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Delgado-Magnero K.H.,University of Habana | Valiente P.A.,University of Habana | Ruiz-Pena M.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas Instec | Perez-Gramatges A.,Pontifical Catholic University of Rio de Janeiro | Pons T.,Spanish National Cancer Research Center
Colloids and Surfaces B: Biointerfaces | Year: 2014

To gain a better understanding of the interactions governing the binding mechanism of proteins with non-ionic surfactants, the association processes of Tween 20 and Tween 80 with the bovine serum albumin (BSA) protein were investigated using molecular dynamics (MD) simulations. Protein:surfactant molar ratios were chosen according to the critical micelle concentration (CMC) of each surfactant in the presence of BSA. It was found that both the hydrophilic and the hydrophobic groups of the BSA equally contribute to the surface area of interaction with the non-ionic surfactants. A novel theoretical model for the interactions between BSA and these surfactants at the atomic level is proposed, where both surfactants bind to non-specific domains of the BSA three-dimensional structure mainly through their polyoxyethylene groups, by hydrogen bonds and van der Waals interactions. This is well supported by the strong electrostatic and van der Waals interaction energies obtained in the calculations involving surfactant polyoxyethylene groups and different protein regions. The results obtained from the MD simulations suggest that the formation of surfactant clusters over the BSA structure, due to further cooperative self-assembly of Tween molecules, could increase the protein conformational stability. These results extend the current knowledge on molecular interactions between globular proteins and non-ionic surfactants, and contribute to the fine-tuning design of protein formulations using polysorbates as excipients for minimizing the undesirable effects of protein adsorption and aggregation. © 2013 Elsevier B.V. Source

Rodriguez-Donis I.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas Instec | Gerbaud V.,National Polytechnic Institute of Toulouse | Gerbaud V.,French National Center for Scientific Research | Joulia X.,National Polytechnic Institute of Toulouse | Joulia X.,French National Center for Scientific Research
Industrial and Engineering Chemistry Research | Year: 2012

This paper shows how knowledge of the univolatility and unidistribution line location and residue curve analysis help to assess the feasibility of batch extractive rectifying or stripping distillation of azeotropic mixtures by using an intermediate boiling entrainer. We consider five minimum boiling (minT) azeotropic mixtures AB with entrainer E, namely, acetone-heptane with benzene, methanol-toluene with triethylamine, methyl acetate-cyclohexane with carbon tetrachloride, dichloromethane-ethanol with acetone, and ethyl acetate-heptane with benzene; and one maximum boiling (maxT) azeotropic mixture, namely, chloroform-ethyl acetate with either 2-chlorobutane, isobutylchloride, bromopropane, or bromochloromethane. All ternary diagrams A-B-E belong to the 1.0-1b class, for which all three possible univolatility, α AB, α BE, and α AE, and unidistribution lines, K A, K B, and K E can exist. With application of the general feasibility criterion of Rodriguez-Donis et al. (Ind. Eng. Chem. Res. 2009, 48 (7), 3544-3559), both azeotropic components, A and B, accomplish the criterion, and they can be recovered, A in an extractive rectifier and B in an extractive stripper. The process efficiency of each alternative depends strongly on the location of the α AB univolatility line interception with the triangle edge, and also depends on the α BE (α AE) in the minT (maxT) case and of the unidistribution line K E closeness to the (E-B) (A-E) edge. Besides, choice of the rectification of A instead of the stripping of B is set by the ratio of α AE/α BE, the ratio of relative volatility variation of the binary mixtures between A or B and E. © 2012 American Chemical Society. Source

Batista-Tomas A.R.,University of Habana | Diaz O.,Cuban Institute of Meteorology InsMet | Batista-Leyva A.J.,University of Habana | Batista-Leyva A.J.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas Instec | Altshuler E.,University of Habana
Quarterly Journal of the Royal Meteorological Society | Year: 2016

The fractal dimension estimated as the area-perimeter relation constitutes a tool for the characterization of clouds. In this article, we apply it for the first time to study the separation of cirrus and cumulonimbus in the Caribbean area. Based on satellite data, we show that the two types can be differentiated by their area-perimeter ratio as follows: DCi = 1.37 ± 0.02 for cirrus, and DCb = 1.18 ± 0.05 for cumulonimbus. We also show that the 'global' area-perimeter ratio can be used to determine the composition of the cloud field. Moreover, we are able to quantify, through the area-perimeter ratio, the transformation of cumulonimbus into cirrus. Our findings have potential applications for the automatic classification of clouds, and for the understanding of their formation processes. © 2016 Royal Meteorological Society. Source

Acosta Avalo J.L.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas Instec | Perez Rojas H.,Institute Cibernetica Matem atica y Fisica ICIMAF
Astronomische Nachrichten | Year: 2015

We demonstrate the existence of a chiral magnetic effect in an electron-positron magnetized gas in QED. A vector current is induced by the electric field related to the pseudo-vector longitudinal Debye massive photon mode propagating along the external magnetic field B and separating opposite charges of the same helicity. A equation associated to the nonconservation of the axial current is obtained in a medium of massive and magnetized charged fermions. The effect is interesting in connection to the QCD chiral magnetic case reported in current literature. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Source

Ferreira D.M.,University of Sao Paulo | Saga Y.Y.,University of Sao Paulo | Aluicio-Sarduy E.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas Instec | Tedesco A.C.,University of Sao Paulo
Current Medicinal Chemistry | Year: 2013

For some time Photodynamic Therapy and electrochemotherapy have been used as alternative therapies against skin cancer. The primary aim of this work was to develop, characterize, and evaluate the in vitro cytotoxic activity of new drug delivery systems based on chitosan nanoparticles containing aminolevulinic acid derivatives such as prodrug (5-ALA and its ester derivative 8-ALA). The second goal of this study was to evaluate the synergistic effect of a combination of classical Photodynamic Therapy and electrochemotherapy, which is routinely utilized to modulate and enhance the permeation of photosensitizers, prodrugs, and other active compounds through the skin, improving the efficiency of PDT in the treatment of cutaneous neoplasms. © 2013 Bentham Science Publishers. Source

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