Medium dependence of asphaltene agglomeration inhibitor efficiency

Applying chemical additives (molecule inhibitors or dispersants) is one of the common ways to control asphaltene agglomeration and precipitation. However, it is not clear why at some conditions the synthetic flocculation inhibitors as well as resins not only do not inhibit the asphaltene agglomeration,, they may also promote it, and why the increasing of the additive concentration may lead to the diminishing of their efficacy. To clarify this issue, in the present work we have performed a set of vapor preassure osmometry experiments investigating the asphaltene agglomeration inhibition by commercial and new inhibitor molecules in toluene and o-diclorobenzene. Monte Carlo computer modeling has been applied to interpret some unexpected trends of molar mass of the Puerto Ceiba asphaltene clusters at different concentrations of inhibitor, assuming that inhibitors efficiency is directly related to their adsorption on the surface of asphaltene or its complexes. It has been found that a self-assembly of inhibitor molecules, induced by relative lyophilic or lyophobic interactions, may be a reason of the inhibitor efficacy declining.Comment: 21 page

Structural properties of fluids interacting via piece-wise constant potentials with a hard core

Publicado en: J. Chem. Phys. 139, 074505 (2013) DOI: 10.1063/1.4818601Se presentan las propiedades estructurales de fluidos cuyas moléculas interactúan a través de potenciales con un núcleo duro más dos secciones constantes de diferentes anchuras y alturas. Éstos se derivan de un desarrollo más general presentado previamente para potenciales con un núcleo duro además de ƞ constante [Condens. Matter Phys. 15, 23602 (2012)] en el que se hizo uso de un método analítico de aproximación racional-función y semi-analítico. Los resultados de casos ilustrativos que comprenden ocho diferentes combinaciones de pozos y barreras son comparadas con datos de simulación y con aquellos que se derivan de la solución numérica de las ecuaciones integrales de Percus–Yevick y cadenas superentrelazadas. Se encuentra que la aproximación racional-funcional generalmente predice una función de distribución radial más precisa que la teoría de Percus–Yevick y es comparable o incluso superior a la teoría de cadenas superentrelazadas. Esta superioridad sobre ambas teorías de la ecuación integral se pierde, sin embargo, en altas densidades, especialmente cuando aumenta la amplitud de los pozos y/o barreras.The structural properties of fluids whose molecules interact via potentials with a hard core plus two piece-wise constant sections of different widths and heights are presented. These follow from the more general development previously introduced for potentials with a hard core plus n piece-wise constant sections [Condens. Matter Phys. 15, 23602 (2012)] in which use was made of a semi-analytic rational-function approximation method. The results of illustrative cases comprising eight different combinations of wells and shoulders are compared both with simulation data and with those that follow from the numerical solution of the Percus–Yevick and hypernetted-chain integral equations. It is found that the rational-function approximation generally predicts a more accurate radial distribution function than the Percus–Yevick theory and is comparable or even superior to the hypernetted-chain theory. This superiority over both integral equation theories is lost, however, at high densities, especially as the widths of the wells and/or the barriers increase.Para Andrés Santos Reyes y Santos Bravo Yuste, este trabajo ha sido financiado por el Gobierno de España, a partir de la beca FIS2010-16587 y de la Junta de Extremadura (España) a partir de la beca GR10158. También han sido parcialmente financiados por fondos FEDER. Pedro Orea ha recibido ayuda del IMP, a partir del Molecular Engineering Progra

Detection of Lysosomal Storage Disorders Using Tandem Mass Spectrometry

Thesis (Ph.D.)--University of Washington, 2014Lysosomal storage disorders is a group of diverse autosomal recessive metabolic diseases. These disorders are caused by a deficiency in an enzyme necessary for the catabolic degradation of proteins, glycolipids, and glycosaminoglycans in the lysosome. Although these disorders can be caused by different mutations of different enzymes, they all manifest themselves through the abnormal accumulation of material within the affected cells. For decades lysosomal storage disorders were considered interesting neurodegenerative fatal disorders with no possibility for treatment. A lot of progress has been made in understanding these diseases and the enzymes behind the malfunction as well as in treatments for some of these disorders. Treatments are more successful when initiated before symptoms manifest; therefore early diagnosis is desired. Tandem mass spectrometry has become a powerful tool in clinical analysis. It is also used in newborn screening laboratories for inborn error detection. Our work focuses on developing assays to detect lysosomal storage diseases in newborns by measuring substrate concentrations and measuring enzyme activity using tandem mass spectrometry as a quantification tool. A new direct assay for palmitoyl protein thioestarase 1 was developed for the clinical diagnosis of infantile neuronal ceroid lipofuscinosis. Dried blood spots (DBS) are incubated in an assay cocktail containing detergent, synthetic peptide substrate and internal standard at 37 ºC for 10 hours. Product and internal standard are detected by electrospray tandem mass spectrometry in positive ion mode using selected reaction monitoring. A new method for determination of sulfatide levels in blood for the detection of metachromatic leukodystrophy (MLD) was also attempted. Measurement of urinary sulfatide levels is used as a baseline method to distinguish healthy individuals from affected MLD individuals. In an effort to easily include our assay with other newborn blood spot screening methods, sulfatides were extracted from dried urine and blood spots using organic solvent and subsequently analyzed using ultra high performance liquid chromatography tandem mass spectrometry. An acceptable separation of sulfatide levels between MLD and non-MLD dried blood spots however was not obtained; because MLD and non-MLD affected individuals had measurable levels of sulfatide. On the other hand, sulfatide levels in dried urine from MLD affected individuals were elevated when compared to non- MLD individuals. A multiplex assay using a single DBS was developed to screen for 6 disorders: Fabry, Pompe, Niemann-Pick A/B, Krabbe, Gaucher, and mucopolysaccharidosis type I. Samples were analyzed using flow injection tandem mass spectrometry. We demonstrate substantial differences in enzyme activity between blanks and blood punches for all six disorders studied. A new cassette of substrates was introduced to improve assay performance. New reagents for mucopolysaccharidoses type II and type VI were synthesized to improve assay performance. Results show that the new reagents have enhanced mass spectrometry sensitivity and thus, a lower detection limit

Ciencia en la noticia

En peligro de extinción, 16 mil 119 especies: UICN. Empresa de alquiler de científicos funciona con éxito en Alemania. El caracol púrpura, en peligro de extinción por su uso en la coctelería. Nanotecnología: ¿se acabó la magia? Casi 90% de las células del cuerpo humano son bacterianas. México desconoce el potencial de sus hongos. Dispendio en luz artificial factor que eleva el cambio climático. El agua y la colonización del norte. Promueven enseñar ciencia a los niños por medio de historias. Agota industria lechera el agua de la zona protegida Cuatro Ciénegas. Presentan en Praga la primera definición científica de planeta. Los medicamentos falsos, entre uno y 50% del mercado mundial. Si desaparece el jaguar peligra la especie humana, dice investigador. Limpia el gobierno canadiense sitios web oficiales sobre cambio climático

Ciencia en la Noticia

En peligro de extinción, 16 mil 119 especies: UICN     Empresa de alquiler de científicos funciona con éxito en Alemania   El caracol púrpura, en peligro de extinción por su uso en la coctelería   Nanotecnología: ¿se acabó la magia?       Casi 90% de las células del cuerpo humano son bacterianas    México desconoce el potencial de sus hongos      Dispendio en luz artificial factor que eleva el cambio climático    El agua y la colonización del norte        Promueven enseñar ciencia a los niños por medio de historias    Agota industria lechera el agua de la zona protegida Cuatro Ciénegas  Presentan en Praga la primera definición científica de planeta     Los medicamentos falsos, entre uno y 50% del mercado mundial   Si desaparece el jaguar peligra la especie humana, dice investigador   Limpia el gobierno canadiense sitios web oficiales sobre cambio climático

Tandem Mass Spectrometry Assays of Palmitoyl Protein Thioesterase 1 and Tripeptidyl Peptidase Activity in Dried Blood Spots for the Detection of Neuronal Ceroid Lipofuscinoses in Newborns

We report new substrates for quantitative enzyme activity measurements of human palmitoyl protein thioesterase (PPT1) and tripeptidyl peptidase (TPP1) in dried blood spots from newborns using tandem mass spectrometry. Deficiencies in these enzyme activities due to inborn errors of metabolism cause neuronal ceroid lipofuscinoses. The assays use synthetic compounds that were designed to mimic the natural substrates. Incubation produces nanomole quantities of enzymatic products per a blood spot that are quantified by tandem mass spectrometry using synthetic internal standards and selected reaction monitoring. The assays utilize a minimum steps for sample workup and can be run in a duplex format for the detection of neuronal ceroid lipofuscinoses or potentially multiplexed with other mass spectrometry-based assays for newborn screening of lysosomal storage disorders