Effect of Polyvinyl Alcohol on Ice Formation in the Presence of a Liquid/Solid Interface

Tuning ice formation is of great importance in biological systems and some technological applications. Many synthetic polymers have been shown to affect ice formation, in particular, polyvinyl alcohol (PVA). However, the experimental observations of the effect of PVA on ice formation are still conflicting. Here, we introduced colloidal silica (CS) as the model liquid/solid interface and studied the effect of PVA on ice formation in detail. The results showed that either PVA or CS promoted ice formation, whereas the mixture of these two (CS–PVA) prevented ice formation (antifreezing). Using quantitative analysis based on classical nucleation theory, we revealed that the main contribution came from the kinetic factor <i>J</i>₀ rather than the energy barrier factor Γ. Combined with the PVA adsorption behavior on CS particles, it is strongly suggested that the adsorption of PVA at the interface has significantly reduced ice nucleation, which thus may provide new ideas for developing antifreezing agents

Plots of the measured relaxation time as a function of the concentration ratio <i>Cp/Cl</i> for the S1-b/ntMGAM system and acarbose/ntMGAM system.

<p>Solid curves are the calculated results using Eq. (2).</p

The Effect of Polyhydroxylated Alkaloids on Maltase-Glucoamylase

<div><p>One of the most important carbohydrate-splitting enzymes is themaltase-glucoamylase which catalyzes the hydrolysis of alpha-glucosidic linkages. Maltase-glucoamylase inhibitors during the last few years have aroused medical interests in the treatment of diabetes. They contribute to a better understanding of the mechanism of maltase-glucoamylase. At present there are many different classes of maltase-glucoamylase inhibitors. This paper focuses on alkaloidal inhibitors of maltase-glucoamylase and structure-activity relationship (SAR) studies between them in order to discover some drugs with better efficiency and lower toxicity for treating diabetes.</p></div

The influence of S1-b on blood glucose of normal ICR rat after sucrose loading.

<p>Acarbose (10 mg/kg of body weight); S1-b (50 mg/kg, 100 mg/kg, 200 mg/kg of body weight).</p

Dissociation constant <i>K</i>_d for acarbose/ntMGAM system and S1-b/ntMGAM system complex determined by relaxation measurements.

<p>Dissociation constant <i>K</i>_d for acarbose/ntMGAM system and S1-b/ntMGAM system complex determined by relaxation measurements.</p

ntMGAM-acarbose interactions.

<p>Schematic representation of interactions (dotted lines) between the ntMGAM side chain residues and acarbose. (PDB entry 2QMJ).</p

The influence of S1-b and acarbose on blood glucose and area under curve (AUC) of normal ICR rat after sucrose loading (Student's t test).

<p>Compared with normal,**P<0.01,***p<0.001;n = 8;X¯±SD. (dl = deciliter).</p

Molecular docking study of different compounds and ntMGAM.

<p>p<i>K</i>_d, the negative logarithm (base 10) of the dissociation constant.</p

Dissolution Mechanism of Cellulose in <i><i>N,N</i></i>-Dimethylacetamide/Lithium Chloride: Revisiting through Molecular Interactions

Understanding the interactions between solvent molecules and cellulose at a molecular level is still not fully achieved in cellulose/<i><i>N,N</i></i>-dimethylacetamide (DMAc)/LiCl system. In this paper, cellobiose was used as the model compound of cellulose to investigate the interactions in cellulose/DMAc/LiCl solution by using Fourier transform infrared spectroscopy (FTIR), ¹³C, ³⁵Cl, and ⁷Li nuclear magnetic resonance (NMR) spectroscopy and conductivity measurements. It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl^–, during which the intermolecular hydrogen bonding networks of cellulose is broken with simultaneous splitting of the Li⁺–Cl^– ion pairs. Simultaneously, the Li⁺ cations are further solvated by free DMAc molecules, which accompany the hydrogen-bonded Cl^– to meet electric balance. Thereafter, the cellulose chains are dispersed in molecular level in the solvent system to form homogeneous solution. This work clarifies the interactions in the cellulose/DMAc/LiCl solution at molecular level and the dissolution mechanism of cellulose in DMAc/LiCl, which is important for understanding the principle for selecting and designing new cellulose solvent systems

Screen Anti-influenza Lead Compounds That Target the PA_C Subunit of H5N1 Viral RNA Polymerase

<div><p>The avian influenza (H5N1) viral RNA polymerase protein PA_C was used as a target to screen nine chlorogenic acid derivatives for their polymerase inhibitor activity. Among them, seven compounds were PA_C ligands, and four inhibited influenza RNA polymerase activity. These results aid in the design of anti-influenza agents based on caffeoylquinic acid.</p> </div