Higher Institute of Technologies and Applied Sciences

About: Higher Institute of Technologies and Applied Sciences is a education organization based out in Havana, Cuba. It is known for research contribution in the topics: Geology & Very-high-temperature reactor. The organization has 49 authors who have published 35 publications receiving 225 citations.

Ultrasonic degradation of sulfadiazine in aqueous solutions

Abstract: Advanced oxidation methods, like ultrasound (US), are a promising technology for the degradation of emerging pollutants in water matrices, such as sulfonamide antibiotics. Nevertheless, few authors report the degradation of sulfonamides by high-frequency US (>100 kHz), and limited information exist concerning the use of ultrasonic-driven processes in the case of sulfadiazine (SDZ). In this study, SDZ degradation was investigated with the aim to evaluate the influence of initial concentration, pH and US frequency, and power. Ultrasonic frequencies of 580, 862, and 1,142 kHz at different power values and SDZ initial concentrations of 25, 50, and 70 mg L−1 were used. The results show that SDZ degradation followed pseudo first-order reaction kinetics with k values and percent removals decreasing for increasing solute initial concentration. Higher SDZ percent removals and removal rates were observed for the lowest operating frequency (580 kHz), higher dissipated power, and in slightly acidic solution (pH 5.5). Addition of the radical scavenger n-butanol confirmed that hydroxyl radical-mediated reactions at the interface of the cavitation bubbles are the prevailing degradation mechanism, which is directly related to the pKa-dependent speciation of SDZ molecules. Finally, addition of H2O2 had a detrimental effect on SDZ degradation, whereas the addition of the Fenton reagent showed a positive effect, revealing to be a promising alternative for the removal of sulfadiazine.

Essential amino acids interacting with flavonoids: A theoretical approach

Abstract: The interaction of two flavonoid species (resorcinolic and fluoroglucinolic) with the 20 essential amino acids was studied by the multiple minima hypersurface (MMH) procedures, through the AM1 and PM3 semiempirical methods. Remarkable thermodynamic data related to the properties of the molecular association of these compounds were obtained, which will be of great utility for future investigations concerning the interaction of flavonoids with proteins. These results are compared with experimental and classical force field results reported in the available literature, and new evidences and criteria are shown. The hydrophilic amino acids demonstrated high affinity in the interaction with flavonoid molecules; the complexes with lysine are especially extremely stable. An affinity order for the interaction of both flavonoid species with the essential amino acids is suggested. Our theoretical results are compared with experimental evidence on flavonoid interactions with proteins of biomedical interest. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

Optimization of radiolytic degradation of sulfadiazine by combining Fenton and gamma irradiation processes

Abstract: Gamma radiation (GR) is a promising technique, among known advanced oxidation processes, degrading water contaminants. Nevertheless, few authors report the degradation of sulfonamides by GR, and limited information exists concerning the use of GR in the case of sulfadiazine (SDZ). The objectives of this work are (1) evaluating GR as an alternative method for treating wastewater contaminated with SDZ and examinating the intensification of GR with oxidants (H2O2 or Fenton reagent). GR was performed with a high-activity 60Co source. The gamma radiation/Fenton process gave the best result, leading to total SDZ removal and high (74.13%) pollutant mineralization.

High rotation speed of single molecular microcrystals in an optical trap with elliptically polarized light

Abstract: We build an experiment of optical tweezers based on the use of an inverted optical microscope for manipulating microsized single crystals, which are made of an organic dye and parallelepiped in shape. The microcrystals are directed so that their long axis is in the axial direction of the trapping beam. Their short axis follows the direction of the linear polarization of the beam. In circular or elliptic polarization, the crystals are spontaneously put in rotation with a high speed of up to 500 turns per second. It is the first time, to the best of our knowledge, that such a result is reported for particles of the size of our crystals. Another surprising result is that the rotation speed was first increased as expected by increasing the incident power, but after passing by a maximum it decreased until the complete stop of rotation, whereas the power continued growing. This evolution was not reversible. Several hypotheses are discussed to explain such behavior.

Theoretical affinity order among flavonoids and amino acid residues: An approach to understand flavonoid–protein interactions

Abstract: The theoretical affinity order previously suggested for the interactions of flavanol species with the 20 amino acid residues was strengthened by different ways: the analysis of the PDB data about the interactions of proteins with flavonoids, the references related with the inhibition of enzymes by flavonoids and the results of docking calculations. The results confirmed that hydrophilic amino acid residues demonstrated high affinity interacting with flavonoid molecules, as it was predicted by the theoretical affinity order. The docking modes among catechin molecules and four proteins (human serum albumin (HSA), transtyretine, elastase and renin) are also supporting this information. The theoretical affinity order among flavonoids and amino acid residues seems to have great applications to the theoretical prediction of flavonoid–protein interactions as a good approach to understand the biological activity of flavonoids.