In Silico Evaluation of the Antimicrobial Activity of Thymol—Major Compounds in the Essential Oil of Lippia thymoides Mart. & Schauer (Verbenaceae)

In this paper, we evaluated the drug-receptor interactions responsible for the antimicrobial activity of thymol, the major compound present in the essential oil (EO) of Lippia thymoides (L. thymoides) Mart. & Schauer (Verbenaceae). It was previously reported that this EO exhibits antimicrobial activity against Candida albicans (C. albicans), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli). Therefore, we used molecular docking, molecular dynamics simulations, and free energy calculations to investigate the interaction of thymol with pharmacological receptors of interest to combat these pathogens. We found that thymol interacted favorably with the active sites of the microorganisms’ molecular targets. MolDock Score results for systems formed with CYP51 (C. albicans), Dihydrofolate reductase (S. aureus), and Dihydropteroate synthase (E. coli) were −77.85, −67.53, and −60.88, respectively. Throughout the duration of the MD simulations, thymol continued interacting with the binding pocket of the molecular target of each microorganism. The van der Waals (ΔE_vdW = −24.88, −26.44, −21.71 kcal/mol, respectively) and electrostatic interaction energies (ΔE_ele = −3.94, −11.07, −12.43 kcal/mol, respectively) and the nonpolar solvation energies (ΔG_NP = −3.37, −3.25, −2.93 kcal/mol, respectively) were mainly responsible for the formation of complexes with CYP51 (C. albicans), Dihydrofolate reductase (S. aureus), and Dihydropteroate synthase (E. coli).     

Physicochemical properties of maize cob cellulose powders reconstituted from ionic liquid solution

Suitable α-cellulose and cellulose II powders for use in the pharmaceutical industry can be derived from maize cob. α-Cellulose was extracted from an agricultural residue (maize cobs) using a non-dissolving method based on inorganic substances. Modification of this α-cellulose was carried out by its dissolution in the ionic liquid 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl), and subsequent regeneration by addition of either water or acetone at room temperature, or of boiling water. X-ray diffraction and infrared spectroscopy results showed that the regenerated celluloses had lower crystallinity, and proved that the treatment with [C₄mim]Cl led to the conversion of the crystalline structure of α-cellulose from cellulose I to cellulose II. Thermogravimetric analysis and differential scanning calorimetry data showed quite similar thermal behavior for all cellulose samples, although with somewhat lower stability for the regenerated celluloses, as expected. The comparison of physicochemical properties of the regenerated celluloses and the native cellulose mainly suggests that the regenerated ones might have better flow properties. For some of the characterizations carried out, it was generally observed that the sample regenerated with boiling water had more similar characteristics to the α-cellulose sample, evidencing an influence of the regeneration strategy on the resulting powder after the ionic liquid treatment.     

M?ssbauer and XRD study of the Fe65Si35 alloy obtained by mechanical alloying

A study was made on the alloy Fe₆₅Si₃₅ using x-ray diffraction and M?ssbauer spectrometry. The alloy was obtained by mechanical alloying in a high energy planetary mill, with milling times of 15, 30, 50, 75 and 100?h. The results show that in the alloys two structural phases are present, a Fe-Si BCC disordered phase and ferromagnetic, and a Fe-Si SC phase, whose nature is paramagnetic and which decreases with milling time. In the temporal evolution of the milling two stages are differentiated: one between 15 and 75?h of milling, in which silicon atoms diffuse into the bcc matrix of iron and its effect is to reduce the hyperfine magnetic field; the other, after 75?h of milling, where the alloy is consolidated, the effect of the milling is only to increase the disorder of the system, increasing the magnetic order.     

A Further Step in the Kinetic Characterisation of the Tyrosinase Enzymatic System

Tyrosinase is a cuproprotein that hydroxylates monophenols to o-diphenols, which it then oxidises to o-quinones, using molecular oxygen. Based on kinetic studies of the steady state and measuring product formation during the action of the enzyme on o-diphenols, we determine the Michaelis constant and the maximum velocity, respectively. Similarly, we determine these kinetic constants for the enzyme acting on monophenols. From these constants obtained for a monophenol/o-diphenol pair, it is possible to calculate a new constant, the Michaelis constant of the enzyme for an o-diphenol acting on the corresponding monophenol, by means of an equation that relates the above-mentioned kinetic constants. Furthermore, it is also possible to establish the relation between the Michaelis constants for the oxygen in the presence of monophenol and in the presence of o-diphenol from the relation between the maximum velocities of the monophenol and o-diphenol experimentally determined by measuring aminochrome. From applying the equations described above to the kinetic data of the many tyrosinases described in the literature, we find that the Michaelis constant for the o-diphenol in the presence of monophenol is much lower than that obtained when the enzyme acts on o-diphenol alone. The Michaelis constant for oxygen in the presence of monophenol is also much lower than that obtained in the presence of its o-diphenol.     

A linear programming formulation of a semi-Markov model to design pig facilities

Housing facilities design represents the main strategic decision in pig farms. This paper introduces a linear programming formulation of a semi-Markov process to approach the facilities design. Thus, the Linear Programming formulation determines the optimum replacement policy and provides the equilibrium distribution of the herd along pig facilities. Then, the calculation of the associated needs of room for each sow facility is derived from sow herd distribution at equilibrium. Results show the flexibility of the model for designing pig facilities and computational advantages in the solving procedure compared to previous proposals. Furthermore, the robustness of the optimal solution is studied by means of sensitivity analysis.     

Fundamentals and development of high‐efficiency supported catalyst systems for atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) is a controlled/living radical polymerization process developed a decade ago that allows the synthesis of tailored macromolecules. It has been widely used in the laboratory for polymer synthesis since but little use has been made of it at the industrial scale for polymer production. This is due to the low activity of the ATRP catalyst that is central to the process. Much work has been done over the years to overcome this challenge, and the greatest successes have been achieved through catalyst supporting and recycling. We present here a historical account of the development of supported ATRP catalysts while shedding light on their present and future challenges. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 553–565, 2007     

Determination of rapeseed methyl ester oil volumetric properties in high pressure (0.1 to 350 MPa)

The isothermal compressibility coefficient, the bulk modulus, the cubic expansion coefficient, the density and the propagation speed of the pressure waves of rapeseed methyl ester oil (RMEO) are the thermophysical properties derived from the specific volume determined in this work and compared with the properties of diesel oil (DO). The temperature measurement interval ranges from 288.15 to 328.15 K and the pressure measurement interval from atmospheric pressure to 350 MPa. The experimental method used consisted of a volume change cell characterised by a linear variable differential transformer (LVDT) magnetic induction system adapted to a high-pressure vessel. To calculate the properties the modified Tait-Tammann equation was used and a high correlation coefficient was obtained with a 95% confidence level. The specific volume and compressibility coefficient were greater for DO than for RMEO; also, cubic expansion was greater for DO than for RMEO. These results pave the way for further practical application.