RESUMEN
Understanding the food protein binding to bioactive compounds is of utmost importance for the development of efficient protein-based delivery systems. The binding of lutein to sodium caseinate (NaCas) or native casein micelle (PPCN) was investigated at pH 7 to evaluate the effect of casein supramolecular structures on the interaction. Fluorescence quenching, UV-vis spectroscopy, and dynamic light scattering were carried out. Under the medium conditions of interaction analysis (DMSO-water and ethanol-water), lutein exists as H-type aggregates. The investigation of lutein/casein interaction showed a predominantly static mechanism of fluorescence quenching and the presence of two fluorophore populations on NaCas and PPCN, but only one accessible to lutein. Moreover, the Scatchard plot indicated that lutein interacted with both caseins in one binding site. The interaction of lutein with caseins occurred with binding constant Kb of 105 M-1, regardless of casein supramolecular structure.
Asunto(s)
Caseínas , Luteína , Dispersión Dinámica de Luz , Micelas , Análisis EspectralRESUMEN
Understanding the mechanism of interaction between food proteins and bioactives constitutes the preliminary step to design food grade nanocarriers. We investigated the interaction between cyanidin-3-O-glucoside (C3G), and 20nm-sized sodium caseinate nanoparticles (NaCas) at pH 7 and pH 2 by fluorescence spectroscopy and dynamic light scattering. The characterization of the C3G-NaCas interaction indicated that the fluorescence quenching mechanism was predominantly static. C3G interacted with two sets of binding sites with association constants Ka of 106 and 105M-1. Electrostatic interactions dominated at pH 7, while hydrophobic effects were the main force at pH 2. Interestingly, the two sets of binding sites were discriminated by ionic strength at pH 7. The binding of C3G slightly modified the average diameter of NaCas nanoparticles without alteration of its surface charge suggesting a complexation of C3G molecules in the internal casein structure. Thus, NaCas constitutes a putative nanocarrier for anthocyanins in new functional foods.
Asunto(s)
Antocianinas/química , Caseínas/química , Glucósidos/química , Antocianinas/metabolismo , Sitios de Unión , Caseínas/metabolismo , Dispersión Dinámica de Luz , Glucósidos/metabolismo , Interacciones Hidrofóbicas e Hidrofílicas , Nanopartículas/química , Concentración Osmolar , Cloruro de Sodio/química , Espectrometría de Fluorescencia , Electricidad EstáticaRESUMEN
Heteroprotein complex coacervation corresponds to the formation of two liquid phases in equilibrium induced by the interaction of two oppositely charged proteins. The more concentrated phase known as coacervate phase, has attracted interest from several fields of science due to its potential applications for example for encapsulation and delivery of bioactives. Prior such application, it is necessary to understand how the presence of small ligands affects the complex coacervation. In this work, we report on the interaction of small ligand with individual proteins ß-lactoglobulin (ß-LG) and lactoferrin (LF) and consequences on their complex coacervation. ANS (8-Anilinonaphthalene-1-sulfonic acid), a fluorescent probe, was used as model ligand. While ANS did not interact with ß-LG, it presented two sets of binding sites with LF inducing its self-aggregation. Depending on its concentration, ANS modulated the shape of ß-LG-LF macromolecular assembly. Coacervates were observed for ANS/LF molar ratio <25 against amorphous aggregates for higher ANS/LF molar ratios. A maximum loading capacity of around 40mg of ANS per gram of LF in the formed heteroprotein coacervates was reached.