Extraction of Proteins by Winsor III Microemulsion Systems

Purification of proteins by microemulsion was improved through use of a 3-phase (“Winsor-III”) microemulsion system instead of the traditionally employed 2-phase (“Winsor-II”) water-in-oil microemulsion system. As a consequence, two of the main problems of the traditional method were improved: the low and slow rate of recovery of proteins encapsulated by the microemulsions and the low protein solubilization capacity of the microemulsions. Microemulsion systems employed a mixture of surfactants, two pH-degradable “cyclic ketal” alkyl ethoxylates (O-[(2-tridecyl, 2-ethyl-1,3-dioxolan-4-yl) methoxy]–O’- methoxy poly(ethylene glycol)n , where n, the average degree of polymerization for the ethoxylate group, equaled 3.0 or 5.45, CK3 and CK7, respectively) and Aerosol-OT (AOT). CK7’s ethoxylate size has broad molecular weight distribution. Partitioning behavior of CK7 molecules as a function of their ethoxylate size, temperature, and the addition of a second surfactant (AOT, CK3, or octyl β-D-glycoside) were investigated. A semi-empirical thermodynamic mathematical model was developed to calculate the phase inversion temperature (PIT) for a surfactant mixture of a specified composition. This information is useful to find the optimal Winsor-III for protein extraction. Finally different Winsor-III systems formed by water, isooctane and surfactant mixtures of CK7, CK3 and AOT were tested in forward extraction of α-chymotrypsin, cytochrome-c, lysozyme, BSA and pepsin. Three approaches were used to obtain Winsor- III systems suitable for forward extraction: employment at 40°C, addition of a more hydrophobic surfactant (CK3, 25°C), and the addition of 1.5 wt. % NaCl (aq) to increase the ionic strength (25°C). Protein concentrations achieved in microemulsion phase were 10 times higher than values reported in the literature for extraction by Winsor-II microemulsion systems. Back extraction was tested for α-chymotrypsin, cytochrome-c, and lysozyme. Aqueous striping solutions used for back extraction contained either a high ionic strength (5 wt. % NaCl) or a high pH (12.0). Back-extraction was fast and total recovery of the activity for α-chymotrypsin was achieved. Other proteins have smaller percentage of mass recovery in the conditions tested but comparable with yields reported in the literature for microemulsion-based extraction

Los jóvenes "mineros" : juventud, transformación de la minería y crisis social en la Cuenca de Río Tinto

En el presente artículo analizamos la construcción social de la edad en relación al acceso de los individuos al mundo laboral en el caso de la Cuenca Minera de Riotino, donde desarrollamos nuestra investigación entre 1991 y 1994. Con este trabajo pretendemos apuntar algunos elementos para la comprensión de las especiales circunstancias que presenta la situación de los jóvenes en una zona que en los últimos años se ha visto profundamente afectada a nivel económico, social y político por un fuerte proceso de crisis y reestructuración la actividad que ha sido la fuente básica de empleo de la comarca y el eje sobre el que se ha sustentado su sociedad.________________________________In this work we analyze the social construction of age in connection with the individual starting in the labor market in the case of Riotinto Mining Region, where we have developed our research from 1991 to 1994. We try to point some elements for understanding about the special characteristics of the situation of oung people in a region deeply affected by the strong process of crisis and re-structuration of the activity being the basic employee's source and the central axip of its society

Méthode de Relaxation Dynamique incrémentale

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/46/ANNEX/r_ZL662YL9.pd

Numerical study of dynamic relaxation with kinetic damping applied to inflatable fabric structures with extensions for 3D solid element and non-linear behavior

International audienceThis work mainly deals with the numerical study of inflatable fabric structures. As implicit integration schemes can lead to numerical difficulties such as singular stiffness matrices, explicit schemes are preferred. Since the final objective of this study is to obtain the final shape of a structure, a dynamic relaxation (DR) method is used. These methods allow us to obtain the final and stable shape of the inflatable fabric structures without doing so many time increments, which is the case when using a classical explicit integration method. Han and Lee [5] proposed an extension of the DR method stated by Barnes [13] suitable for triangular elements and elastic behavior. There are two main contributions in this paper. Firstly, we propose a modification of Han and Lee's method, allowing it to be used with any kind of membrane or solid finite elements and any reversible behavior. Secondly, we propose to rewrite the expression initially introduced by Barnes. Furthermore, these proposals are adapted for incremental loadings, allowing this way to obtain the pseudo-equilibriums of the intermediate phases. Numerical examples from academic problems (rectangular and circular membranes) show the efficiency and the reliability of proposed methods, with linear elasticity behavior, and also with a non-linear incremental behavior and finite deformation states

Catastrophic wear in a metal-on-ceramic total hip arthroplasty

A 51-year-old woman came to our clinic 6 months after a right total hip arthroplasty. She had noticed a slowly growing mass in the proximal thigh and referred progressive pain in the right groin. Plain radiography revealed premature acetabular cup aseptic loosening, and in the computed tomography study, a 14-cm-diameter mass was observed. Revision surgery was performed, showing a metal-on-ceramic bearing surface. The histologic analysis of surrounding tissues was reported as massive metallosis. Although occasionally chosen for primary or revision hip arthroplasty, there is little information available about the in vivo wear behavior of this combination. This important fact should be taken into account before considering such a surface alternativ

Magnetic Core-Shell Nanoparticles Using Molecularly Imprinted Polymers for Zearalenone Determination

This paper describes the synthesis of novel molecularly imprinted magnetic nano-beads for the selective extraction (MISPE) of zearalenone mycotoxin in river and tap waters and further analysis by high-performance liquid chromatography (HPLC) with fluorescence detection (FLD). A semi-covalent imprinting approach was achieved for the synthesis of the molecularly imprinted polymers (MIP). The nanoparticles were prepared by covering the starting Fe3O4 material with a first layer of tetraethyl orthosilicate (TEOS) and then with a second layer using cyclododecyl 2-hydroxy-4-(3-triethoxysilylpropylcarbamoyloxy) benzoate. The last was used with a dual role, template and functional monomer after the extraction of the template molecule. The material was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopies (FT-IR). The solid phase extraction was optimized in all the steps: loading, washing and elution. The optimal conditions allowed the determination of zearalenone in trace levels of 12.5, 25 and 50 µg L−1 without significant differences between the fortified and found level concentrations.Depto. de Química AnalíticaFac. de Ciencias QuímicasTRUEMICINpu

Maximum-likelihood estimation of specific differential phase and attenuation in rain

Precise estimation of propagation parameters in precipitation media is of interest to improve the performance of communications systems and in remote sensing applications. In this paper, we present maximum-likelihood estimators of specific attenuation and specific differential phase in rain. The model used for obtaining the cited estimators assumes coherent propagation, reflection symmetry of the medium, and Gaussian statistics of the scattering matrix measurements. No assumptions about the microphysical properties of the medium are needed. The performance of the estimators is evaluated through simulated data. Results show negligible estimators bias and variances close to Cramer–Rao bounds

Metal levels in corrosion of spinal implants

Corrosion affects spinal instrumentations and may cause local and systemic complications. Diagnosis of corrosion is difficult, and nowadays it is performed almost exclusively by the examination of retrieved instrumentations. We conducted this study to determine whether it is possible to detect corrosion by measuring metal levels on patients with posterior instrumented spinal fusion. Eleven asymptomatic patients, with radiological signs of corrosion of their stainless steel spinal instrumentations, were studied by performing determinations of nickel and chromium in serum and urine. Those levels were compared with the levels of 22 patients with the same kind of instrumentation but without evidence of corrosion and to a control group of 22 volunteers without any metallic implants. Statistical analysis of our results revealed that the patients with spinal implants without radiological signs of corrosion have increased levels of chromium in serum and urine (P < 0.001) compared to volunteers without implants. Corrosion significantly raised metal levels, including nickel and chromium in serum and urine when compared to patients with no radiological signs of corrosion and to volunteers without metallic implants (P < 0.001). Metal levels measured in serum have high sensibility and specificity (area under the ROC curve of 0.981). By combining the levels of nickel and chromium in serum we were able to identify all the cases of corrosion in our series of patients. The results of our study confirm that metal levels in serum and urine are useful in the diagnosis of corrosion of spinal implants and may be helpful in defining the role of corrosion in recently described clinical entities such as late operative site pain or late infection of spinal implant