted estimates. It is shown that both tests have asymptotically a chi-bar squared distribution and the same size. A simulation study is also conducted in order to compare the usual unrestricted test with the corresponding one of ordered hypotheses. Finally, the results are extended to some special cases.     

Two-plane sub-bundles of nonorientable real vector-bundles

Let be a nonorientable m-plane bundle over a CW complex X of dimension m or less. Given a 2-plane bundle over X, we wish to know whether can be embedded as a sub-bundle of . The bundle need not be orientable. When is even-dimensional there is the added complication of twisted coefficients. In that case, we use Postnikov decomposition of certain nonsimple fibrations in order to describe the obstructions for the embedding problem. Emery Thomas [11] and [12] treated this problem for and both orientable. The results found here are applied to the tangent bundle of a closed, connected, nonorientable smooth manifold, as a special case.The writing of this paper was partially supported by CNPq grant     

High-Sensitivity Immunofluorescence Staining: A Comparison of the Liposome Procedure and the FASER Technique on mGR Detection

Flow cytometry has become a widely-used and powerful tool for the characterization of cells according to their expression of specific proteins. However, sensitivity of this method is still limited since conventionally labeled antibodies can be conjugated with at maximum 1–10 dye molecules. This fact resulted in the need to develop new techniques in order to identify molecules which are expressed in very low but functionally relevant amounts. In the past, we have successfully used a liposome-based high-sensitivity immunofluorescence technique to measure the expression of low abundant membrane bound glucocorticoid receptors (mGR) on different cell types. The use of this technique allows the detection of as few as 50–100 antigen molecules per cell which is due to a 100-fold to 1000-fold increase in fluorescence signal intensity compared with conventional methods. The higher sensitivity is achieved since thousands of dye molecules can be enclosed in liposomes. Another modern high-sensitivity immunofluorescence staining method is the purchasable Fluorescence Amplification by Sequential Employment of Reagents (FASER) procedure. Here, we aimed at comparing sensitivity and specificity of these two techniques for the detection of the mGR. Our data demonstrate the FASER technique to be more sensitive and also more specific for the detection of mGR as compared to the liposome technique. However, both methods have advantages and disadvantages which are discussed in detail.     

Study on the formation during the production of lead-free piezoceramics at the morphotropic phase boundary

Because of the environmental concerns, the manufacture of ceramics based on lead titanate zirconate [Pb(Zr_1−xTi_x)O₃−PZT] has been condemned because of the lead toxicity. In this context, the electromechanical properties of sodium, potassium and lithium niobate [(Na_0.5−x/2K_0.5−x/2Li_x)NbO₃−NKLN] at the morphotropic phase boundary granted these materials the position of most suitable candidate to replace PZT. However, the production of these ceramics is rather critical mainly because of a natural tendency of forming secondary phases. To help with the studies of the synthesis of this lead-free piezoceramic, this work presents an evaluation of the crystallization of the (Na_0.47K_0.47Li_0.06)NbO₃ phase by solid-state reactions. TG-DTA, XRD, dilatometric and ferroelectric hysteresis analyses indicated that a secondary phase (K₃Li₂Nb₅O₁₅) crystallizes at temperatures above 850 C and also during the sintering of the powders compacts at 1080 C. To prevent the formation of this phase, the addition of Na₂Nb₂O₆.nH₂O microfibers obtained through a microwave hydrothermal synthesis was performed in the sintering process. After to this addition, the suppression of the K₃Li₂Nb₅O₁₅ phase occurred and an increase of the NKLN electrical properties was then obtained.     

Energetic and structural characterization of 2‐R‐3‐methylquinoxaline‐1,4‐dioxides (R = benzoyl or tert‐butoxycarbonyl): experimental and computational studies

The gaseous standard molar enthalpies of formation of two 2‐R‐3‐methylquinoxaline‐1,4‐dioxides (R = benzoyl or tert‐butoxycarbonyl), at T = 298.15 K, were derived using the values for the enthalpies of formation of the compounds in the condensed phase, measured by static bomb combustion calorimetry, and for the enthalpies of sublimation, measured by Knudsen effusion, using a quartz crystal oscillator. The three dimensional structure of 2‐tert‐butoxycarbonyl‐3‐methylquinoxaline‐1,4‐dioxide has been obtained by X‐ray crystallography showing that the two N? O bond lengths in this compound are identical. The experimentally determined geometry in the crystal is similar to that obtained in the gas‐phase after computations performed at the B3LYP/6‐311 + G(2d,2p) level of theory. The experimental and computational results reported allow to extend the discussion about the influence of the molecular structure on the dissociation enthalpy of the N? O bonds for quinoxaline 1,4‐dioxide derivatives. As found previously, similar N? O bond lengths in quinoxaline‐1,4‐dioxide compounds are not linked with N? O bonds having the same strength. Copyright © 2007 John Wiley & Sons, Ltd.     

The Role of the Eu<Superscript>3+</Superscript> Concentration on the SrMoO<Subscript>4</Subscript>:Eu Phosphor Properties: Synthesis,Characterization and Photophysical Studies

SrMoO₄ doped with rare earth are still scarce nowadays and have attracted great attention due to their applications as scintillating materials in electro-optical like solid-state lasers and optical fibers, for instance. In this work Sr_1−xEu_xMoO₄ powders, where x = 0.01; 0.03 and 0.05, were synthesized by Complex Polymerization (CP) Method. The structural and optical properties of the SrMoO₄:Eu³⁺ were analyzed by powder X-ray diffraction patterns, Fourier Transform Infra-Red (FTIR), Raman Spectroscopy, and through Photoluminescent Measurements (PL). Only a crystalline scheelite-type phase was obtained when the powders were heat-treated at 800 °C for 2 h, 2θ = 27.8° (100% peak). The excitation spectra of the SrMoO₄:Eu³⁺ (λ_Em. = 614 nm) presented the characteristic band of the Eu^3 + 5L₆ transition at 394 nm and a broad band at around 288 nm ascribed to the charge-transfer from the O (2p) state to the Mo (4d) one in the SrMoO₄ matrix. The emission spectra of the SrMoO₄:Eu³⁺ powders (λ_Exc. = 394 and 288 nm) show the group of sharp emission bands among 523–554 nm and 578–699 nm, assigned to the ⁵D₁→⁷F_{0,1and 2} and ⁵D₀→⁷F_{0,1,2,3 and 4}, respectively. The band related to the ⁵D₀→⁷F₀ transition indicates the presence of Eu³⁺ site without inversion center. This hypothesis is strengthened by the fact that the band referent to the ⁵D₀→⁷F₂ transition is the most intense in the emission spectra.     

Determination of Pb,Zr, Ti,Sr, Cr,Nb and La in lead zirconate titanate ceramics by particle‐induced X‐ray emission

A particle‐induced X‐ray emission (PIXE) technique has been used in the determination of the principal components Pb, Zr and Ti and the substituting elements Sr, Cr, Nb and La in lead zirconate titanate ceramics. In general, precision of analysis was concentration dependent from each element under study. For Pb, precision varied between 0.13% and 0.16%, at higher concentration of 59.32–64.5%. It was around 6–9% for Sr, Cr and Nb at concentrations of 1% or lower. Particular attention was devoted to the estimation of the analysis trueness. With this purpose, three methods were applied: (1) comparison of PIXE and inductively coupled plasma optical emission spectrometry concentrations, (2) recovery study and (3) comparison with a laboratory standard. Trueness of analysis was around 100 ± 10% for the evaluated elements Pb, Zr, Ti, Sr and Cr. The expected stoichiometry and elemental composition homogeneity of a wide group of produced ceramics were confirmed by the PIXE technique. Copyright © 2012 John Wiley & Sons, Ltd.