Papers by Christian Espinoza
Journal of The American Academy of Dermatology, 1991
Langmuir, 1994
The partitioning and hydration of 2,3-butanedione and 2,&pentanedione have been measured in sodiu... more The partitioning and hydration of 2,3-butanedione and 2,&pentanedione have been measured in sodium dodecyl sulfate micelles and AOT reverse micelles. In the latter system, the incorporation of both compounds to the micellar pseudophase is proportional to the amount of water at water/AOT ratios higher than 9. This result is interpreted in terms of a dominant incorporation of the diketones to the water pools. With regard to both solubilization and hydration, the water of the reverse micelle pools behaves nearly as bulk water (at water/AOT ratios higher than 9). The addition of sodium dodecyl sulfate to an aqueous solution of 2,3-pentanedione decreases the extent of hydration of the diketone. Measurement of the quenching of 2,&pentanedione fluorescence by iodide allows an evaluation of the extent of solubilization in the micellar pseudophase. From these data and the changes in absorbance of the a-dicarbonyl band with the surfactant concentration (which is a measure of the degree of hydration) the partition constant of the hydrated and nonhydrated forms of 2,3-pentanedione are evaluated. The results obtained indicate that the hydration of 2,&pentanedione molecules bound to sodium dodecyl sulfate micelles is nearly 4.6 times less efficient than in bulk water.
Journal of Lipid Research, 2005
We compared two HPLC methods (anion exchange [AE] and steric exclusion [SE]) for analysis of mous... more We compared two HPLC methods (anion exchange [AE] and steric exclusion [SE]) for analysis of mouse lipoprotein profiles by determining coefficients of variability (CVs) under varying conditions. CVs for AE and SE were comparable on fresh samples. There was an inverse relationship between subfraction curve area and CV [ r ؍ Ϫ 0.65 (AE) and Ϫ 0.50 (SE)], consistent with the interpretation that as curve area decreased, error variance increased and signal-to-noise ratio decreased. Sample storage did not affect SE. In contrast, with AE, alterations in measured lipoproteins were apparent after storage, including a decrease in the HDL subfraction [66.8% (baseline) vs. 15.9% (1 week); P Ͻ 0.01] and an increase in areas under LDL and VLDL peaks. Concomitant with decreasing HDL area, reproducibility deteriorated with the duration of storage. Analysis of the effects of decreasing sample injectate volume to Ͻ 25 l on SE lipoprotein subfractions revealed that areas under LDL and VLDL peaks decreased and persisted as volume was decreased further. Areas under all lipoprotein subfractions measured with either AE or SE were linearly correlated with the amount of cholesterol [ r ؍ 0.69 (AE) and 0.87 (SE)]. Both AE and SE yield reproducible, accurate, and rapid measurements of lipoproteins from small amounts of serum. AE yields more sensitive, highamplitude, well-defined peaks that can be easily distinguished and necessitates the use of smaller sample volumes compared with SE, but sample storage causes alterations in the chromatogram. SE appears better suited to serial analyses involving stored samples. -Neyer, J., C. Espinoza, L. Luppen, T. M. Dohety, S. C. Tripathi, H. Uzui, P. V. Tripathi, G. Lee, P. K. Shah, and T. B. Rajavashisth. A comparison of anion-exchange and steric-exclusion HPLC assays of mouse plasma lipoproteins. J. Lipid Res. 2005. 46: 1786-1795.
ventilada, está automáticamente ventilado. Esto es porque las cañerías no trabajan a sección llen... more ventilada, está automáticamente ventilado. Esto es porque las cañerías no trabajan a sección llena sino a media sección o menos y tienen la posibilidad de ventilación por la parte superior. Si la distancia es de más de 10 metros se debe colocar otra cañería de ventilación. Si hay sobre presión no trabaja el sistema por gravedad.
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Papers by Christian Espinoza