Impact of pH on the Formation and Properties of Whey Protein Coronas around TiO2 Nanoparticles.

In aqueous media, titanium dioxide (TiO2) nanoparticles can interact with proteins in their environment and form a protein corona. The pH of the aqueous media affects the structure and properties of the protein corona, and currently there is a lack of understanding of the effects of pH on the characteristics of protein coronas. In this study, we examined the impact of pH (2-11) on the structural and physicochemical properties of whey protein coronas formed around TiO2 nanoparticles. The pH of the solution influenced the structure of whey protein molecules, especially around their isoelectric point. Thermogravimetric and quartz crystal microbalance analyses showed that the adsorption capacity of the whey proteins was the largest at their isoelectric points and the lowest under highly acidic or alkaline conditions. The majority of the proteins were tightly bound to the nanoparticle surfaces, forming a hard corona. The influence of solution pH on protein corona properties was mainly attributed to its impact on the electrostatic forces in the system, which impacted the protein conformation and interactions. This study provides useful insights into the influence of pH on the formation and properties of protein coronas around inorganic nanoparticles, which may be important for understanding the gastrointestinal and environmental fates.

The Impact of Worksite Supports for Healthy Eating on Dietary Behaviors.

OBJECTIVE: The purpose of this study was to assess the availability of worksite supports (WSS) for healthy eating and examine associations between existing supports and dietary behaviors. METHODS: A cross-sectional, telephone-based study was conducted with 2013 participants in four metropolitan areas in 2012. Logistic regression was used to examine associations between dietary behaviors and the availability or use of WSS. RESULTS: Those reporting the availability of a cafeteria/snack bar/food services at the worksite were more likely to consume fruits and vegetables more than twice/day, and less likely to consume fast food more than twice/week. CONCLUSIONS: Study results highlight the utility of specific WSS to improve employee dietary behaviors while raising questions about why the presence of healthy foods at the worksite may not translate into employee consumption of such foods.

[Improving Analytical Methods by Uncertainty Evaluation with the Case of Determination of Aluminum in Starch Products by ICP-MS].

The measurement uncertainty is a non-negative parameter associated with the result of a measurement that characterizes the dispersion of the quantity values that could reasonably be attributed to the measurand. In the present study measurement uncertainty is estimated using the GUM (ISO/IEC Guide 98: 1993 Guide to the expression of uncertainty in measurement) bottom-up approach. The steps were followed: specifying the measurand; identifying all the associated sources of uncertainty; quantifying the uncertainty components; combining the uncertainty components; determining the extended combined standard uncertainty; reviewing the estimates and reporting the measurement uncertainty. In this process, the major uncertainty components with greater impact were identified; try to eliminate or to reduce the impact of these components can improve measurement methods. Examples were the determination of aluminum in starch and bread crumbs by inductively coupled plasma-mass spectrometry (ICP-MS). The uncertainties of aluminum contents were from measurement repeatability, variability of calibration curve, standard stock solution, dilution, solution volume and sample weighing. The data indicated that the major contributions to the uncertainty budget originating from urel(cAl)1 (the relative standard uncertainty of aluminum content derived from linear least squares calibration), urel(cAl)3 (the relative standard uncertainty of aluminum content derived from the dilution of the standard stock solutions) and urel(rep) (the relative standard uncertainty derived from the repeatability). Based on the analysis of the main individual contributions of each uncertainty source to the total uncertainty value, several modifications were proposed. Firstly helium collision mode was replaced by no gas mode to improve the sensitivity of mass spectrometry. Secondly the number of measurements was increased. Thirdly let the mean of data points in the calibration closer the measurand. Finally the relative error smaller gauges were used. After these modifications, urel(cAl)1, urel(cAl)3 and urel(rep) were from (0.035 8, 0.013 2, 0.008 5) down to (0.006 0, 0.010 5, 0.003 3), respectively; the combined relative standard uncertainty of aluminum was from 0.039 down to 0.013; the expanded uncertainty from 1.8 down to 0.4 mg·kg-1(coverage factor k=2). The improvement effect was significant.