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As water needs and shortages increase, so has focus on freeze desalination as a potential solution to lower cost and more efficient desalination systems. At the molecular level, freeze desalination is caused by the higher solubility of ions in water than in ice – a phenomenon known as the ion rejection. This work reviews the published works and findings since 2004 on ion rejection and ion inclusion via Molecular Dynamics (MD) simulations. It begins with a brief historical background on the ion rejection phenomenon and MD simulations surrounding water and ionic solutions. The fundamentals of MD theory are reviewed and MD simulation practices related to ion rejection are explained. Finally, the current findings on ion inclusion and ion rejection – both the mechanisms and kinetics – are compared and contrasted among various studies. It is hypothesized that the ion rejection phenomenon is caused by dramatic structural rearrangements in the molecular structure around the ions and localized dislocations in the ice lattice that cause energetic differences between phases. To maximize ion rejection for freeze desalination systems, the current data supports temperatures closer to the melting point of the saltwater solution. However, there is not yet an optimized temperature available. Furthermore, further research is required to determine the best water-ion molecular model combination to simulate ion rejection. When compared with the experimental results of large-scale tests, MD simulations overestimate the rate of ion rejection at a given temperature. This is most likely due the inability of MD simulations to account for brine pockets that form due to dendritic ice growth. The aim of this critical review is to serve as an introduction to MD simulations and their use in understanding the fundamental phenomena governing freeze desalination and will facilitate increased interest in use of MD simulations in future freeze desalination research. • Provides a critical review of MD simulations of ion rejection inclusion phenomena in supporting freeze desalination • Conducts a brief overview of different water and sodium chloride models to be used in ion rejection MD simulations • Performs a critical review of recent research findings and provides unique perspectives for future ion rejection research [ABSTRACT FROM AUTHOR]

Abnormal protease activities are associated with cancers, vascular diseases and Alzheimer diseases. Therefore, detection of protease activities has become increasingly important in recent years. Herein, we report a semi-quantitative, liquid crystal (LC)-based protease assay for naked-eye detection of protease activity. In this assay, casein molecules are cleaved by proteases into small peptide fragments, which can be quantified either by using Lowry’s method or using LC. In the latter, peptide fragments adsorb on a solid surface and disrupt LC to produce a bright spot for naked-eye detection. The bright spot is observed only when the surface-adsorbed peptide density exceeds a critical value. In the assay, a major challenge is how to separate undigested casein and remaining protease from peptide fragments to prevent their interferences with LC. To overcome this issue, trichloroacetic acid (TCA) is added to precipitate casein and proteases. By using the assay, we are able to detect 10 ng/mL of protease (activity 7.23 U/mg protease, R 2  = 0.991) or 6.5 μg/mL of peptide fragments. Finally, a continuous protease assay is developed to minimize manual sampling and reduce errors in kinetic studies. [ABSTRACT FROM AUTHOR]

• A liquid crystal-based protease inhibition assay is developed. • This assay is used to assess inhibition efficiency of a protease inhibitor pefabloc. • IC 50 value of pefabloc can be detected by using the color of liquid crystal. • The assay provides detailed information about the transition period from reversible to irreversible inhibition. • Pefabloc inhibits protease activity irreversibly if the incubation time is more than 60 min. Protease inhibitors are essential drug molecules which can be used for treatments of protease-related diseases. Herein, we report an LC-based protease inhibition assay built inside a millifluidic device. This assay can be used to study the inhibition efficiency and reversibility of pefabloc (a serine protease inhibitor) against proteases. LC is employed for the detection of peptide fragments produced from protease activity inside the millifluidic device. LC gives a bright spot when the amount of peptide fragment exceeds a minimum value. By using this assay, we find that IC 50 value of pefabloc for the immobilized protease is 0.45 mg/mL, which is lower than the IC 50 value of pefabloc (0.90 mg/mL) obtained in a homogeneous assay. Moreover, proteases can be immobilized on the millifluidic device to build a heterogeneous protease assay. In this assay, pefabloc blocks the immobilized protease irreversibly after 60 min, which is longer than that in a homogenous protease assay. This reversibility study provides useful information about the transition period of pefabloc from reversible to irreversible inhibition. This protease inhibition assay is potentially useful for high throughput screening of unknown proteases and their inhibitor in a small sample volume. Moreover, this method can be used for dosage test of novel drug molecules which are protease inhibitors. [ABSTRACT FROM AUTHOR]