Characterization of Structural Changes of Casein Micelles at Different PH Using Microscopy and Spectroscopy Techniques.

This study aimed to evaluate the influence of pH changes on morphometric parameters of casein micelles and a general overview of their conformational structure through microscopy techniques, Raman spectroscopy and multivariate analysis. It was found that casein micelles morphology and protein secondary structure depend strongly upon pH. The changes of arithmetic average roughness (Ra), size, and shape of casein micelles at different pH are properly characterized by atomic force and cryo-transmission electron microscopy. Morphometric changes of casein micelles were correlated correctly with folding and unfolding of casein molecules as evaluated by Raman spectroscopy when the pH was varied. The novelty of this contribution consists in demonstrating that there is a close structure-functionality relationship between the morphometric parameters of proteins and their secondary structure. Knowledge about casein micelles can help improve their use of its diverse applications.

Hydration shells of carbohydrate polymers studied by calorimetry and terahertz spectroscopy.

We present a study of the hydration shells of some carbohydrate polymers of commercial and biological importance, namely, agave fructans, inulin, and maltodextrin, employing terahertz time-domain spectroscopy and differential scanning calorimetry. We observe that the hydration numbers calculated using terahertz spectroscopy are marginally higher than those of the calorimetric values. We attribute this discrepancy to the definition of hydration number, which in a way correlates with the physical process used to quantify it. The aqueous solutions show a non-proportional increase in the absorption coefficient and the hydration number, with a decrease in the carbohydrate concentration. We demonstrate that this behavior is consistent with the "chaotropic" or "structure breaking" model of the hydration shell around the carbohydrates. In addition, the study reveals that agave fructans and inulin have good hydration ability. Given the high glass transition temperature and good hydration ability, these carbohydrates may behave as good bio-protectants and hydrating additives for food and beverages.

Ablación transcatéter con radiofrecuencia en taquicardia auricular / Radiofrequency catheter ablation of incessant atrial tachycardia

La taquicardia auricular incesante es una arritmia relativamente infrecuente pero particularmente difícil de controlar médicamente. En los últimos años, la ablación transcatéter con radiofrecuencia ha demostrado su utilidad en el tratamiento definitivo de una variedad de taquicardias supraventriculares. El objetivo de este reporte es dar a conocer nuestra experiencia inicial en el tratamiento de la taquicardia auricular. Diez pacientes, con edad media 28.7 ñ 15 años y con 11 casos de taquicardia auricular incesante, sintomática y refractaria a los antiarrítmicos convencionales, fueron tratados con ablación selectiva del foco anormal usando corriente de radiofrecuencia. Se encontró un mecanismo por automatismo anormal en 10 taquicardias y sólo en 1 se apoyó reentrada intraauricular. La corriente de radiofrecuencia resultó exitosa en 10 de 11 taquicardias; media de 9.3 ñ 6.8 aplicaciones utilizando como principal método de mapeo el tiempo de activación del electrograma auricular local con un valor medio de -54 ñ -31 milisegundos en los sitios de aplicación exitosa. No ocurrieron complicaciones y se documentó recidiva temprana en un solo caso. Todos los pacientes con ablación exitosa se encuentran asintomáticos, en ritmo sinusal y sin antiarrítmicos después de un seguimiento de 1 a 28 meses. Nuestra experiencia inicial confirma que la ablación con radiofrecuencia es una opción segura y eficaz en la taquicardia auricular incesante.